Immunolocalization of Na+,K+-ATPase in Osmoregulatory Organs During the Embryonic and Post-Embryonic Development of the Lobster Homarus Gammarus

Abstract

Immunolocalization and ontogenetical changes in |${\text{Na}}^{+},{\text{K}}^{+}{\text{-ATPase}}$| were investigated in the antennal glands, intestine, and branchial cavity in developing Homarus gammarus. The antennal glands lined by undifferentiated cells are detectable in embryos at stage |${\text{EI}} \,150\, {\rm{\mu m}}$| (EI: eye index; |$640\, {\rm{\mu m}}$| at hatching). From a mesodermic sac and an ectodermic tubular epithelium |$({\text{EI}} \,225\, {\rm{\mu m}}$)|⁠, they develop into coelomosac, labyrinth, and bladder up to larval stage II. In larval stage III, the end parts of the labyrinth fold inward. In the first post-larvae, the coelomosac is completely enclosed in the folded labyrinth, there is no nephridial tubule. The definitive organization of the antennal gland found in adults is achieved in post-larval stage V. At |${\text{EI}} \,425\, {\rm{\mu m}}$|⁠, the intestine epithelium is composed of cuboidal cells, and the branchial cavity is already formed at |${\text{EI}} \,325\, {\rm{\mu m}}$|⁠. The presence of |${\text{Na}}^{+},{\text{K}}^{+}{\text{-ATPase}}$| was detected on the basolateral side of ionocytes lining the epithelium sac of the antennal gland starting at |${\text{EI}} \,425\, {\rm{\mu m}}$|⁠, in the intestine at |${\text{EI}} \,625\, {\rm{\mu m}}$|⁠, and in the epipodites of the branchial cavity at |${\text{EI}} \,525\, {\rm{\mu m}}$|⁠. In post-larvae (stage V), a strong fluorescence was also found on the inner-side of the branchiostegite epithelium. Thus the ontogeny of the osmoregulatory epithelia is completed only after metamorphosis and it conditions the occurrence of the adult pattern of osmoregulation.