The components of an inorganic physiological buffer for Penaeus chinensis

Abstract

Shrimp Penaeus chinensis, 5--8 cm in body-length were held in laboratory aquaria after collection from culture ponds at Laoshan in Qingdao in 1992. The osmotic pressure and the concentration of inorganic components of hemolymph in the shrimp were measured. The optimum pH and osmolarity of the buffer were determined from tests on primary cultures of hepatopancreatocytes in vitro. The results indicate that the hemolymph is homoiosmotic to 27 ppt seawater at 870 mOsm/L; osmotic regulation of shrimp is strong in low-salinity seawater, but weak in high-salinity seawater; the concentration of Mg²⁺ ions in hemolymph is much less than that in seawater, while [K⁺] and [Ca²⁺] are much higher; hepatopancreatocytes in vitro have optimal survival at osmolarity range of 780-1, 100 mOsm/L and pH 6.5. Accordingly, an inorganic physiological buffer for P. chinensis (PPB, Penaeid Physiological Buffer) was prepared and contains NaCl, 23.0 g/L; K₂SO₄, 1.1 g/L; CaCl₂, 1.6 g/L; MgSO₄·7H₂O, 1.6 g/L; NaH₂PO₄·2H₂O, 0.35 g/L; NaHCO₃, 0.05 g/L; pH 6.5; osmolarity, 867.9 mOsm/L. For storage of PPB, 4 stock buffers are made: 1) 10× PPB-A, which contains 230 g/L NaCl, 11 g/L K₂SO₄, and 3.5 g/L NaH₂PO₄·2H₂O; 2) 40× PPB-B, which contains 64 g/L MgSO₄·7H₂O; 3) 40× PPB-C, which contains 64 g/L CaCl₂; and 4) 100× PPB-D, which contains 50 g/L NaHCO₂. In order to increase the buffering capacity, PPB may be modified (to His-PPB), in which 5 g/L Histidine·HCl is used as the buffer reagent in place of NaH₂PO₄ and NaHCO₃.