|Reproductive cycle of the spatangoid echinoid Echinocardium cordatum (Echinodermata) in the southwestern North Sea|Nunes, C.D.A.P.; Jangoux, M. (2004). Reproductive cycle of the spatangoid echinoid Echinocardium cordatum (Echinodermata) in the southwestern North Sea. Int. J. Invert. Reprod. Dev 45(1): 41-57. dx.doi.org/10.1080/07924259.2004.9652572
In: International Journal of Invertebrate Reproduction and Development. Elsevier: Amsterdam. ISSN 0168-8170, more
Echinocardium cordatum; reproduction; gonadal cycle; maturity index;environmental parameters
The reproductive cycle of the spatangoid echinoid Echinocardium cordatum is described from a 3-year survey of a population located in Wimereux (the southwest part of the North Sea). From monthly measurements and histological observations of gonads, seven distinct gonadal stages were described. These are based on the changes observed in the two-cell populations forming the germinal epithelium (germinal cells vs. nutritive cells). The gonad index (GI) and maturity index (MI) were established, and their variations were related to the seasonal changes in temperature. The species has an annual reproductive cycle with spawning beginning in April/May (variable between years) and ending suddenly in June/July. The gonads then enter a resting/recovery period until the onset of the new gametogenic process which starts in December/January. Fully mature individuals were rarely found, suggesting that gametes do not accumulate in the gonads for a long period. Empty gonads were never observed either, suggesting a regulation/interruption of gametogenesis due to the development of the somatic cells of the germinal epithelium. This could account for the annual abrupt cessation of spawning in the species. Calculation of the MI allowed a precise determination of the spawning period, and showed that reproduction is highly synchronized between males and females and well synchronized from year to year in the population. However, changes in GI values revealed different patterns between years, and this index could not be used to characterize the reproductive cycle in this species. A correlation was found between temperature and MI, with gametogenesis beginning each year after the minimal temperature has been reached. However, no clear link appears for E. cordatum between temperature and spawning events. During the resting/recovery period, there is clear evidence of nutrient accumulation resulting in both gamete resorption and food acquisition. The influence of food supply on the annual gonad development in E. cordatum is discussed, particularly with respect to the ecological constraints to which this species is subject.