Reproduction of the freshwater stingray, Potamotrygon magdalenae taken from the Magdalena river system in Colombia, south America
1992
Teshima, K. (Seikai National Fisheries Research Inst., Nagasaki (Japan)) | Takeshita, K.
Reproductive biology of the freshwater stingray, Potamotrygon magdalenae was examined while conducting research on freshwater elasmobranches in Colombia, South America from August 12 through August 19, 1980. A total of 117 P. magdalenae specimens (female; 44, male; 73) were taken by gillnet in lakes near the Magdalena River system in the northern Colombia. After measuring and observing external characteristics of the stingrays, reproductive organs removed were preserved in formalin and brought to Japan for histological observations. Unlike many other female elasmobranchs, oogenesis in P. magdalenae was characterized by unusual folds that were formed on the follicular epithelium. The follicular epithelial folds, that extended inward into the oocyte, filled the oocyte before it reached the maturity. After ovulation, the follicular epithelial folds were freed from the mature oocyte and remained in the postovulatory follicle. Ovulation appears to occur when the oocyte reaches the diameter of about 25mm. P. magdalenae has a non-placental viviparous mode of reproduction and a single embryo develops in each uterus. Size at birth for the embryos is estimated to be about 100mm in disk width. P. magdalenae is estimated to reach the maturity between 170 and 210mm disk width in females and between 170 and 190mm disk width in males. Based on the development of ovaries and testes, the size of embryos found in uteri, and the estimated size at birth, the reproductive activity including ovulation, mating, fertilization, and parturition might take place over an extended period of time, therefore suggesting that P. magdalenae might not have a definitive reproductive season
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