submersible observations of the hydrothermal vent ... · other species were venus’s flower...

663

Journal of Oceanography, Vol. 57, pp. 663 to 677, 2001

Keywords:⋅ Hydrothermal vent,⋅ Iheya-Ridge,⋅ Okinawa Trough,⋅ biological commu-nities,

⋅ Calyptogena,⋅ vestimentiferans.

* Corresponding author. E-mail: [email protected]

Copyright © The Oceanographic Society of Japan.

Submersible Observations of the Hydrothermal VentCommunities on the Iheya Ridge, Mid Okinawa Trough,Japan

SUGURU OHTA1* and DONGSUNG KIM2

1Ocean Research Institute, University of Tokyo, Minamidai 1-15-1, Nakano-ku, Tokyo 164-8639, Japan2Biological Oceanography Division, Korea Ocean Research & Development Institute, Ansan P.O. Box 29, Seoul, Korea

(Received 10 July 2000; in revised form 24 June 2001; accepted 2 July 2001)

During the Dives Nos. 409, 410, 480 and 481 of the Japanese submersible Shinkai2000, conducted on June 10 and 11, 1989 and on May 16 and 17, 1990, several hydro-thermal vents and prosperous vent associated biological communities were found onthe northern slope of the Iheya Ridge in the Mid-Okinawa Trough (27°32.5′ N,126°58.5′ E: depth 1,400 m). The first site we found, the “Calyptogena Site”, was char-acterized by a relatively thick blanket of sediments, pleated and/or laminated lavaflows, with occasional lobate pillows and white and yellow stains. Although no re-markable shimmering water and thermal anomalies were detected during the obser-vations, the extraordinarily dense community must be related to hydrothermal ac-tivities. The community was dominated by the giant white clam, Calyptogena okutanii,in biomass, and by Neolepas-type primitive scalpellids and slender vestimentiferantube-worms in number. The second site, the “Pyramid Site”, situated only 200 m north-ward from the Calyptogena Site has typical clear smokers emitting hot water over200°C, and is characterized by a hard substratum of volcanic rocks and hydrother-mal slabs. No noteworthy succession was perceived at the Calyptogena Site over ayear. Many of the vent members occurred at both sites. However, Calyptogena okutanii,which were confined to the sediment bottom, Neolepas spp. and larger vestimentiferantube-worms were found to thrive only at the Calyptogena Site, being only minor ele-ments in the Pyramid Site. The global distribution of several groups of organisms isdiscussed preliminarily in zoogeographical terms based on comparison with othersubmersible missions and surveys done by surface vessels.

also Okutani et al., 2000; Fujikura et al., 2000). Since1985, similar communities were found to extend even inthe abyssal depths on the landward trench slopes and fur-ther to the hadal zone in the trench axis deeper than 6,000m of the Nankai Trough, the Japan and Kurile Trenches(Le Pichon et al., 1987; Ohta and Laubier, 1987; Fujikuraet al., 2000).

In Japan, ecological studies of deep-sea biologicalcommunities associated with hydrothermalism along theocean-spreading rift systems started only after 1987, re-lated to a foreign project surveying the rift systems in theMariana Back-arc Basin (Okutani and Ohta, 1988; Hessleret al., 1988a; Stein et al., 1988) and the North Fiji Basin(Auzende et al., 1988).

In 1988 hydrothermal vents and associated biologi-cal communities were located on the Iheya Ridge and

1. IntroductionIn recent decades many deep-sea chemosynthesis-

based communities have been reported in severaltectonically and geomorphologically active settings. Thesea around Japan is especially noteworthy in this respect,where the Pacific and Philippine Plates subduct beneaththe Eurasian Plate. In 1984, prolific deep-sea biologicalcommunities dominated by two giant clams, Calyptogena(Archivesica) soyoae and C. (A.) okutanii, were found inthe bathyal zone southeast of Hatsushima Island, SagamiBay, by a Japanese submersible Shinkai 2000 (Ohta etal., 1987; Sakai et al., 1987; Hashimoto et al., 1989; see

664 S. Ohta and D. Kim

Izena Cauldron in the Okinawa Trough (Kato et al., 1989;Kimura et al., 1989; Tanaka et al., 1989), and we cannow access both hydrothermal communities on a diver-gent front and cold-seep communities on the convergentfronts of the earth’s tectonics around Japan.

After that time, Japanese scientific parties went onto study a succession of hydrothermal vent ecosystems,such as Minami-Ensei Knoll (Hashimoto et al., 1995),Kagoshima Bay (Hashimoto et al., 1993) and volcanicarc on the Izu-Bonin (Takeda et al., 2000), and in addi-tion the Western South Pacific the Manus Basin, Centraland South Mariana Basin, and near the triple junction ofthe central Indian Ocean. However, there are few reportson the general description of the site characteristics, faunaland ecological observations of these findings, with theexception of cruise reports and special items or limitedtaxa. Although recent mainstream studies are inclined tofollow the genetic lineage of these fauna on the globalscale, there is also an urgent requirement to prepare de-tailed descriptions of ecological features, not only thegeneral characteristics but also the specific features ofeach site to integrate all of these into a global-scale com-prehension of the deep-sea chemosynthetic communitiesand the mechanisms by which species and ecological di-versities are maintained.

The Iheya hydrothermal field in the Mid-OkinawaTrough is one of the first examples to be described, com-paring its characteristics with those of the Minami-EnseiKnoll (Hashimoto et al., 1995) and Izena hydrothermalfield, both situated in the Mid-Okinawa Trough and sepa-

rated by only several tens or hundreds of kilometers, to-gether with the intra-field differentiation of the ecologi-cal characteristics.

Dives Nos. 409 and 410 of the Japanese submersibleShinkai 2000 in 1989, conducted by the ecological groupof the Ocean Research Institute, University of Tokyo, wereplanned to locate and describe several types of hydro-thermal vents and vent-associated organisms at two siteson the Iheya Ridge and to sample basic constituents ofthe communities. During the dive a new vent communitywas found, dominated by a giant clams, Calyptogena(Archivesica) okutanii (undescribed at that time anderected as a new species by Kojima and Ohta (1997a)),and this was named the “Calyptogena Site”. In theCalyptogena Site, Calyptogena formed dense beds amongthick sediment cover with the characteristic faunule of“hydrothermal” vent communities. No strong indicationof shimmers and bubbling was observed.

The “Pyramid Site” (200 m to the north of theCalyptogena Site) is a typical hydrothermal vent fieldcovered by dacitic volcanic rocks and slabs of hydrother-mal precipitates. It is interesting to compare the twonearby communities, separated by only a few hundredmeters, but having different substrata and, as a result,different community compositions.

A hydrothermal vent is destined to occlude itselfthrough its own precipitation activity, and this fate is es-timated to occur on the order of several decades (Laubierand Desbruyères, 1985). It is therefore expected that thelongevity of the hydrothermal vent communities is com-

Fig. 1. Bottom configuration of the Okinawa Trough. Bottom contour intervals are 200 m.

Hydrothermal Vent Communities on the Iheya Ridge 665

parable to that of the vent itself. Dives Nos. 480 and 481of Shinkai 2000 on May 16 and 17, 1990 were planned tovisit the same spots as Dives Nos. 409 and 410 to com-pare and follow the succession of the vent fields and thebiological communities over a roughly one-year period.

2. Location of the Sites and EquipmentThe location and contour map of the site is shown in

Figs. 1, 2 and 3. The sites are situated on a flat bench ofthe northern slope of the Iheya Ridge at a depth of around1,400 m in the Mid-Okinawa Trough (27°32.5 ′ N;126°58.5′ E). To the north of this dense biological com-munity, there is a topographic high of 50 m in relativealti tude composed of volcanic rocks altered byhydrothermalism (Fig. 3; see Tanaka et al., 1989).

During Dive No. 409 (June 10, 1990) the southernskirt of the topographic high was surveyed from west toeast along the 1,400 m contour. Later this area was ascer-tained to be 150 m to the south of “fissure emanation”found by Tanaka in 1988, and 200 m to the south of large-scale vent field of the Pyramid Site. Dive No. 410 (June11, 1989) first visited the Pyramid Site and ended at theCalyptogena Site.

