Zool 250
Best Annotated Bibliography 2004
Submitted by Marie-Claire St-Jacques


Muntz, W.R.A. and S.L. Wentworth. 1989. Asymmetries in the sense organs and central nervous system of the squid Histioteuthis. Journal of Zoology 219:607-619.

Squids of the family Histioteuthidae all exhibit enlargement of the left eye in adults. These dimorphic eyes are associated with the squid's asymmetrical swimming behavior. How are the structural differences between the eyes and optic lobes related? Does statocyst structure also reflect this behavior?

Statocysts function in equilibrium and perception of the body's orientation. Histioteuthis shows a peculiar swimming behavior, which is to swim inclined at 45 degrees. This is reflected in the dimorphic character of its eyes; the left eye is bigger than the right eye, and also shows a yellow coloration, while the right eye is colorless.

Four specis of Histioteuthis were examined for lense diameter, optic lobes and statocyst volumes, retina structure and spectral absorbance of the lenses. While the size of the optic lobes reflected the size of the dimorphic eyes, the statocysts showed no size difference. Retina structure was similar in both eyes, with thicker parts on the anterior portion of the left eye and the posterior portion of the right eye. The yellow left eye absorbed light of shorter wavelength than the right eye in all four species.

The size of the dimorphic eyes are reflected in the size of the optic lobes, which is due to the fact that the left retina is bigger and therefore has more neurons. The varying thickness of the retinas supports the idea that these squids swim at an angle of 45 degrees, since the thicker areas would receive more light in that position. The reason for differences in pigment absorbance, however, is still unclear.

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(posted Jan. 23 2005)