Libinia emarginata

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Species of crustacean

title: "Libinia emarginata" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["majoidea", "crabs-of-the-atlantic-ocean", "crustaceans-described-in-1815", "taxa-named-by-william-elford-leach"] description: "Species of crustacean" topic_path: "general/majoidea" source: "https://en.wikipedia.org/wiki/Libinia_emarginata" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Species of crustacean ::

| name = Libinia emarginata | image = Libinia emarginata.png | genus = Libinia | species = emarginata | authority = Leach, 1815 | synonyms = Libinia canaliculata Say, 1817 | synonyms_ref =

Libinia emarginata, the portly spider crab, common spider crab or nine-spined spider crab, is a species of stenohaline crab that lives on the Atlantic coast of North America.

Distribution

Libinia emarginata occurs from Nova Scotia to the Florida Keys and through the Gulf of Mexico. It lives at depths of up to 160 ft, with exceptional records of up to 400 ft.

Description

Libinia emarginata is roughly triangular in outline and very heavily calcified, with a carapace about 4 in long and a leg span of 12 in. The whole crab is khaki, and the carapace is covered in spines and tubercles, and, as with other decorator crabs, often clothes itself in debris and small invertebrates.

Reproduction

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b2/Libinia_emarginata.jpg" caption="A mating aggregation of ''L. emarginata''"] ::

Mating takes place, and eggs are produced from June to September. The eggs are initially a bright orange-red, but turn brown during development, which takes around 25 days. The eggs then hatch as zoea larvae, and the female can produce another brood of eggs within 12 hours, unlike many other crab species whose females only mate immediately after molting.

Similar species

Libinia emarginata is very similar to Libinia dubia with which it is largely sympatric. They can be told apart by examining the row of spines along the center of the carapace: in L. emarginata there are nine, while in L. dubia there are only six. Also, the rostrum of L. dubia is more deeply forked than that of L. emarginata.

Ecology and behavior

Libinia emarginata lives on various substrates, at depths of up to 150 ft. Adults are sluggish and not aggressive, and younger crabs are frequently covered with sponges and hydroids.

Despite its small size, in comparison to other predatory crabs, L. emarginata feeds on large starfish such as Asterias forbesi.

Unusually for crabs, L. emarginata preferentially walks forwards, rather than sideways, although they are also capable of sidelong movement. Its skeletal, muscular and neural anatomy more closely resembles that of forward-walking species, rather than that of more closely related sideways-walking species.

L. emarginata will mate in large aggregations. These aggregations may function as a protective mechanism during reproduction. Males of L. emarginata show an unusual "obstetrical behavior", in which gravid females who are about to release their larvae are held behind the male and aggressively protected.

References

References

  1. {{ITIS
  2. Peter K. L. Ng. (2008). "Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world". [[Raffles Bulletin of Zoology]].
  3. Harriet Perry. (2004). "A Picture Guide to Shelf Invertebrates from the Northern Gulf of Mexico". [[Gulf States Marine Fisheries Commission]].
  4. Alice Jane Lippson. (2006). "Life in the Chesapeake Bay". [[JHU Press]].
  5. Gertrude W. Hinsch. (1968). "Reproductive behavior in the spider crab, ''Libinia emarginata'' (L.)". [[The Biological Bulletin]].
  6. Andrew J. Martinez. (2003). "Marine Life of the North Atlantic: Canada to New England". [[Aqua Quest Publications]].
  7. John C. Aldrich. (1976). "The spider crab ''Libinia emarginata'' Leach, 1815 (Decapoda Brachyura), and the starfish, an unsuitable predator but a cooperative prey". [[Crustaceana]].
  8. A. G. Vidal-Gadea. (2009). "Muscular anatomy of the legs of the forward walking crab, ''Libinia emarginata'' (Decapoda, Brachyura, Majoidea)". [[Arthropod Structure & Development]].
  9. A. G. Vidal-Gadea. (2008). "Skeletal adaptation for sideways and forwards walking in three species of decapod crustaceans". [[Arthropod Structure & Development]].
  10. Andrés G. Vidal-Gadea. (2013). "The evolutionary transition to sideways-walking gaits in brachyurans was accompanied by a reduction in the number of motor neurons innervating proximal leg musculature". [[Arthropod Structure & Development]].
  11. R. E. DeGoursey. (1989). "Aspects of a mating aggregation of the spider crab, ''Libinia emarginata''". Wood Hole Oceanographic Institution.

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