Contrasting strategies of osmotic and ionic regulation in freshwater crabs and shrimps: gene expression of gill ion transporters [RESEARCH ARTICLE]

Milene Mantovani and John Campbell McNamara Owing to their extraordinary niche diversity, the Crustacea are ideal for comprehending the evolution of osmoregulation. The processes that effect systemic hydro-electrolytic homeostasis maintain hemolymph ionic composition via membrane transporters located in highly specialized gill ionocytes. We evaluated physiological and molecular hyper- and hypo-osmoregulatory mechanisms in two phylogenetically distant, freshwater crustaceans, the crab Dilocarcinus pagei and the shrimp Macrobrachium jelskii, when osmotically challenged for up to 10 days. When in distilled water, D. pagei survived without mortality, hemolymph osmolality and [Cl–] increased briefly, stabilizing at initial values, while [Na+] decreased continually. Expression of gill V-type H+-ATPase (V-ATPase), Na+/K+-ATPase and Na+/K+/2Cl– symporter genes was unchanged. In M. jelskii, hemolymph osmolality, [Cl–] and [Na+] decreased continually for 12 h, the shrimps surviving only around 15–24 h exposure. Gill transporter gene expression increased 2- to 5-fold. After 10 days exposure to brackish water (25S), D. pagei was isosmotic, iso-chloremic and iso-natriuremic. Gill V-ATPase expression decreased while Na+/K+-ATPase and Na+/K+/2Cl– symporter expression was unchanged. In M. jelskii (20S), hemolymph was hypo-regulated, particularly [Cl–]. Transporter expression initially increased 3- to 12-fold, declining to control values. Gi...
Source: Journal of Experimental Biology - Category: Biology Authors: Tags: RESEARCH ARTICLE Source Type: research