[Immunocytochemical studies on the phase of differentiation of hatching gland cells in brine shrimp, Artemia salina].

Hatching enzyme (HE), synthesized in hatching gland cells (HGCs), plays vital roles in animal hatching. Immunocytochemical techniques employing anti-GST-UVS.2 antiserum, prepared from Xenopus HE and with specificity to brine shrimp HE, were first used to investigate the differentiation and variability of hatching gland cells (HGCs) in the hatching process of embryos of brine shrimp, Artemia salina, in this study. HGCs with immunoreactivity to anti-GST-UVS.2 antiserum were identified, for the first time, in brine shrimp embryos during hatching process. Immunocytochemical staining results showed that, (1) HE-positive immunoreactivity is really specific to Artemia HE, and its appearance and disappearance are closely correlated with the hatching process of Artemia salina. (2) Artemia HGCs, first appeared in embryos 5 hours before hatching and disappeared 4 hours after hatching, were also a transient type of cells, with an existence period of 9 hours. (3) The head portion of Artemia embryo is probably the initial position of HE secretion, and likely to be the main position of HE secretion as well. The detailed process and mechanism need to be studied. (4) The appearance of HGCs is in a synchronous mode from places all over the embryos, and their disappearance is also in a synchronous mode. (5) The number of HGCs increased gradually along with embryo development process and reached a maximum number at hatching. Contrarily, the number of HGCs decreased gradually after hatching, and HGCs disappeared 5 hours after hatching. However, the intensity of HE-positive reaction was almost at the same level at the period of HGCs'presence. (6) Artemia HGCs were distributed throughout the body of embryos at all time during their presence. Therefore, it can concluded that Artemia HGCs, as a transient type of cells, first appeared in embryos 4 hours before hatching and disappeared in embryos 5 hours after hatching, and with distinguished patterns of appearance, disappearance and distribution in embryos. What is the final destiny of Artemia HGCs after hatching? And what is the biological significance of remanet HGCs, still existing until 4 hours after hatching, in fresh-hatched Artemia larvae? Is it possible that the HGCs are involved in larvae yolk digestion? Moreover, what is the molecular mechanism of HGCs' synchronous sudden appearance and disappearance? All these questions remain to be further studied and approved.