Mobula hypostoma (Lesser Devil Ray)

Transcription

1 Mobula hypostoma (Lesser Devil Ray) Family: Myliobatidae (Eagle and Manta Rays) Order: Rajiformes (Rays and Sawfish) Class Chondrichthyes (Cartilaginous Fish) Fig. 1. Lesser devil ray, Mobula hypostoma. [ downloaded 10 March 2016] TRAITS. Mobula hypostoma, more commonly known as the lesser devil ray or Atlantic devil ray, is an eagle ray of the genus Mobula, The devil ray is born fairly large at 55cm disc width and can attain a maximum disc width of 120cm after full maturation. There is very little sexual dimorphism with males only being 4-5 cm larger than females (Robins and. Ray, 1986). It can primarily be identified by its cephalic fins which protrude from the front of the head and curl up tightly to give the appearance of horns (Fig. 1), hence the name devil ray (Boonstra, 2016). The devil ray also has a small sub terminal mouth and long pointed pectoral fins and a small whip-like tail which is the same length as the body. It is black/dark grey on the topside and white/ivory on the underside. The devil ray may also propel itself at high speeds to leap out of the water (Boonstra, 2016).

2 DISTRIBUTION. The Atlantic devil ray is endemic to the western hemisphere and it is found between the latitudes 24-25º south and 34-35º north. These coordinates encompass the Atlantic ocean where the ray can be found from the southernmost coast of the USA (Gulf of Mexico and the Florida Keys), throughout the entire Caribbean Sea, and south to Brazil and Uruguay (Fig. 2) (Robins and Ray, 1986). HABITAT AND ACTIVITY. This devil ray mainly inhabits the pelagic regions (open water) of the Atlantic Ocean and is mostly found in seas, gulfs and bays where it is most often sighted near the surface of the water. It can also be found near continental shelves such as the Brazilian and United States shelves. The devil ray will sometimes come near to the shore for feeding on schools of small fishes or shrimps (Boonstra, 2016). It is not known if the devil ray will sometimes roam into the deeper regions of the Atlantic Ocean (Bizzaro et al., 2009). FOOD AND FEEDING. The devil ray s diet consists mainly of plankton and relatively small crustaceans such as shrimp as determined analyzing the stomach contents of dead devil rays. Also in small quantities some small fishes which swim in schools were found in the stomach of the ray. The way in which the devil ray feeds is by using its cephalic fins or horns to funnel food into the mouth (Boonstra, 2016). POPULATION ECOLOGY. Devil rays can be found either as a singule individuals living on their own, or in small groups and sometimes even in schools depending on the environment (Fig. 3). The overall population ecology of the devil ray is hard to determine as there is currently very little information available on the trends of their population. Most of the devil rays that have been caught are due to being bycatch in trawling exercises carried out by fishermen (Bizzaro et al., 2009). REPRODUCTION. Devil rays reproduce in the same way as all other rays reproduce, they are ovoviviparous which means that there is internal fertilization taking place and that they give birth to live young. After fertilization, the developing ray feeds on the embryonic yolk present inside the mother, this yolk is rich in proteins and lipids (Bigelow and Schroeder, 1953). They may only produce one offspring per mating session (Boonstra, 2016). It is reported that they swim closer to the surface during mating (Bigelow and Schroeder 1953), and there is a long rest period between giving birth and the conception of another offspring. Reported sightings of devil ray mating stated that copulation occurs for around 10 minutes and the rays link together in a ventral paired orientation (Boonstra, 2016). BEHAVIOUR. These rays have few natural predators in the wild. The anti-predator behaviour that these devil rays exhibit can be seen when they quickly swim away when divers approach near them. Sometimes devil rays may also leap out of the water, possibly to escape a predator (Fig. 4).

3 APPLIED ECOLOGY. The lesser devil ray is listed under IUCN as a Data Deficient species and this means that there was not enough research conducted on the species to determine its population. Although it has been stated by the IUCN that due to uncertainty in being able to determine rates at which these devil rays reproduce and grow, they may become endangered in the future if commercial fishing increases (Bizzaro et al., 2009; Boonstra, 2016). The lesser devil ray is considered a delicacy in the central atlantic where its flesh can be salted and cured providing a jerky like texture and other parts of the fish can be used for the production of oil (Bizzaro et al., 2009). Overall the species poses no threats to humans as they are docile organisms but sometimes may be caught up in fishing lines which may cause damage to small boats (Bizzaro et al., 2009). REFERENCES Bigelow, H.B., and Schroeder, W.C.. (1953). Fishes Of The Gulf Of Maine. Washington: U.S. G.P.O. Bizzarro, J., Smith, W., Baum, J., Domingo, A. and Menni, R. (2009). Mobula hypostoma. The IUCN Red List of Threatened Species 2009: e.t161737a IUCN.UK RLTS.T161737A en. Downloaded 10 March Boonstra, R. (2016). Mobula hypostoma, Florida Museum of Natural History downloaded 10 March Robins, C.R. and Ray, G.C. (1986). A field guide to Atlantic coast fishes of North America. Houghton Mifflin Company, Boston, U.S.A. 354 p. Author: Matthew N.D. Ali Posted online: 2016

4 Fig. 2. Lesser devil ray distribution. [ downloaded 10 March 2016] Fig. 3. School of lesser devil rays. [ downloaded 10 March 2016]

5 Fig. 4. A lesser devil ray breaching or leaping out of the water. [ downloaded 10 March 2016] For educational use only - copyright of images remains with original source