Both of the Dives No. 480 (May 16, 1990) and No.481 (May 17, 1990) were dedicated to revisiting theCalyptogena Site and the Pyramid Site on the Iheya Ridgeto obtain additional samples and to observe the succes-sion, if present, of the biological communities andhydrothermalism itself.

The following equipment was installed on the sub-mersible:

Dive No. 409: stereo still cameras set perpendicularto the bottom for the description of the communities,baited traps, hand net, water-tight, heat-insulated samplebox made of PVC, two coring tubes.

Dive No. 410: marker buoy and still camera, PVCsample box.

Dive No. 480: stereo still cameras set parallel witheach other and perpendicular to the bottom for the map-ping of the communities, two small baited traps and adistensible baited trap, two coring tubes, scraper, Pt-re-sistance temperature probe.

Dive No. 481: small baited traps, hand net, two cor-ing tubes, temperature probe, opening-closing planktonnet (modified RMT type) installed on the payload rack ofthe submersible, another opening-closing epibenthicplankton net attached to the port-side sample basket(Kikuchi et al., 1990).

3. Survey Results, Observation and Notes

3.1 Calyptogena SiteThe investigation of the vent community was initi-

ated along the 1,400 m contour line (1,390–1,410 m) fromwest to east (Fig. 3). Below 1,410 m deep, the biotaseemed to be depauperate on steep slopes covered bycoarse debris flow, and the upslope shallower than 1,390m were rocky and/or covered by talus. Between the depthsof 1,400 and 1,410 m, the bottom was rather flat and cov-ered by pale, fine-grained sediment. Synallactidholothurians of body length between 30 and 40 cm wereencountered frequently. They were skimming the very

Fig. 2. Detailed bathymetrical map of the Iheya Ridge, Mid-Okinawa Trough.


surface of the sediment and fed selectively on organicdetritus. This suggests that the film of free-living chem-osynthetic bacteria cover the sediment surface. Hydro-thermal elements may contribute to the composition ofthe sediment, considering the very turbid water and densesuspension of the ambient water. The density of deep-seaeel, Synaphobranchus affinis and/or Ilyophis brunneus,Aldrovandia affinis and chimaerids was apparently higherthan those expected from the ordinary deep-sea floor atcomparable depths. These fishes are not included amongthe usual members of hydrothermal vent communities.However, the density of these fishes suggests the prox-imity of prey and a low density of toxic atmosphere.

After a trip lasting one and a half hour along the 1,400m contour, we came across a place where laminated darkrocks, oblong pillow lavas and pleated sheets of volcanicswere outcropping. The texture of the rocks was not of thetypical MORB (mid-oceanic ridge basalt) lavas, but ap-parently of eruption rocks, considering the glassy surfaceand characteristic features. Rounded prickly white glasssponge Pheronema ijimai aggregates on the rock surface,other species were Venus’s flower basket, Euplectella sp.,large sea anemones, and sabellid polychaete worms (di-ameter of tubes ca. 5 mm). They dwell within a 100 mradius around the Calyptogena Site, as mentioned later.Sponges are filter feeders, and the abundance of suspen-sion feeders suggests ample quantities of suspended mat-ter. On the sediment we witnessed dead shells ofCalyptogena sp.

Near the Calyptogena Site, huge tangles ofvestimentiferan tube-worms were found (probably con-sisted of more than 1,000 individuals). Among the slen-der and coiled vestimentiferan tube-worms, we observed

bresiliid shrimp with milky opaque body color, white eyes,long rostrum and slender walking legs and hippolytidshrimp with orange body color, black eyes, short rostrumand stout walking legs (Photo 2). Just outside of thevestimentiferan tangles, rather thick vestimentiferan tube-worms belonging to the genus Lamellibrachia were seenprojecting their greenish pink obturaculum and scarletpetal-like gills. Medium-sized mussels and Neolepas-typecirripeds covered the rock surface. Among the rock crev-ices, hagfish Eptatretus okinoseanus were aggregating.On the skirt of the rocks, deep-sea galatheids Shinkaiacrosnieri Baba and Williams (1998; Photo 4) and Munidasp. and dead shells of Calyptogena okutanii were scat-tered.

The density gradient of these vent organisms guidedus gradually to the “heavenly garden” of clams, mussels,cirripeds and shrimps named Calyptogena Site (Photo 1).The site was characterized by relatively thick blanket ofsediments, breccia and pyroclastics, pleated and/or lami-nated lava flow, with occasional lobate pillows (the tex-ture of the rocks suggests a rather acidic nature like dacite)and white and yellow stains. Although no remarkableshimmering water and thermal anomalies were detectedduring the observation and sampling of the dense patchesof organisms, the extraordinarily thick community con-vinced us that it was fueled by hydrothermal chemicals.

Fig. 3. Track lines of Dives Nos. 409, 410, 480 and 481 on themulti-narrow beam echo sounder (“Seabeam”) map of therelevant site. Ps: Pyramid Site, Cs: Calyptogena Site. Solidcircle on the Dive No. 410 track line indicates the start point.

Fig. 4. Distribution of representative vent organisms in theCalyptogena Site on the Iheya Ridge, Mid-Okinawa Trough.


Photo 1. The giant clam Calyptogena (Archivesica) okutanii Kojima and Ohta (1997a) colonizing on the sediment and a stonecrab Paralomis sp. (cf. P. verrilli (Benedict)). Scalpellids probably akin to genus Neolepas cover the outcropping rocks.Calyptogena Site.

Photo 2. Two forms of primitive scalpellids probably akin to the genus Neolepas. They are often attached on a tube of the largevestimentiferan tube-worm. Calyptogena Site.


Photo 3. Voracious shrimps Lebbeus washingtonianus (Rathbun) and Alvinocaris longirostris Kikuchi and Ohta (1995) aggregateon the hydrothermal slabs. Pyramid Site.

Photo 4. Galatheid Shinkaia crosnieri Baba and Williams (1998). They bear Beggiatoa-type filamentous bacteria on abdominalsurface. Pyramid Site.


The general configuration of the site was a narrowbench on a southward dipping gentle slope, where darkgrayish brown volcanic table rocks are outcropping amongblanket of fine to coarse sediments. The span of the thriv-ing community was about 5 by 20 m (Fig. 4).

The community was dominated by Calyptogenaokutanii in biomass, and in number by two primitivescalpellids (akin to Neolepas spp. undescribed; Photo 2)and slender vestimentiferan tube-worms. It must be notedthat the C. okutanii were confined to the sediment bot-tom, and other dominant members were occupying theoutcropping surface of the volcanic rocks (Photo 1 andFig. 4). Two kinds of shrimps (bresiliid and hippolytid:Photo 3), two species of mussels, deep-sea galatheidMunidopsis sp., stone crab Paralomis sp. (cf. P. verrilli)(Photo 1) were the representative constituents of the thickcommunity. A larger vestimentiferan tube-wormLamellibrachia sp. (Photo 2), hyaline sponges Pheronemaijimai and Euplectella sp. and the fishes such asAldrovandia affinis, chimaeras and Synaphobranchusaffinis and/or Ilyophis brunneus) surrounded the field ofdense patches of organisms.

Three dense beds (2 by 4 m, 1 by 1.5 m and 1 by 1.5m) of Calyptogena occupied the central portion of thecommunity (Fig. 4). Almost all specimens were livingones, uniform in length (median 14 cm), and half buriedin the sediment in a vertical or oblique position showingthe openings of their short, reddish incomplete siphonsamong the gaping shells (Photo 1). They sometimes ex-pired water jets. The thickness of the sediment was atmost 10 to 15 cm among the clam beds, and less than 5cm thick outside the beds, judging from the probing ofsediment temperature sensor.

The Calyptogena of this site was revealed to be com-mon to the C. (Archivesica) okutanii originally describedon the specimen collected in Sagami Bay, and differs fromC. (A.) solidissima reported from the hydrothermal ventfields of the Minami-Ensei Knoll (Kojima and Ohta,1997a; see also Okutani et al., 1992). Hemoglobin-richblood, unusually thick gills, atrophied alimentary canal,and the mode of occurrence are typical characteristics ofCalyptogena-group inhabiting the cold seepages ofSagami Bay (Hashimoto et al., 1987), the Japan and KurileTrenches (Ohta and Laubier, 1987). Typical coccoidsymbionts in the bacteriocytes of the gill tissue (Kim,1992), ample crystals of native sulfur (based on opticalmicroscope observations of the preserved specimens)suggest sulfur-oxidizing chemosynthetic bacteria.

