|Digestive System Design
Big fleshy lips are great with a sub-terminal sucking mouth
Little or none: Quite common
Incisors for cutting
Canines for grasping food that fights back
Molariform for grinding mollusks
Cardiform or Villiform for invertebrates (depends on how rowdy they are)
None for planktivores
Some fish may rely completely on pharyngeal teeth!
Crushing for mollusks or coral
Tearing for plants
Graspers for pulling prey into the stomach
Gill Rakers: keeps the food from escaping through the gills.
Long comb-like for plankton eaters
medium for omnivores
short for carnivores that eat big stuff.
None in planktivores or detritivores
J-shaped in omnivores
straight in fish that eat other fish
Marine with a saltwater bypass for marine fish
gizzard-like for some fish that eat detritus
Short (1X body length) = carnivore
Medium (2X) = herbivore /omnivore
Long (5-13) = detritivore/ planktivore
Stomach Chemistry: Grinds up and liquefies the food. Produces hydrochloric acid and a protein-digesting enzyme called pepsin. Function, makes big bits into little bits.
Intestine: Neutralizes the acids
Exocrine Pancreas: Adds digestive enzymes including amylase (breaks down carbohydrates), lipases (break down fats), and trypsin (another enzyme for proteins). These enzymes break food down into individual molecules that can be absorbed by the intestine.
Liver: Produces bile and stores it in the gall bladder. The gal bladder releases it into the intestine when the fish needs to digest food high in fat. Bile acts like detergent and breaks the fats into microscopic droplets for absorption.