Mediterranean star rays

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Mediterranean star rays
Raja asterias 1838.jpg

Mediterranean star rays ( Raja asterias )

Systematics
Subclass : Plate gill (Elasmobranchii)
without rank: Stingray (batoidea)
Order : Rajiformes
Family : Real rays (Rajidae)
Genre : Raja
Type : Mediterranean star rays
Scientific name
Raja asterias
Delaroche , 1809

The Mediterranean starry ray ( Raja asterias ) is a Mediterranean endemic occurring rays of the family Rajidae (Skates and rays) in the class of cartilaginous fish ( Chondrichthyes ). The species was first described in 1809 by Delaroche.

classification

The Mediterranean star ray belongs to the class of cartilaginous fish (Chondrichthyes) and their subclass of sharks and rays (Elasmobranchii). Within these R. asterias belongs to the order of the Rajiformes and the family of the Rajidae.

morphology

Adults can reach a length of up to 80 cm; Females are sexually mature from a size of approx. 56 cm, males at approx. 52 cm. The snout is relatively pointed, the wing-like pectoral fins are almost sinusoidal. The ventral side of R. asterias is white, the upper side of the body is brownish in color. The top of the animals is covered with many dark spots, some of which are only faintly indicated. Light to whitish spots, some of which can also be framed by darker ones, are distributed irregularly over the body. An important characteristic here is that these spots do not reach the edge of the body disc. In young animals, the skin is soft and smooth, with increasing development towards the adult animal, spines form on the entire upper side, sometimes also on the underside. These structures are known as the skin dentricle. A row of narrow, curved spines (so-called orbital spines) run centrally along the back and tail. This series of 50–60 slightly irregular spines extends from the neck to the first dorsal fin, and is partially interrupted along the back. One or two individual thorns can also appear between the widely spaced dorsal fins. In some cases there is also a second, parallel row of thorns on the tail, this has so far only been observed in adult animals. R. asterias has a so-called ampoule organ, the Lorenzini ampoules , which are electro-sensitive and can thus be used to search for food. R. asterias can be confused with Raja polystigma , which, however, has clear eye spots and whose dark spots on the upper side of the body also cover the edges of the body disc. Furthermore, this species can be confused with the thorn stingray ( R. clavata ), which however has distinct dark circles on the tail. Around the Mediterranean star rays from the spot rays ( R. montagui ) and the Blond rays ( R. brachyura to) distinguish, must be paid to the bright spots on the body top surface. These are not as distinct in these two species as in R. asterias .

distribution

The very dispersed ray species has a distribution area that is mainly limited to the central and western Mediterranean. In the eastern parts they are only rarely found in the Black Sea. Sightings on the coast of Tunisia, Algeria and the Moroccan coast are also described. In general, the species is considered to be endemic to the Mediterranean, but recent finds of individual individuals in the Atlantic (Gulf of Cádiz) suggest that it is also found outside the Mediterranean.

habitat

Mediterranean star rays prefer to live in coastal (benthic) areas, on sandy or muddy soils, and sometimes they bury their bodies in the sediment. This species occurs in shallow waters down to a depth of 150 m, but mainly in areas of 20–80 m. One specimen was documented in the Ionian Sea at a depth of 343 m.

nutrition

Rays generally live karnivor, the Mediterranean starry ray preferred primarily crustaceans (special crab species), some fish and cephalopods (cephalopods) and polychaete (Polychaeta). The food sources suggest that R. asterias occupies an important position as a predator in the food chain. The search for food takes place, as with most Elasmobranchi, via the electro-sensitive organ ( Lorenzini ampoules ), as well as visually tracking down the prey.

Reproduction

The animals are sexually mature from the age of 3–4 years. Reproduction occurs twice a year, in spring and autumn. The mating in the family of the Rajidae takes place by a so-called hug. Here the male holds the rear edge of the female's right or left pectoral fin firmly in its mouth, swings its caudal fin under that of the female and introduces its Klasper (male mating organ) into the rear end of the reproductive organ. Females lay between 40 and 60 eggs, these are laid in muddy or sandy ground at a depth of 30-40 m. The Mediterranean star ray reproduces, like all species of real rays, oviparously, i.e. the embryonic development takes place outside the mother animal. The eggs have a relatively hard shell, are rectangular in shape and have pointed ends characteristic of Elasmobranchii. Fresh eggs are yellowish to reddish brown in color and 4–5 cm long and approx. 3 cm wide. The embryos feed on the egg yolk until they hatch after a development time of 5–6 months. Depending on when the eggs are laid, this usually happens between March and July. The young are about 8 cm long when they hatch. Shortly thereafter, they migrate into shallow waters near the coast. As they age, they migrate to deeper zones.

threat

The species is not fished commercially. The IUCN classifies the Mediterranean star rays as NT ("near threatened") with a decreasing population ("decreasing"). This development can mainly be explained by the threat posed by commercial fishing. The animals are brought ashore unintentionally, especially through bottom trawls. In the Catalan part of the Mediterranean in particular, there has been a decline in the number of Mediterranean star rays brought ashore over the past 10 years. As so-called K-strategists, who are characterized by slow growth, late sexual maturity and a relatively low number of offspring, rays are generally more threatened by overfishing. The stocks therefore need more time to recover from this decimation.

