2020-Intro to Oceanography-Nekton notes week18 PDF

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2020-Intro to Oceanography-Nekton notes week18...

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GEOL 8- Introduction to Oceanography [Nekton] 1. Fish 2. Reptiles 3. Birds and Mammals Nekton: Large, actively swimming organisms. Fishes, marine mammals, marine reptiles, aquatic birds, cephalopods ● Fish and Fishes ○ The 1st vertebrates ○ Most economically important marine organisms ○ Part of the Nekton ○ Three types: Jawless, cartilaginous, bony ■ Jawless (no true jaw, no paired fins or scales) ■ HAGFISH feed by suction. They are SCAVENGERS; live on dead/decaying matter. ■ FW Lamprey: Parasites or bottom feeders. ■ Cartilaginous (skeleton of cartilage, placoid scales, gill slits, no true swim bladder) ■ Most SHARKS are predators: many are adapted for fast swimming and carnivorous feeding. Long rows of continuously growing teeth aid in prey capture. (The WHALE SHARK is a PLANKTIVORE) ■ RAYS & SKATES have flattened bodies. Many are DEMERSAL (live on bottom). Either carnivorous (stingray, electric ray) or planktivorous (manta ray) ■ Bony (skeleton of true bone, overlapping ctenoid scales, operculum, true swim bladder) ■ 96% of fish are bony fish ■ Have true bones ■ Have round (ctenoid) scales ■ Have a swim bladder to regulate buoyancy ■ Very diverse in size and shape

The Other Nekton 1. Marine Reptiles 1. Turtles, Snakes, Crocodiles 2. Marine Birds 3. Marine Mammals 1. Pinnipeds (Seals, Sea Lions, Walrus) 2. Cetaceans (Whales and Dolphins)

Marine Reptiles ● POIKILOTHERM: Metabolic rate varies with external temperature. ● Marine reptiles get SLUGGISH in cold weather, so most species live in warm climates. ● Skin covered with scales to prevent water loss. ● Leathery eggs to prevent water loss, many species (sea turtles, iguanas) lay eggs on land. Sea Turtles ● Body enclosed w/ armor-like shell that is fused with backbone ● Can not retract head/legs to shell ● Legs modified as flippers ● Large (1000s km) migration routes ● Tropical ● Gender determined by nest temperature: ○ Cooler-males, warmer-females

Other Reptiles: ● Sea snakes are OVOVIVIPAROUS: give birth to live young. ● SALT WATER CROCODILES are the largest crocodile species. They can reach 27 feet in length!!! But they rarely exceed 17’ in the wild. ● Mangrove monitor ● Marine iguana Sea Birds ● HOMEOTHERMS: Metabolic rate does not change with external environment ‘warm blooded’. ● Waterproofing through oil gland @ tail base ● Hard-shelled eggs ● Flight and flightless species ● Many have large migrations (terns, albatross) ● Penguins ○ PENGUINS are flightless. ○ Wings modified as flippers. ○ Unlike most birds, they do NOT have hollow bones. ○ Lay eggs during winter ● The ROYAL ALBATROSS is the largest flighted bird in the world. ○ Nesting colony in New Zealand ○ Mating is for life ● The blue footed booby lives in the Galapagos. It uses colorful feet for courtship ● Gannet ● Puffin ● There are many species of seagulls. They hunt and feed by scavenging. Marine Mammals ● HOMEOTHERMS ● Many species have thick blubber layers for warmth. ● Hair on skin ● Newborns get extensive maternal care ● Most are carnivorous ● Pinnipeds, Otters, Sea Cows, Cetaceans 1. Pinnipeds: (Seals) Carnivorous animals closely related to dogs, cats, bears. ■ Stay warm by thick blubber layer and bristly hair. ■ Seals, sea lions, walruses. ■ Feed on fish, squid & krill ■ Harbor seals, Harp seal, Antarctic fur seal, California sea lion, pacific walrus

2. Sea Otters ■ Primarily eat sea urchins. They live near dense kelp forests, such as along the California coast. 3. Sea Cows Relatives of Elephants ■ Dugong-Always marine, Africa ■ Manatee-SW,FW, or brackish Florida and Atlantic 4. CETACEANS are the largest group of marine mammals. ■ Evolved from terrestrial ancestor. ■ Pair of front flippers, blowhole for breathing, blubber for insulation. ■ Tail = FLUKE, main propulsion ■ MELON in large head used for sensing environment ■ Communicate through sonar, ECHOLOCATION. Toothed and Baleen Whales ● Humpback whales (Baleen) are known for their intricate songs. They can be identified from TAIL FIN markings. ● Blue Whale (Baleen) migration routes - Largest Animal on Earth ● MINKE WHALES are hunted extensively by both Japan and Norway ● TOOTHED WHALES are carnivores. They live on fish, cephalopods, and other marine mammals. ○ Beluga Whale ● Bottle-nosed dolphins live in pods off the E. coast. They migrate, but details of these migrations are unknown. ● Sperm Whales eat Giant Squid ● Killer Whales (Orcas) often hunt in packs...