Horseshoe Crab
Get Horseshoe Crab essential facts below. View Videos or join the Horseshoe Crab discussion. Add Horseshoe Crab to your Like2do.com topic list for future reference or share this resource on social media.
Horseshoe Crab

Limulidae
Temporal range: Late Ordovician-present
Limulus polyphemus.jpg
Limulus polyphemus
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Class: Merostomata
Order: Xiphosura
Suborder: Xiphosurida
Family: Limulidae
Leach, 1819 [1]
Genera

Horseshoe crabs are marine and brackish water arthropods of the family Limulidae, suborder Xiphosurida, and order Xiphosura.[2]

Horseshoe crabs live primarily in and around shallow coastal waters on soft sandy or muddy bottoms. They occasionally come onto shore to mate. They are commonly eaten in Asia, and used as fishing bait, in fertilizer and in science (especially Limulus amebocyte lysate). In recent years, population declines have occurred as a consequence of coastal habitat destruction and overharvesting.[2]Tetrodotoxin may be present in Carcinoscorpius rotundicauda.[3]

Because of their origin 450 million years ago, horseshoe crabs are considered living fossils.[4]

Classification

Horseshoe crabs superficially resemble crustaceans but belong to a separate subphylum of the arthropods, Chelicerata, and are closely related to arachnids.[5] Horseshoe crabs are closely related to the extinct eurypterids (sea scorpions), which include some of the largest arthropods to have ever existed, and the two may be sister groups.[5][6] (Other studies have placed eurypterids closer to the arachnids in a group called Metastomata.)[7] The earliest horseshoe crab fossils are found in strata from the late Ordovician period, roughly 450 million years ago.

The Limulidae are the only recent family of the order Xiphosura, and contains all four living species of horseshoe crabs:[1][2]

  • Carcinoscorpius rotundicauda, the mangrove horseshoe crab, found in South and Southeast Asia
  • Limulus polyphemus, the Atlantic or American horseshoe crab, found along the American Atlantic coast and in the Gulf of Mexico
  • Tachypleus gigas, the Indo-Pacific, Indonesian, Indian or southern horseshoe crab, found in South and Southeast Asia
  • Tachypleus tridentatus, the Chinese, Japanese or tri-spine horseshoe crab, found in Southeast and East Asia

Anatomy and behavior

Underside of a horseshoe crab showing the legs and book gills

The entire body of the horseshoe crab is protected by a hard carapace. It has two compound lateral eyes, each composed of about 1,000 ommatidia, plus a pair of median eyes that are able to detect both visible light and ultraviolet light, a single endoparietal eye, and a pair of rudimentary lateral eyes on the top. The latter become functional just before the embryo hatches. Also, a pair of ventral eyes is located near the mouth, as well as a cluster of photoreceptors on the telson. The horseshoe crab has five additional eyes on top of its shell. Despite having relatively poor eyesight, the animals have the largest rods and cones of any known animal, about 100 times the size of humans',[8][9] and their eyes are a million times more sensitive to light at night than during the day.[10] The mouth is located in the center of the legs, whose bases are referred to as gnathobases and have the same function as jaws and help grind up food. The horseshoe crab has five pairs of legs for walking, swimming, and moving food into the mouth, each with a claw at the tip, except for the last pair.

External video
Limulus polyphemus horseshue crab on coast.jpg
Rendezvous with a Horseshoe Crab, August 2011, 4:34, NewsWorks
The Horseshoe Crab Spawn, June 2010, 5:08, HostOurCoast.com
Horseshoe Crabs Mate in Massive Beach "Orgy", June 2014, 3:29, National Geographic

Behind its legs, the horseshoe crab has book gills, which exchange respiratory gases, and are also occasionally used for swimming.[11] As in other arthropods, a true endoskeleton is absent, but the body does have an endoskeletal structure made up of cartilaginous plates that support the book gills. They are more often found on the ocean floor searching for worms and molluscs, which are their main food. They may also feed on crustaceans and even small fish.[]

Females are about 20-30% larger than males.[12] The smallest species is C. rotundicauda and the largest is T. tridentatus.[13] On average, males of C. rotundicauda are about 30 cm (12 in) long, including a tail (telson) that is about 15 cm (5.9 in), and their carapace (prosoma) is about 15 cm (5.9 in) wide.[14] Some southern populations (in the Yucatán Peninsula) of L. polyphemus are somewhat smaller, but otherwise this species is larger.[12] In the largest species, T. tridentatus, females can reach as much as 79.5 cm (31.3 in) long, including their tail, and up to 4 kg (8.8 lb) in weight.[15] This is only about 10-20 cm (4-8 in) longer than the largest females of L. polyphemus and T. gigas, but roughly twice the weight.[16][17] The juveniles grow about 33% larger with every molt until reaching adult size.[18]

Horseshoe crabs normally swim upside down, inclined at about 30° to the horizontal and moving at about 10-15 cm/s.[19][20][21]
Horseshoe crabs have two primary compound eyes and seven secondary simple eyes. Two of the secondary eyes are on the underside.[22][23]
Painting by Heinrich Harder, c. 1916

