LECTURE NOTESMARINE BIOLOGY (MARSC 180)L. SNYDER

Ch. 6: Marine Vertebrates

Bony Fish, Cartilaginous Fish, Reptiles, Birds, Mammals

Subphylum Vertebrata Features

•All have chordate features, plus:

–Notochord segmented into bony vertebrae

–Segmented skeletal muscles

–Closed circulatory system w/ O2 transported byhemoglobin (in red blood cells)

–Brain & specialized sensory organs

Vertebrate Types

  • Common ancestor is likely Marine
  • Tetrapods: Class Mammalia, Aves, Reptilia, Amphibia
  • Fishes: Osteichthyes, Chondricthyes, Agnathans

Marine Fishes

•50% of all living vertebrates

•Live in water, have fins & scales

•Gills for gas exchange (O2 in, CO2 out)

–Water & dissolved O2 enter mouth & pumped over gills

–O2 flows from gills into blood

–CO2 flows out of blood to gills water

Marine Fishes

•Gill Arch supports 2 Gill filaments (large surface area)

•Active fish (Tuna): 10X more gill surface than body surface

•O2 diffuses from lamellae to capillaries & bloodstream

Countercurrent Gas Exchange

•Water & blood flow in opposite directions

•Blood from body (low O2, High CO2)

•Water in lamellae (High O2, low CO2)

•O2 & CO2 move via Diffusion

• Some fish can extract 85% of DO in water

•Highly efficient form of gas exchange

•Air breathers use ~25% if O2 that enters lungs

Class Agnantha (Jawless Fish)

•Lampreys & hagfishes

•Most primitive of fishes

•Feed by suction (round, muscular mouth & rows of teeth)

•Cylindrical body (like eel, snake)

•Cartilagenous skeletons

•Lack paired fins & scales

Class Chondrichthyes: Cartilagenous Fish

•Sharks, rays, chimeras

•Nearly all marine

•Cartilage skeleton, Paired fins

•Movable jaws with teeth

•Alive for ~280 million years w/ little change

•Hypo-osmotic body fluids (50% less salt than sea water)

•Fluids accumulate Urea (toxic) & trimethylamine oxide (protein) + salt

•Internal ion concentration = external NaCl concentration

Chimeras

•Temperate ocean floor

•Size: up to 2 meters

•Poisonous spine on front of dorsal fin (defense)

•Males use claspers (internal fertilization)

•Lay leathery cased eggs

Skates & Rays

•Most are lie-and-wait predators

•Live on bottom

•Manta rays: pelagic, plankton eaters

•Ovoviviparous: eggs hatch inside female & are born alive

•Except for skates

–Lay eggs (mermaids’ purses): tendrils secure egg in algae

•Flattened bodies

•Wing-like pectoral fins, fused with head

•Gill slits on underside, eyes on top of head

Shark Reproduction

•Internal fertilization

•3 incubation strategies:

  1. Oviparous: Lay eggs (leathery case, yolk) Ex: horn, swell shark

2.Ovoviviparous: Eggs hatch w/in Mom’s reproductive tract, yolk & oviduct fluids nourish young, born alive (Ex: Dogfish)

–Some Oophagus: 1st hatched eat siblings in oviduct (Ex: Makos, sand tiger)

3.Viviparous (live birth): placental link between Mom & young (like mammals)

–Young born alive, fully functional

–EX: Hammerheads, bull, basking sharks

Shark Locomotion

•Fairly immobile pectoral fins

•Side to side movement of Heterocercal Caudal provides forward thrust & lift

•Flattened underside & pectorals aid lift

–No swim bladder (only oily liver)

Why do Sharks have a bad reputation?

•375 shark species: only 30 reported to ever attack a human (4 sp. killed a human)

•Only ~12 potentially dangerous if encountered

•80% harmless

•World Unprovoked Attacks (1874-2004): 212 (61 fatal)

•California (White Shark Attacks): 2004: 6 Attacks ( 1 Fatal)

•World Shark Attacks 1990-2004: Florida: 40%, Calif: 4.3% (most are isolated around Monterrey & San Francisco = “Red Triangle”)

•

•Humans kill ~ 1 million sharks for every human killed by a shark

•You’re 30 times more likely to be killed by lightning than a shark!

•For sport, Fear, Meat, Hides, Medicine (shark catilage), Shark Fin Soup (Finning)

Why Do Sharks Sometimes Attack Humans?

1. Misidentification

•Diver & surfer silhouettes resemble pinnipeds

2. Sharks strike unfamiliar objects to test for food potential

•Decide a prey's palatability while in its mouth

•Prefer prey rich in energy (fat): marine mammals

•Spit out energy-poor prey (not fatty): Humans

Why Should We Protect Sharks?

