WFB 232 Ichthyology Chelsea Mitchell
Order Rhinobatiformes (Greek: ‘rhinos’= nose, ‘batis’= ray) Taxonomy: Superclass: Gnathostomata • Class: Chondrichthyes (cartilaginous fishes) o Subclass: Elasmobranchii (sharks and rays) . Order: Rhinobatiformes • Families: Rhinidae, Platyrhinidae, Rhynchobatidae, and *Rhinobatidae (genera: Aptychotrema, Platyrhina, Platyrhinoidis, Rhinobatos, Trygonorrhina, Zanobatus, Zapteryx; 45 species total). *Due to debated taxonomic status of the order Rhinobatiformes, the information in this overview focuses on the family, Rhinobatidae (aka. guitarfishes or shovelnose rays), which constitutes a major portion of the group described as Rhinobatiformes. Description: Fish of the family, Rhinobatidae, have both shark and ray-like characteristics, as their pectoral fins are very broad (like rays), and their bodies are and rounded elongate (like sharks). They have wedge-shaped snouts and heart-shaped bodies, with ventral gill openings. They have small teeth that are closely packed together and attached to the jaw. Most species of Rhinobatidae reach 1-2m in length, with some exceptions (e.g., giant guitar fish, length is >3m). Habitat: Occupy shallow water and remain in benthic habitats. These animals are mostly marine, but are occasionally found in estuaries or freshwater. Distribution: Found in tropical and subtropical regions of the world, including the Atlantic, Pacific, and Indian Oceans. Ecology and life History: Rhinobatidae feed on benthic invertebrates including mollusks and crustaceans. More recent studies have found these animals also utilize small fish in their diet. They are ovoviviparous, meaning the eggs are internally fertilized and young are born live. Recent research: A study of the chola guitarfish (Rhinobatos percellens) suggests that female guitarfish may experience a “dipause” in their reproductive cycle, where reproductive development is halted for one or more seasons, allowing for birth events to occur during environmentally favorable times (Rocha and Gadig 2013). Recent studies have found species of Rhinobatidae (e.g., Rhinobatos percellens, Zapteryx exasperata) utilize small benthic and pelagic fishes (Blanco-Parra et al. 2012), especially teleosts (Rocha and Gadig 2013), in their diet. Additional details: According to the IUCN Red List, 3 species in the family Rhinobatidae are endangered and one species, the Brazilian guitarfish (Rhinobatos horkelli), is critically endangered. References: Barton, M. 2007. Bond’s biology of fishes, 3rd ed. Thompson Brooks/Cole, California. Blanco-Parra, M., F. Galvan-Magana, J. F. Marquez-Farias, C. A. Nino-Torres. 2012. Feeding ecology and trophic level of the banded guitarfish, Zapteryx exasperata, inferred from stable isotopes and stomach contents analysis. Environmental Biology of Fishes 95: 65-77. Bond, C. E. 1996. Biology of fishes, 2nd ed. Saunders College Publishing, Fort Worth. www.fishbase.org IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2.