Evaluation of Maturity and Ovarian Development of the Hybrids of African Catfish, Clarias gariepinus and Indian Catfish, Clarias batrachus in Comparison to Their Control Siblings

Abstract

Histological study to evaluate maturity of four crosses of African   catfish,   Clarias   gariepinus   and    Indian   magur,    Clarias batrachus (Cg ♀x Cg ♂, Cb♀x Cb♂, Cg ♀x Cb♂ and  Cb♀ x Cg ♂) was carried out by dissecting the ovaries and  examining the stage of oocyte  development on  fishes reared for  one  year.  The  sacrificed fishes were  fixed in 10%  neutral buffer formalin solution (NBF). The ovaries  sampled  for  histology  were   rinsed  to   eliminate  excess formalin solution, dehydrated in an ethanol series of progressive concentrations, cleared in a solvent and  embedded in paraffin. Then 5-μm  thick transversal sections were  made with a  rotary  microtome followed by  staining  with  haematoxylin and  eosin.  Sections  of  the ovaries were  histologically analysed to investigate differences among the  breeds.  The  results indicated that  the  ovaries of both  types of hybrid  (Cg  ♀x  Cb♂  and   Cb♀  x  Cg  ♂)crosses were  comparable, more  or  less  mature uniformly  at  well  progressed stages  (stage 5 and  6)  in contrast to  the  pure  Indian magur  progenies (Cb  x Cb). Although little variation is observed, Cb x Cb appeared more  or less in a  similar oocyte  developmental stages with the  pure  breed of C. gariepinus (Cg x Cg) used as a control in the experimental design. Of all  the  ovaries  examined,  the  pure   C.  batrachus  progenies  were observed at  their  lower  stage of oocyte  development  indicating  that this group  crosses mature too late compared to all the other  siblings of the  same age  groups of individuals.This is usually related to their small size.