Cownose ray

Cownose ray
Conservation status
Near Threatened (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	Myliobatiformes
Family:	Myliobatidae
Genus:	Rhinoptera
Species:	R. bonasus
Binomial name
Rhinoptera bonasus (Mitchill, 1815)

The cownose ray (Rhinoptera bonasus) is a species of eagle ray found throughout a large part of the western Atlantic and Caribbean, from New England, USA to southern Brazil. Cownose rays grow rapidly, and male rays often reach about 35 inches (89 cm) in width and weigh 26 pounds (12 kg). Females typically reach 28 inches (71 cm) in width and weigh 36 pounds (16 kg).

Gestation

The embryo grows within its mother with its wings folded over its body. Initially it is nourished by an egg yolk, although the uterine secretions of the mother nourish it later in its development. There is some dispute about the length of gestation. At full term the offspring is born live, exiting tail first.

Size and Appearance

The cownose ray is 11 to 18 inches (28 to 46 cm) in width at birth. A mature specimen can grow to 45 inches (1.1 m) in width, and weigh 50 pounds (23 kg) or more. There is some controversy over the size that a mature cownose ray can reach. A ray reaching a span of 84 inches has been recorded^{[citation needed]}.

A cownose ray is typically brown-backed with a whitish or yellowish belly. Although its coloration is not particularly distinctive, its shape is easily recognizable. It has a broad head with wide-set eyes, and a pair of distinctive lobes on its subrostral fin. It also has a set of dental plates designed for crushing clams and oyster shells. There are a series of canine teeth that are hidden behind the dental plates. When threatened the cownose ray can use the barb at the base of its tail to defend itself from the threat.

A cownose ray has a stinger, called a spine, on its tail, close to the ray's body. This spine has teeth lining its lateral edges, and is coated with a weak venom that which causes symptoms similar to that of a bee sting.

Feeding Habits

The cownose ray feeds upon clams, oysters, hard clams and other invertebrates. It uses two modified fins on its front side to produce suction, which allows it to draw food into its mouth, where it crushes its food with its dental plates. Cownose rays typically swim in groups, which allows them to use their synchronized wing flaps to stir up sediment and expose buried clams and oysters.

Aquariums

Cownose rays may be seen in selected zoo aquariums and often featured in special 'touch tanks' where visitors can reach into a wide but shallow pool containing the fish which have had their barbs pinched or taken off, making them safe enough to touch. One of these such tanks is located next to the right field stands at Tropicana Field in St. Petersburg, FL, home of the Tampa Bay Rays, a Major League Baseball franchise formerly nicknamed the "Devil Rays" until 2008.^[1]

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  Cownose rays in the Albuquerque Aquarium

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  Cownose Ray fish at the California Academy of Sciences

References

1. ^ "Cownose Sting Ray". http://tampabay.rays.mlb.com/tb/ballpark/rays_touch_tank.jsp. Retrieved 2011-01-09. 

• Barker (2005). Rhinoptera bonasus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is near threatened
• Froese, Rainer, and Daniel Pauly, eds. (2005). "Rhinoptera bonasus" in FishBase. August 2005 version.
• Florida Museum of Natural History Ichtyology Dept: Cownose Rays