Reproductive biology of the spiny butterfly ray, Gymnura altavela (Linnaeus, 1758) (Pisces: Gymnuridae) from off the Tunisian coasts
C. Capapé, J. Zaouali, J.A. Tomasini and J.L. Bouchereau

Aspects of reproductive biology in the spiny butterfly ray, Gymnura altavela (Linnaeus, 1758) from off the Tunisian coasts are described. Size at first maturity of males is 780 mm disk-width (DW). Females do not mature until they reach 670 mm DW, thereafter maturation proceeds between 680 mm and 1020 mm DW at a minimum. The first adult female which was also the first female gravid observed was 1080 mm DW. All the females over that this DW were adult. Females are larger than males, the largest female and the largest male are 1620 mm and 1140 mm DW respectively. G. altavela is an aplacental viviparous species, with two functional uteri. Gestation could last four to nine months at a maximum and until mid-gestation vitellogenesis is blocked, then resumes after parturition until ovulation. Total duration of vitellogenesis is unknown. Parturition occurs at the end of winter. One reproductive cycle occurs per year. Average DW and average weight of fully-developed fetuses are 294 mm and 269.3 g. A calculated chemical balance of development (CBD) based on mean dry-weights of fully-developed fetuses and ripe oocytes is 30.6. Fecundity ranges two to six newborns per litter. Embryos and fetuses are symmetrically distributed in each uterus. Males are more numerous than females in the sample as well as in each category of specimens, However, this is not the case for subadults.

Keywords: Pisces, Gymnuridae, Gymnura altavela, reproductive biology, Tunisian coasts, Mediterranean.
Contents of this volume Sci. Mar. 56(4) : 347-355 Back PDF
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