The development of embryos and larvae of the Atlantic cod, Gadus morhua, with particular emphasis on the ontogeny of chloride cells

• Main Author: Valerio, Paul F.(Paul Federico)
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1995
• Subjects: atlantic cod; Gadus morhua
• Online Access: https://research.library.mun.ca/9854/; https://research.library.mun.ca/9854/1/Valerio_PaulFederico.pdf

Chloride cells are mitochondria-rich ion-transporting cells (ionocytes) that secrete chloride from epithelial surfaces. The origin and differentiation of presumptive chloride-secreting cells in Atlantic cod (Gadus morhua) were studied by a combination of light and electron microscopy. -- By examination of available literature data, in conjunction with data collected from the present study, estimates of the effect of temperature on hatching time in the Atlantic cod were made. Subsequently, methods for the localization of chloride cells were developed, and compared with classical methods of staining ionocytes. Ionocytes were stained using conventional mitochondrial dyes, potential-sensitive fluorescent mitochondrial dyes (including styryl and rhodamine dyes, and a novel aldehyde-fixable rhodamine derivative), a fluorescent probe for the Na⁺, K⁺-ATPase (the ouabain derivative, anthroyl-ouabain), a cardiolipin-specific probe (nonyl-acridine orange), tetracycline, a lipophilic membrane probe (DiOC₆(3)), and conventional precipitation methods for ion localization. -- Staining methods were used to examine the gradual differentiation of ionocytes from mitochondria-rich precursor cells. This information was applied to the analysis of chloride cell differentiation from the embryonic stages through to maturity. -- The development of Atlantic cod embryos and larvae was then observed under various salinity and temperature conditions, and in the presence of hormone or vitamin-supplemented media, to determine the potential role of exogenous factors on the timing of chloride cell differentiation. -- A variety of secretory cells, including sacciform, goblet and ionocytes, developed in the epidermis of cod embryos and larvae. In the embryo, ionocytes first appeared on the yolk sac and buccal/gill (oropharyngeal) cavity epithelium. Such cells were lenticular, and often had a large multilobed nucleus. Some appeared to be binucleate. Beyond yolk sac absorption, ionocytes appeared on the gill filament epithelium, and were retained on ...