Production of live offspring following unilateral (left) ovariectomized Potamotrygon rays (Potamotrygon castexi, Potamotrygon leopoldi, and Potamotrygon motoro)

Abstract

Abstract OBJECTIVE To evaluate the surgical technique and subsequent clinical observations (reproductive and ultrasound findings) of left unilateral ovariectomy in 3 species of Potamotrygon rays—Potamotrygon castexi, Potamotrygon leopoldi, and Potamotrygon motoro—for reproductive management. ANIMALS Between 2018 and 2019, multiple Potamotrygon rays (P castexi, n = 1; P leopoldi, 1; P motoro, 6) underwent left ovariectomies to evaluate this technique for reproductive management. PROCEDURES At time of surgery, patient age ranged from juvenile to adult. Rays were anesthetized with MS222 buffered with sodium bicarbonate, and a left craniodorsal surgical approach was made to isolate and excise the left ovary. All rays had uneventful recoveries. Eight unilateral ovariectomized females and 6 males were combined in a mixed-species freshwater touch pool of Potamotrygon rays and teleost species. RESULTS In December 2020, 3 live and 1 premature autolyzed pup were noted in the habitat. The following day, the adult females were examined via ultrasound and separated from the males. Four dams were identified that produced 8 viable offspring and 4 premature abortions. A large right ovary was observed in all females, with no evidence of left ovarian tissue present via ultrasound. CLINICAL RELEVANCE Previous histologic evaluation of freshwater ray ovarian tissue suggests both ovaries may be functionally active yet maintain left dominance like some other elasmobranch species. This manuscript provides proof the right ovary alone can produce live offspring. Furthermore, the enlarged right ovary observed in these females suggests that removal of the left ovary may result in compensatory enlargement of the right ovary.