Abstract

Little skates (Leucoraja erinacea) and clearnose skates (Raja eglanteria) are oviparous members of the family Rajidae, superorder Batoidea, native to the mid-Atlantic.¹ Reproductive disease has previously been reported in Batoid rays (viviparous cownose rays, southern stingrays), but not in skates.^2–4 Of the female skates maintained in the National Aquarium collection, 2/4 clearnose skates and 4/8 little skates have presented with various reproductive conditions. The remaining clearnose skates and half of the remaining little skates were dispositioned and lost to follow-up. Animals were wild-caught or captive reared without known birth dates, but had been in the collection from 2 to 6 years. Of the animals with reproductive disease, 4/6 were diagnosed postmortem and 2/6 antemortem via ultrasound, historic abnormal laying behavior and abnormal bloodwork (inflammatory leukogram changes). While one animal diagnosed antemortem succumbed due to complications from her reproductive disease, the other underwent successful ovariohysterectomy. Histopathology was consistent with follicular degeneration (1), oophoritis with retained ova (2), bacterial endometritis (1), sterile endometritis and uterine hemorrhage (1) and uterine perforation with ruptured egg casing (1). Reproductive disease was the primary cause of death in 3/5 mortalities. Other intercurrent disease conditions included inanition, meningoencephalitis, bacterial gastritis, bacterial myocarditis, and chronic nephritis. Given these findings, further consideration into the cause and management of reproductive disease in skates is warranted.

Acknowledgments

The authors wish to thank the Blue Wonders, Animal Care and Rescue Center, and Animal Health Departments at the National Aquarium for their tireless care for these animals throughout the years. They would also like to thank the staff at the Department of Molecular and Comparative Pathobiology department for sample processing and evaluation.

Literature Cited

1.  Schoch CL, Siufo S, Domrachev M, Hotton CL, Kannan S, Khovanskaya R, Leipe D, Mcveigh R, O’Neill K, Robbertse B, Sharma S, Soussov V, Sullivan JP, Sun L, Turner S, Karsh-Mizrachi I. 2020. NCBI Taxonomy: a comprehensive update on curation, resources and tools. Database (Oxford).

2.  Garner MM. 2013. A Retrospective study on Disease in Elasmobranchs. Vet Pathol 50(3): 377–389.

3.  George RH, Steeil J, Baine K. 2017. Chapter 35; Diagnosis and treatment of common reproductive problems in elasmobranchs. In: Smith M, Warmolts D, Thoney D, Hueter R, Murray M, Ezurra J, editors. Elasmobranch Husbandry Manual II: Recent Advances in the Care of Sharks, Rays, and their Relatives. Columbus (OH): Special Publication of the Ohio Biological Survey. p 357–362.

4.  Mylniczenko ND, Sumigama S, Wyffels JT, Wheaton CJ, Guttridge TL, DiRocco S, and Penfold LM. 2019. Ultrasonographic and hormonal characterization of reproductive health and disease in wild, semiwild and aquarium-housed southern stingrays. Am J Vet Res 80(10): 931–942.