the vivarium & aquarium news : issue 3 - vol 1

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Editorial

Contents

Terrestrial hermit crabs

Wild killies from Peru

The Redbellied Shortneck Turtle

NEW ON THE MARKET!

The Malagasy Giant Chameleon

Focus on the Lesser Siren

3-14

34-36

27-33

22-26

18-21

15-17

Ashley RademacherAnimal Care and Education CoordinatorZoo Med Labs

For many people, summertime means vacation, traveling, and sunny days at the beach or the lake. For reptile keepers like me, summertime means extra feeding, collecting eggs, caring for newly hatched babies, tending the greenhouse and turtle yards, and maybe even a reptile or fish show! While this tends to be the busiest time of year for us and our ectothermic pets, it is also the

most exciting. By the middle of May this year, the incubators at Zoo Med held over 300 eggs and babies had already begun to hatch. This year has been especially exciting with the hatching of our very first Yellow Blotch Sawback Turtle! We have also hatched eight other turtle species in-cluding Box Turtles, Sawbacks, Diamondback Terrapins, and other aquatic turtles. Our lizards have been busy as well with nine different spe-cies hatching such as Jeweled Lacertas, Green Basilisks, Electric Blue Dwarf Geckos, and Vei-led Chameleons. One of the most rewarding events that can happen in our animal room is to watch a new baby hatch. It is then that I realize that our efforts have paid off. We have provided care for the parent animals -frequently since they were babies themselves, in a way that has allo-wed them to grow to adulthood, remain healthy, perform natural breeding behaviors, select nes-ting sites and lay eggs. We have provided an en-vironment that has made these animals feel com-fortable and secure. We have done our research to learn the requirements of the animals and of their eggs. Finally, we have tended the eggs and waited patiently for the offspring to emerge. The cycle is complete and it is time to begin again. So, whether you are on vacation, planning your trip to the lake, or at home cleaning tanks and yards, I hope you enjoy your summer and this issue of The Vivarium and Aquarium News!

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The Vivarium - Issue 33

Terrestrial hermit crabs

Hermit crabs can easily be recognized by the fact that they usually protect the pos-terior part of their body by concealing it in an empty gastropod shell. Some species also use the empty homes of other crea-tures, for example tubeworms, and there are also specialized species that live in symbiosis with stinging coelenterates or sponges that grow around the posterior body of these hermit crabs. But all these specialists are exclusively marine spe-cies that won’t be discussed further here. by Wolfgang Löll

Coenobita clypeatus from the USA are very attractively colored.

Coenobita brevimanus from South East Asia

There are, however, two genera of terrestrial hermit crabs – Birgus and Coenobita – which

are regularly offered for sale in the pet trade.

MorphologyOf the five pairs of peraeopods or walking legs - the hermit crabs are decapods (Decapoda) – only three are readily visible. The powerful pair of claws constitutes the first pair of peraeo-pods. A typical feature of all Anomura (the next zoological-systematic category down from the

Decapoda, and that to which the hermit crabs are assigned) is that one of the two claws is lar-ger than the other. The claws are used to block the opening of the shell the hermit crab has cho-sen as its residence and make it impregnable. Next there are two large, well-developed pairs of peraeopods. The fourth pair of peraeopods are much abbreviated and located inside the shell; they are used to move the crab backwards and forwards within the shell. The fifth pair of peraeo-pods are even more specialized; the tips are mo-dified and brush-like and are used to clean the complex structure of the respiratory apparatus and expel excrement. The posterior body (pleon) is soft and curved.


Coenobita compressus from Ecuador.

This Coenibita clypeatus turned up in a consignment from Ecuador!

Sexual dimorphismThe females have pleopods (legs on the posteri-or body, absent in males), which they use to hold the eggs securely in place. At the end of the ple-on we find the uropods, which are used to an-chor the crab securely in the shell. In females the sexual openings (gonopores, again lacking in males) are located at the base of the third pair of peraeopods.There are no sexual differences visible in hermit crabs that are ensconced in their shells. The only way of differentiating the sexes reliably is to exa-mine the underside of the pleon and the base of the third pair of peraeopods. But this is not pos-sible in the pet store as a hermit crab cannot be persuaded to leave its shell without resorting to measures that constitute cruelty to animals. Un-der no circumstances whatsoever should such an attempt be made! The only possible exception – and this requires both patience and skill – invol-ves exploiting the fact that many hermit crabs are rather “impatient” members of their kind. If the shell is picked up and held so that the opening is directed upwards then they will relatively quick-ly endeavor to turn the shell back into the cor-rect position, i.e. with the opening downwards. In the process they come a long way out of their “house” and in relatively large specimens the practiced observer can then see whether or not there are gonopores present at the base of the third pair of peraeopods. And it is also often pos-sible in such situations to see the pleopods in fe-males. Sometimes, however, the attempt will be thwarted by the hermit crab remaining obdurately in its shell for hours…... Terrestrial hermit crabs don’t nip very often, but

when they do it hurts, even with small specimens. So if you allow one to clamber over your hand, make sure that the latter is fully outspread, as if the crab decides to grab hold of a fold of skin with its claws then it may well deliver a powerful nip!In the final analysis males grow larger than fema-les, but, as all hermit crabs available in the trade are wild-caught specimens of indeterminate age, this fact is only rarely of practical help. So there is often nothing for it but to buy a large number of hermit crabs and hope thereby to obtain both se-xes. But this is a good idea anyway, as terrestrial hermit crabs are sociable creatures that should not be kept singly (see below).


The stripe on the second joint of the leg is species-typical for Coenobita compressus.

Reproductive behaviorAll hermit crabs belong to the primitive reproduc-tive type and thus must return to the sea in order to breed. The larvae pass through several zoëa stages, then a megalopa stage, before adopting the lifestyle of their parents. To date there have been no reports of the breeding of terrestrial her-mit crabs by private individuals, but it is nevert-heless essentially possible, as Coenobita com-pressus, for example, has already been reared successfully under laboratory conditions (BRO-DIE & HARVEY, 2001) and marine aquarists have already reported success in rearing some small marine species. The rearing of the zoëae takes place in full-strength sea water using Ar-temia nauplii as food. The zoëae are positively phototactic, in other words they will swim towards a light source. This means they can be attracted using “light-traps”. And because Artemia nauplii are also positively phototactic it is in addition rea-dily possible to concentrate the zoëae and the food organisms with the aid of a localized light source.The number of zoëa stages varies, even within a single species. In Coenobita compressus, for

example, 88% of the larvae undergo five zoëa stages and 12 % four such stages, before meta-morphosing into megalopae after 21 to 33 days at 78 °F (26 °C). The megalopae leave the water after seven days and bury themselves in damp sand for 29 days. A further one to five days later their metamorphosis into fully-formed little terre-strial hermit crabs is complete.The rearing of hermit crabs is undoubtedly time-consuming and of no economic interest, but it is extremely interesting to work with the offspring of these crabs. On the one hand details of the reproductive behavior of many species are still completely unknown, while on the other hand some, for example the Palm Thief (Birgus latro), are seriously endangered in parts of their natural distribution. Thus it may one day prove to be exceptionally popular and are expedient to stabilize some populations by planned breeding programs - and that will be possible only if the appropriate knowledge is available.Hermit crabs mate in a belly-to-belly position and come a long way out of their shells to do so. The male transfers spermatophores (sperm packets) into the gonopores of the female.


