Premium
Effects of osmolality and ions on the motility of stripped and testicular sperm of freshwater‐and seawater‐acclimated tilapia, Oreochromis mossambicus
Author(s) -
Linhart O.,
Walford J.,
Sivaloganathan B.,
Lam T. J.
Publication year - 1999
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1999.tb02080.x
Subject(s) - oreochromis mossambicus , seawater , biology , sperm , sperm motility , freshwater fish , tilapia , motility , zoology , fishery , ecology , fish <actinopterygii> , botany , genetics
A significantly higher concentration of testicular spermatozoa was obtained from freshwater Oreochromis mossambicus (9·9×10 9 spermatozoa ml −1 ) than seawater O. mossambicus (4·6×10 9 spermatozoa ml −1 ). The mean osmolality of the urine of freshwater fish (78·5 mOsmol kg −1 ) was significantly different from that of seawater fish (304·8 mOsmol kg −1 ). The mean length of the mid‐piece of the spermatozoa together with the tail was more variable in freshwater O. mossambicus (8·80±0·23μm) than in seawater specimens (8·27±0·18 μm). Stripped sperm of freshwater O. mossambicus was highly contaminated by urine which was a good activator of sperm motility in O. mossambicus held in both fresh and sea water. The osmolality for initiation of motility in freshwater O. mossambicus spermatozoa was from 0 to 333 mOsmol kg −1 while for seawater O. mossambicus spermatozoa it was from 0 to 1022 mOsmol kg −1 . The optimum osmolality for motility was from 70 to 333 mOsmol kg −1 for freshwater O. mossambicus spermatozoa and from 333 to 645 mOsmol kg −1 for seawater fish. In freshwater O. mossambicus spermatozoa, the presence of 20 mM CaCl 2 increased the permissive osmolality of NaCl from 184 to 645 mOsmol kg −1 . For seawater O. mossambicus spermatozoa, solutions of NaCl devoid of CaCl 2 were unable initiate motility, but the addition of 1·5 to 30 mM CaCl 2 to the NaCl solution (0–934 mOsmol kg 1 ) had a full motility initiating effect.