EYES OF DEEP-SEA CRUSTACEANS

II. SERGESTIDAE

¹ From the Woods Hole Oceanographic Institution and the Biological Laboratories, Harvard University

1. Fourteen species of Sergestes have been taken in closing nets from the western part of the North Atlantic and the size and structure of their eyes have been related to the depth at which certain species occur and to the presence or absence of photophores.

2. Sergestes mollis is ordinarily taken below the photic zone and this species lacks photophores. The corneal portion of the eye of this form is smaller in relation to body size than is that of any other species studied. The eyes, however, are not so degenerate structurally as those of Hymenodora glacialis, an acanthephyrid having a similar vertical distribution.

3. Sergestes tenuiremis, S. grandis, S. crassus and S. robustus have been shown to possess organs which are probably photophores and these four species have the largest eyes in respect to body size of all which have been studied. Hence it may be concluded that the production of light by such an organism influences in some way the development of the eye. This agrees with the findings on the acanthephyrids.

4. The remainder of the sergestids studied which live within the photic zone have eyes smaller than those which possess photophores and in certain cases (S. arcticus and S. armatus) the pigmentation of the eye is quite unusual.