•Apex predators: control prey populations & maintain ecological balance

•Part of complex food web:

•Feed on fish, shellfish & mammals

•Sick & dying

•Larger animals (whales, seals, tuna) that have few predators

•If removed, ecosystem balance is altered

•If shark numbers decrease, population sizes of seals & sea lions increase, which causes fish populations to decrease because there are too many seal/sea lions.

•This ultimately will decrease the fish availability for other species including humans (results in crashes of commercial fisheries – no fish dinner for you)

Class Osteichthyes (Bony fish)

  • Skeleton at least partially made of bone
  • 98% of all fishes (> 50% marine)
  • ~75–100 new species described each year
  • Most have scales protected by mucus
  • Operculum: bony plates that cover & protect gills
  • 2 sub-classes:

1.Coelacanths & Lungfishes

2.Ray Fins

Coelacanth

•1st appear in fossil record (Devonian) ~400 million years ago (MYA)

•Thought extinct 60 MYA

•Fresh, dead specimen discovered 1938

•Found in Indian Ocean below 100m

–Rocky caves, more active at night

Order Teleost (Largest Rayfin Order):

•90% of all fish

•60% are marine

•Neutral Bouyancy (swim bladder), scales

•Hypo-osmotic body fluids

•Great camouflage

•Movable fins = controlled swimmers

•Adapted to many habitats = great diversity

Camouflage & Body Structure varies by Habitat

Cryptic Coloration – common in benthic species
Countershading: Dark back, Light Belly – pelagic sp.

Body Plan Variety

•Sprinting (Long, thin):  being sighted as chase prey

•Maneuvering: egg-shaped, long fins ( drag, but  surface for fine adjustment

•Cruising: Large, streamlined body, packed with muscle

Swim Bladder Allows for Greater Maneuverability

•Shark’s flat, rigid pectoral fins must provide lift

•Swim bladder provides buoyancy = fins free for other uses (break, turn, balance)

Caudal Type Helps Determine Speed

•Rounded fin produces a lot of drag: Slower fish w/ high maneuverability

•Forked & Lunate fins greatly  drag: Fast, cruising fish (Marathon swimmers)

•Drag: resistance to movement in a fluid

Species Maintenance of Males

•Many species don’t maintain equal #’s of males as females

•One male may mate w/ multiple females

•Hermaphroditic species often produce males as needed

•CA Sheephead: Females become males after ~ age 8

•All individuals contribute to producing & carrying young

Marine Tetrapods

•Four-limbed, air breathers (lungs)

•Reptiles, Birds, Mammals

•All have terrestrial ancestors

•Depend on sea for food & spend significant time in/on sea

•Hypo-osmotic body fluids

Class Reptilia

•Land reptiles that returned to Sea

•Ectothermic, lungs (air), scales

•Salt glands excrete excess salt

•Kidneys produce concentrated urine

•Most live in tropics or subtropics

Marine Reptiles

•Sea Snakes (61 species, most highly venomous)

•Sea Turtles (7 sp.)

•Marine Iguana (1 sp.)

•Estuaries: snakes, caymens, alligators, crocodiles

Marine Iguana: Endemic to Galapagos (found nowhere else)

•Eat marine algae

•Long claws to hang on rocks

•Wide tail acts like rudder

•Sea Turtles

•Live up to 80 yrs.

•Tropical & subtropical

•Food: sea jellies, algae, crustaceans, molluscs

•Threatened: hunted (meat, shell, eggs); beach & nest destruction; tangled in nets; pollution; eat plastic (mistake for jellies)

Sea Turtles Lay Eggs on Beaches

•Hatched Babies Must Return to the Sea

Egg-laying Marine Reptiles & Birds

•Most reptiles (not snakes), all birds

•Internal fertilization

•Egg Incubation: Fluid-filled sack w/ food, waste storage, gas exchange

•Surrounded by protective
shell (hard or leathery)

Class Aves (Birds)

•Front appendages adapted for flight

•Streamlined, insulated bodies (Feathers)

•Endotherms (Homeotherms) = warm blooded

•Flyers have light, hollow bones

•All lay eggs on land

•Salt excreting glands

•Marine birds: feed in sea, some only return to land to breed

•More diverse than reptiles or mammals

•Prey acquisition & bill shape determined by prey type

Gulls & Terns

Coastal

Successful fishers & scavengers

Shorebirds

•Estuaries, shore

•Eat fish & marine invertebrates

•Most migrate from northern (summer) breeding grounds TOSouthern, winter grounds

•Rest & winter in estuaries

Shorebird Beak Types

•Dependent on prey type & feeding location

•Minimize competition based on beak length
•Long beaks feed in deeper water

•Penguins & Allies (Puffins,
auklets, murres)

•Penguins: Can’t Fly, Great Swimmers, Southern Hemisphere only

•Pelicans & Allies (Cormorant):

•Throat pouch

•Brown Pelican: Endangered species in Calif. (DDT)

•White Pelican: Cooperative feeders

•Cormorants:Deep diving birds (Great divers & swimmers, but Bad flyers)

•Solid bones & oily feathers help them to dive, but make flying difficult

Tubenoses (Albatross, shearwater, Jaeger)

Come on land only to breed

Some are Deep divers (some shearwater sp. dive up to 50 ft. – compete with dolphin, tuna for schooling fish (anchovy, mackerel, etc.)