Coenobita pseudorugosus, red morp.

Terrestrial hermit crabs – Coenobitidae: overview of the speciesThe family Coenobitidae Dana, 1851 contains two genera and 17 species, 16 of which belong to the genus Coenobita LATREILLE, 1829. The name is derived from the Latin coenobium, which actually means “monastery”, but what is meant is life in a religious community. The genus name perhaps relates to the fact that the lifestyle of hu-man hermits is usually religiously motivated, but perhaps the original describer was aware that Coenobita species live in colonies.There is also the monotypic genus Birgus LE-ACH, 1816 (the name Birgus is supposedly a personal name, but whose is unknown). The-se are highly specialized animals which, when adult, live entirely on land. You can read about the Palm Thief in AQUALOG News no. 80, which can be downloaded free of charge at www.aqua-log.de. A number of the 16 known species of the ge-nus Coenobita are regularly seen in the trade, with further species available occasionally. But it isn’t always clear which species are involved as they are very similar to one another. The easiest way of identifying the species is by their origin, as only two come from the New World: C. com-pressus H. MILNE EDWARDS, 1837 (the speci-fic name means compressed) comes exclusively from the west (Pacific) coast, while from the east coast (Florida, Caribbean, and parts of the At-

lantic coast) we have C. clypeatus (FABRICIUS, 1787) (the name signifies “shield-bearing”, from the round shield known as a clypeus carried by Roman legionaries). These two species are fre-quently seen in the pet trade.Additional Coenobita species are exported from south-east Asia, mainly via Singapore and Thai-land. The following names have been applied to them: C. brevimanus, C. cavipes, C. perlatus, C. purpureus, C. rugosus, C. variabilis, and C. violascens. All these species are valid, and all are widespread in the western Indo-Pacific area, but in general it is doubtful whether the imported species are correctly identified.

Coenobita clypeatusUntil recently C. clypeatus was the species most frequently sold in the USA, while this species turns up only comparatively rarely in the Europe-an pet trade. C. clypeatus maintained correctly in a terrarium can attain an age of more than 30 years. These crabs grow astonishingly large and can supposedly achieve basketball size, though I personally have never yet seen such a giant. In fact specimens the size of a good-sized fist are generally considered large.These hermit crabs appear to follow a seaso-nal cycle, as mating and egg-laying have so far been achieved only under outdoor maintenance in Florida. A winter rest period at lower tempera-tures, and above all a reduced photoperiod, may

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The huge smooth claw is typical for Coenobita brevimanus.

Coenobita perlatus is very attractively colored.

be a prerequisite for successful breeding. It has been established that in three of the larger (Asi-an) Coenobita species (C. brevimanus, C. cavi-pes, and C. perlata) females by preference cast their young adrift at new moon. The lunar cycle thus appears to be important in the breeding of Coenobita species. The eggs are very numerous and visible when the gravid female emerges from her shell. In C. clypeatus the eggs attached to the pleopods change color from brick red to dark gray during the development period. The initial coloration derives from the color of the yolk and changes as the embryos develop.When the eggs are ready to hatch they develop a mechanism that allows them to rupture very quickly when they come into contact with sea wa-ter. This adaptation clearly makes sense as the female could easily drown if she had to remain in the water for too long.In captivity, as soon as the eggs are ready to hatch the female will automatically make for the water if a suitably large dish filled with sea water is available. Full-strength sea water is necessary for rearing. The zoëae can be fed with Artemia nauplii. Under laboratory conditions – to date there have been no published reports of suc-cessful rearing by private individuals – the zoëae are reared either individually in 20 ml containers or in groups of five in 75 ml containers.

Coenobita compressusC. compressus, the Pacific coast counterpart of Coenobita clypeatus, is very similar, although it appears to remain considerably smaller. As far as aquarists are concerned the best way to dis-tinguish them is by differences in coloration. It is a fact that all decapods are very variable in their coloration, and this applies equally to Coenobita species, but essentially C. clypeatus has a red-dish or red-brown base coloration verging on vi-olet, while C. compressus tends more towards gray and brown shades, and is often also stri-ped. Because strikingly red-colored specimens are sometimes to be found among Coenobita compressus imported from Ecuador, it cannot be ruled out that Coenobita clypeatus has made use of the Panama Canal and now also occurs on the Pacific side of the Americas. A relatively reliab-le distinguishing characteristic between the two species is the coloration of the merus (i.e. the third element of the leg, counting from the tip of the foot) of the second pair of peraeopods. In C. compressus the upper surface of this leg element

always exhibits a dark stripe, absent in C. clype-atus. If these two Coenobita species are compa-red in anatomical terms, then it is noticeable that C. clypeatus is “hairier” and has more “pimples” on the upper surfaces of the peraeopods. Egg-bearing females of C. compressus have been observed in Panama from March to May.

Australian and Indo-Pacific speciesThere are two species of hermit crab in Australia: Coenobita variabilis and C. perlatus. Of these two species, however, only C. variabilis (the specific name means “variable”) is endemic to Australia. But this species is not available in the internatio-nal pet trade, as since the 1980s no commercial exports of living wild animals or plants have been permitted from Australia. That is a pity, as to date C. variabilis is the only Coenobita species that has been shown to have an abbreviated larval development, making the breeding of the spe-cies under vivarium conditions at least a possi-


Coenobita compressus.