The density was the closest-pack state, and deadspecimens were scarce. They dominated in biomass, andthe standing crop was estimated to be more than 10kg m–2, which is 3 to 4 orders of magnitude higher thanthe average biomass at a comparable depth of the ordi-nary deep-sea floor (Ohta, 1983).

On the outcropping rocks of the clam beds, twoundescribed scalpellids both having an ancient body-planwere crowded (Photos 1 and 2). Slender and coiledvestimentiferan tube-worms (probably belonging to thegenus Alaysia) were entangled. They were muffled by“snow” of chemical precipitate and/or bacterial mats andsponges. These two groups of organisms dominated innumber on the outcropping rocks.

The giant clams and the tube-worms were sampledwith the manipulator. Ophiothrichid ophiuroids were en-countered among the slender tube-worms. Possibly theyare feeding on the detritus trapped among the bush, ratherthan taking shelter among them.

We could differentiate two species of shrimpsthrough the porthole of the submersible. During DivesNos. 409 and 410 they escaped easily from the hand netoperated by manipulator, except when the clashed clamswere used as a lure. During Dives Nos. 480 and 481, theywere efficiently collected by the baited traps. The bresiliidshrimp was described as a new species Alvinocarislongirostris Kikuchi and Ohta (1995) and is very akin toand congeneric with Alvinocaris lusca Williams andChace (1982) described on the hydrothermal vents of theEast Pacific Rise about 7,000 km away. The hippolytidshrimp was identified as Lebbeus washingtonianus. Thisspecies also occurs in the Minami Ensei Knoll vent fields(Hashimoto et al., 1995); the southern extension of geo-graphical distribution to the Okinawa Trough and the oc-currence of the hippolytid shrimp bound tohydrothermalism are noteworthy (Kikuchi and Ohta,1995).

Amphipods were the first to be attracted to the smalltraps baited with clam meat. Alvinocaris and Lebbeusfollowed the amphipods, but they were rather cautious atthe entrance to the traps. They sometimes stretched theirlegs to grasp the bait at the entrance, and took out themoiety of the food. However, before long, the traps werefull of the two shrimps. The density of the shrimps in thefields was estimated to be 200 individuals per squaremeter, and Alvinocaris accounted for 80 to 90% of them.There was a slight difference in the approach to the bait.Alvinocaris leapt at the clam meat, whereas Lebbeus camesomewhat later, walking on their stout legs. Although theyare not large predators, they are voracious and swift inmotion, and probably play the role of most influentialconsumers.

Although the mussels Bathymodiolus spp. are sub-ordinate to the Calyptogena, they fasten themselves withbyssus to the rock substratum and also to slender andcoiled vestimentiferan tube-worms. Two species of mus-sels occurred in this field and are described anew asBathymodiolus platifrons Hashimoto and Okutani (1994)and B. aduloides Hashimoto and Okutani (1994). Theshells are medium-sized (3–10 cm) compared to the con-


generic species of the East Pacific Rise, the Mariana Back-arc Basin and the North Fiji Basin. As a member of thefamily Mytilidae of the order Filibranchia, the gill fila-ment is rather thin and essentially free. However, eachfilament is unusually wide, and most of the “gill tissue”is transformed into the bacteriocytes layer bearing chem-osynthetic bacteria, and this is reminiscent of theCalyptogena group (Kim, 1992). The gill, however, stillfunctions as a respiratory and filter feeding organ, andthe alimentary canal is intact. The mussels can collectflocks of free-living chemosynthetic bacteria to feed on(Lilley et al., 1983). The high infection rate of exoparasiticpolychaetes aiming to snatch off the particles on the gillalso supports this (Miura and Ohta, 1991). Therefore themussels are mixotrophs depending nutritionally on theirown alimentary canal and chemosynthetic endosymbionts(Kim, 1992; Kim and Ohta, 2000).

Large fish, Synaphobranchus and/or Ilyophis and astone crab Paralomis sp. roamed around the site as preda-tors. Two eelpouts occurred among the dense communi-ties. They seem to be endemic to this hydrothermal ventfield. They usually lay with their bodies motionless, andnever showed feeding behavior. They paid no attentionto the baited traps containing swordfish Cololabis saira,whereas synaphobranchids and amphipods are attractedquickly to the baited trap.

A large, yellow-colored stone crab Paralomis sp. cf.P. verrilli (Photo 1) was captured by the manipulator ofthe submersible. Carapace width attained 15 cm. In con-trast to the case of Paralomis jamsteci reported from thehydrothermal vent field of the Minami-Ensei Knoll(Takeda and Hashimoto, 1990). They are not bound tohydrothermal vents, but are attracted and accumulate justas in the case of Paralomis multispina in Sagami Bay(Hashimoto et al., 1987). However, they must be quiteresistant to the chemical atmosphere of the vent fields.Although they can expel the shrimps and pick up and feedon the clams, mussels, cirripedes and polychaetes amongthe sediment with their stout chelae, their sluggish mo-tion may not cope with the quick response of the twoshrimps and amphipods.

A few individuals of deep-sea galatheid with flat ros-trum Shinkaia crosnieri (Photo 4) were also recognizedin the field, but they remained almost motionless, and wecould not imagine how and what items they feed on.

White patches of about 10 by 30 cm were scatteredhere and there in the field. We tried in vain to collect thewhite stuff with coring tubes with core catchers. Theywere easily blown off by the bow wave, because they arenot sticky as in the case of filamentous bacterial mats.They are probably composed mainly of chemical precipi-tates such as carbonates, sulfates and/or silicates.

Surrounding the Calyptogena Site, largevestimentiferan tube-worms, roughly 1 cm in the diam-

eter of distal opening, 30 to 70 cm in total length, werescattered on the basement rock covered thinly by coarsesediments. The anterior 1/3 of the tube was held perpen-dicular to the sea floor, whereas the remaining posteriorportions were attached among the rock crevices and/orbeneath the boulders, hence the obturacula occupies be-tween 10 and 20 cm above the bottom. They reminded usof asparagus in the field. This species does not form agregarious bush as was observed in the case of thevestimentiferans of Sagami Bay (Hashimoto et al., 1987;Ohta, 1990b). The highest density was 20 individuals persquare meter. Pale greenish obturacula projected into thewater column as slender funnels. This corresponds to the“pistil” of a flower, and the lamellate gill slits form pet-als of scarlet color (due to the presence of hemoglobin inthe body fluid). The general configuration of the “flower”and the occurrence of several distinct trumpet-shapedcorrugations on the distal portion of their tubes differen-tiate them from the possibly congeneric species ofLamellibrachia found in the cold seepages in Sagami Bay(Ohta, 1990b). Most of them bear a few individuals ofsmooth Neolepas-type cirripeds on the distal portions ofthe tubes (Photo 2). They slowly but regularly protrudeand draw in the “flowers” at the openings.

The prickly scalpellid, Neolepas-type sp. A (Photo2; left) dominated in number. They gregariously covermost of the rock surface. Another species of smoothscalpellid, Neolepas sp. B (Photo 2; right), as inclined todwell in relative solitude on the rocks or on the tubes ofvestimentiferan tube-worms. Most of the Neolepas sp. Boccupied the distal extremities of the tubes. This at leastsuggests that the cirripede finds its own position after thegrowth of vestimentiferan tube-worm, and further sug-gests that they are rather opportunistic in reproductionstrategy. The cirripeds in the hydrothermal vents areequipped with very long and fine appendages adapted tocollect the fine flocks of free-living bacteria and/or bac-terial clots suspended in the ambient seawater (Newman,1979; Newman and Hessler, 1989; Yamaguchi andNewman, 1997a, b).

We noticed small ophiuroids walking among the matsof coiled vestimentiferan tube-worms or on theoutcropping rocks. Also Ophiura-type ophiuroids oc-curred among the Calyptogena beds. They are not negli-gible members in number, and the dimensions were al-most uniform.

Although Dives Nos. 480 and 481 were conductedwith the theme in mind, i.e., to follow the temporal vari-ation (succession) of the biological communities at theCalyptogena Site over a year, we could not notice theslightest difference in the hydrothermalism and the ventcommunities. The Calyptogena Site seems to be in a sta-ble climax phase.


