Chapt 10 Bony Fishes

Ichthyology “the study of fish”

Phylum Chordata• Class Actinopterygii

– “modern bony fish”– 25,000 species or ½ of all vertebrate species– So diverse no one characteristic can differentiate

them from sharks, skates, and rays (cartilaginous fish)

• Taxonomy of fishes is concentrated on order or family rather than phylum (b/c phylum is too broad)

– Taxonomy of fishes are still changing as new technology and research reveal new characteristics

Phylum Chordata

• Characteristics– Presence of swim bladder or lung– Bones– Bony scales– Fin rays

Coelacanths “primitive fish”• Historic fish that give rise to modern day amphibians• Were thought to be extinct 65 million years ago until

living specimens were discovered in 1938 and as time goes on finding more and more individuals “living fossils”

• Live at depths 150-250 meters• Bony skeleton but vertebrae is almost all cartilage

(like sharks)• Maintain high amount of urea to maintain

homeostasis• Reproduction: ovoviviparous

Ray-finned Fishes

• Most numerous and diverse of ALL vertebrates in ocean

• Characteristic-fins attached to body by fin ray

2 major groups• Subclass Chondrostei

– Heterocercal tail– Skeleton made mostly of

cartilage– Ganoid scales

• Armored appearance• Florida Gar

• Subclass Neopterygii– Homocercal tails

• Backbone does not extend into tail

– Cycloid OR Ctenoid scales

• Both are thinner and more flexible than ganoid scales

Body Shapes-determined by habitat

• Fusiform- streamlined shape for active swimmers

• Laterally compressed- flattened so can maneuver though corals

• Flattened: bottom-dwellers

• snakelike: burrowing fish

Respiration

• Gills: receive oxygen and remove CO2, and maintain salt balance– Made of gill filaments: blood flows in opposite

direction of incoming H2O

• Water must continuously pass over gills– Meets with blood with lower O2 and higher CO2

• Diffusion moves from where to where?????

– Fish actually “pump” H2O over gills

Cardiovascular

• Close circulatory system: Heart, veins, arteries– Most complex we’ve seen so far!– 4 chambered heart

• Draw diagram in your notes

KOI Circulatory System :D

Staying neutrally bouyant

• Buoyancy– Swim bladder: gas filled sac; add and remove to

adjust buoyancy• SCUBA divers must adjust air in BCD for same purpose

– To go down: let air/gas out– To go up: add air/gas

Nervous System

• Brain, spinal cord, nerves• Senses

– Olfaction: sense of smell: olfactory pits (nostrils)– Taste: receptors on head, jaws, tongue, mouth

and barbels on some fish (catfish)– Hearing: Eyes Lack eyelids

• Most set on sides of face: each eye see own independent view.

Reproduction

• Vast: depends on species– Blue headed wrasse can change sex

• Perch: separate sexes– Males and females spawn eggs

• FEMALES MUCH LARGER THAN MALES DURING BREEDING-> FULL OF EGGS (female on bottom ↑)

– Early spring in sandy, shallow sediments– Females lay more than 20,000 eggs at a time; male

comes afterward to fertilize• No parental care for young

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Perch Anatomy