Cape lobster

Cape lobster
Herbst's 1792 illustration[Note 1]
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda
Family: Nephropidae
Genus: Homarinus
Kornfield, Williams & Steneck, 1995 [2]
Species: H. capensis
Binomial name
Homarinus capensis
(Herbst, 1792) [3]
Synonyms [4]
  • Cancer (Astacus) capensis Herbst, 1792
  • Astacus fulvus Fabricius, 1793
  • Homarus fulvus: Weber, 1795
  • Astacus capensis: Latreille, 1802
  • Cancer (Astacus) fulvus: Turton, 1806

The Cape lobster, Homarinus capensis, is a species of small lobster that lives off the coast of South Africa, from Dassen Island to Haga Haga. Only a few dozen specimens are known, mostly regurgitated by reef-dwelling fish. It lives in rocky reefs, and is thought to lay large eggs that have a short larval phase, or that hatch directly as a juvenile. The species grows to a total length of 10 cm (3.9 in), and resembles a small European or American lobster; it was previously included in the same genus, Homarus, although it is not very closely related to those species, and is now considered to form a separate, monotypic genus – Homarinus. Its closest relatives are the genera Thymops and Thymopides.

Distribution and ecology

Extreme points of the range of Homarinus capensis in South Africa

The Cape lobster is endemic to South Africa. It occurs from Dassen Island, Western Cape in the west to Haga Haga, Eastern Cape in the east, a range of 900 kilometres (560 mi).[5] Most of the known specimens were regurgitated by fish caught on reefs at depths of 20–40 metres (66–131 ft).[5] This suggests that the Cape lobster inhabits rocky substrates, and may explain its apparent rarity, since such areas are not amenable to dredging or trawling, and the species may be too small to be retained by lobster traps.[5]

Description

Homarinus capensis is considerably smaller than the large northern lobsters of the Atlantic Ocean, Homarus gammarus (the European lobster) and Homarus americanus (the American lobster), at 8–10 centimetres (3.1–3.9 in) total length, or 4–5 cm (1.6–2.0 in) carapace length.[4][6] Accounts of the colouration of H. capensis are very variable, from tawny, red or yellow to "a rather dark olive", similar to Homarus gammarus.[7]

Homarinus and Homarus are considered to be the most plesiomorphic genera in the family Nephropidae.[8] Nonetheless, the Cape lobster differs from Homarus in a number of characters. The rostrum of the Cape lobster is flattened, while that of Homarus is rounded in section, and curves upwards at the tip.[5] The three pairs of claws[Note 1] are covered with hairs in Homarinus, while those of Homarus are hairless.[4] The telson tapers along its length in Homarus, but has sides which are nearly parallel in Homarinus.[5] Although no egg-bearing females have been collected, the gonopores (openings of the oviducts) of female Cape lobsters are much larger than those of Homarus gammarus and Homarus americanus.[5] This is thought to indicate that Homarinus bears fewer, larger eggs than Homarus, and that either the larvae develop quickly into juveniles after hatching, or that the eggs hatch directly into juveniles.[5][10]

Taxonomy and evolution

Cape lobsters are elusive and rare, with only fourteen specimens having been collected between 1792 (the date of its first description) and 1992.[7] These include five males in the collections of the South African Museum (Cape Town), two in the Natural History Museum (London), one in each of the East London Museum, the Rijksmuseum van Natuurlijke Historie (Leiden) and the Albany Museum (Grahamstown), and one male and one female in the Muséum national d'histoire naturelle (Paris).[6] In 1992, a Cape lobster was discovered at Dassen Island, and the publicity the find generated resulted in more than 20 additional specimens being reported.[5]

The Cape lobster was first described by Johann Friedrich Wilhelm Herbst in 1792 as Cancer (Astacus) capensis.[9][11] It was independently described in 1793 by Johan Christian Fabricius as Astacus flavus, possibly based on the same type specimen.[9] When Friedrich Weber erected the genus Homarus in 1795, he included Fabricius' species in it, but this placement was not followed by later authors.[9] The species reached its current classification in 1995, when the monotypic genus Homarinus was erected by Irv Kornfield, Austin B. Williams and Robert S. Steneck.[7]