Coenobita cavipes is only rarely imported.

bility. According to Harvey (1992), following two non-feeding zoeal stages, the feeding megalopa larvae develop in only six days at 86 °F (30 °C); they metamorphose only on land, similar to what was described for C. compressus.The second species mentioned above, C. perla-tus, occurs in Australia only on coral islands and is regarded as rare there. It is unclear what the species name signifies. It probably represents a Latinized form of the word “pearl” and hence me-ans “pearly”, referring to the striking white gra-nulae (i.e. the little “pimples”) on the surface of the armor in this species. The Latin for pearl is margarita, but the Italian is perla.The rare occurrence of the species in Australia has been blamed on excessive collecting for the

pet trade, but it is difficult to determine whether that is in fact the case or merely propaganda from those who oppose the keeping of pet animals, who have a powerful lobby in Australia. There are confirmed locations for C. perlatus in Poly-nesia (the Gambier Archipelago, the Marque-sas, the Society Islands and Tuamotu) and other South-Sea islands. The species supposedly also occurs from the Seychelles to Madagascar, on isolated islands, and on the East African coast opposite. Its easternmost occurrence is given as Japan. The species has purportedly been intro-duced elsewhere by Man, who uses it for culinary purposes, and hence there are nowadays even self-sustaining colonies reported from the USA (e.g. Cape Cod, Massachusetts). In many cases, however, it appears that the species may have been incorrectly identified.C. perlatus is a very attractive species, known in English-speaking countries as the Strawberry Hermit, which describes its coloration very apt-ly. Full-grown specimens are bright red and the numerous granulae on the claws and legs are whitish. Juveniles are white initially and later be-come beige with brown stripes. At all stages the antennae are red, and this is regarded as a dia-gnostic characteristic for distinguishing this crab from other, similar species.The other species are likewise distributed in the western Indo-Pacific. Coenobita brevimanus (the species name means ”with a short hand”) and C. rugosus (the species name means ”wrinkly”) are imported quite frequently, and occasionally C. cavipes (the species name means ”hollow foot”),


Coenobita clypeatus.

C. pseudorugosus (the species name means “false rugosus”), C. purpureus (the species name means ”purple”), and C. violascens (the species name means ”with a violet sheen”) are seen for sale. The last two species listed originate from Japan. In view of the considerable variability in coloration in all these species, however, it is highly debatable whether they are always actual-ly correctly identified in the pet trade.

MaintenanceWe have already looked at the most important species of terrestrial hermit crabs and discussed their biology. Now it’s time to summarize the fra-mework of conditions required for the successful maintenance of all terrestrial hermit crabs.All terrestrial hermit crabs are fundamentally nocturnal and become active during the day only if the humidity is appropriately high. This means – in terms of terrarium maintenance – that their quarters should be sprayed once or more per day and that a relative humidity of 70% to 80% needs to be achieved for a period of several hours du-ring the day (and if necessary also during the night). If this isn’t the case then the terrestrial hermit crabs will initially respond with inactivity and ultimately die.Because terrestrial hermit crabs have evolved to breathe via “lungs” instead of gills, they will drown in water after just a few hours! Hence their main-tenance is possible only in a terrarium. They do, however, require water to be permanently availa-ble in shallow dishes, into which they can easily climb - and also get out again – in order to drink and moisten their respiratory cavities. There are species or populations that originate from entirely



Terrestrial hermit crabs are sociable creatures.

fresh water, while others require full-strength sea water. But because you can’t tell which from their appearance, the terrestrial hermit crab terrarium should always contain a dish of clean fresh water and one of clean sea water. Only top quality salt mixes, such as are manufactured for coral-reef aquaria, are suitable for preparing the sea water. Cooking salt intended for human consumption is unsuitable and can even prove lethal to the crabs if it contains an admixture of iodine or fluorine. This also applies to so-called “sea salt” from the health-food shop. Ideally the sea water should be mixed according to the instructions given (4.4oz of salt per gallon (33 grams of salt per liter)) and stored in a container made of food-quality plastic, so that the daily changing of the water requires little effort.A third essential prerequisite for the successful maintenance of terrestrial hermit crabs is an ade-quate depth of substrate, which should be kept moist (but never wet!). “Adequate depth” means at least three times as deep as the crab is long, and in any case at least 6 in (15 cm). The subs-trate should consist of a mixture of three to five parts sand and one part garden soil. The garden soil will serve as a binder to help stabilize the caves and passages excavated by the hermits. It will also simultaneously introduce a bacterial and fungal flora that will prevent the substrate from going bad.Hermits need to “dig themselves in” when mol-ting. Molting is generally the most dangerous phase for a terrestrial hermit crab in the terrari-um. Many owners do not realize that the hormo-ne required for molting is secreted in adequate quantity only in darkness, and this, fundamental-ly, is the reason why terrestrial hermit crabs dig in to molt. From this it can be deduced that an inadequate depth of substrate is the commonest cause of death in terrestrial hermit crabs in cap-tivity. Of course Mother Nature is flexible and, in extremis, terrestrial hermit crabs can also molt on the surface of the soil, but that causes the-se creatures enormous stress, especially when they are maintained in groups, and does them no good in the long term (i.e. over the course of several years). In addition, terrestrial hermit cr-abs need to remain underground for some time after molting, while they regenerate and the new armor hardens. The younger the hermit crab the more times it molts every year and the shorter


Coenobita pseudorugosus, blue variant.

the periods required for molting and regenerati-on. It may thus be that they survive for a few ye-ars even if an adequate depth of substrate isn’t available, especially in the case of specimens kept alone. This is, however, the absolute excep-tion and should not normally be the case.In principle it can be stated that a young Coeno-bita will molt several times per year and disap-pear into the substrate for around two weeks per molt, while fully grown individuals molt only once every 12-18 months and then bury themselves in the substrate for up to three months (!).There are various indications that a hermit is about to molt. Firstly, it will dig relatively more than otherwise. But because terrestrial hermit crabs are nocturnal this may go unnoticed. Se-condly, the terrestrial hermit crab that is about to molt will spend more time than usual at the salt-water dish, as it requires salts to generate suffi-cient pressure for splitting the old armor. Thirdly the crab will eat more than usual, as it needs to be in good condition in order to survive the period after molting when it has nothing to eat except its old skin. Supplies of food and water are stored in a bubble-like structure on the posterior body. If this is full to bursting this often means that the crab is about to molt. And finally, it is often noti-ceable that a hermit that is about to molt changes to a smaller snail shell. That may sound para-doxical, as in the final analysis the crab grows larger by molting, but this behavior may be linked to digging in. Specifically, while as large a snail shell as possible is advantageous on the surfa-

ce of the soil, as the crab can withdraw well into it on encountering a potential predator, a large snail shell with a correspondingly large opening is more of a hindrance when digging in.When it comes to feeding, terrestrial hermit cr-abs are simple to keep. They are carrion feeders that will take any sort of organic material of ani-mal or plant origin. There are also special foods that have been developed for terrestrial hermit crabs and are available from any well-equipped pet store. Surprisingly these crabs often eat only small amounts of food. A cuttlefish bone can be placed in the terrarium as a nutritional supple-ment. These can be obtained in the pet trade, where they are sold as a calcium supply for cage birds. There are in fact hermits that simply ignore such a source of additional minerals, but there are many other Coenobita that will utilize it with enthusiasm. Food can be simply scattered on the substrate. It makes no sense to offer food in dishes. Leftover food should be removed when it starts to go moldy or dry out, even though, being carrion eaters, terrestrial hermit crabs are not particularly fussy.A frequently seen phenomenon is that these cr-abs spontaneously change their snail shell. But if they leave their home and run around “naked” that is a sign of enormous stress! Although they live in large colonies in the wild, these crabs are often very quarrelsome among themselves and may squabble vehemently over a particu-lar snail shell, while another, apparently equally suitable by human standards, is ignored and left


