 Like other stingrays , the common stingray is aplacental viviparous : the embryos are initially sustained by yolk , which is later supplemented by histotroph ( " uterine milk " , enriched with proteins , fat , and mucus ) delivered by the mother through numerous extensions of the uterine epithelium called trophonemata . Females bear two litters of 4 – 9 pups per year in shallow inshore waters , following a gestation period of four months . Various authors have generally reported birthing in summer , between May and September or over a narrower timeframe such as July to August . Mature rays are known to aggregate off the Balearic Islands from mid @-@ June to July , possibly for reproductive purposes . Newborns measure about 8 cm ( 3 @.@ 1 in ) across and 20 cm ( 7 @.@ 9 in ) long . Males reach sexual maturity at 22 – 32 cm ( 8 @.@ 7 – 12 @.@ 6 in ) across , and females at 24 – 38 cm ( 9 @.@ 4 – 15 @.@ 0 in ) across . The oldest known individual from the wild was ten years of age , but the species has lived up to 21 years in captivity . Known parasites of the common stingray include the flukes Heterocotyle <unk> and Entobdella diadema , and the tapeworm <unk> minimum . 
