http:// hammerhead sharks (8 species known) sea of cortez has the scalloped hammerhead
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http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm
Hammerhead sharks (8 species known)Sea of Cortez has the scalloped hammerhead (Sphryrna lewini)School around seamountsSlow reproductive rate: females mature at 15 yrs, 12 month
gestation, 1 year off between pregnanciesFished for food and sport
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http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm
Why the hammerhead shape?- spreads out sensory ability (electric, olfactory) (disadvantages: prevents jaw protusion & 3D vision)-use the hammer to pin down stingrays and eat them
(stingray spines often found in heads)
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Figure 8.1
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http://www.germantown.k12.il.us/html/Fishy.html
Three groups of fishes
Jawless fish (Agnatha)
Cartilagenous fish (Chondricthyes)
Bony Fish (Osteichthyes)
lamprey
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Class Osteichthyes (Bony Fish)
- Dominant vertebrate in the sea
- 26,000 species (96% of all fish, 50% of all vertebrates)
http://www.germantown.k12.il.us/html/Fishy.html
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Figure 8.8
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Figure 8.14
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Sharks (blood = seawater)- concentrate urea- excrete salt in urine,feces, rectal gland
How to cope with salt in seawater (tend to lose water)
Bony fish (blood<seawater)-kidneys conserve water-excrete salts in urine, feces,gills, skin
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Figure 8.16
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Figure 8.9Streamlined(fusiform)Fast-open water
Flattened topto bottom -Bottom dweller
Flattenedside to side-bottom orcoral reef
Slow -reef
Live invegetation/coral
Trunklike orround - slowmoving, reef
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Figure 8.13
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Maintaining buoyancy
Large oily live, light skeleton,pectoral fins for stability
Gas-filled swimBladder, pectoralfins freed for other uses-great diversity of forms
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modes of swimming
Undulation flex caudal region move fins tail fin( eels) (tuna) surgeonfish boxfish
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Figure 8.22
Skipjack tunaTropical speciesthat travels to temperate water tofeed. Halfway acrossglobe each year.
SalmonAnadromous =Spend lives atsea feeding, returnto rivers to breed:Magnetic field and smellof home rivers
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Figure 8.22Conservation threatsPolluted rivers, damsWater harvestedIntroduced species offarmed salmon
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Catadromous - breed at sea, migrate into rivers to grow (16 spp freshwater eels)
adults spawn and die in Sargasso Sea / larvae in plankton 1 yr+/ metamorphose into juveniles / grow and mature in rivers
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Why do fish school?
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“selfish herd theory”(middle is safest place to be)
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Buoyancy - how to regulate
Cartilagenous fish (sharks, rays, chimaeras)-large oily liver, light skeleton- pectoral fins needed for stability/steering
Advantages: rapid changes in depth possible
Bony fish– Swim bladder (gas-filled sac above intestine)Advantages: freed up pectoral fins for other uses
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Strange reproductive practices of fish
• Hermaphrodites
• Sex change (born one sex, become the other)
Large fish in harems are often sex-change males
Large fish in non-harem species are often sex-change
females
• Parasitic males
• “Sneaker” males that look like females
• Sex-role reversal (male pregnancy in seahorses)
• Males often do parental care in fish
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http://www.geocities.com/thesciencefiles/angler/fish.html
Anglerfish adaptations for deep water habitat:
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http://www.geocities.com/thesciencefiles/angler/fish.html
Anglerfish adaptations for deep sea (food and mates scarce)sit and wait predatory behaviorbioluminescent lure parasitic males
- once males encounter female, they don’t leave
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http://www.oceanoasis.org/fieldguide/thal-luc.html
Rainbow wrasseThalassoma lucasanum
Two types of malesTwo types of reproduction.
1) Females(yellow/red lateral stripes)2) Primary males(look like females)3) Terminal males(blueheads) - born female, turninto males
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http://www.oceanoasis.org/fieldguide/thal-luc.html
Rainbow wrasseT. lucasanum
Two types of reproduction
1) Broadcast spawning Many males and females rush
to surface and release gametes
2) Harems: one terminal maleguards group of females and mates with them individually.
Death of secondary male-large female turns into newterminal male
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Mass spawning of the rainbow wrasseThalassoma lucasanum
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Barred serranoSerranus psitticinusSea of Cortez
Simultaneoushermaphrodite(can act as male orfemale at any time)-dominant male in harem mates with “females”.
Serranus annularis CaribbeanOrange back basslet
http://www.qualitymarineusa.com/fish/basslets.html#top
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Lecture ended here.
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http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/
Male pregnancy in seahorses-Placenta- Long-term pair bond-Daily dance of pair
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http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/
Conservation of Sea Horses20 million caught each year
- 95% chinese medicine- 5% aquarium trade
32 species (threatened status)
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Coelocanth (lobe-finned fish)