The relationship between blood PH, ammonia excretion and adaptation to low salinity in the blue crab callinectes sapidus

Abstract

b l u e crabs absorb Na a g a i n s t a gradient, b u t n o t those i n which crabs remain i n s a l t balance w i t h t h e medium. Net a c i d o u t p u t does n o t c l e a r l y vary w i t h s a l i n i t y . The balance between ammonia and urea o u tp u t s h i f t s towards ammonotelism a t : ow s a l i n i t y . These r e s u l t s , and the temporal responses o f b l o o d NH change, support the hypothesis tha? excess ammonia i n b l o o d p l a y s an i m p o r t a n t r o l e i n osmoregulation as w e l l as opposing t h e e f f e c t of s a l t r e d u c t i o n on t h e oxygen t r a n s p o r t system. The output+of ammonia increases i n d i l u t e waters i n which , Na+ and C 1 -a f t e r a s a l i n i t y I n t h e e s t u a r i n e b l u e crab C a l l i n e c t e s sapidus Rathbun, b l o o d PH v a r i e s i nv e r s e l y w i t h a c c l i m a t i o n s a l i n i t y . The decrease i n H+ c o n c e n t r a t i o n a t low sal i n i t y o l j p o s e s t h e e f f e c t o f s a l t r e d u c t i o n on t h e oxygenation o f hemocyanin, and t h e n e t r e s u l t i s an e n a n t i o s t a t i c c o n d i t i o n o f t h e oxygen t r a n s p o r t system (Weiland and Mangum, '75). c o m i t a n t changes i n b l o o d H+ and s a l t , i t was suggested t h a t (1) t h e e l e v a t e dblood PH a t low s a l i n i t y r e s u l t s l a r g e l y from t h e b i n d i n g o f H+ t o t h e NH3 p r oduced i n c a t a b o l i s m o f f r e e amino acids, as i n t r a c e l l u l a r f l u i d s e q u i l i b r a t e w i t h a d i l u t e blood, and ( 2 ) by evidence o f increased ammonia c o n c e n t r a t i o n s a t low s a l i n i t y (Gerard and G i l l e s , ' 7 2 ) and by t h e c o r r e l a t i o n o f H+ changes w i t h osmotic and s a l t con-I n a study o f t h e r e s p i r a t o r y consequences o f con-129

Salinity-induced changes in ammonia excretion rate of the shrimp Crangon crangon over a winter tidal cycle

“…However, under simulated tidal conditions close to our own, Armitage and Morris (1982) did not observe any significant changes in amino-acid concentrations over the ebb phase nor the flood phase of the cycle. On the other hand, it was demonstrated that the active sodium uptake following the transfer into a hypotonic medium was related to an increased ammonia output (Mangum et al, 1976;Pressley et al, 1981). By contrast, a reduction of the Na+/NH4+ exchanges (Pequeux and Gilles, 1981) and a possible reversal of these exchanges (Armstrong et al, 1981) were observed following transfer into a hypertonic medium.…”

“…In conjunction with this, significant changes in ammonia excretion rate were observed in crustaceans (Needham, 1957;Haberfield et al, 1975;Mangum et al, 1976;Farmer and Reeve, 1978;Armstrong et al, 1981;Pressley et al, 1981;Spaargaren et al, 1982). However, the salinity effect on nitrogen excretion was dependent on the species and its osmoregulatory abilities.…”

Osmoregulation and salinity-induced oxidative stress: is oxidative adaptation determined by gill function?

“…Mangum et al, 1976); posterior gills contain osmoregulatory structures (e.g. Copeland and Fitzjarrell, 1968;Gilles et al, 1988;Péqueux, 1995) and constitute the important ion-regulating organs (e.g.…”

Nitrogen excretion and changes of hemocyanin, protein and free amino acid levels in the hemolymph of Penaeus monodon exposed to different concentrations of ambient ammonia-N at different salinity levels

“…Nitrogen metabolism and the role of FAA in the regulation of intracellular osmolarity and volume regulation have been widely studied and reviewed by Claybrook (1983) and Gilles & Pequeux (1983). Several studies have reported an increase of ammonia excretion and a spontaneous decrease of tissue FAA when crustaceans are exposed to hypo-osmotic conditions (Haberfield et al 1975, Mangum et al 1976). Effects of salinity on FAA composition have been examined for Kuruma shrimp Penaeus japonicus by Dalla Via (1986) and for P. monodon by Fang et al (1992).…”