Abstract

Abnormal spinal curvatures have been noted in captive sand tiger shark (Odontaspis taurus) populations, but incidence and etiology are unknown. A preliminary survey addressing these questions was sent to 18 institutions listed as exhibiting sand tigers. Fifteen institutions responded, 13 indicated that one or more of their sand tigers had developed spinal deformities and 21 cases were identified. There were no other shark species from these collections reported to have spinal abnormalities.

Clinical presentation was the development of a conspicuous hump or spinal curve in the region between the pectoral fins and the cranial dorsal fin. In cases where the severity of the deformity worsened, additional clinical problems developed including anorexia, difficulty in maintaining body position, and obtundation. Radiographs, magnetic resonance imaging (MRI), and/or computed tomography (CT) studies on six euthanatized animals revealed kyphoscoliosis with either single or multiple subluxations or compressed vertebral bodies. Histologic examination of skeletal tissue revealed cartilaginous proliferation and degeneration. Moderate to severe degeneration and fibrosis were noted in the epaxial muscle from affected areas.

All sand tigers were wild-caught, using gillnets, long-line, pound nets or trawls. The average age (based on size) at onset of the condition for 14 animals was between 2–4 years (60–160 cm). One additional animal was noted to have developed the deformity at approximately 8 years of age (240 cm). Length of time the affected animals were on exhibit prior to onset of the condition encompassed a broad range including several months to several years. 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 sand tigers to have been fed more frequently and at a higher percentage of body weight. Minimal growth information was provided.

Numerous etiologies have been suggested, including nutritional (dietary excess vs. essential ingredient deficiencies), musculoskeletal disease, and trauma. More detailed information needs to be collected including growth data of both captive and wild populations, incidence of skeletal lesions in recently collected animals, food analysis and nutritional requirements, evaluation of collection and transport methods, as well as physiologic and biomechanical comparisons (intervertebral ligament structure and composition, muscle and skeletal development) with other species.

Acknowledgments

We would like to thank the following individuals for their assistance:

• 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
• Port Defiance Zoo/Aquarium—Chris Spaulding
• Texas State Aquarium—Thomas H. Schmid, Director of Husbandry and Interpretation
• UnderWaterWorld, Bloomington, Minnesota—Reid Withrow, Curator; Amy Kizer, Aquarist
• UnderWaterWorld, Perth, Australia—Paul Groves
• Virginia Marine Science Museum—Beth Firchau, Aquarist