Oceanic Nekton

1. Oceanic Nekton Composition of the Oceanic Nekton

2. Phylum: Chordata • Notochord and dorsal nerve cord • Gill slits, and a post-anal tail • Tunicates (sea squirts)

3. Class: Agnatha • Jawless fish • Lampreys and hagfish • Represent ancestors of bony fish and sharks

4. Class: Chondrichthyes • Skeleton made of cartilage – adaptation to be less buoyant • Gill slits • Placoid scales (origins same as teeth) • Internal Fertilization – male clasper: lay eggs, or live young • Sense electric, chemical, magnetic cues

6. Sharks & Rays

7. Subclass: ElasmobranchiiBottom dwellers (benthic) • Skates, rays, and some sharks • Flattening of the body and expanded fins • Catch fish • Dig clams and worms from the sediment • Manta Rays are plankton feeders • Many lay eggs • May have a large, sharp, defensive spine on the tail

8. Subclass: ElasmobranchiiPelagic (open water) sharks • Streamlined torpedo-shaped bodies • 1 or 2 dorsal fins • Pair of large pectoral fins • Pair of pelvic fins • Single ventral anal fin • Heterocercal caudal fin (upper lobe elongated)

9. Most predators • Whale & basking shark are filter feeders Slow to mature with low reproductive rates Some lay eggs others have live birth

11. Shark Attacks More people die from pigs each year in the U.S. than sharks Result because of mistaken identity We put out sounds or odors like normal prey • Possession of hooked or speared fish thrashing in the water • Splashing creates low frequency vibrations that imitate the thrashing of a wounded animal

12. How to Avoid a Shark Attack • Always swim in a group • Don’t wander too far from shore • Avoid the water at night, dawn, or dusk • Don’t enter the water if bleeding

13. Don’t wear shiny jewelry • Don’t go into waters containing sewage • Avoid water being fished and those with lots of bait fishes

14. Don’t enter the water if sharks are present • Don’t splash a lot • Use care near sandbars or steep drop-offs • Avoid an uneven tan and brightly colored clothing • Don’t relax just because porpoises are nearby • Don’t try to touch a shark if you see one • If attacked: the general is “Do whatever it takes to get away!”

15. Types of Shark Attacks Provoked – caused by humans touching sharks Unprovoked – sharks make the first contact, 3 forms • Hit-and-run – near beaches, mistake the movements of humans for fish; legs and feet are often bitten; injuries minor and deaths rarely • Sneak – deeper water; victim doesn’t see the shark before the attack; serious injury or death, especially if shark continues to attack • Bump-and-bite – shark circles and bumps the victim with its head or body before biting; cause serious injury or death

16. Sharks Under Attack • Humans kill 20-30 million sharks per year through commercial and sport fishing

17. Class: Osteichthyes – Bony fish • Skeleton made of bone • Gills protected by an operculum • Expend energy to separate salt from water to prevent dehydration • Swim bladder in most • Most reproduce externally • Lateral lines – detect water motion and vibrations

18. Bony Fish

19. Fin Design – Diversity of Fish Wrasses - Use pectoral fins as oars • Provides slow but precise motion Seahorses & pipefish • Limited motility to maintain camouflage Triggerfish – undulate dorsal and anal fins • Great control and ability to sink vertically or backward into reef crevices Eels – dorsal, anal & tail fins are fused • Swim like snakes Tuna – crescent-shaped tail • Highly streamlined Flying Fish – elongated pectoral fins like wings Remoras – modified dorsal fin serves as a suction device • Attach to sharks, turtles, whales for a free ride • Detach to feed on scraps

20. Fishes

21. Fins • Caudal fin – provides thrust, and control the fishes direction • Pectorals – act mostly as rudders and hydroplanes to control yaw and pitch. Also act as very important brakes causing drag • Pelvic fins – mostly controls pitch • Dorsal/anal – control roll

22. Body Shapes • Fusiform – swiftest of all fish – torpedo shape • Depressed – flattened-dorso ventrally – use camouflage instead of speed for survival • Compressed – flattened – side to side – gives fish great agility for movement and sudden bursts of speed • Attenuated - Eel-like – allows it to wiggle into small crevices where it hunts prey

23. Body Shapes Flatfish • Begin life as ordinary fish • One eye migrates over the top of the head to the other side • Many also have ability to alter their colors to blend in

24. Behavior and Special Body Features • Bioluminescence – built in light system • Barbels – look like whiskers but are not hairs. Used for feeling and tasting • Anglerfishes – fishing lure – to attract prey • Strange mouths – many animals mouths allow them to feed on foods others cannot catch or eat • Electricity – produced by special body organs

25. Importance of Color • Camouflage – blend in with surroundings • Disruptive Coloration – spots and stripes break up the body shape and conceal them against backgrounds • False Eye Spots – May hide vulnerable parts of an animal’s body • Counter shading – dark backs blend in with the darkness of the deep ocean and light bellies make it hard for a predator to see them against bright sunlit surface waters.

