Small-spotted catshark

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Small-spotted catshark
Scyliorhinus canicula.jpg
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Scyliorhinidae
Genus: Scyliorhinus
Species: S. canicula
Binomial name
Scyliorhinus canicula
(Linnaeus, 1758)
Kleingefleckter KatzenhaiMap.png
Range in blue

The small-spotted catshark or lesser spotted dogfish, Scyliorhinus canicula, is a catshark of the family Scyliorhinidae. It is found on the continental shelves and the uppermost slopes off the coasts of Norway and the British Isles south to Senegal, including the Mediterranean between latitudes 63° N and 12° N. It can grow up to a length of 1 m (3 ft 3 in), and it can weigh more than 2 kg (4.4 lb).[1] It is found primarily over sandy, gravelly, or muddy bottoms at depths of a few metres down to 400 m.[2] S. canicula is one of the most abundant elasmobranchs in the Northeast Atlantic and Mediterranean Sea. The majority of the populations are stable in most areas.[3]

Description[edit]

Adult in aquarium

The S. canicula are small, shallow-water sharks with a slender shaped body with a blunt head. The two dorsal fins are located towards the tail end of the body. The texture of their skin is rough, similar to the coarseness of sandpaper.[4] The nostrils are located on the underside of the snout and are connected to the mouth by a curved groove. The underside is a lighter greyish-white colour and the upper side is greyish-brown with darker spots. Dorsal colour is sandy and tightly tan, with numerous small spots and dark brown or nearly black in colour. The teeth of S. canicula in males are larger than in females. In male S. canicula from West African waters, their jaws are stronger, larger and more calcinated. The reasons for the changes in their mouth dimensions during maturation could explain their feeding habits and adaptations for reproductive behavior.[5]

Reproduction[edit]

Egg with mature embryo

Reproduction is oviparous. They deposit egg-cases that are protected by a horny capsule with long tendrils. The deposited egg-cases are mostly on macroalgae in shallow coastal waters. When the egg-cases are deposited farther from shore, they are placed on sessile erect invertebrates. These eggs usually measure 4 cm by 2 cm, without ever exceeding 6 cm.[6] These egg-cases can be found around the coasts of Europe. The embryos develop for 5–11 months, depending on the sea temperature and the young are born with a measurement of 9–10 cm. Spawning can take place almost all year round.[6] However, there are can be seasonal patterns in spawning activity as well. For example, S. canicula females that are located off the Mediterranean coast of France, lay their eggs from March to June and in December. In the waters surrounding Great Britain, egg laying occurs in spring with a gap between August and October. In the Tunisian Coast, the sharks lay their eggs starting in spring, peaking in the summer and then slightly decreasing during Autumn.[7] Males reach sexual maturity with a length of about 37.1-48.8 cm. Females reach sexual maturity with a length of 36.4-46.7 cm.[8]

Feeding[edit]

S. canicula is considered an opportunistic species which preys on a wide range of food, such as, molluscs, echinoderms, polychaetes, crustaceans, sipunculids and tunicates. However, decapod crustaceans and fishes are their main food.[2] The dietary preferences change with age; younger animals prefer small crustaceans, older animals prefer hermit crabs and molluscs. It was also observed that the feeding intensity was highest during the summer due to the higher availability of prey life. Diet composition varies with body size. There are no significant differences in the feeding habits of the male and female S. canicula.[2] Behavioral analysis showed that the S. canicula uses a consistent behaviour pattern termed 'scale rasping', as a feeding mechanism. The sharks uses this mechanism by anchoring food items near their tail so that their rapid head and jaw movements can tear away bite-sized pieces from their prey. They are able to anchor food items near their body due to the tooth-like structures that are embedded in their skin. These structures normally assist with protection from predators, parasites and abrasions to the skin. This type of feeding in S. canicula can also be done due to their elongated body morphology.[9]

Model organism[edit]

The S. canicula is well-suited for comparative analysis of gastrulation for several reasons.