Coenobita brevimanus.

lying nearby. These quarrels can even result in fatalities. It often happens that a hermit crab is evicted from its snail shell by a conspecific and then wanders around homeless. For this reason a certain number of snail shells of various sizes should always be available to permit freedom of choice. Obtaining suitable snail shells can be a problem, but a specialist pet shop will usually be able to acquire some.The various Coenobita species also have diffe-rent preferences when it comes to snail shells. Thus, for example, C. perlatus prefers the shells of Tonna spp. and Turbo spp., which have relati-vely round entrances. But because the identifica-tion of tropical marine snails is not exactly easy, and in view of the usually uncertain identification of the hermits themselves, it makes little sense to list their preferred snail genera here. Instead it is advisable to obtain suitable extra snail shells when buying the hermits themselves. Because of the curvature of their pleons, terrestrial her-mit crabs are able to occupy only right-handed snail shells. The direction of a snail shell can be

determined by holding it with the opening facing you and the tip of the shell pointing upwards. If the coils wind clockwise then it is a right-han-ded shell, if they wind counterclockwise then it is left-handed. There are companies, at least in the USA (where terrestrial hermit crabs are par-ticularly popular), that manufacture artificial snail shells especially for terrestrial hermit crabs. I do not know if these products are available in Euro-pe as well or whether they are any good.It may seem difficult to believe, but terrestrial her-mit crabs are skilled and enthusiastic climbers, so it is strongly recommended that a number of branches for climbing should be included in the terrarium. The best-suited are those of fruit trees (apple, pear, cherry), as they not only look attrac-tive, but are also guaranteed non-toxic and they rot comparatively slowly. However it is important to make sure they aren’t taken from trees that have been sprayed with insecticide, as only tiny traces of such sprays are lethal to Coenobita. It is best to take such branches from old gardens that have been allowed to go wild.


Coenobita pseudorugosus, red-orange variant. The species can also be colored deep red or blue.

As far as the rest of the décor is concerned, it is important that rockwork, if included, is founded on the bottom glass of the terrarium. Otherwise it will inevitably be undermined, collapse, and be-come a death trap for the hermits. Piles of dry leaves are far better. Here too the leaves of fruit trees are again very suitable, but those of oak or beech can also be used. In addition “tunnels” of bark lying on the bottom are very suitable as daytime hiding-places for the crabs.The terrarium itself should – as can be gathered from the suggestions for setting up (deep subst-rate, branches for climbing) – be tall rather than long. The size of terrarium required is a matter of some debate, as restricted space is often a sub-ordinate problem when it comes to the captive maintenance of wild creatures, including Coeno-bita. But at the same time they must, of course, be provided with adequate freedom to move around. A bottom area of 20-32 x 16-20 in (50-80 x 40-50 cm) with a height of 16-32 in (40-80 cm) will be adequate for a group (6 to 15 specimens) of small hermits 1 to 2 in (3 to 5 cm) in length. If the container is too large then it will not be easy

to keep tabs on the secretive nocturnal hermits. But if it is too small then group maintenance is likely to result in deaths, as the hermits will cause reciprocal stress. By the same token, correspon-dingly more space is required for larger hermits. However, as can be seen from everything said above, terrestrial hermit crabs are suitable for maintenance only by enthusiasts with a special interest, as they are nocturnal and secretive in their habits and require relatively time-consuming daily care. Hence there is no need for a lengthy discussion of terrarium size here.Another controversial question is whether they are best kept singly or in groups. The species of the genus Coenobita live in colonies in the wild. We know that these creatures have de-veloped highly evolved communication among themselves, even including the production of sounds. (These noises sound like a gentle chir-ping and are produced using special stridulation organs. Stridulation means that the sounds are produced by friction and not, as in us humans, by vocal chords being set in motion by air pres-sure.) Coenobita are thus essentially social ani-


mals. Even so, the assertion that Coenobita that are kept singly will live shorter lives than those maintained in groups belongs to the realm of le-gend. On the contrary, it can be argued that ter-restrial hermit crabs that are kept singly will have a higher individual life expectancy because of the absence of social stress. As already mentioned, Coenobita have lived to more than 30 years old in the terrarium! It is a fact that terrestrial hermit crabs that are kept singly are less active, but the interpretation of this as a reduction in enjoyment of life is in any case anthropomorphic. Nobody knows how and what an animal feels, let alone when in the case of a creature as remote from us in terms of evolutionary history as a terrestrial hermit crab. The reduction in activity in a Coeno-bita kept singly versus one kept in a group can equally well be interpreted as a sign of inner pe-ace and relaxation.Nevertheless, group maintenance should de-finitely be regarded as preferable, as the main object of maintaining wild creatures should be to study their behavioral repertoire in full. This inclu-

des aspects of social interaction such as mating, battles for order of rank, and so forth. Only spe-cies that are strictly solitary or have only a very small degree of social tolerance towards cons-pecifics should be kept singly as the method of choice. But obviously several individuals can be maintained even then – albeit in separate con-tainers – in order to observe the complete life cycle of the species in question under vivarium conditions. Hence for purely pragmatic reasons it is suggested that particularly expensive species that will be difficult to obtain again should initi-ally be maintained separately. Once they have settled in you can try keeping them together. In any case this procedure increases the likelihood of successful acclimatization of imported speci-mens.

And finally, it is important always to buy an ade-quate number of individuals of the same popula-tion of a species right at the start. It is often im-possible to acquire suitable additional specimens at a later date. Essentially you should buy 6 to 15 specimens right at the beginning.


