Fishes Lecture 4: Vision and Chemoreception

Chemoreception

Occurs in numerous locations in the body and includes olfaction and gustation

Olfaction

(Smell) epithelium of olfactory rosette within nose and innervated by 1st cranial nerve

Gustation

(Taste) dispersed through the buccal cavity, sensory barbels (mouth and head) and innervated by 7th, 9th and 10th cranial nerves

4 major chemicals that act as olfactory stimuli

Amino acids, sex steroids, prostaglandins and bile acids/salts

Olfactory functions

Deletion of food, predators, mates alarming substances and orientation to its environment

How are the nostril, olfactory sac and mouth connected?

THEY AREN’T (except for lungfish)

Forward propulsion

(Ram ventilation) How water is circulated and pumped by constriction of sensory and accessory nasal sac (sniffing) cilia in olfactory sac

Olfactory rosettes

Flower-like organs in fish that detect specific odors in water (like to find food, mates, avoiding predators, etc.)

Lamella

Folded tissues that help detect chemical cues in the water (made up of sensory cells)

Sensory epithelium

Located on the olfactory rosette and is dependent on size (importance of the sense). Like how eels have a large rosette and olfactory lobe while pufferfish have a small rosette and olfactory lobe because they rely on sight for feeding

Olfactory receptors

Are unevenly distributed (different sized rosettes and lamelle produce different levels of smell)

Sensory information patterns

Rosettes→olfactory nerve→olfactory lobe→cerebrum

Taste buds

The primary sensory organ and are comprised of 100-150 elongate gustatory (sensory) cells within microvilli

Tongue/palate epithelium

Where mammals taste buds are located

Mouth/pharynx

Where elasmobranchs taste buds are located

Mouth, gill arches/rakers, pectoral fins, barbels, scales

Where teleosts taste buds are located

7th cranial nerve

Impulses (action potentials) from the skin

9th and 10th cranial nerve

Where impulses (action potentials) from the mouth

Bitter, sweet, salty and sour

What fish can taste

In response to amino acids, nucleotides, quinine, CO2 and H+

They are able to detect food from a distance, assess food quality and avoid potential toxins

Higher than humans for acidity and lower for salts and sugars

How fish have different sensitivities to tastes than humans

Photorecpetion

How light runs from 400-700nm in red, yellow, green, blue and purple

How light gets absorbed in water

You are able to see purple/red up top and blues/greens at the bottom

Surface condition, wavelength of light entering, abiotic and biotic factors

What light penetration is determined by

Fish eye

The lens “bulges” through opening pupil (almost touches the cornea) and allows for a wide field of view like 260 or some even 360