chapter 8: marine fish

characteristics of all chordates

characteristics of all chordates

notochord, dorsal hollow nerve cord, pharyngeal slits, postanal tail

examples of a jawless fish

lamprey and hagfish

class chondrichthyes (cartilaginous fish)

sharks, skates, rays, and ratfish

spiracles

used to take in water and ventilate the gills, out the gill slits

-open directly in water

-acts like a straw sticking out of the sand

scales

protects their skin

claspers

modified pelvic fins on a male shark that allows for transfer of sperm to female

osteichthyes (bony fish)

class sarcopterygii (lobed fin fished)

-ex: coelacanth

class actinioptergii

-ex: ray finned fishes

agnatha (hagfish and lampreys)

-jawless fish with a muscular, circular mouth with rows of teeth in rings

-exclusively marine

-long, cylindrical body

-lack paired fins and scales seen in other fish

hagfish

feed on dead and dying fish and marine mammals

live in burrows in soft sediments

-excretes slime in response to a threat

lampreys

some spend a large portion of life in the sea, but return to freshwater to breed

-sucker like mouth for consuming blood, tissue, and body fluids

what do both cartilaginous and bony fish have?

-highly efficient gills

-scales cover the body

-streamline (body shape to help swim through water)

-paired fins

-wide variety of jaw and feeding types

-lateral line and other sensory organs

what are lateral lines used for

system of tactile sense organs that serve to detect vibrations and water movement

-small pores from snout to tail

-potential prey/predators can sense change in pressure

ratfishes

-deep water fish

-mouth with plate like grinding teeth

-venomous spine in front dorsal fin

-no scales

heterocercal tail

caudal fin that is longer on the top than the bottom, asymmetrical

elasmobranchs

a collective name for the sharks, skates, rays, and sawfish

-primarily marine but some travel up rivers

-heterocercal tail

-2 dorsal fins

-skeleton of cartilage

-spongy cartilage snout

-carnivorous or planktonic

-about 350 extant species

ram ventilators

move water over gills by swimming and ramming water into their mouths and out the gills

buccal pumping

forcing water over gills by opening and closing mouth

spiracle breathing

opening on head to bring water in so they don't open mouth

placoid scales (dermal denticles)

skin teeth: hard enamel tightly together

-tips go backward

-made for drag and noise reduction

-intricate adaptation so they are a top predator

ampullae of lorenzini

sensory organs used to detect electrical currents when sharks are close to an object

-electroreceptors: jelly filled pores

shark liver

3 lobed liver (left, right, and middle)

-no swim bladder, able to maintain buoyancy with large livers rich in oil

-the liver can comprise 25% of a shark's total body weight

-sharks like to sink when not in motion and there is no lift. aided by the "lift" provided by the position and stiffness of the pectoral fins

demersal

bottom dwelling fish (ex rays and skates) who feed on organisms on the ocean floor

-think of shark lagoon at AOP and how shallow the tanks are

-nurse sharks rest on the floor

neritic

near continental shelf, shallow part of ocean

ex: shortfin mako shark, great white

oceanic (pelagic)

open blue water where animals dwell

ex: basking shark, whale shark

how many different shark species are there

over 500 species of sharks

what is the largest shark species

whale shark

examples of cartilaginous filter feeders

manta ray, megamouth shark, whale shark, basking shark

sharks and people

subject to disastrous fishing

-fished for their oil, skin, and fins (shark fin soup)

similar things about skates and rays

-entire body is dorsoventrally flattened

-spend much of their time on the bottom, partially covered in sand

-large flattened teeth for feeding on inverts

-most have fleshy long whip like tails

-mouth on ventral side of body

skates

-large wing like pectoral fins

-spiracles behind eyes

-fleshy tail with no spine on tail

-always lay egg cases

-feed primarily on molluscs

-found at depths greater than 4,000 meters

ex: shovelnose guitarfish, longnose skate

rays

-pectoral fins are expanded into wings and entire body is dorsoventrally flattened

-most like long whip like tails; spine at the base of the tail with an associated poison gland in sting rays