Focus on the Lesser Siren

Siren intermedia

Salamanders have four legs and possess external gills during their larval stages, lo-sing the latter as they change into adults and adopt a more terrestrial lifestyle. The-re are exceptions, though, the best-known of which is the Axolotl (Ambystoma mexi-canum), which permanently retains its ex-ternal gills and aquatic lifestyle. And then there are salamanders that not only retain their gills throughout their lives, but have just two, rather than four, legs! by John Dawes

These interesting creatures are known as si-rens (family Sirenidae). At the moment only

two genera are recognized: Pseudobranchus (two species) and Siren (two species). The two Pseudobranchus are commonly referred to as dwarf sirens, while Siren lacertina, the largest of all the four species, is known as the Greater Si-ren. Quite logically, therefore, the subject of this article, the Lesser Siren, lying – as it does – half-way between the dwarves and its larger sibling, is known as Siren intermedia.

The size attained by adult Lesser Sirens varies quite widely, with the range given as 7-27 in (18-68 cm). The Greater Siren, by comparison, can grow to nearly a meter in length, while the dwar-ves attain only some 10 in (25 cm) in total length.

The species Siren intermedia is widely distribu-ted in the USA and Mexico, occurring in Florida, Virginia, Texas, north-eastern Mexico, Illinois, In-diana, along the Mississippi valley, and in Michig-an. It isn’t found in every part of these states, but it is, nevertheless, relatively abundant, except in Michigan.

As often (almost always!) happens in species which have a wide geographical distribution, dis-tinct differences can be detected between Les-ser Sirens from different locations, and these forms are generally recognized as subspecies: the Eastern Lesser Siren (S. i. intermedia), the Western Lesser Siren (S. i. nettingi), and the Rio Grande Lesser Siren (S. i. texana).

The reference to being “generally recogni-zed as subspecies” is made above because there are authors who dispute the identity of the third-mentioned subspecies. Some belie-ve that the Rio Grande Lesser Siren may be a


subspecies not of S. intermedia but of the greater Siren, S. lacertina. There are also those who be-lieve that it constitutes a separate species alto-gether.

Irrespective of the debate, all types of Lesser Siren exhibit the typical characteristics of their family. These include a flattened head, a small dorsal fin located well back on the body, four-toed front legs (but no back legs), well-formed feathery external gills, and a long eel-like body. This last characteristic is responsible for one of the common names of these salamanders: Two-Legged Eels!

Although Lesser Sirens are predominantly noc-turnal, they can also be active during the day in the aquarium, especially once they settle down. Once this happens they will feed quite happily, even in brightly illuminated aquaria. Indeed, some individuals can become quite aggressive at feeding time, with less-dominant specimens being bullied by their more active tankmates. Steps should therefore be taken to ensure that

every siren gets a square meal.With regard to the actual range of organisms that can be offered as food, the choice is quite wide. All types of worms will be consumed, the actual kind and size chosen depending on the size of the sirens themselves. Snails, silkworm pupae, meat chunks, fish, and other meat-based items will all be accepted. However, the diet must be varied to ensure that no essential nutrients and vitamins are missed out. Juveniles can be fed daily, while adults are fine being fed two or three times per week (but see below).

While juvenile Lesser Sirens can be accommo-dated in a relatively small aquarium, say, 9-10 gallons (35-40 liters), adults should be provided with more room (15 gallons (60 liters) upwards, depending on the size and number of individu-als).A well-fitting cover is important, as are efficient filtration and regular water testing to ensure that ammonia and/or nitrite levels don’t rise too much. As a preventive measure, regular partial water changes will help maintain water quality (not as

The mouth of the Lesser Siren is subterminal.


a replacement for an efficient filter, but as an additional measure), especially if water testing isn’t possible. Water quality is particularly import-ant because of the wastes produced by these ‘substantial’ animals. In addition, any uneaten food must be removed to prevent water-quality problems from arising.

Lesser Sirens are quite powerful creatures. Hen-ce the shelters that should be provided, whether of rock, or bogwood, or whatever, should be stur-dy enough to resist their attentions. If rocks or other objects are to be piled on top of one ano-ther, they must either be too heavy for the sirens to shift, or should be stuck together, e.g. with aquarium sealant.

The rooting around that these creatures per-form not only poses risks for their safety (from collapsing shelters), but also spells disaster for rooted plants, unless these are really well ancho-red, e.g. by being secured with the rocks used to construct the shelters. If the decorative element provided by submerged plants is desired, it may be sensible to use synthetic types, as these can stand up to rough treatment better than their na-tural counterparts; they can also be washed, if necessary.

Owing to its wide geographical distribution, S. intermedia can tolerate temperatures ranging from those associated with coldwater aquaria to those suitable even for warmth-loving fish spe-cies, such as discus. Consequently water kept anywhere between 59 and 82 °F (15 and 28 °C) will be OK. The sirens will, of course, be much more active at the higher end of this spectrum, requiring more feeding, tighter water quality con-trol, etc.In the wild Lesser Sirens breed from December to April, depending on location. Breeding in capti-vity is, however, rare, though the few reports that are available indicate that it occurs more or less at these same times of the year. Females can de-posit anywhere between 200-700 eggs (although some reports refer to 12-300 eggs). These are usually laid in bunches and, while it is not known with absolute certainty if they are guarded in the wild, at least one report of captive breeding sta-tes that the eggs, which had been laid in a de-pression, were defended by an adult. Courtship appears to be a rough affair, if the bite marks ob-served in adults during the breeding season are anything to go by. Fertilization is presumed to be external, since females lack a cloacal sperm-sto-ring chamber. Incubation may take 1-2 months and the larvae measure around 0.4 in (1.1cm) at birth.

Lesser Sirens swimming in open water look like eels with little arms.


The Malagasy Giant Chameleon

The huge island of Madagascar off the East African coast is an Eldorado for zoo-logists. The island, which is the fourth lar-gest in the world, separated off from the ancient continent of Gondwana some 135 million years ago. Since then evolution there has followed a unique course and more than 90% of the Malagasy species are endemic – in other words they occur nowhere else on Earth. There are nume-rous chameleon species on Madagascar, including the largest chameleon species of them all, the Malagasy Giant Chamele-on, Furcifer oustaleti. by Thorsten Holtmann

How large can it grow?In fact nobody knows precisely. There are rumors of individuals up to a meter long, but the largest specimen measured to date was “only” 27 in (68.5 cm) in length. But that is total length, i.e. including the tail.

DistributionThe Malagasy Giant Chameleon is found in the coastal lowlands of Madagascar. It is found all over the island, but its occurrence in the eastern part of Madagascar is linked to the relatively high temperatures there. The species is well adapted to the hot savannah climate and hence has be-nefited from alterations to the landscape resul-ting from human activity (deforestation). There is supposedly an introduced population in Kenya (Ngong Forest near Nairobi) and a breeding po-pulation also exists in southern Florida.

