Life History – Arianna's Space

This page covers the life history of Potamotrygon motoro with information regarding the age and growth of the species as well as reproductive methods.

Reproduction

The reproductive cycle of Potamotrygon motoro is distinguished from most elasmobranch cycles for being dependent on rainfall instead of seasonal cues. Mating season occurs during periods of low rainfall followed by a 6 month gestation period before birth occurs during periods of high rainfall (Oliveira et al. 2017, Spiegel 2013). This punctuated reproductive cycle occurs annually (Oliveira et al. 2017). The method of copulation is standard among elasmobranchs with males latching onto the underside of females using their jaws so they can insert their claspers into the female’s cloaca. This species enacts a form of alternating polygony where males will mate with multiple females non-simultaneously. The period between a male copulating with different females was at least multiple weeks (Spiegel 2013).

Photo by David J. Stang. License: Creative Commons Attribution-Share Alike 3.0 Unported License.

Females have sequentially functional ovaries, with one litter being born every year for three years. This burst of reproductive capability is followed by a multi-year long pause in reproduction (Spiegel 2013). Developmentally, this species utilizes histotrophy with the embryos fed by maternal energy sources through a trophonemata (Thorson et al. 1983). Average litter size in the wild is 7 pups with a captive ray recorded as having up to 16 pups in a single litter (Spiegel 2013, Motoro Ray).

Age and Growth

The average size at birth is a disc width of 96.8 millimeters with females being larger than males (Spiegel 2013). The size and age at maturity are unknown, though estimates vary. Recent size estimates place males reaching sexual maturity at a disc width of 390 millimeters and females reaching sexual maturity at a disc width of 440 millimeters (Spiegel 2013, Froese et al.). The life span of Potamotrygon motoro in the wild is currently unknown (Freshwater Stingray).

References

Freshwater Stingray (no date)https://nationalzoo.si.edu/animals/freshwater-stingray

Froese R, Capuli E, Garilao C, Pauly D (no date)Potamotrygon motoro. https://www.fishbase.us/summary/SpeciesSummary.php?ID=6382&genusname=Potamotrygon&speciesname=motoro&AT=Potamotrygon+motoro&lang=English (accessed April 25, 2024)

Motoro Ray (no date)https://www.georgiaaquarium.org/animal/motoro-ray-2/ (accessed April 25, 2024)

Oliveira AT, Araujo MLG, Lemos JRG, Santos MQC, Pantoja-Lima J, Aride PHR, Tavares-Dias M, Marcon JL (2017) Ecophysiological interactions and water-related physiochemical parameters among freshwater stingrays. Braz J Biol 77.

Spiegel J (2013) Potamotrygon motoro Black river stingray (Also: Ocellate river stingray; South American freshwater stin). https://animaldiversity.org/accounts/Potamotrygon_motoro/ (accessed April 25, 2024)

Thorson TB, Langhammer JK, Oetinger MI (1983) Reproduction and development of the South American freshwater stingrays, Potamotrygon circularis and P. motoro. Environ Biol Fish 9:3–24.