Role of sodium bicarbonate on the initiation of sperm motility in the Japanese eel

ABSTRACT:   In order to find out the role of sodium bicarbonate (NaHCO₃) on the initiation of sperm motility in the Japanese eel Anguilla japonica , interactions were investigated between NaHCO₃ and various reagents (K⁺ channel blocker 4-aminopyridine [4-AP], ammonium chloride [NH₄Cl], sodium acetate and calcium chloride [CaCl₂]) that could regulate internal factors (intracellular K⁺, intracellular pH [[pH]_i] and intracellular Ca²⁺) in sperm motility. Contradictory effects of NaHCO₃ were observed (i.e. an inhibitory effect when 4-AP was absent and a promoting effect when 4-AP was present). Sodium bicarbonate inhibited the initiation of sperm motility in the Japanese eel. However, NaHCO₃ restored the motility of immotile sperm that 4-AP inhibited. The inhibitory effect of NaHCO₃ disappeared with the addition of NH₄Cl, which raised [pH]_i, but the promoting effect was not affected by [pH]_i. Although NaHCO₃ recovered motility in the presence of 4-AP, this recovery was also observed with the addition of CaCl₂ instead of NaHCO₃. In the initiation of sperm motility in the Japanese eel, two roles for NaHCO₃ are suggested: an inhibitory role relating to the regulation of [pH]_i and a promoting role relating to the uptake of another initiation factor, which could be Ca²⁺.     

Population structure of the climbing perch,Anabas testudineus,in the lower Mekong River basin

Abstract Genetic variation in the climbing perch Anabas testudineus (Bloch) was investigated by sequencing 1047 base pairs of the mitochondrial ND2 gene. A total of 367 fish samples were collected from the Mekong River. The samples were separated into two genetically differentiated intra‐specific groups, the Laotian and Cambodian group, showing a population structure roughly in accordance with geographical location. Genetic differentiation between groups was confirmed by high pairwise F‐statistic values (0.52–0.98). Molecular clock analysis indicated that both populations were separated approximately 240 000 years ago. Additionally, samples within both groups could be divided into several regional small populations. Their genetic variation might have been supported not only by environmental factors including physical barriers, but also by historical events such as migration routes and/or timing of invasions into the Mekong River. These results could be valuable in identifying management units for the conservation of the species and its resource.