Fig. 5. Generalized map showing the central part of the Pyra-mid Site (after Gamo et al., 1991). Small concentric circlesand squares denote the location of marker buoys and/or scaledeployed during submersible dives.

Many ctenophores were noticed during the dives. Wemust take into account the occurrence of “hydrothermalplankton” in the vent fields.

3.2 Pyramid SiteThe second site, the “Pyramid Site”, situated only

200 m northward to the Calyptogena Site (Fig. 2), hastypical clear smokers and is characterized by the hardsubstratum of volcanic rocks and hydrothermal slabs.

Dive No. 481 was dedicated to ecological observa-tions and sampling of the Pyramid Site. Following thenetwork of broad and white altered streaks and theshimmering of hot water, we approached the western flankof the vent field (Fig. 5). The Pyramid Site as a wholeconsists of hard substrata of huge volcanic rocks coveredby hydrothermal precipitation slabs composed mainly ofcalcium carbonate and magnesium carbonate (Gamo etal., 1991). In the eastern part, a pyramidal edifice standsseveral meters high as a conical tower (Fig. 5). It emitshot water (more than 200°C) mainly through the smallcentral collapsed cauldron, as well as through the gaps inthe skirt. Slender and coiled vestimentiferan tube-worms,probably of the genus Alaysia, mussels Bathymodiolus,shrimps of Alvinocaris and Lebbeus, galatheids andeelpouts are the main constituents of the vent openingcommunity. Dense beds of mussels and small spongesencircled the vent opening community, and large potato-shaped sponges (5–10 cm in diameter) populated the pe-riphery. Limpets of 1.5 cm diameter were sometimes at-tached to the rocks and bivalves.

The most dominant organisms in number wereshrimps, Alvinocaris longirostris and Lebbeuswashingtonianus (50 individuals per 50 × 50 cm quadrat),and Bathymodiolus platyfrons and B. aduloides were scat-

tered in threes and fives (20 individuals per 2 × 2 mquadrat). The most dominant organisms in biomass mustbe mats of several species of sponges. The density of free-living deep-sea galatheid Munidopsis were around the1/4 of that of the mussels. On the other hand, largervestimentiferan tube-worms, Calyptogena and Neolepas-type cirripeds were not witnessed in the Pyramid Site.

Shrimps of unusual appearance were sometimesfound. Body length reaches 7 to 8 cm (ca. 1.3 times largerthan and about twice as wide as the ordinary ones), andthey bear “white moss” over 2/3 of the cephalothorax.They must be full-grown and senile individuals ofAlvinocaris, considering the body’s pale opaque color,colorless eyes, long rostrum and relatively slender walk-ing legs. The “moss” suggests the tufts of filamentousbacteria, but its ecological implications remain as openquestion due to the failure of sample collection.

Eelpouts lie among the beds, flexed in sinusoidalfashion. Sometimes they maintain this posture even inthe water column. Again, they never pay attention tobaited traps. Possibly they may be satiated in the densecommunities.

It must be noted that four asteroids Henricia sp. wereseen on the rocks.

The top and middle portion of the pyramid (a hydro-thermal chimney) are blurred with shimmering hot wa-ter. The surface of the pyramidal body was covered withthe mossy tubes of vent-specific polychaetes, Paralvinellahessleri Desbruyères and Laubier (1989; see also Miuraand Ohta, 1991).

The galatheids Shinkaia crosnieri gathered gregari-ously on the diffuse chimney top, hiding almost all of itssurface, where a rather high temperature gradient and highconcentration of hydrogen sulfide are expected. Appar-ently they are tolerant to these environments where noother members except the Paralvinella dare to invade.They may probably feed on the polychaetes and “culture”filamentous bacteria on their abdominal surface (Photo4).

Groups of sabellid polychaetes were observed on theflanks and overhang of the chimney. The habitat of thesabellid polychaetes is separated by, say, 1 m from thatof paralvinellids. They are not exposed directly to thewarm water.

4. DiscussionSince the discovery of hydrothermalism and the as-

sociation of deep-sea communities along the GalapagosRift in 1977, many interdisciplinary works have beenperformed to explain the unusual prosperity of the biota.Demonstration of the occurrence of free-livingchemoautotrophs (Lilley et al., 1983; Jannasch and Mottl,1985; Johnson et al . , 1986) and symbiosis withchemoautotrophic bacteria among several large repre-


sentatives of the vent organisms (Felbeck, 1981;Cavanaugh et al., 1981) explained the prosperity, up to20–30 kg m–2 standing stock (Hessler and Smithey, 1983;Somero et al., 1983; Laubier and Desbruyères, 1984; Steinet al., 1988). The detailed explanation of the nutritionalbackgrounds of this kind of ecosystem is ubiquitous inmany references.

Now we have available data on the biological sam-ples of the Okinawa vent fields (the Iheya Ridge, the IzenaCauldron and the Minami-Ensei Knoll; e.g. Hashimotoet al., 1995; Okutani et al., 2000; Fujikura et al., 2000;Okutani and Fujiwara, 2000), the vent fields along thevolcanic front of the Izu-Ogasawara Ridge (KaikataSeamount, Kasuga Seamount, Mokuyo and SuiyoSeamounts; e.g. Takeda et al., 2000), and the vent fieldsof the back-arc and/or microplate rift systems (MarianaBack-arc Basin, Manus Basin, the North Fiji Basin andthe Lau Basin; e.g. Desbruyères et al., 1994) of the West-ern and Southwestern Pacific areas. A comparison withthose of the Juan de Fuca Ridge, the East Pacific Rise ofthe Eastern Pacific (see the review by Tunnicliffe, 1991),together with the data set of the subduction zones alongthe Northwestern Pacific (Sibuet and Olu, 1998; Ohta andHashimoto, unpublished data), demands that we startstudy the global distribution and generalization of thedeep-sea ecosystems bound to tectonics.

As for the dominant members of the vent fields—i.e., Calyptogena, Bathymodiolus, vestimentiferan tube-worms, shrimps, cirripedes, and polychaetes—morpho-logical work and molecular phylogeny studies are nowunder way by many collaborators. The amino acidsequencing of the hemoglobin molecules together withthe systematic positioning of Calyptogena andvestimentiferan tube-worms have already been demon-strated (Suzuki et al., 1988, 1989a, 1989b, 1989c, 1990a,1990b), and the systematics and phylogeny ofCalyptogena and vestimentiferan tube-worms of the West-ern and South Pacific are now being fixed. Here we fo-cus very briefly on the problems of zoogeography of thevent and cold-seep organisms around Japan.

4.1 Notes on biogeography of vent organisms aroundJapanTo start with the white giant clams Calyptogena, we

can count at least more than 10 species of extantCalyptogena sensu lato around Japanese waters, rangingfrom several hundred meters to the depth of 6,800 m(Metivier et al., 1986; see descriptions and review byOkutani et al., 2000; Fujikura et al., 2000). Among them,the species from the Minami-Ensei Knoll and Iheya-Izenafields in the Okinawa Trough are associated withhydrothermalism, and most of the remainders are recordedfrom cold seepage areas, and a few undescribed speciesare not related to active tectonics, as will be discussed

later. However, all Japanese species are collected fromsediment floor, contrasting strikingly to the Calyptogenamagnifica found among crevices of basaltic rocks, even-tually without sediment cover (Hessler and Smithey, 1983;Hessler et al., 1985). The latter species is reported to takeup hydrogen sulfide through the foot muscle protrudingdownward into the crevices. However, all JapaneseCalyptogena together with that found recently in theManus Basin, Solomon Sea, exclusively inhabit the sedi-ment bottom (Ohta, unpublished data) and sometimes theyroam about the field with their pelecypods (Ohta andLaubier, 1987). The Pyramid Site where hard substratadominate, and volcanism and hydrothermalism are moreactive than in the Calyptogena Site lacked theCalyptogena. So far, we can conclude that the giant clamof the western side of the Pacific needs soft substrata.