While analyses of morphology suggest a close relationship between Homarinus and Homarus, molecular analyses using mitochondrial DNA reveal that they are not sister taxa.[8] Both genera lack ornamentation such as spines and carinae, but are thought to have reached that state independently, through convergent evolution.[8] The closest living relative of Homarus is Nephrops norvegicus, while the closest relatives of Homarinus are Thymops and Thymopides.[8]

Notes

  1. 1 2 Johann Friedrich Wilhelm Herbst reported that the Cape lobster has five pairs of claws, based on an illustration sent to him from Copenhagen.[9] Later authors, including Thomas Roscoe Rede Stebbing, concluded that the illustrator must have made the error.[9]

References

  1. ↑ A. Cockcroft; M. Butler; T. Y. Chan; A. MacDiarmid & R. Wahle (2011). "Homarinus capensis". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. Retrieved January 1, 2012.
  2. ↑ "Homarinus Kornfield, Williams and Steneck, 1995". Integrated Taxonomic Information System. Retrieved June 25, 2011.
  3. ↑ "Homarinus capensis (Herbst, 1792)". Integrated Taxonomic Information System. Retrieved June 25, 2011.
  4. 1 2 3 Lipke B. Holthuis (1991). Homarus Weber, 1795 (PDF). Marine Lobsters of the World. FAO Fisheries Synopsis No. 125. Food and Agriculture Organization. pp. 57–60. ISBN 92-5-103027-8.
  5. 1 2 3 4 5 6 7 8 Ryusuke Kado; Jiro Kittaka; Yasuhiro Hayakawa & D. E. Pollock (1994). "Recent discoveries of the "rare" species Homarus capensis (Herbst, 1792) on the South African coast". Crustaceana. 67 (1): 71–75. doi:10.1163/156854094x00305. JSTOR 20104967.
  6. 1 2 Torben Wolff (1978). "Maximum size of lobsters (Homarus) (Decapoda, Nephropidae)". Crustaceana. 34 (1): 1–14. doi:10.1163/156854078x00510. JSTOR 20103244.
  7. 1 2 3 Irv Kornfield; Austin B. Williams (1995). "Assignment of Homarus capensis (Herbst, 1792), the Cape lobster of South Africa, to the new genus Homarinus (Decapoda: Nephropidae)" (PDF). Fishery Bulletin. 93: 97–102.
  8. 1 2 3 4 Dale Tshudy; Rafael Robles; Tin-Yam Chan; Ka Chai Ho; Ka Hou Chu; Shane T. Ahyong; Darryl L. Felder (2009). "Phylogeny of marine clawed lobster families Nephropidae Dana, 1852, and Thaumastochelidae Bate, 1888, based on mitochondrial genes". In Joel W. Martin; Keith A. Crandall; Darryl L. Felder. Decapod Crustacean Phylogenetics. CRC Press. pp. 357–368. doi:10.1201/9781420092592-c18. ISBN 978-1-4200-9258-5.
  9. 1 2 3 4 5 L. B. Holthuis (1986). "J. C. Fabricius' (1798) species of Astacus, with an account of Homarus capensis (Herbst) and Eutrichocheles modestus (Herbst) (Decapoda Macrura)" (PDF). Crustaceana. 50 (3): 243–256. doi:10.1163/156854086X00278.
  10. ↑ Bruce F. Phillips (2006). Lobsters: Biology, Management, Aquaculture and Fisheries. John Wiley & Sons. p. 62. ISBN 978-1-4051-2657-1.
  11. ↑ Tin-Yam Chan (2010). Martyn E. Y. Low; S. H. Tan, eds. "Annotated checklist of the world's marine lobsters (Crustacea: Decapoda: Astacidea, Glypheidea, Achelata, Polychelida)" (PDF). Zootaxa. Suppl. 23: 153–181.

External links

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