26. Importance of Color • Advertising coloration – attracts attention and advertises a special service • Warning – Some animals are so well protected with spines, poisons, and armor that their coloration is a warning for other species to stay away

27. Cleaning behavior Specialized form of predation where small fish or shrimps remove various ectoparasites from other larger fish Occurs on all reefs Cleaning stations – advertise their presence through bright, contrasting colors • Fish to be cleaned remain motionless as the cleaner moves over its body removing the parasites • May even enter the mouth and gill chambers of fish • Fish may line up at these stations

28. Reptiles Turtles Sea snakes Marine Iguanas • Not pelagic Saltwater crocodiles • Not pelagic

29. Class: Reptilia • Cold-blooded • Breathe with lungs • Scales • Lay internally fertilized eggs

30. Order: Squamata – sea snakes and lizards Snakes • 50 species confined to tropical Pacific and Indian Oceans • Distant relatives of cobras and are highly venomous • Their tail is flattened and serves as an oar Iguanas • 1 species • Confined to Galapagos Islands • herbivorous

31. Iguanas

32. Order: Crocodila • Alligators, crocodiles, and caimans • Semi aquatic • Carnivorous • Seldom grow beyond 6 meters • Inhabit mangrove swamps and seacoasts • Been known to attack people

33. Crocodiles

34. Alligators

35. Order: Chelonia – Sea Turtles • 7 species • Limbs are modified as flippers • Shells smooth, plated, and lightly built • Inhabit warm seas • Some herbivorous others predaceous • Turtle skin is partially covered with scales

36. Sea Turtles

37. Turtles are the only reptiles with a shell Their extremities are always outside their shell. The backbone of the turtle is fused to their top shell as are their ribs.

38. Turtles

39. The domed top of the turtle shell is called the carapace • The bottom part is called the plastron. • The number and arrangement of bony plates, on the carapace and plastron, can be used to determine each species.

40. Turtles may have ectoparasites on their shell and skin. • do not harm the turtle, they are just hitching a ride • Barnacles often grow on turtle shells. • Crabs may be found hanging onto skin folds of marine turtles, especially around the tail.

41. Tagging Turtles

42. Most species will not reproduce until they are 15-50 years old. • Male and female couples are seen mating in the ocean near beaches. • Male marine turtles have longer tails than the females • Females come ashore at night to build nest and lay eggs • A body pit is dug above the high tide line by the nesting female • About 100 eggs are laid • Process is repeated 3 to 7 times at two-week intervals • When nesting is finished they mate and sperm can be stored for 2 or 3 years • Eggs incubate for about 2 months • get out of their egg case they use an "egg tooth" which is on the tip of their mouth. • Many are eaten by gulls • Very few survive to become reproducing adults

43. All Marine Turtles are Endangered • Loss of nesting habitat • Nesting females are poached Nests are dug up and eggs taken • Humans and wild animals Caught and drowned in shrimp trawler nets • Turtle exclusion device

44. Fibropapilloma • Tumorous tissue growth • More common in females • Viruses – retro and herpes viruses Effects • Slower growth, reproduction? Can block gut, eyes and lead to death • Reduced immunity Vector • Saddle wrasses known to carry virus and clean turtles

45. Case Study: Green Sea Turtle • Green-colored fat tissue • Chelonia mydas • Hatchlings weigh 1 oz; have carapace 2 in • Subadults avg 200-350lbs; with carapace at least 2 1/2 ft long • Adults – grow 4 ft and weigh up to 400lbs; carapace mottled dark brown on • top and creamy white below • Carapace often covered in green algal • Males develop a single mating claw on • the trailing edge of their fore flippers

46. Distribution and Range • Found throughout the world’s oceans

47. Feeding • Green body fat because of the green algae they eat • Primarily herbivorous • Juveniles are omnivorous feeding on plankton – jellyfish and fish eggs

48. Reproduction • Reach sexual maturity at 25 sometimes taking up to 50 yrs • Adults migrate from foraging grounds to nesting grounds • Males appear to migrate every year • Females migrate every 2-4 years • Mating starts in march • Nesting occurs late April through September with a peak in June and July

49. Each female comes ashore as many as 5 times at 11 to 18 day intervals • Dig a broad pit with fore flippers and an egg chamber with rear flippers • Deposit clutch of 100-120 ping pong ball sized eggs • Gently cover the nest by flinging dirt over it with flippers • T of the eggs during incubation determines the gender: lower produces males

50. Hatching occurs at night after about 60 days • Hatchlings work as a group to dig to the surface • Head to the ocean attracted to the light reflected off the ocean • Seabirds, crabs and fish are often waiting nearby to grab an easy meal • Live up to 80 years