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Interspecies Effects of Sea Urchin Hyalin on Archenteron Elongation and Attachment

The sea urchin embryo is a simple model system to study the molecular basis of cellular interactions that may be important in less accessible higher organisms. Recently, using a microassay to quantitatively evaluate the effects of exogenously added molecules on sea urchin gastrulation, we found that hyalin, a large sea urchin glycoprotein purified from the hyaline layer, dramatically affected gastrulation (Razinia, et al., Zygote, in press; see abstract 307 in these proceedings). In this study, hyalin isolated from Strongylocentrotus purpuratus embryos was tested for its effects on another species of sea urchin, Lytechinus pictus. Fifty seven (57) micrograms of purified S. purpuratus hyalin/ml, in low calcium artificial sea water (ASW), were incubated with 24 hr L. pictus embryos in 96‐well polystyrene flat‐bottom microplates, containing about 12 embryos per well, for 24 hrs. Control wells contained ASW, NaCl‐KCl low calcium ASW or low calcium ASW. The results from replicate experiments were plotted as mean percentages of embryos exhibiting the following archenteron morphologies: complete attached archenterons, unattached archenterons, no invagination, exogastrulated archenterons, plus/minus standard error of the mean. Most of the hyalin treated embryos exhibited unattached archenterons, while in the controls, the archenterons were complete and attached to the blastocoel roof. Hyalin, therefore, has interspecies effects and may be involved in archenteron elongation and/or attachment to the blastocoel roof