  • It is harvested in large numbers along all the coasts of Europe, and it is the only elasmobranch species known to us from which any stage of development can be obtained in abundance at any time of year.[3]
  • Fertilization is internal in the dogfish, but eggs are laid at early stages of development, before the formation of the blastocoel. Once laid, they can go on developing normally in the laboratory, simply in oxygenated seawater.[10]
  • The size and accessibility of the embryo makes analysis easier.
  • Five well-characterized stages can be distinguished between the onset of gastrulation and the beginning of neurulation.[10]

Threat level[edit]

The S. canicula is one of the most abundant elasmobranchs in the northeast Atlantic and Mediterranean. It is regularly used by near-shore fisheries for human consumption. The majority of S. canicula that are taken by commercial fisherman and recreational anglers are discarded. However, studies have shown that post-discard survival rates are extremely high, around 98%. Although localized depletion may have occurred in some areas, surveys have shown that populations are stable or are even increasing throughout the majority of its range. However, continued monitoring of landing and discarded data is important to avoid any future decline. This species is currently listed under "least Concern" on the IUCN Red List of Threatened Species, because there is no evidence to indicate that the global population has declined significantly. There are currently no conservation actions in place.[11]

See also[edit]

References[edit]

  1. ^ Kindersley, Dorling (2001,2005). Animal. New York City: DK Publishing. ISBN 0-7894-7764-5.  Check date values in: |date= (help)
  2. ^ a b c Rodriguez-Cabello, C., Sanchez, F., Olaso, I. 2007. Distribution patterns and sexual segregations of Scyliorhinus canicula (L.) in the Cantabrian Sea. Journal of Fish Biology. 70: 1568-1586
  3. ^ a b Ballard, W., Mellinger, J., Lechenault, H. 2005. A series of normal stages for development of Scyliorhinus canicula the lesser spotted dogfish (Chondrichthyes: Scyliorhinidae). Journal of Experimental Zoology. 267: 318-336
  4. ^ McNeill, Ian. "Habitas :: National Museums Northern Ireland." Habitas :: National Museums Northern Ireland. N.p., n.d. Web. 16 Dec. 2010. <http://www.habitas.org.uk>
  5. ^ Erdogan, Z., Koc, H., Cakir, D. 2004. Sexual Dimorphism in the Small-Spotted Catshark, Scyliorhinus Canicula (L., 1758), From the Edremit Bay (Turkey). Ser. his. nat, 262: 4-18.
  6. ^ a b Ellis, J.R., Shackley, S.E. 1997. The reproductive biology of Scyliorhinus canicula in the Bristol Channel, U.K. Journal of Fish Biology, 51: 361-372
  7. ^ Capae, C., Reynaud, C.,Vergne, Y., Quignard, J. 2008. Biological observations on the smallspotted catshark Scyliorhinus canicula (Chondrichthyes: Scyliorhinidae) off the Languedocian coast (southern France, northern Mediterranean). Pan-American Journal of Aquatic Sciences, 3: 282-289
  8. ^ Ivory, P., Jeal, F., Nolan, C.P. 2005. Age determination, growth and reproduction in the lesser-spotted dogfish, Scyliorhinus canicula (L.). J. Northw. Atl. Fish. Sci., 35: 89-106.
  9. ^ Southall, E.J., Sims, D.W. 2003. Shark skin: a function in feeding. Proceedings of the Royal Society of London Series B-Biological Sciences, 270: 47-49.
  10. ^ a b Mazan, S., Sauka-Splengler, T. 2004. "Gastrulation in the chondrichthyan, the dogfish Scyliorhinus canicula." Gastrulation: from cells to embryo. Ed. Claudio D. Stern. Cold Spring Harbor Laboratory Press. New York, NY, 151-155 pp.
  11. ^ GIibson, C., Valenti, S. V., Fowler, S. L., Fordham, S. V. 2006. The Conservation Status of Northeast Atlantic Chondrichthyans; Report of the IUCN Shark Specialist Group Northeast Atlantic Regional Red List Workshop. VIII + 76pp. IUCN SSC Shark Specialist Group.