Dogfish hair cells sense hydrostatic pressure

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Dogfish hair cells sense hydrostatic pressure

• By Peter J. Fraser, Richard L. Shelmerdine

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BACKGROUND

• Many marine invertebrates and fishes do not have
  swim bladders.
• Swim bladders are used in most marine vertebrates
  to detect pressure and respond to it.
• The vestibular system helps maintain balance.
• When one ear of a dogfish is cut of, the fish
  swims towards that side when both ears are cut
  off, the dogfish swims in any direction (Pincher,
  1948).

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Dogfish (Scyliorhinus canicula)
http//www.fishing-in-wales.com/wildlife/fishes/do
gfish1.htm
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PURPOSE

• To study the effect of hydrostatic pressure on
  the vestibular hair cells in the labyrinth of the
  dogfish (Scyliorhinus canicula)

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QUESTIONS?

• Do vestibular hair cells modulate spontaneous
  activity?
• Do vestibular hair cells modulate response to
  angular acceleration?
• Why do vertebrate hair cells have low resting
  activity?
• How do fish without swim bladders sense
  hydrostatic cues?

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METHODS

• Labyrinths of seven Dogfish were placed in a
  pressure chamber and oscillated at 1 Hz at 70
  degrees Celsius every two minutes.
• A computer controlled pressure regulator was used
  to change the pressure inside the chamber.
• Spike frequencies of vestibular type-II hair
  cells were recorded

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Figure 1. Extra cellular recording of spike
frequencies of dogfish hair cells in pressure
chamber with increasing pressure
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CONCLUSION

• Dogfish hair cells responded differently to
  oscillations when pressure increased and
  decreased.
• Increased pressure caused increased response to
  oscillations and decreased pressure caused
  decreased response to oscillations.
• Increases in the activity of vertebrate hair
  cells in response to oscillations under higher
  pressure imply a mechanism by which dogfish may
  sense depth.

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REFERENCES
Fraser, P.J. and Shelmerdine, R.L. (2002) Dogfish
hair cells sense hydrostatic pressure. Nature.
415. 495 496 Pincher, C. 1948. A Study of
Fish, 1st Edition. Duell, Sloan and Pearce, Inc,
New York, 342pps. http//www.fishing-in-wales.com
/wildlife/fishes/dogfish1.htm