Fish taste good too Fin rays Barbels Cirri

Mechanoreception What is sound? How is it different in water? Two primary systems for detecting vibrations (sound) and changes in water pressure 1.Lateral line system 2.Inner ear

Sensory hair cell Lateral line system—vibration sensing structure Sensory neuron Cilia Nucleus Synapse Neuromast Support cell Nerves Cupula

Exposed, free standing on skin or in grooves Function depends on species/habitat Habitats with flowing water or high turbulence – Few neuromasts Habitats with still or turbid water – Many neuromasts Lateral line system—superficial neuromasts

Individual/population level variability in superficial neuromasts Natural selection acts on sensory systems to better adapt a species to its habitat

Shielded from large-scale water motion – Better at detecting high frequency sound Lateral line system—canal neuromasts Epidermis Scale Lateral line canal Lateral line pore NerveNeuromast

Lateral line system—canal neuromasts Anterior lateral line system—pores or canals Uses of the lateral line system?

Lateral line system—toadfish example

Lateral Line—Elasmobranchs

Fish have pair of inner ear structures Two chambers—top chamber connects three semicircular canals – Canals filled with fluid & contain sensory hair cells – Acceleration & direction change Inner ear—for balance

Three otoliths – Mostly CaCO 3 —dense Otolith #1 for acceleration & equilibrium Inner ear—for balance Sensory hair cells Otolith 1 3 2

Otoliths #2-3 for hearing Lower chamber lined with sensory hair cells Sagitta—biggest otolith Inner ear—for hearing 1 3 2

Inner Ear—Pearl fish e.g.

Magnetic Reception Sensing the Earths magnetic field for navigation Poorly studied in fishes – Magnetite (FeO 4 ) & iron deposits – Lab studies Important for small- & large-scale migrations

Electric fields—a sphere where charged particles (e -, Na +, Cl - ) experience magnetic force – Salt water great conductor Organisms produce electric fields – Cells maintain voltage across membranes Neurons, muscle cells – Field fluctuates & attenuates with distance Electroreception What contributes most to a hiding fish’s electric field?

Ampullary Receptors—Ampullae of Lorenzini Arise from same precursor cells as neuromasts Detect external sources Respond to gradients in field strength – Sense size & distance Ancestral vertebrate characteristic – Secondarily lost in Neopterygii – Secondarily evolved in some teleost groups Uses? Locations?

Ampullary receptors—diversity

Ray & catfish ampullary pores