Osmoregulation and Total Serum Protein of Two Species of Penaeidean Shrimps From the Pacific Coast of Mexico

Abstract

Stress caused by different salt concentrations has been detected by measurements of total protein and total osmotic pressure in blood serum of Penaeus vannamei and P. stylirostris. P. vannamei is more tolerant despite the fact that P. stylirostris naturally occurs in coastal areas where conditions are virtually marine with little fresh-water influence. The effect of low salinity on survival is similar in both species and appears to be less important in controlling their distribution during the year. A very significant decrease in total blood protein is observed for P. stylirostris at a salinity of 50‰ associated with an extremely high osmotic pressure in an effort to osmoregulate. Hemocyanin may be an important osmoregulatory factor producing free amino acids at high salinities.