 Like other stingrays , the diamond stingray is aplacental viviparous : the embryos are initially nourished by yolk , and later by histotroph ( " uterine milk " , rich in proteins and <unk> ) produced by the mother . Only the left ovary and uterus are functional in adult females . Several bays along the Pacific coast of Baja California are known to serve as nurseries . Most of the life history information available on this species has come from Bahía Magdalena , where females bear one litter of 1 – 4 <unk> per year . <unk> and mating occurs in late summer from July to August , but due to a ten @-@ month period of either sperm storage or <unk> ( wherein the embryo becomes <unk> ) , embryonic development does not begin until the following year and is completed within 2 – 3 months . <unk> takes place in summer from July to September in shallow estuaries ; the newborns measure 18 – 23 cm ( 7 @.@ 1 – 9 @.@ 1 in ) across . During El Niño years , the higher temperatures appear to shift the timing of birth forward . The diamond stingray has the lowest growth rate of any stingray species yet studied . Males reach sexual maturity at around 43 – 47 cm ( 17 – 19 in ) across and 7 years of age , while females grow slower still , reaching maturity at around 57 – 66 cm ( 22 – 26 in ) across and 10 years of age . The maximum lifespan has been estimated at least 19 years for males and 28 years for females . 