Malagasy Giant Chameleons and humansChameleons are generally regarded as easily upset. They are noted/notorious for some parti-cularly territorial species suffering stress-induced kidney problems as the result of a conspecific simply being constantly in view (for example if two individuals can see one another in adjacent terrariums), and this can lead to death! The Ma-lagasy Giant Chameleon is, however, a compa-ratively calm and peaceful member of the cha-meleon tribe. Males don’t tolerate one another, and gravid females are likewise strictly solitary.

Males of the Malagasy Giant Chameleon have a brown or gray base color.


But they can generally be kept in pairs in an ade-quately large terrarium (a winter garden is a lot better in view of the size of these animals). Ma-lagasy Giant Chameleons also exhibit this laid-back attitude towards humans. They don’t get excessively upset even when they are picked up carefully; and the threatening mouth-opening known from many other chameleons is seen in Malagasy Giant Chameleons only if they are se-riously provoked. Researchers in the field say that you can usually simply perch a Malagasy Gi-ant Chameleon on your shoulder and it will stay there quietly for hours on end.Because the Malagasy Giant Chameleon is com-paratively common and is also associated with human settlements, the native people like to make use of the greedy appetites of these ani-mals, and place these chameleons in their gar-dens, where they devour unwanted pests up to the size of a mouse and thereby keep them in check.However, these positive (from a maintenance viewpoint) characteristics of the Malagasy Giant Chameleon don’t alter the fact that these animals can develop a quite remarkable turn of speed when necessary.

Malagasy Giant Chameleons in the terrariumAll the usual basic rules of chameleon main-tenance apply to the Malagasy Giant Chamele-on. These include a relatively high food require-

ment, which is, however, easy to satisfy in the case of the Malagasy Giant Chameleon, as they will take not only all the usual food insects (cri-ckets, grasshoppers, and Zophabas beetles, but also baby mice - in the wild they also eat small birds and reptiles. All food insects should always be dusted with one of the usual calcium-vitamin powders available in the trade.The high requirement for drinking water al-ways makes chameleon maintenance rather time-consuming, as the majority of individu-als don’t automatically learn to drink from a dish. For this reason they need to be given water via a pipette at least every other day.

The Malagasy Giant Chameleon is a relatively peaceful and sociable species.

The females of Furcifer oustaleti, the Malagasy Giant Chameleon, are very attractively colored.


There are, however, a number of tricks to get round this. Many chameleon-keepers use drop dispensers, which drip water at intervals of 1-2 seconds into a collecting container placed below. This simulates rain water, which the chameleons recognize as such and drink. The most natural way of providing chameleons with water to drink is by spraying, with the reptiles taking the water from plant leaves, etc. But that too is labor-in-tensive and can also result in the terrarium be-coming too wet. A more elegant method is the installation of an artificial waterfall using a small aquarium pump. However, such systems are so-mewhat prone to disturbance and the pump may fail – and, following Murphy’s Law, invariably at the least convenient time, for example when you are on holiday. A very neat way of setting the wa-ter in the drinking dish in motion, and thus ma-king it recognizable as water to the chameleons, is to aerate the dish with one of the standard aquarium air pumps available in the trade. You simply suspend the airline in the dish and set the air supply to produce around two bubbles per se-cond from the airline. A nice side-effect of this method is that it simultaneously raises the humi-dity in the terrarium; in the case of the Malagasy Giant Chameleon this should be a relative humi-

dity of around 70% during the day, rising to up to 100% at night.Because of its natural habits, the Malagasy Giant Chameleon can be classified as one of the easier chameleon species to maintain, as it doesn’t im-mediately react adversely, followed by the onset of illness, if things get a bit too warm in the ter-rarium. The daytime temperature should be bet-ween 71 °F and 82 °F (22 and 28 °C), rising to up to 113 °F (45 °C) under the spot-lamp. It is, ho-wever, essential always to provide these reptiles with a relatively cool, well-ventilated area in the terrarium, to visit when they so choose.

Breeding Furcifer oustaleti is an egg-laying species. After a gravid period of around six weeks the females lay up to 61 eggs. At an incubation temperature of around 82 °F (28 °C) it takes between 210 and 280 days until the young hatch.Many breeders use vermiculite as a brood sub-strate. The young grow very rapidly and attain sexual maturity in as little as a year. All in all, maintenance and breeding are similar to those of the well-known Panther Chameleon, Furcifer pardalis.

When resting, the Malagasy Giant Chameleon usually curls up its “fifth leg”, the prehensile tail.


NEW ON THE MARKET!

Geophagus harreri

This attractive “eartheater” has recently been available commercially in Germany for the

first time ever. The parent stocks originated from Surinam - the Tapanahoni River, to be precise, although the species also occurs in other rivers in Surinam (the Maroni, for example). These fish prefer a moderate to strong current, but move to habitats with less current for breeding. Maintenance conditions: this species needs comparatively high water temperatures - at least 82 °F (28°C), and it will experience no problems at all up to 90 °F (32 °C)! Soft, acid water with a low bacteria count will improve coloration and condition in general.

Maximum size: probably around 10 in (25 cm). Males grow larger and are more elongate. Fe-males remain smaller and look plumper. Old fish may develop a slight hump, but this seems not to be sex-linked.

© Text & Photos: Thomas Weidner


G. harreri is an open brooder and uses wood or stones for spawning. The species can be very aggressive compared to other eartheaters, and hence should be kept only in very spacious tanks (80 in (200 cm) minimum length). It is possible to keep the species with other large cichlids (other eartheaters, Mesonauta, Heros, Uaru, etc), and keeping them in the company of numerous other fish reduces the aggression. I personally have so

far had up to 150 fry, but I guess that a good pair can produce around 400 young.

Lexicon: Geophagus means „eartheater“. harreri: named in honor of one of the collectors of the type material.

Suggested common name: Marowijne Eartheater

© Text & Photos: Thomas Weidner


Corydoras sp. “San Juan”

This pretty and very variably colored cory ori-ginates from Peru. It remains an open questi-

on whether the „San Juan“ belongs to Corydoras napoensis, C. bilineatus, or an undescribed spe-cies. The Corydoras elegans group, to which the „San Juan“ without doubt belongs, is in need of revision.

Be that as it may, the „San Juan“ is a very pretty, peaceful, and active (note the large caudal fin!) species of Corydoras.