Breeding

Horseshoe crabs mating
Horseshoe crab eggs

During the breeding season, horseshoe crabs migrate to shallow coastal waters. A male selects a female and clings to her back. Often, several males surround the female and all fertilize together, which makes it easy to spot and count females as they are the large center carapace surrounded by 3-5 smaller ones. The female digs a hole in the sand and lays her eggs while the male(s) fertilize them. The female can lay between 60,000 and 120,000 eggs in batches of a few thousand at a time. In L. polyphemus, the eggs take about two weeks to hatch; shore birds eat many of them before they hatch. The larvae molt six times during the first year.[24]

Natural breeding of horseshoe crabs in captivity has proven to be difficult. Some evidence indicates that mating takes place only in the presence of the sand or mud in which the horseshoe crab's eggs were hatched. It is not known with certainty what is in the sand that the crab can sense, nor how they sense it.[25]Artificial insemination and induced spawning has been done at a relatively large scale in captivity, and eggs/juveniles collected from the wild are often raised to adulthood in captivity.[26][27]

Threats

Harvest for blood

Horseshoe crabs use hemocyanin to carry oxygen through their blood. Because of the copper present in hemocyanin, their blood is blue. Their blood contains amebocytes, which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens. Amebocytes from the blood of L. polyphemus are used to make Limulus amebocyte lysate, which is used for the detection of bacterial endotoxins in medical applications.[28] This means there is a high demand for harvesting the blood, which involves collecting and bleeding the animals, and then releasing them back into the sea. Most of the animals survive the process; mortality is correlated with both the amount of blood extracted from an individual animal, and the stress experienced during handling and transportation.[29] Estimates of mortality rates following blood harvesting vary from 3-15%[30] to 10-30%.[31][32][33] Approximately 500,000 crabs are harvested annually.[34]

Bleeding may also prevent female horseshoe crabs from being able to spawn or decrease the number of eggs they are able to lay. Up to 30% of an individual's blood is removed, according to the biomedical industry, and the horseshoe crabs spend between one and three days away from the ocean before being returned. Some scientists are skeptical that certain companies return their horseshoe crabs to the ocean at all, instead suspecting them of selling the horseshoe crabs as fishing bait.[35]

Fishery

Horseshoe crabs are used as bait to fish for eels (mostly in the United States) and whelk, or conch. However, fishing with horseshoe crab is temporarily forbidden in New Jersey (moratorium on harvesting) and restricted to male crabs in Delaware. A permanent moratorium is in effect in South Carolina.[36] The eggs are eaten in parts of Southeast Asia and China.[37]

A low horseshoe crab population in the Delaware Bay is hypothesized to endanger the future of the red knot. Red knots, long-distance migratory shorebirds, feed on the protein-rich eggs during their stopovers on the beaches of New Jersey and Delaware.[38] An effort is ongoing to develop adaptive-management plans to regulate horseshoe crab harvests in the bay in a way that protects migrating shorebirds.[39]

Shoreline development

Development along shorelines is dangerous to horseshoe crab spawning, limiting available space and degrading habitat. Bulkheads can block access to intertidal spawning regions as well.[40]

