FishKingdom - AnimaliaPhylum - Chordata Subphylum - VertebrataClass - AgnathaClass - Chondrichthyes Class - Osteichthyes

Agnatha

General Characteristics

● No jaws, stomach, paired fins, or body scales

● Have notochord and light sensitive pineal eye

● Skeleton made of cartilage● Possibly earliest

vertebrates - 500 mya

Agnatha: Hagfish

Hagfish (also called slime eels)

● Lives in cold oceans of both hemispheres in large groups

● Feed on small invertebrate and/or scavenges○ Slow metabolism - can go months without eating

● Completely blind○ Uses tentacles around mouth to sense food

● Glands along sides produce a thick, sticky slime ● Can form body into knot

Agnatha: Hagfish

Agnatha: Lamprey

Lamprey

● Adults feed on marine fish○ Oral disc has rasping tongue with keratin

“teeth”● Spawning occurs in freshwater

○ Anadromous○ Male builds the nest, fertilizes eggs and

buries them○ Larvae can remain in rivers for 2 to 3 years

■ Return to ocean to metamorphose into adult form

Agnatha: Lamprey

Chondrichthyes

General Characteristics

● Skeleton made of cartilage● Placoid scales● 760 species

○ Large variety in shape and size (up to 15m)

● Two subclasses:○ Elasmobranchii (sharks, skates,

and/or rays)○ Holocephali (chimaeras, or ratfish)

Chondrichthyes: Sharks

General Characteristics

● Move caudal fin to swim○ Heterocercal or homocercal

● Males have modified pelvic fins called claspers that help facilitate the dispersal of semen

Male vs. FemaleSharks

Chondrichthyes: Sharks

General Characteristics

● Buoyancy○ Remain in constant motion○ Large livers produce squalene

■ The density of squalene is less than that of seawater

Chondrichthyes: Sharks

Sensory Systems

● Vision○ Eye on either side of head give them a nearly 360° view

■ Blind spot in front of snout and behind head○ Tapetum lucidum - layer of mirrored crystals that allows them to

see in low light and murky conditions● Olfaction

○ Acute sense of smell

Chondrichthyes: Sharks

Sensory Systems

● Lateral Line System○ Canals that run from snout down either side of the fish with

microscopic hairs that accompany it○ Senses vibrations in the water

● Vibrations○ Ampullae of Lorenzini - electroreceptors

Chondrichthyes: Sharks

Digestion

● Rows of sharp teeth● Stomach, short intestine

with spiral valve

Chondrichthyes: Sharks

Osmoregulation

● Osmoconformers○ Equal concentration of solutes in body as

there are in environment● Ion regulators

○ Regulate the amount of urea in their system to remain in balance with external environment

● Rectal Gland○ Secretes excess ions

Chondrichthyes: Sharks

Reproduction

● Oviparity (primitive)○ Mother lays zygotes as

eggs (generally within a leathery pouch) with little embryological development inside mom (like birds))

Chondrichthyes: Sharks

Reproduction

● Ovoviviparity (most common)○ Zygotes are retained within

mother or father, but no nutrition provided (like a seahorse)

Chondrichthyes: Sharks

Reproduction

● Viviparity (most recent to evolve)○ Zygotes develop into young inside

of the mother, leading to live birth, often nourished by uterine milk

Chondrichthyes: Skates and Rays

Sharks vs. Skates and Rays

● Flat bodies● Large pectoral fins● Reduced dorsal and caudal fins● Eyes and spiracles on top of head● Ventral gill slits

Chondrichthyes: Skates and Rays

Skates vs. Rays

● Rays “fly” and skates “ripple”● Rays have sharp venomous tails

and skates have small, fleshy, non venomous tails

● Rays can grow up to 7m and skates up to 2.4m

● Rays are ovoviviparous and skates are oviparous (mermaid's purse)

Chondrichthyes: Skates and Rays

Chondrichthyes: Skates and Rays

Defense Mechanisms

● Electric rays○ Modified muscles on either side of the head

produce a shock■ some as strong as 220V

● Stingrays○ Sharp and serrated spine that produced venom

● Sawfish○ Rostrum makes up ⅓ of body size and is lined

on either side with sharp teeth

Chondrichthyes: Chimaeras

● Long pointed heads and long slender tails● Covered gills

○ Water enters through nostril● Males have claspers on head and pelvic fins● Oviparous, leathery cases● Flat plates instead of teeth● Bottom dwellers

○ Feed mostly on fish and crustaceans● Also known as ratfish, rabbitfish, and spookfish

Chondrichthyes: Chimaeras

Osteichthyes

General Characteristics

● 25,000 species○ Half of all vertebrates and 95% of all fish

● Swim Bladder● Skeleton made of bone (Osteo- = bone)● Fin Rays● Two subclasses:

○ Sarcopterygii (Lobe-finned fish)○ Actinopterygii (Ray-finned fish)

Osteichthyes

Scales!

