Interpopulation variability of the reproductive cycle of Arbacia lixula (Echinodermata: Echinoidea) in the Mostaganem shallow-water area (south-western Mediterranean)

Abstract

The study on the reproductive biology of the black sea urchin Arbacia lixula was carried out at two different sites on the west coast of Algeria (Mostaganem) (one located at Salamandre considered polluted and the other at Stidia is relatively healthy). A monthly sampling was carried out from January 2015 to December 2016. The sex ratio at the two sites is slightly in favour of males. Monthly monitoring of the gonad index showed maximum values during the month of May, and minimum values in September. The gonad index for both male and female evolves in the same way. Histological study of the male and the female gonads confirmed the results obtained for the gonad index. The sexual resting stage takes place in winter, followed by maturation in spring. Finally, the spawning phase occurs between spring and summer. The variability of the seasonal temperature values appears to influence the maturation of the gonads and the spawning process in A. lixula. The results obtained in this study show the existence of an annual cycle in A.lixula with the presence of a massive spawning in July, the duration of which depends on the combined effect of stress factors (increase in temperature and presence of pollution).