Pelagic stingray

Lore & Background

The pelagic stingray was originally described by French naturalist Charles Lucien Bonaparte in 1832 as Trygon violacea. American zoologist Henry Weed Fowler later placed it in the subgenus Pteroplatytrygon, which was elevated to full genus by later authors, though some taxonomists dispute its separation from Dasyatis. Lisa Rosenberger's 2001 phylogenetic analysis found it to be a basal member of its family, sister to a clade containing Pastinachus, Dasyatis, and Indo-Pacific Himantura species. Common names include blue stingray and violet stingray.

Its distribution extends nearly worldwide in tropical to warm-temperate pelagic waters between 52°N and 50°S, including the Atlantic, Pacific, and parts of the Indian Ocean. It prefers water temperatures above 19 °C and performs seasonal migrations following warm water masses. In the northwestern Atlantic, it moves north of the Gulf Stream from July to September; in the Pacific, it migrates from near the equator to higher latitudes in spring. Off southeastern Brazil, upwellings of cold water push it into inshore waters less than 45 m deep.

The pelagic stingray has a thick, wedge-shaped disc one-third wider than long, minute eyes that do not protrude, and a whip-like tail up to twice the disc length with an extremely long serrated spine. Young are smooth-skinned; adults develop prickles and a row of small thorns along the midline. It exudes thick black mucus when handled. Captive specimens have reached 68 cm across (male) and 94 cm across (female).

Reader's Guide

The pelagic stingray is significant as the only stingray adapted to a midwater pelagic lifestyle, which has driven unique evolutionary changes. Unlike bottom-dwelling relatives that undulate their disc margins, it swims by flapping its pectoral fins like eagle rays, improving cruising efficiency at the cost of maneuverability. It is adept at swimming backwards, compensating for reduced fine control. Vision is more important for finding food than in other stingrays, and it has less than one-third the density of electroreceptive ampullae of Lorenzini on its underside, though it can detect electric fields of well under 1 nV/cm at up to 30 cm.

Its diet consists of free-swimming invertebrates and bony fishes; it actively hunts and uses its pectoral fins to trap and move food to its mouth, taking advantage of seasonal opportunities like spawning squid. Reproduction is aplacental viviparous, with a short gestation of 2–4 months, allowing females to bear two litters of 4–13 pups per year, typically in warm equatorial waters. This prolific life history, combined with a global distribution, has led the IUCN to assess it as Least Concern. Rarely encountered except by fishery workers, it can inflict severe or fatal wounds with its tail spine. It is caught as bycatch throughout its range, usually discarded with high mortality, but numbers may be increasing due to heavy fishing of its natural predators and competitors such as sharks.

Did You Know?

• It can detect an electric field of well under 1 nV/cm at a distance of up to 30 cm.
• Females may bear two litters of 4–13 pups per year due to a short gestation period of 2–4 months.
• When handled, it exudes a thick black mucus that covers its body.