Catshark

Catsharks are ground sharks of the family Scyliorhinidae. They are the largest family of sharks with around 160 species placed in 17 genera.[2] Although they are generally known as catsharks, some species can also be called dogfish due to previous naming.[3] However, a dogfish may generally be distinguished from a catshark as catsharks lay eggs while dogfish have live young.[3] Like most bottom feeders, catsharks feed on benthic invertebrates and smaller fish. They are not harmful to humans.[3] The family is paraphyletic, containing several distinct lineages that do not form a monophyletic group.[4]

For additional species called "dogfish", see Dogfish (disambiguation).

Catsharks
Temporal range:
Whitesaddled catshark, Scyliorhinus hesperius
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Carcharhiniformes
Family: Scyliorhinidae
T. N. Gill, 1862

Genera
Small-spotted catshark
Small-spotted catshark, Scyliorhinus canicula

The family includes 17 genera and over 150 species,[1] making it the largest family of sharks.[5]

Cladogram
  • Scyliorhinidae
    • Scyliorhininae
    • Galeinae
      • Pentanchini
      • Galeini
        • Galeina
        • Halelaelurina
    • Atelomycterininae
    • Schroedericthyinae

Anatomy and appearance

Catsharks may be distinguished by their elongated, cat-like eyes and two small dorsal fins set far back. Most species are fairly small, growing no longer than 80 cm (31 in); a few, such as the nursehound (Scyliorhinus stellaris) can reach 1.6 m (5.2 ft) in length. Most of the species have a patterned appearance, ranging from stripes to patches to spots.

Characteristics of genus Apristurus are mostly dark bodies, and having a long anal fin that ends in front of where the lower caudal fin begins. The snouts of the species of Apristurus are flat. They also present upper and lower labial furrows.

The sonic hedgehog dentition expression is first found as a bilateral symmetrical pattern and is found in certain areas of the embryonic jaw.[6] Sonic hedgehog (a secreted protein that, in humans, is encoded by the SHH gene) is involved in the growth and patterning of different organs.[7] Every 18–38 days the teeth are replaced as is a common characteristic of the developmental process of sharks.

The "swell sharks" of the genus Cephaloscyllium have the curious ability to fill their stomachs with water or air when threatened, increasing their girth by a factor of one to three.

Some catsharks, such as the chain catshark are biofluorescent.[8][9][10]

Distribution

Catsharks are found around seabeds in temperate and tropical seas worldwide, ranging from very shallow intertidal waters to depths of 2,000 m (6,600 ft) or more, such as the members of genus Apristurus.[11] The red-spotted catshark lives in the shallower rocky waters ranging from Peru to Chile and migrates to deeper waters during the winter.[12] They are usually restricted to small ranges. Juvenile and adult chain dogfish live on the soft or rocky bottom of the Atlantic from Massachusetts to Nicaragua. Adults tend to live on the soft, sandy bottoms possibly due to their need of egg deposition sites.[13]

Behaviour

Some catsharks do not undergo long distance migrations because they are poor swimmers. Due to being nocturnal, some species sleep close together in crevices throughout the day and then go hunting at night.[2] Some species such as the small spotted catshark, Scyliorhinus canicula, are sexually monomorphic and exhibit habitat segregation, where males and females live in separate areas; males tend to live in open seabeds, while females tend to live in caves.[14] Some species of catsharks may deposit egg cases in structured habitats, which may also act as nurseries for the newly hatched sharks.[13]

Reproduction
Catshark egg (mermaids' purse)

Many species of catsharks, like the chain dogfish, are oviparous and lay eggs in tough egg cases with curly tendrils at each end, known as "mermaid's purses", for protection, onto the seabed.[15] Almost a year is needed for a catshark to hatch from the egg. Instead of laying the eggs and letting them sit for a year, some species of catsharks hold onto the eggs until a few months before the shark hatches. Some catsharks exhibit ovoviviparity, aplacental viviparous, by holding onto the embryos until they are completely developed and then give live birth.[2] Some species of catsharks mate by biting and holding the female’s pectoral fins and wrestle her into a mating position.

