The blue stingray (''Dasyatis chrysonota'') is a species of

whiptail stingray The whiptail stingrays are a family, the Dasyatidae, of rays in the order Myliobatiformes. They are found worldwide in tropical to temperate marine waters, and a number of species have also penetrated into fresh water in Africa, Asia, and Austra ...

of the family Dasyatidae often found in the coastal waters of

southern Africa Southern Africa is the southernmost subregion of the African continent, south of the Congo and Tanzania. The physical location is the large part of Africa to the south of the extensive Congo River basin. Southern Africa is home to a number of ...

Distribution and similar species

The species' common geographical distribution ranges from

St. Lucia Saint Lucia ( acf, Sent Lisi, french: Sainte-Lucie) is an island country of the West Indies in the eastern Caribbean. The island was previously called Iouanalao and later Hewanorra, names given by the native Arawaks and Caribs, two Amerin ...

on the southern tip of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

up to

Angola , national_anthem = " Angola Avante"() , image_map = , map_caption = , capital = Luanda , religion = , religion_year = 2020 , religion_ref = , coordina ...

and a depth distribution ranging from the surf zone to 110m depth. Although this is the typical geographical distribution, the species has also been found off the

Mediterranean coast The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the eas ...

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

and in the Gulf of Gabčs in southern

Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa , image_map2 = , capital = Tunis , largest_city = capital , ...

. ''D. chrysonota'' is easily distinguishable from other stingray species by the appearance of faint blue splotches and lines on its light-brown triangular disc body.

Growth and appearance

Their disc can reach a maximum width of approximately 75 cm. There are four size classes: small, medium, large, and very large. The ranges of each size class are as follows: small = <30 cm, medium = 30–45 cm, large = 45–60 cm, very large = >60 cm. The size of male and female blue stingray show no distinction from birth until adolescence (approximately 4 years old) in which sexual differences become noticeable. Once this threshold is reached, females exhibit a faster growth rate than males. The minimum age-at-maturity is 5 for males and 7 for females. Age estimates of ''D. chrysonota'' are often made based on the

vertebral centra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

which exhibits narrow dark bands and wide translucent bands that create a bunching effect. Seasonal fluctuations in temperature and light are likely significant controlling factors in growth rate and band formation. Months with warm temperatures often show higher growth rates than months with cold temperatures. One

opaque Opacity or opaque may refer to: * Impediments to (especially, visible) light: ** Opacities, absorption coefficients ** Opacity (optics), property or degree of blocking the transmission of light * Metaphors derived from literal optics: ** In lingu ...

and one

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions a ...

band is formed annually when the stingray is kept in captivity, which is also true for other closely related species such as '' Dasyatis dipterura'', the diamond stingray.Smith Wade D., Cailliet Gregor M., Melendez Everardo Mariano (2007) Maturity and growth characteristics of a commercially exploited stingray, Dasyatis dipterura. Marine and Freshwater Research 58, 54-66.

Diet and feeding habits

The

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

occupies different habitats throughout their lifetime and although they may feed on a wide variety of prey items, the proportions of the different prey could vary among different life stages and corresponding size classes. This could be a result of what is and isn't accessible to a small stingray versus a relatively large stingray that is able to dig deeper into sediment and extract particular types of prey like the

bat ray The bat ray (''Myliobatis californica'')Gill, T.N. (1865). "Note on the family of myliobatoids, and on a new species of ''Aetobatis''". ''Ann. Lyc. Nat. Hist. N. Y.'' 8, 135–138. is an eagle ray found in muddy or sandy sloughs, estuaries and ...

(''Myliobatis californica'') is able to do. ''D. chrysonota'' feed on a wide variety of benthic

epifauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zool ...

and infauna with an opportunistic feeding strategy. Although primary prey type changes between size classes of the stingray and the habitat that it feeds in, the main prey groups are

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made ...

s and

hemichordate Hemichordata is a phylum which consists of triploblastic, enterocoelomate, and bilaterally symmetrical marine deuterostome animals, generally considered the sister group of the echinoderms. They appear in the Lower or Middle Cambrian and includ ...

s. Crustaceans and molluscs are the most common prey among other closely related species of stingray. The feeding process includes prey searching, prey detection, and prey capture. Prey is searched for by gliding along the surface of the ocean, and once it is found the stingray lands upon the prey and the prey is drawn into its mouth with use of the jaw. The medium and large size classes of ''D. chrysonota'' are important predators in the nearshore sandy beach ecosystem in the

surf zone As ocean surface waves approach shore, they get taller and break, forming the foamy, bubbly surface called ''surf''. The region of breaking waves defines the surf zone, or breaker zone. After breaking in the surf zone, the waves (now reduced i ...

of southern African waters, however the majority of prey for the very large class size is found nearshore and offshore, mostly consisting of ''Callianassa spp.'' which does not occur in the surf zone.

Reproduction

Sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

of males is reached at a smaller size and at an earlier age than that of females. The

reproductive cycle In biology, a biological life cycle (or just life cycle or lifecycle when the biological context is clear) is a series of changes in form that an organism undergoes, returning to the starting state. "The concept is closely related to those of the ...

of the male blue stingray indicates a peak in sperm production from the month of September until December, resulting in a mating season consisting mostly of the austral spring and some of the austral summer. ''D. chrysonota'' have a relatively low fecundity which ranges from 1 to 7, with an average of 2–3 embryos per litter. Unlike other related ray species, a strong maternal size to litter size relationship does not exist. This may be related to uterus capacity of this species. Courtship and mating behavior of ''D. chrysonota'' is a rare occurrence. The species follows an annual reproductive cycle with birth following a nine-month gestation period.

Ovulation Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized ...

appears to start soon after

parturition Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...

, with ovulation and hence fertilization occurring between January and April. An offshore winter migratory pattern in which the rays are found inshore in the summer and disperse offshore during winter months coincides with their reproductive seasonality. Large ovarian eggs may range from 8–14 mm in diameter. The reproductive success of ''D. chrysonota'' is low based on average fecundity and active reproductive life span.

Value to humans

''D. chrysonota'' is a popular target species for recreational and competitive rock and surf anglers as well as recreational ski boat fishers. The species is at risk of over-exploitation as there is currently no proper management strategy in place for the protection of the species.

References

{{Taxonbar, from=Q2716553

blue stingray The blue stingray (''Dasyatis chrysonota'') is a species of whiptail stingray of the family Dasyatidae often found in the coastal waters of southern Africa. Distribution and similar species The species' common geographical distribution ranges ...

Ovoviviparous fish Marine fauna of Southern Africa