Immunolocalization of S-crystallins in the developing squid (Loligo opalescens) lens.

S-crystallins are the predominant soluble proteins of the squid lens. Of these, S-III crystallin is the major component and S-I and S-II crystallin are the minor lens components. The lens has a posterior and anterior segment, each derived from separate groups of ectodermal cells referred to as lentigenic cells. In the present study, the appearance of S-crystallins during the development of the lens of Loligo opalescens was followed by immuno-cytochemistry. S-crystallins of the lens and lentigenic cells were first observed at day 17 (Arnold stage 27) of embryogenesis. S-crystallins were not confined to a single region, but were present in the middle group (group 2) of lentigenic cells, the posterior lens primordium, and the processes connecting the lentigenic cells and the posterior lens primordium. Two days later (Arnold stage 28), the S-crystallins were also observed in the anterior group (group 1) of lentigenic cells, the anterior lens primordium, and the processes connecting the cells with the anterior lens primordium. Thus, during development, S-crystallins accumulate first in the posterior lens primordium and subsequently in the anterior lens primordium and their respective lentigenic cells and connecting lentigenic processes. Incubated sections of the adult lens and lentigenic cells also show specific immuno-peroxidase staining when compared with controls. This evidence in combination with a recent investigation (West [1993] Ph.D. dissertation), which indicates that the cephalopod lens continues to grow throughout adulthood, suggests that squid lens crystallins are synthesized during adulthood.