Aquaria

The Australian marbled catshark, Atelomycterus macleayi, is a favored type for home aquaria, because it rarely grows to more than 60 cm (24 in) in length. The coral catshark, however, is the most common scyliorhinid in home aquaria.[5]

References
  1. Froese, Rainer, and Daniel Pauly, eds. (2009). "Scyliorhinidae" in FishBase. January 2009 version.
  2. Compagno, L. J.; Dando, M.; Fowler, S. L. (2005). Sharks of the world. Princeton University Press. p. 186.
  3. Torrance, Jeremy. "What's in a name?". bbc.co.uk. BBC. Retrieved 22 August 2021.
  4. A. Soares, Karla D. (June 2020). "Comparative anatomy of the clasper of catsharks and its phylogenetic implications (Chondrichthyes: Carcharhiniformes: Scyliorhinidae)". Journal of Morphology. 281 (6): 591–607. doi:10.1002/jmor.21123. ISSN 0362-2525. PMID 32271501.
  5. Michael, Scott W. (March 2004). "Sharks at Home". Aquarium Fish Magazine. pp. 20–29.
  6. Smith, M. M.; Frase, G. J; Chaplin, N.; Hobbs, C.; Graham, A. (April 7, 2009). "Reiterative pattern of sonic hedgehog expression in the catshark dentition reveals a phylogenetic template for jawed vertebrates". Proceedings of the Royal Society B: Biological Sciences. 276 (1660): 1225–1233. doi:10.1098/rspb.2008.1526. PMC 2660956. PMID 19141424.
  7. Dassule, Helene; Lewis, Paula; Bei, Marianna; Maas, Richard; McMahon, Andrew P. (October 24, 2000). "Sonic Hedgehog regulates growth and morphogenesis of the tooth". Development. The Company of Biologists Ltd. 127 (22): 4775–4785. doi:10.1242/dev.127.22.4775. ISSN 1477-9129. PMID 11044393.
  8. "Scientists Discover 180 Species of Glowing Fish". Wired. Retrieved 2015-07-08.
  9. "Sharks Light Up in Neon Colors". video.nationalgeographic.com. Retrieved 2015-07-08.
  10. Sparks, John S.; Schelly, Robert C.; Smith, W. Leo; Davis, Matthew P.; Tchernov, Dan; Pieribone, Vincent A.; Gruber, David F. (January 8, 2014). "The Covert World of Fish Biofluorescence: A Phylogenetically Widespread and Phenotypically Variable Phenomenon". PLOS ONE. 9 (1): e83259. Bibcode:2014PLoSO...983259S. doi:10.1371/journal.pone.0083259. PMC 3885428. PMID 24421880.
  11. Gomes, U. L.; Signori, C. N.; Gadig, O. B. (2006). "Report on the smallfin catshark Apristurus parvipinnis Springer & Heemstra (Chondrichthyes, Scyliorhinidae) in Western South Atlantic with notes on its taxonomy". Panamjas.
  12. Farina, Jose M.; Ojeda, F. Patricio (May 3, 1993). "Abundance, Activity, and Trophic Patterns of the Redspotted Catshark, Schroederichthys chilensis, on the Pacific Temperate Coast of Chile". Copeia. 1993 (2): 545–549. doi:10.2307/1447159. JSTOR 1447159.
  13. Able, K.W.; Flescher, D. (1991). "Distribution and Habitat of Chain Dogfish, Scyliorhinus retifer, in the Mid-Atlantic Bight". Copeia. 1991 (1): 231–234. doi:10.2307/1446270. JSTOR 1446270.
  14. Wearmouth, V. J.; Southall, E. J.; Morritt, D.; Thompson, R. C.; Cuthill, I. C.; Partridge, J. C.; Sims, D. W. (2012). "Year-round sexual harassment as a behavioral mediator of vertebrate population dynamics". Ecological Monographs. 82 (3): 351–366. doi:10.1890/11-2052.1.
  15. Castro, J. I.; Bubucis, P. M.; Overstrom, N. A. (1988). "The Reproductive Biology of the Chain Dogfish, Scyliorhinus retifer". Copeia. 1988 (3): 740. doi:10.2307/1445396. JSTOR 1445396.
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