Calyptogena are well-known organisms that housesymbiotic bacteria within their gills (hence, they are seem-ing “producers”), and they are often the dominant mem-ber of the vent and seep communities around the Japa-nese waters and along EPR. On the other hand, in thehydrothermal fields of the back-arc (and/or microplate)rift systems of the Western and Central Pacific, the domi-nant members bearing chemosynthetic symbionts wereseveral species of large gastropods, such as Alviniconchahessleri and Ifremeria nautilei (the Mariana Basin:Okutani and Ohta, 1988; Ohta, 1988 in Hessler et al.,1988a; Stein et al., 1988; the Manus Basin: Both et al.,1986; the North Fiji Basin: Kojima et al., 2001; Lau Ba-sin: Bouchet and Warren, 1991). We must note that thedistance between the hydrothermal vent fields of theOkinawa Trough and the rift systems of the Western andSouth Pacific regions is several thousands of kilometers,whereas the Okinawa Trough is separated from the EPRby more than ten thousand kilometers, if we do not in-clude the Calyptogena of the cold-seep areas.

However, considering that Calyptogena is also thedominant species in the cold-seep fields along subduc-tion zones, and further they seem not to be obligatorilybound to a well-defined chemosynthetic environment(Ohta, unpublished data), the pan-Pacific distribution canbe understood. Recent finding of the occurrence ofCalyptogena on the Rodriguez Triple Junction in the Cen-tral Indian Ocean (Ohta, unpublished data) may shed lighton another possible propagation route.

Two species of the exoparasite polychaetes to thegills of mussels and clams in the Iheya Ridge vent fieldswere reported as new to science; Shinkai longipedata andBranchipolynoe pettiboneae. They have, so far, been re-ported only from the type locality. On the other hand,paralvinellid polychaete of the Iheya-Izena fields wasconcluded to be conspecific to Paralvinella hessleri re-ported from the Mariana Back-arc Basin, the North FijiBasin and the Lau Basin in the central South Pacific


(Miura and Ohta, 1991), and the species is even conge-neric with those recorded along the entire region of theEast Pacific Rise. The forms of Paralvinella are reportedfrom every hydrothermal vent field in the world. Theylay off-spring within their tubes, hence they must behandicapped in their larval dispersal. This mode of re-production is still puzzling problem for the ecologists(Laubier and Desbruyères, 1985).

Vestimentiferan and pogonophoran tube-worms arealso famous representative members of the vent and coldseep fields, depending for their nutrition on symbioticchemoautotrophs. The phylum Vestimentifera was erectedin 1981, and so far 5 families and more than 10 specieshave been described from the region along the EPR (Jones,1985, 1987, 1988) and Japanese waters (Hashimoto et al.,1993; Miura et al., 1997).

Japanese vestimentiferans of about ten forms and/orspecies, from hydrothermal fields and cold seepage, willprobably belong to the genera Lamellibrachia, Escarpia,Arcovestia and Alaysia. The genus Lamellibrachia wasoriginally reported from supposedly reduced environmentof cold seepage (Webb, 1969; Hecker, 1985). As a gen-eral rule the vestimentiferans, at least the adult stage ofthem, completely lack alimentary canals. However, thespongy posterior portion of their bodies, the“trophosome”, without exception, houses symbiotic bac-teria (Kim, 1992).

After the finding of the most ancient form ofcirripedes, Neolepas zevinae in the vent fields of the EPR,a wealth of collections of so-called living fossils of thecirripedes was found, to which Japanese groups contrib-uted greatly. This lead to the systematics and phylogenyof the cirripedes drastically renewed (Newman, 1979;Newman and Hessler, 1989; Yamaguchi and Newman,1997a, b). Neoverruca brachylepadoformis Newman andHessler (1989) from the Mariana Back-arc Basin, situ-ates the main stock of the Verrucomorpha, Eoverrucaohtai from the vent fields of the North Fiji Basin situatesthe main stock dividing Verrucomorpha andBalanomorpha.

The Neolepas zevinae are based on very limited num-bers of specimens, and they were a minor group in thevent fields of the EPR. However, Neolepas-type sp. A andNeolepas sp. B in the Calyptogena Site of the Iheya Ridgedominated in number and also in the standing crop, andthey are comparable to those of clams and mussels (seePhotos 1 and 2). From a geological point of view, theOkinawa Trough is considered to be an incipient back-arc rift system just beginning to spread open. The occur-rence of the most ancient forms of cirripedes already ar-rive at the rift system is thus astonishing.

We collected Alvinocaris longirostris and Lebbeuswashingtonianus in the Okinawa Trough. However, wecould not find typical rimicarid shrimps at these sites in

the Okinawa Trough. The rimicarid group dominates inthe Mariana Back-arc Basin, in the North Fiji Basin andthe Lau Basin of the Western Pacific, and along the Mid-Atlantic and Central Indian ridge systems. Occurrence ofAlvinocaris and no collection of rimicarid group suggestthe affinity of the fauna of the Okinawa Trough to that ofthe EPR.

During the successive dives Nos. 411 and 412 in 1989to the Izena Hole in the Okinawa Trough (ca. 40 km southto the Iheya Ridge) during the same leg of the submers-ible, we had the chance to inspect the biological samplesfrom a black smoker. On the ores collected from the flankof the black smoker, we found undescribed cirripeds andlimpets. The latter turned out to be another “missing link”which bridges the Verrucomorpha and Balanomorpha(T. Yamaguchi, personal communication). Incidentally,two Neolepas-type forms found in the Iheya fields werenot collected from the Izena Cauldron.

Paralvinella hessleri were also found among the oredeposits, which were famous for very wideeurythermalism, together with very wide zoogeographicaldistribution, as mentioned before.

No bythograeid crabs have been collected, so far,from both of the Iheya and Izena fields. Vestimentiferantube-worms occur in both sites.

Although the Izena Hole fields have a sediment-cov-ered habitat, rather limited numbers of Calyptogena wereencountered in the Izena fields. This may due to; 1) anepisodic “explosion event”, which must occur in the Izenasmoker area (Kato et al., 1989) will depopulate the lessmobile species like Calyptogena; 2) a high concentrationof carbon dioxide in the Izena Site as clathrate or bub-bles will be awkward for Calyptogena; and/or 3) Japa-nese species group of Calyptogena require rather thicksediment cover as a reactor bed, where the reduction ofsulfate from seawater will occur coupled with the inputof methane beneath the sediment, because all theCalyptogena living in methane-rich environments have,without exception, sulfur-related symbionts and high con-centration of native sulfur within their soft tissue. So far,the study of stable isotope ratios of sulfur favors the lasthypothesis (Sakai et al., 1990, 1991; Kim et al., 1990).

Apart from the geographical distribution,bathymetrical segregation of vent and cold seep associ-ates also deserves to be studied in near future (Kojimaand Ohta, 1997b; Fujikura et al., 2000).

4.2 Succession of the vent fields and vent faunaNo apparent change was observed in the biota and

emission of venting fluid in both sites of the Iheya Ridgeover 13 months. The trial of the 1-year continuous re-cording of the fluid venting activity in the Pyramid Siteof the Iheya Ridge using temperature probes failed dueto heavy chemical corrosion of the stainless steel hous-


ing of the temperature probe. However, the temperaturemeasurements of each year showed almost the same value.

There are several reports to describe the successionof the vent and vent organisms over a few years (Laubierand Desbruyères, 1985; Hessler et al., 1985, 1988b; Fustecet al., 1987; Campbell et al., 1988; Johnson et al., 1988).According to these reports, vestimentiferan tube-wormsand Calyptogena, both of which are obligatorily in sym-biosis with chemoautolithotrophs, are climax phase rep-resentatives; mussels, one of the typical mixotrophs, canbe both a pioneering species and also the declining phaseinhabitant. At any rate we have a good field to test thesehypothesis around the Japanese waters in near future.

4.3 Occurrence of echinoderms around vent fieldsAlthough we assumed that the dense biological com-

munities, especially those in the Calyptogena Site of theIheya Ridge are hydrothermal ones, we could not per-ceive the characteristic shimmering of hot water or gasbubbling as observed in the typical vents of the Izena andIheya fields (Sakai et al., 1990). Here temperature probesshowed only slight thermal anomalies of +0.3–0.5°C com-pared to the ambient seawater temperature of 3.1°C. Thesite may be a field of low-temperature, methane rich ema-nation often reported on a sediment-covered back-arcbasin (Ishibashi et al., 1990; Gamo et al., 1991).

