Reproductive bionomics and population structure of Conus coronatus Gmelin, 1791 (Gastropoda, Conidae) of Buleji and Manora, Pakistan

Abstract

Present study describes the reproductive cycle, sex ratio, stages of the gonadal development and gonadal index (GI) of Conus coronatus collected from Buleji and Manora, Karachi. A total of 641 (329 from Manora and 312 from Buleji) C. coronatus of different sizes had randomly collected from April 2015 to March 2016. The females showed predominance in the population at both sites. Five different stages of the reproductive cycles of male and female C. coronatus: resting, developing, ripe, partially spawned, and spawned out were found. Spawning was observed throughout the year. At resting phase all the stages of spermatogenesis and oogenesis were absent. At developing stage oogonia, oocytes, spermatogonia, and spermatocytes were abundantly present in their respective follicles. At ripe stage, in males follicle countless spermatids and spermatozoa were observed however, in female the vitellogenic oocytes were been packed in follicles. At partially spawned stage, male follicles were partially empty while in female follicles unspawned mature ova were seen. At spawned out stage, both male and female follicles were empty. Gonadal development in males was at its highest peak (4.37) in summer (September 2015) at Manora and (4.00) in summer and winter (May 2015 and February 2016) at Buleji. However, in females, the highest value (5.00) of GI was observed only in summer (July and October 2015) at Manora and (4.36) in September (2015) at Buleji.