© Frank Schäfer / Aquarium Glaser


Aequidens patricki

This cichlid originates from a comparatively small collecting site in Peru and hence is im-

ported only very occasionally. The species lives in soft, acid water in the wild, but is very hardy and adapts well to variable water conditions in the aquarium. Another plus point is that it is quite

peaceful. Hence, despite its maximum size of 5-6 in (12-15 cm), this fish can be bred even in rather small tanks with a volume of 50 gallons (200 li-ters) upwards. But always bear in mind that small surface-dwelling fishes, e.g. hatchetfishes, may be taken as food by the cichlids!

Male.

Male and female. © Frank Schäfer / Aquarium Glaser


The Redbellied Shortneck Turtle

(Emydura subglobosa)

- a dream of an aquatic turtle

These attractive turtles, in which males attain a carapace length of some 8 in (20 cm) and

females a good 10 in (25 cm), have been in the hobby since the late 1970s. The past master of the terrarium hobby, Wilhelm Klingelhöffer, didn’t mention them at all in his standard work Terra-rienkunde in 1959, but in 1984 Obst, Richter & Jacob wrote in their classic Lexikon der Terraris-tik und Herpetologie that the species had been bred for generations and was suitable even for beginners. What a change in the space of just 20 years or so! Until the 1990s captive-bred Emy-

dura subglobosa were available everywhere, but then things all went quiet as far as the species was concerned. Not until around 10 years ago did the species re-surface, and since then it has enjoyed constantly increasing popularity.

Confused nomenclatureInitially the Redbellied Shortneck Turtle was known in the hobby under the name Emydura albertisii. This species was described in 1888

There is always a demand for easy-to-keep, attractive, lively turtles that don’t grow too large. And the Redbellied Shortneck Turtle is just the animal to pro-vide all these attributes. The tongue-twis-ter of a popular name is undoubtedly the most complicated thing about this turtle! by Christoph Fritz, www.reptilia24.com

In Emydura the neck is withdrawn into the shell in an S shape (sideneck turtles). Photo: F. Schäfer

Young Emydura subglobosa are delightful. Photo: Chris Lukhaup


Mainly aquatic The Redbellied Shortneck Turtle is a fluviatile turtle that only occasionally comes ashore. There are reports on maintenance that state that they can be kept in an aquarium that is completely wi-thout a land area, but I don’t recommend that. Although the species suns itself appreciably less frequently than many other turtles, on the one hand individual specimens differ considerably in their preferences in this respect, and on the other the presence of a dry (!) land area helps prevent disease as, being an inhabitant of run-ning water, E. subglobosa has high requirements as regards water quality. If the latter is poor then these turtles tend towards infectious diseases of the skin and shell. But even when the water is in good order these turtles, like all creatures, can sometimes fall ill, and they then like to seek out the land area and sun themselves, and in this way slight infections often clear up by themsel-ves, without any intervention at all by the owner.

The aquarium for Redbellied Shortneck TurtlesBecause of its splendid pink, black, and white co-loration Emydura subglobosa is an excellent or-namental animal that can be readily maintained in large aquaria with a variety of décor. It is parti- ... and from beneath.

Adult male viewed from above....


http://www.usark.org


by Boulenger, who regarded it as distinct from E. subglobosa. But it was subsequently realized that the two species were one and the same and so E. albertisii became a junior synonym of E. subglobosa, which had been described back in 1876 by Krefft. The species is quite obviously rather variable and other names have also been assigned to it; the most recent scientific review of the turtles of Australia (Georges & Thomson, 2010) distinguishes the typical red-bellied form from southern New Guinea (where it occurs from the Vogelkop and Bomberi peninsulas in the west to the Kemp Welsh drainage in the east) and the Jardine River on the Cape York Peninsula in Aus-tralia as Emydura subglobosa subglobosa, and another, yellow-bellied subspecies, E. s. worrelli, which in addition develops a broader head with age, from the upland drainages of the Arnhem Land plateau in the Northern Territory and the ri-vers that empty into the Gulf of Carpentaria. The scientific description of the latter was severely criticized by the authors, but that doesn’t alter its validity. On the other hand it cannot be ruled out that the two subspecies actually represent sepa-rate species.

Be that as it may, wild-caught Redbellied Shortneck Turtles are so rare in the trade that one can safely say that they don’t occur at all, and that all the strains found in the hobby corre-spond to the nominate form, while E. s. worelli, is maintained only by a small number of specialists, if at all.

Portrait of an adult Redbellied Shortneck Turtle.Photo: C. Fritz, www.reptilia24.com

Portrait of a male. Photo: F. Schäfer


cularly advisable to keep fish in the same aqua-rium, as the latter will very quickly indicate (by falling ill) that the water quality isn’t as good as it might be, and they also help produce a varied, constantly interesting scene. Adequately fed turt-les rarely go hunting fish. Occasionally a sick or weak small fish may fall prey to the turtles, but the same would also happen in the wild.

A tank of length 60 in (150 cm) or more should be chosen for a paludarium of this type. This will make it easier to set up and will suit the turtles very well, as they are excellent swimmers with a strong urge to keep moving. The water chemistry is of lesser importance, while the water tempe-rature should be 72-79 °F (22-26 °C). A powerful filter will ensure clear, good quality water. For sa-fety reasons it will ideally contain an integrated heater - a separate heater-stat such as is used in fish-only aquaria is less suitable because of

Underside of an adult female.



the risk of breakage by larger turtles. It is ext-remely important that the air temperature above the aquarium is not significantly lower than the water temperature, as otherwise respiratory di-seases can easily occur. The temperature on the land area beneath the heat lamp should reach 86-95 °F (30-35 °C). It is wisest to choose a spot-lamp with a UV component. Heavily gravid fema-les in particular will make extensive use of this “sun bed”. Redbellied Shortneck Turtles are usually very pe-aceful among themselves so group maintenance is possible. If space permits, one male should be kept with several females, in order to allow the females a little rest from the constant attentions of the male. But even males tolerate one another astonishingly well. After the onset of sexual ma-turity the males can be recognized very easily by the length of their tails – almost double that of the females.

Mainly carnivorousFeeding the Redbellied Shortneck Turtle is easy. These turtles are mainly flesh-eaters (carnivoro-

us). Adults can be fed with proprietary food sticks, dried Gammarus, and deep-frozen foods such as shrimps, whitebait, mussel meat, squid, etc. As far as possible warm-blood meat shouldn’t be of-fered, as it is only poorly digested and heavily pollutes the water. But balls of raw meat are use-ful treats if the turtles need to be given medicati-on via their food.