Formerly, the echinoderms, in general, were thoughtto be so sensitive to the chemical constituents of theseawater that they avoid the vent environments full oftoxic substances such as heavy metals, hydrogen sulfideand aromatic hydrocarbons (Hessler and Smithey, 1983;Grassle, 1986). In particular, it is often reported that evena trace amount of heavy metals disturbs the early devel-opment. However it is noticed that a group of brisingidasteroids always encircles the hydrothermal vents as aperipheral member of vent communities in the MarianaBack-arc Basin, North Fiji Basin and also in the vent fieldsof N13° (on the East Pacific Rise). Just on the vent open-ings of the diffuse hydrothermal vent fields of the NorthFiji Basin and also of the Manus Basin, a group ofchiridotid holothurian (Trochodota sp. undescribed) werefound to occur as if they are bond to the vent openingenvironment. Furthermore, large five-armed asteroidDistorasterias stichantha were observed to pray on theclam Calyptogena soyoae and/or C. okutanii in their densebeds and together with small ophiuroids (Ohta, 1990a),and large synallactid holothurians were roaming aroundthe Calyptogena bed in the cold seepage of the TenryuCanyon (Ohta and Laubier, 1987).

Fairly large numbers of echinoderms were encoun-tered in the hydrothermal vent fields (though not verynear the vents) of the Okinawa Trough. Taking accountof the fact that the hydrothermal emission in the Okinawa

Trough is thought to be of gas-liquid separated type be-neath the sea floor (Sakai et al., 1990), and is also alteredchemically through the thick sediment, as is usual in theisland-arc type rift systems (Ishibashi et al., 1990), theemitted water is not always rich in hydrogen sulfide andheavy metals of crustal origin.

Our frequent encounters with deep-sea eels,Aldrovandia affinis and chimaeras, that are not bound tohydrothermalism, suggest that the atmosphere of the Iheyafields are not so toxic to these fishes. Therefore, the Iheyasite is a rather open ecosystem as compared to other typi-cal vent fields, such as those of Juan de Fuca Ridge.

Incorporating additional survey results, the Iheyahydrothermal field is becoming one of the more inten-sively explored vent fields, and we can depict detailedgeological and ecological settings over a fairly wide area,and this ecological description will offer good basis forthe intercomparison of other typical vent fields as thoseof the Minami Ensei Knoll (Hashimoto et al., 1995) sepa-rated only 100 km, and that of the North Fiji Basin(Desbruyères et al., 1994) separated by several thousandkilometers.

As a whole, the Iheya vent field has typical island-arc hydrothermalism, compared to those of the mid-oce-anic ridge hydrothermalism. It embraces both the hardsubstratum composed of hydrothermal slabs and mounds,and is also influenced by the thick sedimentation exem-plified by the chemical composition of the vent fluid(Sakai et al., 1990, 1991) and the bottom features. Thefield is a complex of heterogeneous ecological habitatswithin a relatively short span, and concomitantly the mi-cro-distribution of vent fauna to each habitat was regu-lated by the spatial allocation of the vent type and also bythe succession stage of the vents. At the same time, theIheya Field was situated on a rather convex topography,and the faunal composition suggested a rather “open”ecosystem, contrasting with that of the Minami-Enseihydrothermal field which is situated in caldrons and filledby hydrothermal atmosphere in the topographic depres-sions.

Anyway, we are looking for compilation of goodecological description of every vent field including de-tailed and dynamic descriptions of the life-forms, alloca-tion and adaptation to the special environmental settings,and the mode of larval dispersal to synthesize with thecompilation of a knowledge of the morphology and sys-tematic lineage of constituent vent organisms.

AcknowledgementsWe would like to express to the captain Mr. Ochi

and crew of the tendership Natsushima and the formercommander Mr. K. Danno and diving support team ofShinkai 2000.


ReferencesAuzende, J.-M., E. Honza, X. Boespflug, S. Deo, J.-P. Eissen,

J. Hashimoto, P. Huchon, J. Ishibashi, Y. Iwabuchi, P. Jarvis,M. Joshima, K. Kisimoto, Y. Kuwahara, Y. LaFoy, T.Matsumoto, J.-P. Maze, K. Mitsuzawa, H. Monma, T.Naganuma, Y. Nojiri, S. Ohta, K. Otsuka, Y. Okuda, H.Ondreas, A. Otsuki, E. Ruellan, M. Sibuet, M. Tanahashi,T. Tanaka and T. Urabe (1988): L’accretion recente dans leBassin Nord-Fidjien: premiers resultats de la campagnefranco-japonaise Kaiyo 87. C. R. Acad. Sci. Paris, Ser. II,306, 971–978.

Baba, K. and A. B. Williams (1998): New Galatheoidea (Crus-tacea, Decapoda, Anomura) from hydrothermal systems inthe West Pacific Ocean: Bismarck Archipelago and OkinawaTrough. Zoosystema, 20, 143–156.

Both, R., K. Crook, B. Taylor, S. Borgan, B. Chappell, E.Frankel, L. Liu, J. Sinton and D. Tiffin (1986): Hydrother-mal chimneys and associated fauna in the Manus Back-ArcBasin, Papua New Guinea. Eos, 67, 489–491.

Bouchet, P. and A. Warren (1991): Ifremeria nautilei, nouveaugastéropode d’évents hydrothermaux, probablement associéa des bactéries symbiotiques. C. R. Acad. Sci. Paris, Ser.III, 312, 495–501.

Campbell, A. C., T. S. Bowers, C. I. Measures, K. K. Falkner,M. Khadem and J. M. Edmond (1988): A time series of ventfluid compositions from 21, East Pacific Rise (1979, 1981,1985), and the Guaymas Basin, Gulf of California (1982,1985). J. Geophys. Res., 93(B5), 4537–4549.

Cavanaugh, C. M., S. L. Gardiner, M. L. Jones, H. W. Jannaschand J. B. Waterbury (1981): Prokaryotic cells in the hydro-thermal vent tube worm Riftia pachyptila Jones: possiblechemoautotrophic symbionts. Science, 213, 340–342.

Desbruyères, D. and L. Laubier (1989): Paralvinella hessleri,new species of Alvinellidae (Polychaeta) from the Marianaback-ark basin hydrothermal vents. Proc. Biol. Soc. Wash-ington, 102, 761–767.

Desbruyères, D., A.-M. Alayse-Danet, S. Ohta and the scien-tific parties of BIOLAU and STARMER Cruise (1994):Deep-sea hydrothermal communities in Southwestern Pa-cific back-arc basins (the North Fiji and Lau Basins); com-position, microdistribution and food web. Mar. Geol., 116,227–242.

Felbeck, H. (1981): Chemoautotrophic potential of the hydro-thermal vent tube worm, Rift ia pachyptila Jones(Vestimentifera). Science, 209, 336–338.

Fujikura, K., S. Kojima, Y. Fujiwara, J. Hashimoto and T.Okutani (2000): New distribution records of vesicomyidbivalves from deep-sea chemosynthesis-based communitiesin Japanese waters. Venus (Jap. J. Malac.), 59, 103–121.

Fustec, A., D. Desbruyères and S. K. Juniper (1987): Deep-seahydrothermal vent communities at 13° on the East PacificRise: microdistribution and temporal variations. Biol.Oceanogr., 4, 121–164.

Gamo, T., H. Sakai, J. Ishibashi, T. Oomori, H. Chiba, K.Shitashima, K. Nakashima, Y. Tanaka and H. Masuda(1991): Growth mechanism of the hydrothermal mounds atthe Clam Site, Mid Okinawa Trough, inferred from theirmorphological, mineralogical and chemical characteristics.JAMSTECTR Deepsea Res., No. 7, 163–184.

Grassle, J. F. (1986): The ecology of deep-sea hydrothermalvent communities. Adv. Mar. Biol., 23, 301–362.

Hashimoto, J. and T. Okutani (1994): Four new mytilid mus-sels associated with deepsea chemosynthetic communitiesaround Japan. Venus (Jap. J. Malac.), 53, 61–83.

Hashimoto, J., T. Tanaka, S. Matsuzawa and H. Hotta (1987):Surveys of the deep sea communities dominated by the gi-ant clam, Calyptogena soyoae, along the slope foot ofHatsushima Island, Sagami Bay. JAMSTECTR DeepseaRes., No. 4, 177–188.