Albatross:Great flyers Horrible at landing

Jaegers – kleptoparasites = steal food on wing from other birds

Marine Mammal Characteristics

1)Large Brain

2)Internal fertilization

3)Live young (Viviparous)

4)Embryo nourished via a placenta

5)Young fed milk (mammary glands)

6)Endothermic (warm blooded)

7)Body hair

8)Specialized Teeth

9)Separate, external opening for reproductive tract

Marine Mammal Classification

Class Mammalia:

3 Orders

3 Suborders

•Evolved from land mammals

•Returned to sea 50 MYA

Order Carnivora (Polar Bears, sea otters, Pinnipeds)

Polar Bears (Marine bear)

  • Semi-aquatic (will swim out to sea up to ~ 40 miles)
  • Related to land bears – grizzly
  • Rely on sea ice to hunt for prey (seals, small whales, etc.)
  • Thick fur & blubber
  • Threatened by Global Warming: melted sea ice will inhibit hunting

Sea Otters

  • Are mustelids = related to weasels, skunks, etc,)
  • Range: PacificCoast from Baja California to Alaska/Russia (especially around Aleutian & Russian islands)
  • Hunted to near extinction for fur
  • Keep warm with:
  • Dense fur (densest of all animals), little blubber
  • Air between fur & skin
  • High metabolic rate: Eat 15-20 lbs/day (25-30% of body wt.)
  • Use tools (rocks, shells) to eat urchin, shellfish

Sub-Order Pinnipedia: Sea Lion, Seals, Walrus

  • Predators, Blubber, Breed on land
  • Seal lions = external ears, long neck, rotation of flippers
  • Seal – no external ear, short neck, limited rotation of flippers
  • Walrus – eat benthic invertebrates, Stiff whiskers are feelers

Order Sirenia [Manatee, Dugong, Steller’s Sea Cow (extinct)]

•Warm, shallow, tropical seas

•Herbivores, no pelvic limbs

•Severely Endangered

•Boat propellers kill & injure

•Steller’s Sea Cow: hunted to extinction in 30 years (1741)

•Bering Sea & Aleutian Islands

•35 ft. long, fed on marine algae

Order Cetacea: Whales, Dolphins, Porpoises Baleen Whales

Sub-Order: Mysticeti (Blue, finback, gray humpback, right, minke, sei)

  • Baleen = fibrous protein (keratin) “teeth”
  • Strains water or mud (gray whale): plankton, krill, sm. Fish, benthic inverts.
    Tongue pushes food to throat, excess water/mud spit out
  • 2 Blowholes
  • Communicate with low frequency sounds (songs). Humpback over very long distances

Sub-Order: Odontoceti (Sperm, pilot, orca, dolphin, porpoise, narwhale, beluga)

  • Toothed Whales(Peg Teeth)
  • 1 Blowhole
  • Social (family pods)

Mammal Oxygen Storage

Respiratory system collects/retains O2:

  1. Excellent O2 storage in blood (High [Myoglobin] + Hemoglobin)
  2. Bradycardia: slows heart rate while underwater to conserve O2
  3. Collapse lungs when diving ( water pressure & Nitrogen gas buildup in blood)
  4. Vasoconstriction: shunt blood to vital organs (brain, heart)

Vertebrate Sensory Capabilities

•Specialized sensory organs convert chemical, mechanical, electromagnetic stimuli into nerve impulses

–Sent to Brain

1. Chemoreception (smell, taste)

–Fish: little taste, excellent olfaction

–Tetrapods: Don’t smell in water (stop breathing)

•Cetaceans: lost ability to smell

2. Electroreception (Ampullae of Lorenzini) sharks detect electrical fields of prey w/ pits in snout

3. Mechanoreception (Lateral Line System): Detect vibrations

•Small canals with receptors (hair cells)

•Detect predators, prey,

•schooling

4. Sound Reception: Sound transmitted 5X faster in water than air

–Lateral line = feel sound vibrations

–Excellent Hearing

–Echolocation (toothed whales)

–Produce sounds (clicks)

•“See” 3D picture of environment

•Detect food (type & size of prey)

•May stun prey

•Clicks emitted, bounce off of prey, jaws receive reflected sound (fat bodies in jaw transmit sound to middle ear), transferred to ears & then brain

•Biological Sonar!