Individual evidence

  1. ↑ a b c SERENA, F. 2005 Field identification guide to the sharks and rays of the Mediterranean and black sea. Rome, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, 63
  2. ↑ a b c d MCEACHRAN, JD (main reference), fishbase.org - Raja asterias, accessed December 19, 2019
  3. ↑ a b c d LOUISY, P., 2015. Europe and Mediterranean Marine Fish Identification Guide. Paris, Ulmer Verlag, 2015.
  4. ↑ HUREAU, L.-C. (ed.) species-identification.org - Raja asterias, accessed December 19, 2019
  5. ↑ a b c d NAVARRO, J., COLL, M., PREMINGER, M. & PALOMERA, I. 2013. Feeding ecology and trophic position of a Mediterranean endemic ray: consistency between sexes, maturity stages and seasons. Environmental Biology of Fishes, 96, 1315-1328.
  6. ↑ FERRA, C., FABI, G., POLIDORI, P., TASSETTI, AN, LEONI, S., PELLINI, G. & SCARCELLA, G. 2016. Raja asterias population assessment in FAO GFCM GSA17 area Abundance, distribution and demographic composition of the Mediterranean starry ray, Raja asterias (Chondrichthyes: Rajidae), in the Northern and Central Adriatic Sea. Mediterranean Marine Science, 17, 651-660.
  7. ↑ C. Capapé: Contribution à la biology of Rajidae des côtes tunisiennes. IV. Raja asterias Delaroche, 1809: répartition geographique et bathymétrique, sexualité, reproduction et fécondité. (Contribution to the biology of the Rajidae from the Tunisian coasts. 4. Raja asterias Delaroche, 1809. Geographic and bathymetric distribution repartition, sexuality, reproduction, fecundity). Bulletin du Muséum National d'Histoire Naturelle de Paris, 435, 1977, pp. 305-326.
  8. ↑ ORDINES, F., BARO, J., RAMIREZ-AMARO, S., SERENA, F. & SOBRINO, I. 2017. First Substantiated Record of Raja Asterias Delaroche, 1809 (Elasmobranchii: Rajiformes: Rajidae) in the Gulf of Cadiz , North-Eastern Atlantic. Acta Ichthyologica Et Piscatoria, 47, 101-106.
  9. ↑ a b c SERENA; F .; ABELLA, A., WALLS, R. & DULVY, N. 2015. Raja asterias. The IUCN Red List of Threatened Species 2015: e.T63120A48913317. doi : 10.2305 / IUCN.UK.2015-1.RLTS.T63120A48913317.en Accessed December 19, 2019
  10. ↑ Chryssi Mytilineou, Chrissi-Yianna Politou, Costas Papaconstantinou, Stefanos Kavadas, Gianfranco D'Onghia & Leticia Sion: Deep-water fish fauna in the Eastern Ionian Sea. Belgian Journal of Zoology, 135, 2005, pp. 229-233
  11. ↑ LUER, CA & GILBERT, PW 1985. Mating-Behavior, Egg Deposition, Incubation Period, and Hatching in the Clearnose Skate, Raja-Eglanteria. Environmental Biology of Fishes, 13, 161-171.
  12. ^ M. Barone, S. De Ranieri, O. Fabiani, A. Pirone & F. Serena: Gametogenesis and maturity stages scale of Raja asterias Delaroche, 1809 (Chondrichthyes, Raijdae) from the South Ligurian Sea. Hydrobiologia, 580, 2007, pp. 245-254.
  13. ↑ a b c Alessia Cariani, Silvia Messinetti, Alice Ferrari, Marco Arculeo, Juan J. Bonello, Leanne Bonnici, Rita Cannas, Pierluigi Carbonara, Alessandro Cau, Charis Charilaou, Najib El Ouamari, Fabio Fiorentino, Maria Cristina Follesa & Fausto Tinti: Improving the Conservation of Mediterranean Chondrichthyans: The ELASMOMED DNA Barcode Reference Library. Plos One, 12, 2017
  14. ↑ PORCU, C., MARONGIU, MF, BELLODI, A., CANNAS, R., CAU, A., MELIS, R., MULAS, A., SOLDOVILLA, G., VACCA, L. & FOLLESA, MC 2017. Morphological descriptions of the eggcases of skates (Rajidae) from the central-western Mediterranean, with notes on their distribution. Helgoland Marine Research, 71.
  15. ↑ IUCN REDLIST www.iucnredlist.org - Raja asterias, accessed December 19, 2019

Web links

Commons : Mediterranean Star Rays  - Collection of images, videos and audio files