-manta ray: plankton feeder in mid water; gill rakers used for filtering water

ex: bat ray, round ray, manta ray

internal fertilization

Process in which eggs are fertilized inside the female's body

viviparous

live birth

ex: blue shark, lemon shark

oviparous

egg laying

ex: zebra shark, horn shark

ovoviviparous

eggs hatch within the body

ex: great white, nurse shark

cryptic coloration

camouflage

warning coloration

conspicuous coloration to warn off predators of their bad taste or poisonous nature

buoyancy in fish vs sharks

swim bladder vs liver

Nictating membrane (third eyelid)

transparent eyelid that can move across the eye to protect it underwater, especially during feeding

-position of lens changes like in a camera

operculum

A protective flap that covers the gills of fishes

-gastropods have these as well: able to close them off to the environment like a trap door

fusiform body shape

spindle shaped, looks like a lemon

-used for fast continual swimming

-species that have this are well adapted for feeding and survival

-little flexibility except in caudal fin

actinopterygian

ray-finned fish

-may contain only spiny rays, only soft rays, or both

-spines are generally stiff and sharp

-rays are generally soft, flexible, segmented, and may be branched

*dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fishf

sarcopterygian

lobe-finned fish

-fleshy, lobed, paired fins, connected to body by a single bone

-coelacanth has essentially not evolved from it's ancient form, and is regarded as a living fossil

fish gills

-supports entire structure: gill rakers are on the forward surface of the gill arch and the gill filaments trail behind the arch

-exchange of oxygen and carbon dioxide takes place on these surfaces (increases surfaces area)

swim bladder

swim bladder used for buoyancy control

ctenoid scales

thin flexible and overlapping scales that have tiny spines

cycloid scales

thin, smaller overlapping scales with a smooth posterior edge that are found in some of the more primitive bony fishes

countershading

dark on top, light on bottom

disruptive coloration

color pattern that confuses the predator (bars or stripes)

-normally found on slower swimming fish

eye spot mimicry

circular patterns on/near caudal fin

-confuses predators who are not sure which end of the fish is the head

compressiform

usually do not swim rapidly, exceptionally maneuverable

-compressed from side to side

-quick bursts of speed over short distances

ex: angel fish, moon fish

depression

flattened from top to bottom

-live on the bottom

-slow

ex: flounders, skates, rays

filiform

elongated bodies

-live in soft sediment, sand, mud

-slither like motion (eel like shape)

ex: pipefish, sand lance

caudal fin shapes

rounded, forked, indented, square, lunate, pointed

homoceral (rounded)

symmetrical

-large amount of surface area allows sharp turns and quick starts to avoid predators

-creates drag-fish tires easily

ex: clownfish, northern puffer

homoceral (truncate)

-allows short bursts of speed to escape predator or constant slow swimming

-less drag than rounded

-bottom-dwelling fish

ex: flounder, sculpin

homoceral (forked)

for constant swimming over long distances, reduces drag

-open water fish

-do not need speed to feed or for protection

ex: many schooling fish, pilot fish

homoceral (lunate)

half moon shaped

-fast moving, oceanic fish

-less drag, great acceleration, reduced manueverability

ex: tuna, swordfish

heteroceral

asymmetrical: top longer than bottom

-medium speeed

-provides lift when no air bladder

-reduced maneuverability

ex: many sharks

swimming patterns

fish exhibit a "s-shaped" swimming pattern

-depending on the type of fish, different fins may be used primarily for the forward movement

acquiring and processing food

mouth structure reveals dietary preferences of fish

ex: parrotfish beak (fused teeth) allows for the fish to scrape algae and other organisms off of hard surfaces

-butterfly fish used its long tube like mouth to feed on corals

-barracuda uses rows of sharp teeth and a wide mouth to capture prey

territoriality

posturing is used to show their aggression

-can include raised fins, open mouth, darting

ex: triggerfish

reproduction in fish

hermaphroditic (possess male and female reproductive organs)

-some possess these structures at the same time (simultaneous hermaphrodites)

-other species possess these structures at different times during their life (sequential hermaphrodites)

protogyny

Born a female, change to a male

protandry

Born a male, change to a female