Abstract

Southern stingrays (Dasyatis americana) under managed care in aquaria have presented with abnormal ovaries and fluid-filled uteri, sometimes resulting in lethargy, anorexia and eventually death (Mylniczenko, Penfold 2012a). To evaluate the prevalence of disease, multiple institutions participated in a prospective year-long study. Ultrasound images and plasma for endocrine analysis were collected from 46 adult aquarium-managed females and 31 adult free-ranging female stingrays kept in an enclosed bay in the Bahamas, as well as two line-caught adult females off the coast of North Carolina. Ultrasound images were scored by one individual and independently reviewed by a second individual. Ovaries and uteri were categorized by grades 1–5 based on previously established criteria (Mylniczenko, Penfold 2012b; Sumigama et al. 2014). Enzyme-linked immunoassays were developed and validated for southern stingrays for plasma progestin, estrogen and testosterone. Data analysis revealed that degree of reproductive disease to be extensive in managed animals (abnormal ovary: 91%, abnormal uterus 84%) but not free-ranging stingrays (abnormal ovary: 12%, abnormal uterus 3%) and that disease grade was not tightly linked to circulating steroid hormones (p > 0.05). No seasonal patterns in disease were noted, though age/disk width was correlated (p < 0.05) with an increased likelihood of disease. Treatment of affected females with 5 mg/kg Depo-Provera was ineffective in altering hormone concentrations or in decreasing the grade of the disease though preliminary results using 20 mg/kg look promising. Continuing studies will investigate the use of higher concentrations of exogenous progestin or GnRH vaccine as possible treatments of this widespread and serious health problem in this species of stingray.

Acknowledgments

The authors wish to thank the veterinary and husbandry staffs at the Florida Aquarium, Georgia Aquarium, Jacksonville Zoo & Gardens, the Minnesota Zoo, New England Aquarium, North Carolina Aquarium, Ripley's Aquarium, the Seas with Nemo and Friends, Walt Disney World Resorts®, and SeaWorld Orlando®, with special thanks to Charlene Burns and Cayman Adams.

* Presenting author

Literature Cited

1.  Mylniczenko ND, Penfold, LM. Uterine and ovarian disease in single gender housed southern stingrays (Dasyatis americana). In: Proceedings from the American Association of Zoo Veterinarians Conference, Oakland, CA, USA; 2012a.

2.  Mylniczenko ND, Penfold LM. Ultrasound findings in southern stingrays (Dasyatis americana) with and without reproductive disease. In: Proceedings from the IAAAM Conference; 2012b.

3.  Sumigama S, Penfold LM, Mylniczenko ND. Development of criteria for categorizing ultrasonographic images of uterine health assessments in the southern stingray (Dasyatis americanus). In: Proceedings from the American Association of Zoo Veterinarians Conference, Orlando, FL, USA; 2014.