Lecture 20 Fish Flashcards
Deuterostomes include (4)
Echinodermata, Hemichordata, Xenoturbellida, Chordata (include vertebrates)
Common ancestor trait for deuterostomes
Pharyngeal gill slits
Unique traits (3) for Chordates
Dorsal hollow nerve cord
Notochord
Muscular, post-anal tail
Describe pharyngeal slits (pouches)
Located on lateral surface of head
Seem to be an ancestral trait in deuterostomes
Lost in echinoderms
In vertebrates, supported by arches
Note: Obvious in human fetus, present as middle ear and in throat
Functions of pharyngeal slits
- Filter feeding
- Respiration in vertebrates
-Water come in mouth pass thru slits
-O2 and CO2 exchanged thru gills
Characteristics of vertebrates (4)
- Axial skeleton
-Cranium (skull)
-Vertebral column (spine)
-Ribs - Appendicular skeleton
-pectoral girdle
-pelvic girdle - Closed circulatory system
-ventral heart - Organs suspended in coelom
Relation btw gill slits and gill arches
Pharyngeal slits = gill slits
Bars btw slits = gill arches:
-bone or cartilage
-gill filaments are on arches
Bony fishes have 4 pairs of arches, each has pairs of filaments
Bony fishes also have gill cover (operculum)
Structure of gill filament
= thin, vascularized, high surface area
* blood vessels flow through gill arches
* capillary beds in gill filaments; gas exchange
* filament epithelium is one cell thick (1-2 µm)
* water & blood flow in opposing directions
Describe countercurrent exchange’s effect on circulatory system and 3 examples of it
- blood flows in opposite direction to water flow
- ensures partial pressure gradients are maintained
- achieves maximum exchange of gases (O2 & CO2)
Example: limbs, kidney, swim bladder
Describe fish circulatory system
Describe fish heart
= 2 chambers
* strong, muscular pump
* ventrally located
* maintains blood flow
* 2+ chambers (auricle/atrium and ventricle)
* one-way valves inside
Describe 2 groups that are vertebrates but not gnathostomes (jawless fishes) aka agnathans
- 2 groups: lampreys and hagfish
- no jaws
- cartilaginous skeleton
- notochord present
- gill slits
- no paired fins
- no swim bladder
- no scales
Describe hagfish (Mixinoidea)
- scavengers
- osmotic concentration same as seawater
- used for leather products
- knot tying
- mucous production
Describe Lamprey (Petromyzontoidea)
-no jaw (“oral disc” instead)
- very distinct larval form (ammocoete)
- adults of many species are parasitic on fishes
Describe evolution of jaws
- not present in early fishes and present-day agnathans
- evolved from anterior gill arches
- teeth evolved from scales in mouth
- greatly improved ability to feed and diversify