**I forgot to put this in before printing your notes so take your own!**

Osteichthyes: Lobe-finned Fish

Coelacanths

● Skeleton of bone and cartilage

● Fat-filled swim bladder for neutral buoyancy

● Live in twilight rocky areas with steep subsurface gradients

● Evolutionary relics that gave rise to land vertebrates

Osteichthyes: Lobe-finned Fish

Osteichthyes: Ray-finned Fish

Body Shape

● Fusiform○ Active swimmers / Fast○ Streamlined○ ie. tuna, marlin

● Laterally compressed○ Narrow○ Navigate easily through reefs○ ie. butterflyfish, angelfish

Osteichthyes: Ray-finned Fish

Body Shape

● Depressed○ Flattened from top to bottom○ Feeds and/or rests on bottom○ ie. flounder

● Globular○ Enlarged pectoral fins○ Sedentary fish○ Ie. anglerfish, scorpionfish

Osteichthyes: Ray-finned Fish

Body Shape

● Attenuated○ Snake like○ Burrowing and/or

maneuvering tight spaces○ ie. moray eels

Osteichthyes: Ray-finned Fish

Osteichthyes: Ray-finned Fish

Coloration

● Countershading○ Lighter lower half than top

■ Ie. Marilin

● Disruptive Coloration○ Helps break the outline of the

organisms■ Ie. Butterfly Fish

Osteichthyes: Ray-finned Fish

Coloration

● Cryptic Coloration○ Allows fish to blend in with

environment■ Ie. Scorpion Fish

● Poster Colors and Aposematic Coloring○ Warning Coloration; Usually very

bright■ Ie. Reef Fish and Lionfish

Osteichthyes: Ray-finned Fish

Locomotion

● Methods of Movement○ Drifting○ Burrowing○ Crawling○ Gliding ○ Swimming

■ Bands of muscles (myomeres) in the trunk alternately contract pushing the fish forward

Osteichthyes: Ray-finned Fish

Locomotion

● Swimming Methods○ Eels - undulate entire trunk○ Marlin - undulate only posterior○ Triggerfish - use only dorsal and anal

fins○ Flying fish & Wrasse - primarily use

pectoral fins

Osteichthyes: Ray-finned Fish

Respiration and Osmoregulation

● Gills○ Gas exchange and aid in maintaining salt

balance● Gill Structure

○ Countercurrent multiplier system○ Continuous movement of water past gills to

oxygenate blood○ Water is consumed and chloride cells help

eliminate excess salt

Osteichthyes: Ray-finned Fish

Osteichthyes: Ray-finned Fish

Cardiovascular System

● Fish have lower blood pressure● Active swimmers have

countercurrent arrangement of veins and arteries to maintain higher body temperature and increase swimming efficiency

Osteichthyes: Ray-finned Fish

Buoyancy Regulation

● Swim bladders help regulate buoyancy● Regulation of swim bladders

○ Gulping air○ Gas gland/diffusion

● Some fish do not use swim bladders○ Pelagic, active fish○ Bottom dwellers○ Deep-sea fish

Osteichthyes: Ray-finned Fish

Osteichthyes: Ray-finned Fish

Nervous System and Senses

● Olfaction○ Olfactory pits

● Taste and hearing○ Taste receptors○ Barbels○ Lateral line system

● Vision○ Monocular

Osteichthyes: Ray-finned Fish

Feeding Types

● Great diversity in feeding types and diets

● Carnivores○ Boxfish/puffer fish: strong jaws○ Butterfly fish: tiny mouths○ Groupers: largemouth,

pharyngeal teeth● Herbivores

Osteichthyes: Ray-finned Fish

Feeding Types

● Herbivores○ Broad flat teeth, often with

sharp edge○ Parrotfish: scrape/bite coral

● Filter Feeders○ Gill rakers collect food when

water passes through gills

Osteichthyes: Ray-finned Fish

Osteichthyes: Ray-finned Fish

Adaptations to Avoid Predation

● MANY different ways:○ Pufferfish○ Flying fish○ Pearlfish○ Surgeonfish○ Triggerfish○ Stonefish

Osteichthyes: Ray-finned Fish

Reproduction

● External fertilization○ Males and females release

hundreds to thousands of eggs and sperm into the water

● 3 classifications:○ Non-guarders○ Guarders○ Bearers

Osteichthyes: Ray-finned Fish

Reproduction

● Non-guarders – Fish that do not protect their eggs and young once spawning has been completed○ Two types:

■ Open-substrate spawners■ Brood Hiders

Osteichthyes: Ray-finned Fish

Reproduction

● Non-guarders○ Open-substrate spawners

■ Pelagic Spawners● assure that young become widely dispersed by water

currents■ Benthic Spawners

● Eggs are adhesive and stick to substrates or, in long strings, attach to the surface of substrate

Osteichthyes: Ray-finned Fish

Reproduction

● Non-guarders○ Brood Hiders

■ Hide the eggs as part of their spawning behavior, but do not show parental care● Most build nest and

bury eggs

Osteichthyes: Ray-finned Fish

Reproduction

● Guarders - Hide their eggs and guard the fertilized eggs until they hatch○ Two types:

■ Substratum chooser● do not build nest but choose a substrate

■ Nest spawners● Construct some sort of structure or cavity

Osteichthyes: Ray-finned Fish

Reproduction

● Bearers – Fish that carry their embryos around with them (sometimes carry young as well)○ Two types:

■ External bearers● Ie. Seahorse

■ Internal bearers● Ie. Seahorse

Osteichthyes: Ray-finned Fish

Reproduction

● Larval Development○ Planktonic

■ nourished by yolk sac

○ Juveniles actively eat

Osteichthyes: Ray-finned Fish

Reproduction

● Hermaphroditism○ Synchronous - possess both ovarian and testicular tissue○ Sequential - individual changes sex

■ Protogyny● Female to male: male controls harem (ie. parrotfish)

■ Protandry● Male to female: large female dominates (ie. anemone fish)

Osteichthyes: Ray-finned Fish

Fish Migrations

● Daily○ Ie. Lantern Fish

● Seasonal○ Ie. Herring

● Oceanic○ Ie. Albacore Tuna

● Between Sea and Freshwater○ Ie. Freshwater Eels - Catadromous (live in freshwater, spawn in sea)

○ Ie. Salmon - Anadromous (live in sea, spawn in freshwater)