Hashimoto, J., S. Ohta, T. Tanaka, H. Hotta, H. Matsuzawa andH. Sakai (1989): Deep-sea communities dominated by thegiant clam, Calyptogena soyoae, along the slope foot ofHatsushima Island, Sagami Bay, Central Japan.Palaeogeogr., Palaeoclimatol., Palaeoecol., 71, 179–192.

Hashimoto, J., T. Miura, K. Fujikura and J. Ossaka (1993): Dis-covery of vestimentiferan tube-worms in the euphotic zone.Zool. Sci., 10, 1063–1067.

Hashimoto, J., S. Ohta, K. Fujikura and T. Miura (1995):Microdistribution pattern and biogeography of the hydro-thermal vent communities of the Minami-Ensei Knoll in theMid-Okinawa Trough, Western Pacific. Deep-Sea Res., 42,577–598.

Hecker, B. (1985): Fauna from a cold sulfur-seep in the Gulf ofMexico: comparison with hydrothermal vent communitiesand evolutionary implications. Bull. Biol. Soc. Washington,1985(6), 465–473.

Hessler, R. R. and W. M. Smithey, Jr. (1983): The distributionand community structure of megafauna at the GalapagosRift hydrothermal vents. p. 735–770. In Hydrothermal Proc-ess at Seafloor Spreading Centers, ed. by P. A. Rona, K.Boström, L. Laubier and K. L. Smith, Jr., NATO Confer-ence Series IV, Plenum Press, New York.

Hessler, R. R., W. M. Smithey, Jr. and C. H. Keller (1985):Spatial and temporal variation of giant clams, tube wormsand mussels at deep-sea hydrothermal vents. Bull. Biol. Soc.Washington, 1985(6), 411–428.

Hessler, R. R., P. Lonsdale and J. Hawkins (1988a): Patternson the ocean floor. New Scientist, No. 24, 47–51.

Hessler, R. R., W. M. Smithey, M. A. Boudrias, C. H. Keller, R.A. Lutz and J. J. Childress (1988b): Temporal change inmegafauna at the Rose Garden hydrothermal vent(Galapagos Rift; Eastern Tropical Pacific). Deep-Sea Res.,35, 1681–1709.

Ishibashi, J., Y. Sano, H. Wakita, T. Gamo, M. Tsutsumi and H.Sakai (1990): Geochemical studies on the hydrothermalactivity in the Mid-Okinawa Trough: characterization ofhydrothermal fluids from chemical and isotopical compo-sition of the gas compounds. JAMSTECTR Deepsea Res.,No. 6, 63–68.

Jannasch, H. W. and M. J. Mottl (1985): Geomicrobiology ofdeep-sea hydrothermal vents. Science, 229, 717–725.

Johnson, K. S., C. L. Beehler, C. M. Sakamoto-Arnold and J. J.Childress (1986): In situ measurements of chemical distri-butions in a deep-sea hydrothermal vent field. Science, 231,1139–1141.

Johnson, K. S., J. J. Childress, R. R. Hessler, C. M. Sakamoto-Arnold and C. L. Beehler (1988): Chemical and biologicalinteractions in the Rose Garden hydrothermal vent field,


Galapagos Spreading Center. Deep-Sea Res., 35, 1723–1744.

Jones, M. L. (1985): The vestimentiferans of the Eastern Pa-cific, with comments on specimens from the Gulf of Mexico.Bull. Biol. Soc. Washington, 1985(6), 117–158.

Jones, M. L. (1987): On the status of the phylum-name, andother names, of the vestimentiferan tube worms. Proc. Biol.Soc. Washington, 100, 1049–1050.

Jones, M. L. (1988): The vestimentifera, their biology and sys-tematic and evolutionary patterns. p. 69–82. In Actes duColloque Hydrothermalisme, Biologie et Ecologie, ed. byL. Laubier, Special Vol. No. 8, Oceanol. Acta.

Kato, Y., K. Nakamura, Y. Iwabuchi, J. Hashimoto and Y.Kaneko (1989): Geology and topography in the Izena Holeof the Middle Okinawa Trough—the results of diving sur-veys in 1987 and 1988. JAMSTECTR Deepsea Res., No. 5,163–182.

Kikuchi, T. and S. Ohta (1995): Two caridean shrimps of thefamilies Bresiliidae and Hippolytidae from a hydrothermalfield on the Iheya Ridge, off the Ryukyu Islands, Japan. J.Crust. Biol., 15, 771–785.

Kikuchi, T., T. Toda, T. Nemoto and S. Ohta (1990): Prelimi-nary survey on the deepsea near bottom zooplankton bymeans of deep-sea submersible Shinkai 2000. JAMSTECTRDeepsea Res., No. 6, 115–122.

Kim, D.-S. (1992): Oceanographic and ecological studies ofhydrothermal vent and cold seep communities of the West-ern Pacific. M.Sc. Thesis, The University of Tokyo, 117 pp.

Kim, D.-S. and S. Ohta (2000): TEM observation studies onthe chemoautotrophic symbiotic bacteria of invertebratesinhabiting at vents and seeps. Ocean Res., 22, 1–13.

Kim, E.-S., H. Sakai, T. Gamo, J. Hashimoto, S. Ohta and F.Yanagisawa (1990): Carbon, nitrogen and sulfur isotopicratios in hydrothermal vent animals from the Mid-OkinawaTrough. JAMSTECTR Deepsea Res., No. 6, 129–137.

Kimura, M., T. Tanaka, M. Kyo, M. Ando, T. Oomori, E. Izawaand I. Yoshikawa (1989): Study of topography, hydrother-mal deposits and animal colonies in the middle OkinawaTrough hydrothermal areas using the submersible Shinkai2000 system. JAMSTECTR Deepsea Res., No. 5, 223–234.

Kojima, S. and S. Ohta (1997a): Calyptogena okutanii n. sp., asibling species of Calyptogena soyoae Okutani, 1957(Bivalvia, Vesicomyidae). Venus (Jap. J. Malac.), 56, 189–195.

Kojima, S. and S. Ohta (1997b): Bathymetrical distribution ofthe species of the genus Calyptogena in the Nankai Trough,Japan. Venus (Jap. J. Malac.), 56, 293–297.

Kojima, S., R. Segawa, Y. Fujiwara, K. Fujikura, S. Ohta and J.Hashimoto (2001): Phylogeny of hydrothermal-vent-en-demic gastropods Alviniconcha spp. From the Western Pa-cific revealed by mitochondrial DNA sequences. Biol. Bull.,200, 298–304.

Laubier, L. and D. Desbruyères (1984): Les oasis du fond desoceans. La Recherche, No. 15, 1506–1517.

Laubier, L. and D. Desbruyères (1985): Oases at the bottom ofthe ocean. Endeaver, New Series, 9(2), 67–76.

Le Pichon, X., T. Iiyama, J. Boulegue, J. Charvet, M. Faure, K.Kano, S. Lallemant, H. Okada, C. Rangin, A. Taira, T. Urabeand S. Uyeda (1987): Nankai Trough and Zenisu Ridge: a

deep-sea submersible survey. Earth Planet. Sci. Lett., 83,285–299.

Lilley, M. D., J. A. Baross and L. I. Gordon (1983): Reducedbases and bacteria in hydrothermal fluids: the GalapagosSpreading Center and 21 East Pacific Rise. p. 411–449. InHydrothermal Processes at Seafloor Spreading Centers, ed.by P. A. Rona, K. Boström, L. Laubier and K. L. Smith, Jr.,Plenum Press, New York.

Metivier, B., T. Okutani and S. Ohta (1986): Calyptogena(Ectenagena) phaseoliformis n. sp., an unusual vesicomyidbivalve collected by the submersible Nautile from abyssaldepths of the Japan and Kurile Trenches. Venus (Jap. J.Malac.), 45, 161–168.

Miura, T. and S. Ohta (1991): Two polychaete species from thedeep-sea hydrothermal vent in the Middle Okinawa Trough.Zool. Sci., 8, 383–387.

Miura, T. , J . Tsukahara and J. Hashimoto (1997):Lamellibrachia satsuma, a new species of vestimentiferanworms (Annelida; Pogonophora) from a shallow hydrother-mal vent in Kagoshima Bay, Japan. Proc. Biol. Soc. Wash-ington, 110, 447–456.

