Feeding, Digestion, & Trophic Adaptations : Fish Biology Midterm II

Teleost Digestive Tract Flow

Buccal Cavity → Esophagus → Stomach → Phyloric Caeca → Intestines

Buccal Cavity

Captures and Manipulates prey; lined with mucus cells and taste buds

Esophagus

Distensible passage featuring voluntary striated muscle transitioning to involuntary smooth muscle

Stomach

Executes mechanical triturating; secretes pepsinogen and HCL for chemical protein breakdown

Pyloric Caca

Blind pouches located at the pyloric sphincter that increase total absorptive surface area

Intestines

Primary site of enzymatic hydrolysis and nutrient absorption; length scales with herbivory vs. carnivory

Herbivory Intestines

longest intestines, coiled in the body to increase mineral extraction (some have bacteria in gut)

Terminal

opens forward at snout tip; active midwater column predators

Inferior/Ventral

Opens downwards towards the bottom; typical of benthic (sea floor) species

Superior

Opens upwards towards the surface; surface-feeding specialists

Pharyngeal Jaws

Modified 5th branchial arch elements located in the throat used to rake, crush, reposition, or immobilize prey before swallowing

Morary Eel Raptorial Feeding

Living in tight reef crevices limits head expansion and suction generation. Mobile, raptorial pharnygeal jaws with sharp recurved teeth that extend forward into the oral cavity to grip prey and transport it into the esophagus

Digestion

Herbivorous teleosts rely on endosymbiotic gut microflora (specialized bacteria) executing anaerobic microbial fermentation to break down complex structural agal cell walls

Bluespine Unicornfish vs. Sohal Surgeon fish

Each microbe is specialized to break down the kinds of algae their host fish eat

(Bluespine Univorn fish: eat mostly brown algae and have microbes of Type J; Sohal Surgeonfish: eat mostly red and green algae and have Type A1 microbes)