Activity of the pituitary gland in embryo and larval stages of coho salmon, Oncorhynchus kisutch

Abstract

L~ATHERLAND, J. F.,andL. LIN. 1975. Activity ofthe pituitary gland in embryo and larval stages of coho salmon, Oncorhynchus kisutch. Can. J . Zool. 53: 297-310. Embryos of coho salmon appear to regulate their internal osmotic environment actively before hatching (Weisbart 1%8). However, at the time of hatching the pituitary contains only small numbers of differentiated cell types and it is only within the 1st week after hatching that a rudimentary follicular rostral pars distalis containing active eta (prolactin) acidophils becomes apparent. This suggests that prolactin, which in adult salmonids appears to be involved in freshwaterosmo(iono)regulation, may not be involved in the same way in the early larval stages.Late-stage coho alevins can withstand ambient salinities up to 65% seawater for a period of 3 to 4 days. Under these conditions the prolactin cells become less active than in similar fish acclimated to distilled water or well water. The data indicate that the endocrine regulation of freshwaterosmo(iono)regulation in late alevins and early fry stages may be similar to that found in adults. The evidence for the involvement of other pituitary factors in the hydromineral regulation of coho fry in hypoosmotic or hyperosmotic environs is i~conclusive.Morphological studies of the chorion of the egg and of the yolk sac of the embryo and alevin suggest that these organs are not actively involved in hydromineral regulation. LEATHERLAND, J. F., et L. LIN. 1975. Activity of the pituitary gland in embryo and larval stages of coho salmon, Oncorhynch~ts kis~rtch. Can. J . Zool. 53: 297-310.Chez les embryons de saumons argentis, il s m b l e y avoir une Ggulation active de la pression asrnotique interne avant l'iclosion (We~sbart I=). Cependant. au moment de I'tclosion, I'hypophyse ne contient quhn petit nombre de types diferenciks de cellules et ce n'est qu'au cours de la sernaine qui suit I'kclosion qu'apparait un rudiment de pars d~stalis rostralefollicufa~re contenant des acidophlles eta (pmlactine). La prolactine qui.chez les salmonidae aduttes. semble jouer un r6le dans la regulation dc la pression osmotique (ionique) en eau douce, pournit ne pas 2tre impliquee de la m2me f s o n durant les premiers stades larvaires.Les alevins avances du saumon argente peuvent tolerer des salinites ambiantes allantjusqu'a 65% d'eau de mer pour une pkriode de 2 ? I 3 jours. Dans ces conditions, les cellules a prolactine deviennent moins actives que chez des poissons similaires acclimads a de I'eau distillee ou a de I'eau de puits. Les donnees indiquent que le contr6le endocrinien de la rkgulation osmotique (ionique) en eau douce chez les alevins avances et les petits tacons serait semblable ?I celui que I'on rencontre chez I'adulte. L'hypothese selon laquelle d'autres facteurs hypophysaires seraient impliquts dans la kgulation hydrominerale des tacons en milieux hypoosmotique et hyperosmotique n'est pas appuyee par des preuves suffisantes.L'examen morphologique du chorion de I'a~uf et du sac de vitellus de I'embryon et de I'alevi...

Structure of the yolksac epithelium and gills in the early developmental stages of rainbow trout (Salmo gairdneri) maintained in different ambient salinities

“…The ultrastructure of the yolksac epithelium in rainbow trout was similar to that of coho salmon, 0. kisutch (Leatherland & Lin 1975). In early embryos it does not appear to contain significant numbers of cell types possessing the capability for active osmoregulation and/or ionoregulation .…”

“…The structure of the yolksac epithelium was essentially the same as that in coho salmon, Oncorhynchus kisutch (Leatherland & Lin 1975). It consisted of an outer layer of cells which formed an intact epithelium exposed to the ambient medium, and one to two layers of basal cells (Fig .…”

Immunohistochemically detected ontogeny of prolactin and growth hormone cells in the African catfish Clarias gariepinus

“…In addition, the endocrine actions of GH and PRL may vary among species. Thus far the ontogeny of GH-and PRL-expressing-cells has been studied by light microscopy or electron microscopy combined with histochemical and later on immunohistochemical identification in teleosts such as Anguilla anguilla [2], Cynolebias whitei [35], Dicentrarchus labrax [8], Hexogrammos otakii [20], Oncorhynchus mykiss [36], Oncorhynchus kisutch [24], Oreochromis mossambicus [19], Oryzias latipes [37], Pleuronectes platessa [12], Poecilia reticulata [21] and Sparus aurata [31]. A single histochemical study of development has been reported for a catfish, Clarias batrachus [5].…”

Environmental influences on prolactin cell development in the cyprinodont fish, Cynolebias whitei

“…This indicates that the osmoregulatory func tion of PRL cells is developed shortly after hatching. The inactivation of PRL cells in Oncorhynchus kisutch alevins transferred to 65% SW (Leatherland and Lin 1976) and the increase in the size of PRL cell nuclei in larvae of the 599 marine tcleost Hexagrammus atakii transferred to FW (Ichikawa 1973), have also led to the conclusion that PRL cells are involved in the control of osmoregulation shortly after hatching.…”

“…Immunocytochemical evidence for the presence of PRL cells in the pituitary of two cyprino dont fishes at the time of hatching has been published re cently (Schoots et al 1983). Ichikawa (1973) and Leatherland and Lin (1976) have exposed newly hatched fish to environments with different salinities to investigate the osmoregulation of these animals. The differences that appear in the size of PRL cells or PRL-cell nuclei suggest that PRL controls osmoregulation shortly after hatching.…”