Selected Adaptive Strategies: Bioluminescence  Fishes - important nektons  Many are deepsea predators  Need their own light to attract prey  … to attract mates  luciferin + luciferase

More Nekton Strategies  predator/prey  must be swift and efficient swimmers  move swiftly to –eat –avoid being eaten.  Thus fish have evolved to maximize their ability to move through water.

Caudal (Tail) Fins most important for speed flared to increase vertical thrust (Figure 9-22)

ROUNDED fin (e.g., flounder) very flexible, slow-speed manuevering

TRUNCATE fin (e.g., angel fish) somewhat flexible, manuevering

FORKED fin (e.g., goatfish or herring) somewhat flexible, manuevering

LUNATE fin (e.g., blue marlin or tuna) very rigid, no good for manuevering, built for pure speed

HETEROCERCAL fin (“uneven tail) most of mass & surface area in upper part to produce lift pectorals balance to aid lift limits manueverability

Caudal Fins  rounded –very flexible, manuevering  truncate & forked –somewhat flexible, manuevering  lunate –very rigid, propulsion  heterocercal –“uneven tail” for lift and propulsion

Built for Speed  speed related to body length –4-foot yellowfin tuna, 46 mph –13-foot bluefin tuna, 90 mph (theoretically) –9-foot porpoise, 25 mph –30-foot killer whale, 34 mph

Squid: traps water in mantle and forcefully jettisons it from siphon in head

active predator of fish arms to capture tentacles to bring to beak both lined with suckers

They Exist! up to 20 feet long!

Colossal Squid Captured Wellington, NZ, April pounds - 16 feet long