Morphometric and Meristic Divergence of Two Hybrid Catfish: Backcross (F1 hybrid female x Pangasianodon gigas Chevey 1931 male) and Reciprocal Backcross (P. gigas, female x F1 hybrid male)

Abstract

The parental F1 hybrids (Pangaisianodon gigas, PG Chevey 1931, male x Pangasianodon hypophthalmus, PH (Sauvage 1878), female) were used as brood-stock. The two new catfish hybrids, backcross, BC {F1 hybrid, female x PG, male} and reciprocal backcross, RCBC {F1 hybrid (male) x PG (female)} were successfully produced. Both the BC and the RCBC types showed fast growth; however, at the fingerling stage it is very difficult to distinguish between the two hybrids because of their very similar morphology. The aim of this study was to identify the characteristics of BC and RCBC types and to compare the results with two purebred catfish specimens (PG and PH) at a total length of 13-15 cm. using 14 morphometric and 4 meristic measurements, respectively. The parental hybrid catfish were produced from PG (male) x PH (female). The results revealed statistically significant differences (p< 0.05); the BC exhibited distinct variations in anal fin height, anal fin length, body depth (BD), body width (BW), and head length (HLSL) from the other fish. The RCBC showed the highest level of distance from snout to isthmus (DSI) and dorsal fin length (DFL). A multifactor analysis (MFA) was used to perform clustering after the principal component analysis (PCA) had been done from both the morphometric and meristic traits and indicated that the backcross was greater in terms of BD and BW parameters when compared with the other groups. The RCBC, however, was intermediate between the two purebreds. The combined morphometrics and meristics data demonstrated that the BC and the PH had the most divergent morphology. The original group cases correctly classified the results for the morphometric and meristic characteristics, and their combined data from all the results were 100%, 66.1% and 100%, respectively. The results indicated that the two catfish species and their hybrids were highly different from one another and all characteristics except the dorsal fin ray count could be utilized for the identification of the two pangasiid catfish species and the two hybrids at the fingerling stage.