Bowmouth Sharkray

The bowmouth guitarfish, scientifically known as Rhina ancylostoma and also referred to as the shark ray or mud skate, is a distinctive species within the family Rhinidae. Despite ongoing scientific inquiry, its evolutionary relationships remain partially unresolved. This rare species is distributed across the tropical coastal waters of the western Indo-Pacific, inhabiting depths up to 90 meters (300 feet). The bowmouth guitarfish is easily recognizable by its broad, thick body, rounded snout, and prominent shark-like dorsal and tail fins. Its mouth is notably W-shaped, and its body features multiple thorny ridges. The dorsal surface is marked by numerous white spots set against a bluish-grey to brown background, with striking black markings over the pectoral fins. This substantial species can grow up to 2.7 meters (8.9 feet) in length and weigh as much as 135 kilograms (298 pounds).

Typically residing near the sea floor, Rhina ancylostoma favors sandy or muddy environments adjacent to underwater structures. It is a proficient swimmer and an effective predator, preying on bony fish, crustaceans, and molluscs. Reproduction is viviparous, with females birthing litters ranging from two to eleven pups, sustained by yolk during gestation. The International Union for Conservation of Nature (IUCN) classifies this species as Critically Endangered, primarily due to extensive capture by artisanal and commercial fisheries targeting its prized fins and meat. Additionally, trawling activities view the species as problematic given its physical bulk and thorny skin, both detrimental to netted catches. Habitat degradation further exacerbates the challenges to its survival. Nonetheless, the bowmouth guitarfish is adaptable to captivity and is often featured in public aquariums.

Described in 1801 by German naturalists Marcus Elieser Bloch and Johann Gottlob Schneider, Rhina ancylostoma was initially cataloged based on a 51-centimeter (20-inch) specimen collected from the Corundefineddel Coast of 🇮🇳 India. The genus name, Rhina, derives from the Greek "rhinos," meaning "snout," while the specific epithet "ancylostoma" combines Greek words for "curved" or "crooked" and "mouth." Although some literature still uses the variant "ancylostomus," modern convention predominantly supports the use of "ancylostoma." The species is also known by various common names, including shark ray, mud skate, shortnose mud skate, bow-mouthed angel fish, and bow-mouthed angel shark.

Rhina ancylostoma's morphology includes a short, wide, and flattened head with large spiracles and medium-sized eyes, clearly distinguished from the body. Dental anatomy features approximately 47 upper and 50 lower tooth rows with low, blunt, ridged teeth, ideally suited for crushing hard-shelled prey, such as crustaceans and molluscs. Dorsally, the species exhibits robust, thorny ridges, while the dorsal color palette ranges from bluish to brownish gray with a scattering of white spots. Juveniles exhibit more vibrant coloration compared to adults.

Rhina ancylostoma's geographic distribution encompasses the coastal reefs of the Indo-Pacific, from 🇿🇦 South Africa's KwaZulu-Natal (🇿🇦 South Africa) to the 🌊 Red Sea, 🇮🇳 Indian subcontinent, and Southeast Asia, extending to 🇦🇺 Australia, Korea, 🇯🇵 Japan, 🇵🇬 New Guinea, and New South Wales. Typically dwelling at depths between 3 and 90 meters, this ray frequents sandy or muddy bottoms and may occasionally be spotted in mid-water or near reefs and shipwrecks. Although generally nocturnal and non-territorial, this species is an adept swimmer relying on its tail for propulsion, similar to sharks.

The ecosystem supports various parasites associated with Rhina ancylostoma, including multiple species of tapeworms, leeches, trematodes, monogeneans, and copepods. Additionally, marine interactions have been observed between this species and cleaner wrasses. Notably, the tiger shark (Galeocerdo cuvier) preys upon the bowmouth guitarfish, although its thorny defenses provide a degree of protection.

Reproductive biology in Rhina ancylostoma is characterized by viviparity, with two distinct ovaries and uterine horns in females. Sexual maturity is reached at 1.5–1.8 meters (4.9–5.9 feet) for males and over 1.8 meters (5.9 feet) for females, with females generally attaining larger sizes than their male counterparts.