Newman, W. A. (1979): A new scalpellid (Cirripedia); aMesozoic relic living near an abyssal hydrothermal spring.Transact. San Diego Soc. Nat. His., 19, 153–167.

Newman, W. A. and R. R. Hessler (1989): A new abyssal hy-drothermal verrucomorphan (Cirripedia; Sessilia): The mostprimitive living sessile barnacle. Transact. San Diego Soc.Nat. His., 21, 259–273.

Ohta, S. (1983): Photographic census of large-sized benthicorganisms in the bathyal zone of Suruga Bay, central Ja-pan. Bull. Ocean Res. Inst., Univ. Tokyo, No. 15, 1–244.

Ohta, S. (1988). Biological processes in the hydrothermal ventfields. Geochemistry, 22, 87–95.

Ohta, S. (1990a): Several ecological notes on the seepage eco-system of Sagami Bay. JAMSTECTR Deepsea Res., No. 6,181–196.

Ohta, S. (1990b): Hydrothermal vent communities on the IheyaRidge, Okinawa Trough. JAMSTECTR Deepsea Res., No.6, 145–156.

Ohta, S. and L. Laubier (1987): Deep biological communitiesin the subduction zone of Japan from bottom photographstaken during “Nautile” dives in the Kaiko Project. EarthPlanet. Sci. Lett., 83, 329–342.

Ohta, S., H. Sakai, A. Taira, K. Ohwada, T. Ishii, M. Maeda, K.Fujioka, T. Saino, K. Kogure, T. Gamo, Y. Shirayama, T.Furuta, T. Ishizuka, K. Endo, T. Sumi, H. Hotta, J.Hashimoto, N. Handa and M. Horikoshi (1987): Initial re-port of the Calyptogena communities to the southeast ofHatsushima, Sagami Bay, Japan. JAMSTECTR DeepseaRes., No. 3, 51–60.

Okutani, T. and Y. Fujiwara (2000): Gastropod fauna of a ther-mal vent site on the North Knoll of Iheya Ridge, OkinawaTrough. Venus (Jap. J. Malac.), 59, 123–128.

Okutani, T. and S. Ohta (1988): A new gastropod mollusk asso-ciated with hydrothermal vents in the Mariana Back-arcBasin, Western Pacific. Venus (Jap. J. Malac.), 47, 1–9.

Okutani, T., J. Hashimoto and K. Fujikura (1992): A new spe-cies of vesicomyid bivalve associated with hydrothermalvents near Amami-Oshima Island, Japan. Venus (Jap. J.


Malac.), 51, 225–233.Okutani, T., K. Fujikura and S. Kojima (2000): New taxa and

review of vesicomyid bivalves collected from the North-west Pacific by deep sea research systems of Japan MarineScience & Technology Center. Venus (Jap. J. Malac.), 59,83–101.

Sakai, H., T. Gamo, K. Endow, J. Ishibashi, T. Ishizuka, F.Yanagisawa, M. Kusakabe, T. Akagi, G. Igarashi and S. Ohta(1987): Geochemical study of the bathyal seep communi-ties at the Hatsushima Site, Sagami Bay, Central Japan.Geochem. J., 21, 227–236.

Sakai, H., T. Gamo, E.-S. Kim, M. Tsutsumi, T. Tanaka, J.Ishibashi, H. Wakita, M. Yamano and T. Oomori (1990):Venting of carbon dioxide-rich fluid and hydrate formationin Mid-Okinawa Trough backarc basin. Science, 248, 1093–1096.

Sakai, H., M. Yamano, T. Tanaka, T. Gamo, E.-S. Kim, J.Ishibashi, K. Shitashima, T. Matsumoto, T. Omori, F.Yanagisawa and M. Tsutsumi (1991): Geochemical studiesof the hydrothermal system at the Izena Cauldron usingShinkai 2000—report on dive numbers 413 and 415, andon the liquid CO2 bubbles and hydrate collected during divesnumber 414. JAMSTECTR Deepsea Res., No. 6, 69–85.

Sibuet, M. and K. Olu (1998): Biogeography, biodiversity andfluid dependence of deep-sea cold-seep communities at ac-tive and passive margins. Deep-Sea Res., 45, 517–567.

Somero, G. N., J. F. Siebenaller and P. W. Hochachka (1983):Biochemical and physiological adaptations of deep-sea ani-mals. p. 261–330. In Deep-Sea Biology, The Sea, Vol. 8, ed.by G. T. Rowe, Wiley, New York.

Stein, J. L., S. C. Cary, R. R. Hessler, S. Ohta, R. D. Vetter, J. J.Childress and H. Felbeck (1988): Chemoautotrophic sym-biosis in a hydrothermal vent gastropod. Biol. Bull., 174,373–378.

Suzuki, T., T. Takagi and S. Ohta (1988): N-terminal aminoacid sequence of the deep-sea tube worm haemoglobin re-markably resembles that of annelid haemoglobin. Biochem.J., 255, 541–545.

Suzuki, T., T. Takagi and S. Ohta (1989a): Amino acid sequenceof the dimeric hemoglobin (Hb I) from the deep-sea cold-seep clam Calyptogena soyoae and the phylogenetic rela-tionship with other molluscan globins. Biochim. Biophys.Acta, 993, 254–259.

Suzuki, T., T. Takagi and S. Ohta (1989b): Primary structure ofa dimeric haemoglobin from the deep-sea cold clamCalyptogena soyoae. Biochem. J., 260, 177–182.

Suzuki, T., T. Takagi, K. Okuda, T. Furukohri and S. Ohta(1989c): The deep-sea tube worm hemoglobin: subunitstructure and phylogenetic relationship with annelidhemoglobin. Zool. Sci., 6, 915–926.

Suzuki, T., T. Takagi and S. Ohta (1990a): Primary structure ofa linker subunit of the tube worm 3000-kDa hemoglobin. J.Biol. Chem., 265, 1551–1555.

Suzuki, T., T. Takagi and S. Ohta (1990b): Primary structure ofa constituent polypeptide chain (AIII) of the giant haemo-globin from the deep-sea tube worm Lamellibrachia: a pos-sible H2S-binding site. Biochem. J., 266, 221–225.

Takeda, M. and J. Hashimoto (1990). A new species of the ge-nus Paralomis (Crustacea, Decapoda, Lithodidae) from theMinami-Ensei Knoll in the Mid-Okinawa Trough. Bull. Nat.Sci. Mus., Ser. A (Zool.), 16, 79–88.

Takeda, M., J. Hashimoto and S. Ohta (2000): A new species ofthe family Bythograeidae (Crustacea, Decapoda, Brachyura)from the hydrothermal vents along volcanic front of thePhilippine Sea Plate. Bull. Nat. Sci. Mus., Ser. A (Zool.),26, 159–172.

Tanaka, T., K. Mitsuzawa and H. Hotta (1989): Shinkai 2000diving surveys in the east of Iheya Small Ridge in the cen-tral Okinawa Trough. JAMSTECTR Deepsea Res., No. 5,267–282.

Tunnicliffe, V. (1991): The biology of hydrothermal vents: ecol-ogy and evolution. Oceanogr. Mar. Biol. Rev., 29, 319–407.

Webb, M. (1969): Lamellibrachia barhami, gen. nov., sp. nov.(Pogonophora), from the Northeast Pacific. Bull. Mar. Sci.,19, 18–47.

Williams, A. B. and F. A. Chace, Jr. (1982): A new carideanshrimp of the family Bresiliidae from thermal vents of theGalapagos Rift. J. Crust. Biol., 2, 136–147.

Yamaguchi, T. and W. A. Newman (1997a): A new and primi-tive barnacle (Cirripedia: Balanomorpha) from the NorthFiji Basin, abyssal hydrothermal field, and its evolutionaryimplications. Pac. Sci., 44, 135–155.

Yamaguchi, T. and W. A. Newman (1997b): The hydrothermalvent barnacle Eochionelasmus (Cirripedia, Balanomorpha)from the North Fiji, Lau and Manus Basins, South-WestPacific. Zoosystema, 19, 623–649.

submersible observations of the hydrothermal vent ... · other species were venus’s flower...

Documents