Fish & Invertebrate Otorhinolaryngology

Question 1

Describe the auditory anatomy of fish.

What is the labrinth composed of?

What are otoliths?

How does the swim bladder play a role in hearing?

What are the three methods of sound production in fish?

Answer 1

Auditory Anatomy

• Acoustic organs - info on acoustic stimuli, gravity forces, linear and angular acceleration
• Labyrinth -> semicircular canals, inner ear ampullae, otoliths or otoconia
  
  • Otoliths - calcified stones overlay sensory epithelium, surrounded by endolymph - facilitates their movement for sound perception and equilibrium
    
    • Most ray-finned - single otolith per chamber, but can be several
    • Can be used for age and bony fish ID
  • Pathology of inner ear can lead to loss of equilibrium
• Swim bladder and other gas cavities - conduct sound w/ bones known as Weberian apparatus (carp, bowfin, tetras, etc.)
• If direct/indirect connect from swim bladder to perilymphatic system (inner ear) allows high frequency perception (carp, catfish > cod)
• Three methods of sound production
  
  • Stridulatory (teeth, fins, spines, bones)
  • Hydrodynamic (swimming movements)
  • Muscle vibrations around swim bladder
• Clinically - difficult to evaluate these structures
  
  • Swim bladder, otoliths - XR, CT, MRI
  • Swim bladder disease may result in reduced functional hearing (catfish - reduced freq. range)

Question 2

Describe olfaction and gustation in fish.

How is smell detected in fish?

What species have large olfactory pits? What species lack nasal sacs?

Where are taste buds found on fish?

What are the three anatomically different taste buds?

Answer 2

Olfactory and Gustatory Anatomy

• Water-soluble chemicals detected by olfaction (smell) or gustation (taste)
• Paired nares on rostrum w/ olfactory epithelium; hagfish + lampreys have only single naris
  
  • Water 🡪 nares 🡪 stimulates receptors 🡪 signal 🡪 olfactory bulbs w/in forebrain (telencephalon)
    
    • Some have nasal sacs/accessory nasal sacs 🡪 actively pump water over epithelium
  • Some rely heavily on olfaction w/ large olfactory pits (moray eels, true eels)
• Some visual reliant, lack nasal sacs (pufferfish)
• Some species - males have more developed olfaction
• Taste buds - epidermal, in oral cavity, lips, head, barbels, body all, fins, esophagus
  
  • In some, external outnumber internal by as much as 90%
  • Up to 3 anatomically different taste buds - amino, nucleic and organic acid reception
  • Do have aversive and preferential responses but extensive research has not been done