An Analysis of Aquaporin in the Oocyte Maturation of Teleosts, Clarias gariepinus and Channa punctatus

Abstract

Aquaporin or water channels have been reported to play a significant role in reproduction of marine and freshwater fishes. This study deals with the elucidation of the role of aquaporins 1 and 3 during oocyte maturation and hydration in benthophil and pelagophil eggs of fishes. Partial sequencing of aqp1 and aqp3 genes of Clarias gariepinus and Channa punctatus was carried out. Expression of aquaporin genes (aqp1 and aqp3) was assessed, and a direct correlation was observed between the transcript number of aqp1 and water content of oocytes during oocyte maturation and ovulation in demersal eggs of C. gariepinus. Treatment of oocytes with channel blockers under in vitro conditions elucidated the role of aquaporins in hydration. It alludes the role of aquaporins presumably associated with the hydration at the time of oocyte maturation. In silico characterisation of aquaporin 1 of Clarias magur, a congeneric species of C. gariepinus and aquaporin 3 of C. gariepinus, established the presence of conserved NPA (asparagine-proline-alanine sequences) motifs in them. The comparison of expression pattern for both the aquaporins 1 and 3 were also observed in the preliminary study of pelagophil eggs collected from C. punctatus. Elucidation of the role of aquaporins in the movement of fluids in teleost gonads and gametes may help to enhance the success rate of oocyte cryopreservation and thus will help in improving the breeding programs of cultured fishes and also the protection of endangered fishes.