Polymorphic β and γ Lens Crystallins Demonstrate Latitudinal Distribution of Threatened Walking Catfish Clarias batrachus (Linn.) Populations in North-western India

SDS-PAGE profiles of soluble eye lens nuclei proteins of walking catfish, Clarias batrachus (Linn.) revealed the existence of eight distinct porymorphs along the western region of Uttar Pradesh, India. On the basis of their molecular weights (M sub(r)) and isoelectric points (pI), the polypeptides were identified as beta - and gamma -crystallins. The crystallins characteristically focused between pI values of 5.2 to 8.7 and had molecular weights of 19 to 34 kDa. Statistical analysis of polymorphs within random catches indicated a latitudinal pattern of fish distribution. We propose that the observed distribution pattern is the consequence of limited terrestrial migration of C. batrachus. Nocturnal migration to nearby water bodies is its outstanding characteristic as an air-breathing and walking silurid, specifically during rainy season. Population substructure is genetically recognizable into three zones: upper, central and lower; out of which the latter two are most inhabited. F-value according to ANOVA was 1.095 indicating that at different locations, polymorphs existed in differing frequencies (p = 0.375). Present results thus suggest that with the exception of the flood-prone locations, selection pressures which have limited the output of this threatened catfish have not disturbed the homogeneity of population structure in the investigated region.