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 seamounts Slow reproductive rate: females mature at 15 yrs, 12 month gestation, 1 year off between pregnancies
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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
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)
Figure 8.1
http://www.germantown.k12.il.us/html/Fishy.html
Three groups of fishes
Jawless fish (Agnatha)
Cartilagenous fish (Chondricthyes)
Bony Fish (Osteichthyes)
lamprey
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
Figure 8.8
Figure 8.14
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
Figure 8.16
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
Figure 8.13
Maintaining buoyancy
Large oily live, light skeleton,pectoral fins for stability
Gas-filled swimBladder, pectoralfins freed for other uses-great diversity of forms
modes of swimming
Undulation flex caudal region move fins tail fin( eels) (tuna) surgeonfish boxfish
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
Figure 8.22Conservation threatsPolluted rivers, damsWater harvestedIntroduced species offarmed salmon
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
Why do fish school?
“selfish herd theory”(middle is safest place to be)
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
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