Eye structure of the phyllosoma larva of the rock lobster Jasus edwardsii (Hutton, 1875): How does it differ from that of the adult?

Abstract

Summary During the planktonic phase of Jasus edwardsii (Hutton, 1875), its eye increases in size from ca. 100×180 to 1000×1800 μm, while central facets grow from 24.5 to about 60 μm in diameter. Adults possess square facets, but up to the puerulus stage the facets of the larvae are hexagonal. In both the phyllosoma and the adult, 7 retinula cells form the bulk of the rhabdom, but while in the adults a small finger-like and banded “distal rhabdom” is distinguishable from the more voluminous, multilobed, non-banded “proximal rhabdom”, the phyllosoma rhabdom is always spindle-shaped and banded throughout. A clear-zone, separating dioptric from photoreceptive structures in the adult, is absent from the phyllosoma eye. The eye of the phyllosoma, therefore, cannot function on the principle of superposition, although it would seem capable of e-vector discrimination. The latter capacity could be useful for navigational purposes and would enhance contrasts under water. Collectively the structural differences between the phyllosoma and adult eye suggest that overall light sensitivity of the eye is increased at the expense of e-vector discrimination as soon as the young rock lobsters change from a planktonic to a benthic life style.