Thursday, 3 December 2015

Common stingray - Dasyatis pastinaca (Linnaeus, 1758)

The common stingray (Dasyatis pastinaca) is a species of stingray in the family Dasyatidae, found in the northeastern Atlantic Oceanand the Mediterranean and Black Seas. It typically inhabits sandy or muddy habitats in coastal waters shallower than 60 m (200 ft), often burying itself in sediment. Usually measuring 45 cm (18 in) across, the common stingray has a diamond-shaped pectoral fin disc slightly wider than long, and a whip-like tail with upper and lower fin folds. It can be identified by its plain coloration and mostly smooth skin, except for a row of tubercles along the midline of the back in the largest individuals.
The predominant prey of the common stingray are bottom-dwelling crustaceans, though it also takes molluscs, polychaete worms, and small bony fishes. It is aplacental viviparous: the embryos are nourished by yolk and later histotroph ("uterine milk") produced by the mother. Females bear 4–9 young twice per year in shallow water, after a gestation period of four months. The common stingray can inflict a painful, though rarely life-threatening, wound with its venomous tail spine. During classical antiquity, its sting was ascribed many mythical properties. This species is not sought after by commercial fisheries, but is taken in large numbers as by catch and utilized for food, fishmeal, and liver oil. Its population is apparently dwindling across its range, though there is not yet sufficient data for the International Union for Conservation of Nature (IUCN) to assess it beyond Data Deficient.
The common stingray is found throughout the Mediterranean and Black Seas. It also occurs, though in significantly lower numbers, in the northeastern Atlantic Ocean from southern Norway and the western Baltic Sea to Madeira and the Canary Islands.This bottom-dwelling species can be found from the shore to a depth of 200 m (660 ft), though it is not usually found deeper than 60 m (200 ft). It favors sandy or muddy bottoms in calm water, and is also sometimes encountered near rocky reefs or in estuaries, as it is tolerant of low salinity.Off the Azores, common stingrays are most abundant in summer and least abundant in winter, suggestive of a seasonal shift in range and/or depth as has been documented in other ray species
The common stingray has been reported to reach a width of 1.4 m (4.6 ft) and a length of 2.5 m (8.2 ft), though a width of 45 cm (18 in) is more typical. The flattened pectoral fin disc is diamond-shaped and slightly wider than it is long, with narrowly rounded outer corners. The leading margins of the disc are almost straight and converge on a pointed, slightly protruding snout; the trailing margins of the disc are convex. The eyes are smaller than the spiracles (paired respiratory openings), which are placed closely behind. There are 28–38 upper tooth rows and 28–43 lower tooth rows; the teeth are small and blunt, and arranged into flattened surfaces. There are five papillae (nipple-like structures) across the floor of the mouth.
The tail is slender and whip-like, measuring approximately half as long as the disc. A stinging spine with strong serrations, measuring up to 35 cm (14 in) long and equipped with a venom gland at its base, is positioned about a third of the distance along the tail. A second or even third spine may also be present, as the spines are regularly replaced and new spines grow in before existing ones have been shed. The tail behind the spine bears a low cutaneous fold on top and a short, deep fold underneath. The body and tail are smooth, save for a few dermal denticles on the leading edge of the disk; older individuals may also develop a row of bony knobs along the midline of the back. This species is a solid gray, brown, reddish, or olive-green above, and whitish below with dark fin margins. Young rays may have white spots
Encountered singly or in "social" groups, the common stingray appears to segregate by sex to some degree and may be more active at night, tending to bury itself in sediment during daytime. It feeds on a wide variety of bottom-dwelling organisms, including crustaceanscephalopodsbivalvespolychaete worms, and small bony fishes. It is reportedly does great damage tocultured shellfish beds. One study in the Gulf of İskenderun off Turkey found that crustaceans comprised some 99% of its diet, with fish prey becoming increasingly important with age. Another study off the coast of Cilicia, Turkey, found the most important dietary component to be the penaeid shrimp Metapenaeus stebbingi, followed by the pistol shrimp Alpheus glaber and the swimming crab Charybdis longicollis; cephalopods were relatively important for males, while fishes were important for females.[17]Common stingrays have been observed closely following each other in the presence of food, possibly to take advantage of other individuals' foraging success.From Wikipedia, the free encyclopedia
Underwater photos and video Akamas 3/10/2015  by Kostas Aristeidou
Underwater photos 25.06.2016 by Costas Constantinou

No comments:

Post a Comment