Abstract

Aquariums have noted the development of spinal deformities in captive sandtiger shark (Odontaspsis taurus) populations but incidence and etiology are unknown. An initial survey was sent to the husbandry staff at eighteen institutions reported to exhibit sandtigers. Of thirteen institutions responding, nine indicated that one or more of their sandtigers had developed spinal deformities.

Data from the survey identified 18 cases. All sandtigers were wild-caught, using gill nets, pound nets or trawls. Fourteen affected sandtigers were estimated to be approximately 1-3 years of age when collected (based on size) and the age at onset of the condition for these animals was between 2-4 years (60 cm to 160 cm). One animal developed the deformity at approximately 8 years of age (240 cm). Both males and females were affected. Diets consisted of herring, capelin, squid, mackerel and bonita and all diets were supplemented with vitamins, although amounts and types varied. There was an enormous variation in feeding schedules but there was a slight tendency for affected sandtigers to have been fed more frequently and at a higher percentage of body weight. Growth records were unavailable. Twelve of the affected sharks were housed in a mixed group display. There were no reported observations of any traumatic incidents.

The clinical presentation was the gradual appearance of a pronounced hump or spinal curve in the area between the pectoral fins and the cranial dorsal fin. As the severity of the condition progressed, additional clinical problems included anorexia, difficulty in maintaining body position and obtundation (animals colliding into walls). Extensive diagnostic evaluations were conducted in four euthanized animals. Radiographs, magnetic resonance imaging (MRI) and computed tomography (CT) studies revealed scoliosis and kyphosis of the vertebral column with subluxated and compressed vertebral bodies. Histological evaluation of skeletal and epaxial muscle tissue from affected areas indicated moderate to severe degenerative and fibrotic changes.

We propose that at this time the condition be referred to as "idiopathic spondylopathy" in sandtiger sharks. Numerous etiologies have been suggested including nutritional (dietary excess vs. essential ingredient deficiencies), musculoskeletal disease, congenital anomalies exacerbated during growth, trauma, and even tank design (inadequate glide time, turning radius, etc.). Young, growing animals appear to be at risk. Further investigation is warranted and more detailed information needs to be collected including food analysis, captive vs. wild growth data, incidence of spinal deformities in wild populations, as well as extensive clinical evaluation of both living and euthanized specimens.

Acknowledgements

We would like to thank the following individuals for their assistance with different aspects of this study: The Florida Aquarium--Hugh Purgley, Life Support and Exhibit Coordinator; Reed Murtagh, MD, University Diagnostic Institute, University of South Florida, Sea World of Florida--Ray Davis, Assistant Curator of Fishes; John Kerivan, Curator of Fishes, New England Aquarium--Howard N. Krum, VMD, MS; Darlene Ketton, PhD, Regina Babcock, RTRCT and Cheryl Condon RTR, Massachusetts Eye and Ear Infirmary; dive staff at NEA, Albuquerque Biological Park--William M. Brooks, PhD and Benito Montoya, Center for Non-Invasive Diagnosis, University of New Mexico; Dr. Blaine A. Hart, MD, Department of Radiology, UNM; John Thilsted, DVM, PhD, ACVP, NM Veterinary Diagnostic Services, Acquario di Genova--Pietro Pecchioni, Curator of Sharks, Mystic Marinelife Aquarium--Catherine M. Ellis, Senior Aquarist, NY Aquarium for Wildlife Conservation--Dennis Thoney, PhD, Curator; Hans Walters, Animal Department Supervisor Loro Parque, Tenerife--Sarah London, Aquarium Curator, Texas State Aquarium--Thomas H. Schmid, Director of Husbandry and Interpretation, Virginia Marine Science Museum--Beth Firchau, Aquarist