Abstract
Twenty-five traditional and thirty-four geometric morphometric comparisons were carried out on pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822). Thirty fish samples each of the C. gariepinus (CH), P. hypophthalmus (PH), Pangapinus (♀PH × ♂CG) and the two distinct morphotypes of the Clariothalmus (♀CG × ♂PH) (Clarias-like and Panga-like) between the ages of four and six months were used for this study. Phenotypically, the Clarias-like Clariothalmus and the Pangapinus progenies were indistinguishable from their maternal parents while the Panga-like Clariothalmus was a phenotypic intermediary of the putative parents but looks more closely to the paternal parent. Hence, both univariate proportion and multivariate analysis of the collected data successfully separated the different fishes into three multivariate spaces. The analysis of the dendrogram with complete linkage and Euclidean distance further showed the close relationship of the isolated Panga-like Clariothalmus progenies to the paternal parent, however, Clarias-like Clariothalmus and the Pangapinus were completely intermingled with their maternal parents. The most important index of discrimination of these fishes into different multivariate spaces was the fin characteristic which showed 100% exclusive ranges for the individual groups in many cases.
Highlights
The need for genetic improvement and aquaculture diversification has been the justification for hybridization in fishes
One portion was used for the production of pure progenies (♀CG × ♂CG and ♀P. hypophthalmus (PH) × ♂PH); while the other portion was used for the reciprocal crosses Clariothalmus (♀CG × ♂PH) and Pangapinus (♀PH × ♂CG)
To ensure that variations in this study were only attributed to body shape differences, and not to the relative sizes of the fish, size effects from the data set were eliminated, by standardizing the morphometric parameters using the allometric formula given by Elliott et al.[20]: Madj = M (Ls/Lo)b; where M is the original measurement, Madj is the size-adjusted measurement, Lo is the total length (TL) of the fish, and Ls is the overall mean of the TL for all fish from all samples
Summary
Standard length (Snout to the median of the attachment of the caudal fin to the tail). Dorsal attachment of the caudal fin to the tail to the posterior point of the eye. Ventral attachment of the caudal fin to the tail to the posterior point of the eye. Dorsal attachment of the caudal fin to the tail to the posterior end of the anal fin. Geometric morphometric on the other hand is a landmark-based technique and considered the most rigorous morphometric technique ever[9,10,11] It is capable of processing morphometric data from digital images with landmark points quickly and with high precision[9,12,13]. We produced novel hybrid progenies from intergeneric crosses of Asian catfish Pangasianodon hypophthalmus (S.) and African catfish Clarias gariepinus (B.)[17,18]. 6.76 ± 0.09c 17.78 ± 0.21a 33.17 ± 0.18a 36.21 ± 0.19a 4.34 ± 0.07a 10.87 ± 0.18a 42.97 ± 0.29c 4.52 ± 0.06c 14.99 ± 0.17a 30.67 ± 0.22c 12.82 ± 0.13a 10.50 ± 0.15a 25.42 ± 0.34a 8.41 ± 0.07a 22.66 ± 0.19a 13.13 ± 0.17c
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