marine bio lec 21
Terms
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Holo-epipelagic
Mero-epipelagic -
live in epipelagic throughout life
Tuna,
many spawn in epipelagic but juveniles develop elsewhere (e.g. esturaries) - How do nekton swim so fast?
- ) Nekton use propulsive force to move through the water, and reduce resistance by streamlining
- – aspect ratio
- fin height2/fin area
-
Rounded with aspect ratio =
Truncate with aspect ratio =
forked with aspect ratio
Lunate with aspect ratio =
In sharks:
⬢ Heterocercal with aspect ratio -
1
3
5
7-10
2 - Why are tuna so fast?
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• Optimal streamlining
• Efficient caudal fin to generate thrust
• Reduced drag due to
– small scales, non-bulging eyes, and small medial finlets
Muscle composition -
Whales
seals/walruses -
(Cetaceans)
(Pinnipeds) - Lateral line system
-
•Rows of small tubes that are open to seawater
–Sensitive to pressure changes
•Found in schooling fish - ⬢ SR (sinking rate) =
- (w1 - w2) / R * Vw) where w1 is the density of an organism, w2 is the density of seawater, R is the surface resistance and Vw is the viscosity of water (related to temperature and salinity)
- ⬢ Density reduced by
-
–manipulating ionic composition
–using lipid storage reserves
–maintaining gas-filled inclusions -
siphuncle
⬢Depth limit for Nautilus -
tube like tissue that connects inner tissues in nautilus
500m -
Two types of swim bladders:
⬢Physostomous
Physoclist -
⬢ type has a duct to connect to the esophagus (salmon)
⬢lacks a duct (more common type) - Counter-current exchange system (rete mirabile system)
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– Incoming vessels low in oxygen and outgoing vessels rich in oxygen run side-by-side
–Diffusion concentrates oxygen in the incoming vessel - spermaceti organ
- ⬢Fat-filled melon in sperm whales generates and focuses (as an acoustic lens) sounds
- Great white shark
-
carcharodon carcharias
⬢ Stealthy approach along the bottom (strong countershading helps), swim up from below and bite prey
⬢Prey is pulled underwater and held until it dies