The rearing of specimens available in the trade presents no problems. Essentially, they should be treated in the same way as adults, though natu-rally the food should be correspondingly smaller. In addition to the items listed above, deep-frozen bloodworms (for aquarium fish) are an important food for rearing.You can try offering vegetable food as well now and then, for example sweet fruit, Dandelion, or similar. Some individuals enjoy this a lot, while others won’t touch it – this is something their ow-ner must find out for himself. It should be borne in mind, however, that green food is highly laxative and hence should be used with care.

Adult albino specimen. Photo: Christoph Fritz, www.reptilia24.com


Easy and productive to breedThe world demand for Redbellied Shortneck Turtles in the terrarium trade has long been met by captive-bred stocks. Even though no species of animal has ever yet gone extinct through being traded alive, this is a positive sign, as it shows that we are getting everything about the main-tenance of these attractive turtles right.

Albino specimens (in this case white with red eyes) sometimes occur as a very rare mutation among captive broods.

The Redbellied Shortneck Turtle is very producti-ve and a female can easily produce several clut-ches per year, each comprising 6-12 (maximum 15) eggs. These turtles aren’t very demanding when it comes to somewhere to lay their eggs. If necessary they will even lay them under water, but such eggs are not normally viable. The eggs should be incubated in damp Vermiculite or simi-lar at 81-86 °F (27-30 °C) and 90-95% relative humidity, with hatching taking place after 45-60 days.The courtship behavior of the male, which is cha-racterized by a very rapid nodding of the head, is interesting to watch. If a male is bothering the female(s) excessively then it is advisable to re-move him from the group, at least for a while.

Being inhabitants of the tropics, these turtles don’t actually require special over-wintering. It has, however, proved beneficial to keep them for 3-4 months at a lower water temperature (68-72 °F (20-22 °C)) - no cooler, and if in doubt some-what warmer is better!) so that the female(s) can recover properly from egg-laying.

All in all, the Redbellied Shortneck Turtle is one of the most suitable aquatic turtle species for ter-rarium maintenance. So if you are now filled with the desire to keep these turtles, then your pet dealer can undoubtedly order them for you from a wholesaler of his acquaintance.

The attractive red color of the shell is retained life-long. Photo: Frank Schäfer

Redbellied Shortneck Turtle

Emydura means „Emys with tail“; Emys is ano-ther turtle genus.albertisii: named in honor of the collector, the controversial Italian explorer Luigi Maria d’Al-bertis (1841-1901).subglobosa: refers to the shape of the shell and means „almost spherical“.worrelli: named in honor of Eric Worrell of the Australian Reptile Park, Gosford, New South Wales.

Lexicon:


Wild killies from Peru

The name “killifish” for the egg-laying toothcarps has become current all over the world. To the uninitiated it may sound somewhat brutal, but it has nothing to do with the English word “kill”. The name killifish originated in the New York area, where it was used for the species Fundu-lus heteroclitus macrolepidotus. by Wolfgang Löll

The first mention of the name in the literature dates from the year 1788, when D. J. Schoe-

pf published a paper entitled “Beschreibungen einiger Nord- Amerikanischer Fische, vorzüglich aus den Neu-Yorkischen Gewässern” (= Descrip-tions of some North American fish, mainly from the waters of New York) in the journal Schriften der Berlinischen Gesellschaft naturforschender Freunde. In this paper he gives the local com-mon name for the above-mentioned Fundulus as “Killfish”, but doesn’t explain it. There are two possible derivations for the name: the com-

monest is that the word killifish comes from the Dutch word kill (meaning river) plus fish, in other words, “river fish”. However, this Fundulus hardly ever lives in rivers; hence the second derivation may well be the correct one, according to which the phrase “killing bait” is used for a particularly effective angling bait. To the present day Fundu-lus heteroclitus is used as a bait fish in the area around New York. Be that as it may, the name killifish in no way reflects the behavior of these wonderful creatures in the aquarium!

Aphyolebias schleseri, male

Aphyolebias peruensis, female


Wild-caught or captive-bred?Only a few groups of fish have so many aqua-rium populations as the killifish, or are bred to such a high level of (scientifically demanding) ex-pertise. In theory there is no need to rely on im-ports for the hobby. Nevertheless the importation of wild-caught killifish species is very welcome, as although inbreeding isn’t usually a significant problem in aquarium fish (the high reproducti-ve rate of fish invariably permits any inheritable defects in captive-bred strains to be eliminated by careful selection), the majority of aquarium strains trace their ancestry to only a very small number of founder specimens. This means that often only very little is known about the range of natural intraspecific variation. The importation of comparatively large numbers of specimens can fill these gaps in our knowledge and thus help us understand the biology of such species. The capture of these fish for live maintenance poses no problems from a conservation viewpoint, so there is really no need to have a guilty conscien-ce about buying wild-caught specimens.

Seasonal fish and survival specialistsAll the species discussed here live under extre-me conditions in the wild. For starters, there are the classic seasonal fish, including Austrolebias schleseri, A. peruensis, and Moema cf. pirana. Seasonal fish is the term used for killifish that in the wild sometimes inhabit waters that dry up the periodically. A feature they have in common is the ability to grow incredibly rapidly; from hatching to sexual maturity takes only a few weeks. And Moema cf. pirana, for example, can easily reach 6 in (15 cm) long! But others, such as Austrole-bias schleseri, attain barely 2 in (5 cm) in length. From the moment that they attain sexual maturity these fish mate every day. The species discus-

sed here are bottom-divers, i.e. the spawning pair dive right into the substrate of the body of water and lay their eggs “underground”. In the wild the lifespan of such fish is usually only a few months. Then their home waters dry up and they die. Only the eggs survive in the substrate and hatch many months later when it next rains. They live considerably longer in the aquarium.

Moema cf. ortegai, male

Rivulus retrocaudatus, male

Rivulus retrocaudatus, femaleRivulus ornatus, female


Rivulus, the “grasshoppers”The strategy of the Rivulus species is quite diffe-rent. These slender fish have learned to travel on land. In wet weather they jump out of the water and cling to damp terrestrial plants. In this way they significantly reduce predation pressure from piscivorous fish and can simultaneously colonize small waters that in fact hardly deserve the name, such as damp meadows containing a few small puddles. These fish live considerably longer than their fellow killies, the seasonal fish. Rivulus are adhesive spawners that lay their eggs on plants, among fine roots, etc. The eggs usually develop within 2-3 weeks. Because Rivulus are particu-larly fond of mosquito larvae they are of great in-terest for the biological combating of mosquitoes.

Rivulus ornatus, male Aphyolebias schleseri, female

Aphyolebias peruensis, male

Moema cf. ortegai, female

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