A. Hassan

Erythrocyte characteristics of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

In this study, erythrocyte characteristic of pure and reciprocal crosses of African catfish Clarias gariepinus (Burchell, 1822) and Asian catfish Pangasianodon hypophthalmus (Sauvage, 1878) were evaluated. Blood smear was made from the progenies of C. gariepinus (CG), P. hypophthalmus (PH), Pangapinus (♀PHxa0×xa0♂CG) and in two morphotypes (Clarias-like and Panga-like) of Clariothalmus (♀CGxa0×xa0♂PH) obtained from similar breeding history. Erythrocyte measurement of the cell and nuclear axis was done under the microscope, while many other parameters were calculated. Result obtained suggests a preponderant maternal influence on the erythrocytes shape and size characteristics of the reciprocal crosses. Erythrocytes from progenies with C. gariepinus maternal origin was rounded in shape (not less than 90%) while those with P. hypophthalmus maternal origin had relatively high oval shaped erythrocytes (between 76 and 64%). Also, significant size variations were recorded for the different group. Principal component analysis and biplot of component loading of the trio comparison of hybrid progenies and the pure crosses suggest the possibility of discriminating the direction of hybridization of the reciprocal crosses. However, it was impossible to describe the hybridization status of the progenies assessed in this study. This approach may be a simple and viable alternative to molecular markers which characterizes maternal inheritance in hybrid crosses provided that there is significant shape difference between the fishes. Erythrocyte characterization coupled with morphological and cytogenetic studies is recommended for clearer understanding of the nature of hybrid progenies.

Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

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 (♀PHu2009×u2009♂CG) and the two distinct morphotypes of the Clariothalmus (♀CGu2009×u2009♂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.

Hematological parameters of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

Comparative study on the hematological parameters of pure and reciprocal crosses of the African and Asian catfish was done to establish a reference range for fingerlings of the novel fish. Blood was collected from Clarias gariepinus (CG), Pangasianodon hypophthalmus (PH), Pangapinus (♀PHu2009×u2009♂CG), and the two observed morphotypes (Clarias-like and Panga-like) of Clariothalmus (♀CGu2009×u2009♂PH) obtained from similar breeding history. Result obtained revealed that red blood cell counts and white blood cell counts were significantly lower in Panga-like Clariothalmus (1.08xa0×xa0106/mm3 and 6.99xa0×xa0103/mm3, respectively) compare to other groups with similar higher counts (between 2.09xa0×xa0106/mm3 and 2.65xa0×xa0106/mm3; 13.60xa0×xa0103/mm3 and 17.27xa0×xa0103/mm3, respectively). However, Pangapinus and pure P. hypophthalmus had significantly higher values of packed cell volume (33.10 and 32.50%, respectively) and hemoglobin content (12.63 and 11.72xa0g/dL, respectively); similar values were recorded in those fish with Clarias maternal origin (between 25.00–27.80% and 6.67–8.03xa0g/dL, respectively for PCV and Hb). Calculated values for mean corpuscular volume was higher in Panga-like Clariothalmus (198.8xa0fL and 80.26xa0pg, respectively) while mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration values were higher in the Pangapinus and pure P. hypophthalmus (between 48.10–56.98xa0pg and 38.28–35.96xa0g/dL, respectively). This result obtained is suggestive that the Panga-like Clariothalmus may have reduced fitness as compared to the other progenies. The baseline values established in this study could serve as a standard for physiological, pathological, and toxicological references in future studies.