Digestive System
Digestive System - basic plan
 Mouth (toothed jaws, oral valves)
 Oral cavity (vomerine, palatine teeth, tongue w/
teeth)
 Pharynx (pharyngeal tooth pads, gill arches/rakers)
 Esophagus (gullet)
 Stomach
Digestive System - basic plan
 Pylorus (pyloric valve, pyloric caeca)
 Small intestine (ducts bring in bile, pancreatic
secretions)
 Large intestine/cloaca
 Anus
Variation based on diet, lifestyle
Mouth & Oral Cavity
Teeth in Jaws
 Food generally
swallowed whole
 Teeth used for
capture, not
chewing
Pharynx - gill rakers
Gill rakers
 Gill rakers on
anterior side of each
gill arch - prevent
escape of prey
 Gill filaments on
posterior side of
each gill arch
Size and shape of rakers depend on
types of foods eaten
Short, blunt gill rakers
 Large prey
QuickTime™ and a
decompressor
are needed to see this picture.
Long, fine gill rakers
 Particle or
suspension feeder
Developmental changes
 Gill rakers can
change in form as
fish develops
Paddlefish - suspension feeder
 Long, fine gill rakers
to strain plankton
from water column
Zooplankton’s view!
Pharyngeal teeth
Pharyngeal Teeth
 Variety of teeth in
the same general
region
 Derived from gill
arches
Feeding
Pharyngeal teeth
 Aid oral teeth in
holding “prey”,
directing them into
esophagus
 Modified for
crushing, grinding,
shearing of foods
Pharyngeal Teeth
 Present in many herbivores that eat plants,
algae, and/or phytoplankton
 E.g., Grass carp
 Esophagus & stomach
 Structure varies with diet
 Simple tube to blind-sac, elastic pouch
Pylorus
Pyloric caeca
 Pyloric valve controls release of stomach contents
 Ray-finned fishes peculiar among vertebrates
 Possess numerous pyloric caeca - digestive/secretory glands
Intestines
Carnivore intestines
 Intestine usually very short in carnivores
 Animal foods digested, absorbed easily
Herbivore intestines
 Intestine usually very long in herbivores,
detritivores
 Plant foods digested, absorbed slowly
Chondrichthyes
Shark digestive system
Spiral valve in sharks
Increases food passage time through intestine
- improves absorption
Typhlosole in lampreys
Flap of tissue extending
into lumen of intestine
-increases surface area
for absorption
Disclaimer - this is a
picture of an earthworm,
not a lamprey
Circulatory System
 Fish have a singleloop circulatory
system
Typical pathway
Heart to gills to
body, back to heart
Major vessels run along (ventral to) vertebral
column
Branches to organs, muscles (segmental)
Heart
 Fish have a 2chambered heart
Lungfish Circulatory System
 Lungfish have added
features
Lungfish Circulatory System