|Range of the Rhinobatos productus|
The shovelnose guitarfish, Rhinobatos productus, is a ray that becomes sexually mature at an estimated seven to eight years. Males are between 90–100 cm, while females are around 99 cm at this time. The ray can live up to 11 years, and full grown sizes are around 120 cm for males, and females reach sizes of 137 cm. Their habitat ranges from central California down to the Sea of Cortez. While remaining the same species, there is a morphological and genetic variation in the mitochondrial DNA in those found in the Sea of Cortez, evidencing the isolation from the rest. Because of this, the conservation of this species must be carefully managed to preserve the biological diversity. The shovelnose is considered to be a primitively developed ray, with many features of both sharks and rays.
The Rhinobatos productus has magnetic particles in the vestibular receptors, and it is presumed that the magnetic particles are exogenous in origin. The magnetic particles have a spatial arrangement that may aid in the sensitivity of the receptors to movements, but additional research is required.
The visual system of the shovelnose is more extensive and developed than other Elasmobranchii, with multiple large projections connecting to the brain. Almost the entire dorsal and ventral hypothalamus is connected to the visual system, but still maintains a similar lack of differentiation as with sharks.
This species has had one documented case of an attack on a diver when a male guitarfish was interrupted during mating. Because of the tooth structure of the guitarfish, this attack could have resulted in a "gumming" at worst.
Shovelnose ray was first considered to be a shark because of its dorsal fin's shape.
- Timmons, M Bray RN (2004). "Age, growth, and sexual maturity of shovelnose guitarfish, Rhinobatos productus (Ayres)". Fishery Bulletin 95 (2): 349–359.
- J. Sandoval-Castillo, A. Rocha-Olivares, C. Villavicencio-Garayzar, E. Balart (2004). "Cryptic isolation of Gulf of California shovelnose guitarfish evidenced by mitochondrial DNA". Marine Biology 145 (5): 983–988. doi:10.1007/s00227-004-1378-7.
- D.P. O’Leary, J. Vilches-Troya, R.F. Dunn and A. Campos-Muñoz (1981). "Magnets in guitarfish vestibular receptors". Cellular and Molecular Life Sciences 37 (1): 86–88. doi:10.1007/BF01965587. PMID 7202681.
- Ebbesson, S.O.E. and Meyer, D.L. (1980). "The visual system of the guitar fish (Rhinobatos productus)". Cell and Tissue Research 206 (2): 243–250. PMID 7388890.
- Márquez et al. (2005). Rhinobatos productus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes justification for why this species is near threatened
- "Rhinobatos productus". Integrated Taxonomic Information System. Retrieved 24 January 2006.
- Froese, Rainer and Pauly, Daniel, eds. (2005). "Rhinobatos productus" in FishBase. August 2005 version.
- Timmons, M and Bray, R. Age, growth, and sexual maturity of shovelnose guitarfish, Rhinobatos productus. Fishery Bulletin 95:349–359 (1997).
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