References

  1. ^ a b K?ichi Sekiguchi (1988). Biology of Horseshoe Crabs. Science House. ISBN 978-4-915572-25-8. 
  2. ^ a b c Stine Vestbo; Matthias Obst; Francisco J. Quevedo Fernandez; Itsara Intanai; Peter Funch (2018). "Present and Potential Future Distributions of Asian Horseshoe Crabs Determine Areas for Conservation". Frontiers in Marine Science. 5 (164): 1-16. doi:10.3389/fmars.2018.00164. 
  3. ^ Attaya Kungsuwan; Yuji Nagashima; Tamao Noguchi; et al. (1987). "Tetrodotoxin in the Horseshoe Crab Carcinoscorpius rotundicauda Inhabiting Thailand" (PDF). Nippon Suisan Gakkaishi. 53 (2): 261-266. doi:10.2331/suisan.53.261. 
  4. ^ David Sadava; H. Craig Heller; David M. Hillis; May Berenbaum (2009). Life: the Science of Biology (9th ed.). W. H. Freeman. p. 683. ISBN 978-1-4292-1962-4. 
  5. ^ a b Garwood, Russell J.; Dunlop, Jason A. (13 November 2014). "Three-dimensional reconstruction and the phylogeny of extinct chelicerate orders". PeerJ. 2: e641. doi:10.7717/peerj.641. PMC 4232842Freely accessible. PMID 25405073. Retrieved . 
  6. ^ Clarke JM, Ruedemann R. The Eurypterida of New York. 
  7. ^ Weygoldt P, Paulus HF (1979). "Untersuchungen zur Morphologie, Taxonomie und Phylogenie der Chelicerata". Zeitschrift für zoologische Systematik und Evolutionsforschung. 17 (2): 85-116, 177-200. doi:10.1111/j.1439-0469.1979.tb00694.x. 
  8. ^ Anatomy: Vision - The Horseshoe Crab
  9. ^ "Horseshoe Crabs, Limulus polyphemus". MarineBio.org. 
  10. ^ Palumbi, Stephen R.; Palumbi, Anthony R. (23 February 2014). "The Extreme Life of the Sea". Princeton University Press – via Google Books. 
  11. ^ "The biology of cartilage. I. Invertebrate cartilages:Limulus gill cartilage". ResearchGate. 
  12. ^ a b Zaldívar-Rae, J.; Sapién-Silva, R.E.; Rosales-Raya, M.; Brockmann, H.J. (2009). "American horseshoe crabs, Limulus polyphemus, in México: open possibilities". In J.T. Tanacredi; M.L. Botton; D.R. Smith. Biology and Conservation of Horseshoe Crabs. Springer. pp. 97-113. ISBN 9780387899589. 
  13. ^ "About the Species". The Horseshoe Crab. Retrieved 2018. 
  14. ^ T.C. Srijaya; P.J. Pradeep; S. Mithun; A. Hassan; F. Shaharom; A. Chatterji (2010). "A New Record on the Morphometric Variations in the Populations of Horseshoe Crab (Carcinoscorpius rotundicauda Latreille) Obtained from Two Different Ecological Habitats of Peninsular Malaysia". Our Nature. 8 (1): 204-211. doi:10.3126/on.v8i1.4329. 
  15. ^ Azwarfarid Manca; Faridah Mohamad; Amirrudin Ahmad; Muhd Fawwaz Afham Mohd Sofa; Noraznawati Ismail (2017). "Tri-spine horseshoe crab, Tachypleus tridentatus (L.) in Sabah, Malaysia: the adult body sizes and population estimate". Journal of Asia-Pacific Biodiversity. 10 (3): 355-361. doi:10.1016/j.japb.2017.04.011. 
  16. ^ "Horseshoe Crab (Limulus polyphemus)". WAZA. Retrieved 2018. 
  17. ^ A. Raman Noor Jawahir; Mohamad Samsur; Mohd L. Shabdin; Khairul-Adha A. Rahim (2017). "Morphometric allometry of horseshoe crab, Tachypleus gigas at west part of Sarawak waters, Borneo, East Malaysia". AACL Bioflux. 10 (1): 18-24. 
  18. ^ Lesley Cartwright-Taylor; Julian Lee; Chia Chi Hsu (2009). "Population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore" (PDF). Aquatic Biology. 8 (1): 61-69. doi:10.3354/ab00206. 
  19. ^ Manton SM (1977) The Arthropoda: habits, functional morphology, and evolution Page 57, Clarendon Press.
  20. ^ Shuster CN, Barlow RB and Brockmann HJ (Eds.) (2003) The American Horseshoe Crab Pages 163-164, Harvard University Press. ISBN 9780674011595.
  21. ^ Vosatka ED (1970). "Observations on the Swimming, Righting, and Burrowing Movements of Young Horseshoe Crabs, Limulus Polyphemus" (PDF). The Ohio Journal of Science. 70 (5): 276-283. Archived (PDF) from the original on November 25, 2017. 
  22. ^ Battelle, B.A. (December 2006), "The eyes of Limulus polyphemus (Xiphosura, Chelicerata) and their afferent and efferent projections.", Arthropod Structure & Development, 35 (4): 261-74, doi:10.1016/j.asd.2006.07.002, PMID 18089075. 
  23. ^ Barlow RB (2009) "Vision in horseshoe crabs" Pages 223-235 in JT Tanacredi, ML Botton and D Smith, Biology and Conservation of Horseshoe Crabs, Springer. ISBN 9780387899589.
  24. ^ "The Rabbit and the Horse Shoe Crab". September 23, 2014. Retrieved . 
  25. ^ David Funkhouser (April 15, 2011). "Crab love nest". Scientific American. 304 (4): 29. doi:10.1038/scientificamerican0411-29. 
  26. ^ Yan Chen; C. W. Lau; S. G. Cheung; C. H. Ke; Paul K. S. Shin (2010). "Enhanced growth of juvenile Tachypleus tridentatus (Chelicerata: Xiphosura) in the laboratory: a step towards population restocking for conservation of the species". Aquatic Biology. 11: 37-40. doi:10.3354/ab00289. 
  27. ^ Ruth H. Carmichael; Erik Brush (2012). "Three decades of horseshoe crab rearing: A review of conditions for captive growth and survival". Reviews in Aquaculture. 4 (1): 32-43. doi:10.1111/j.1753-5131.2012.01059.x. 
  28. ^ "Data". /www.horseshoecrab.org. 
  29. ^ Lenka Hurton (2003). Reducing post-bleeding mortality of horseshoe crabs (Limulus polyphemus) used in the biomedical industry (PDF) (M.Sc. thesis). Virginia Polytechnic Institute and State University. 
  30. ^ "Crash: A Tale of Two Species - The Benefits of Blue Blood - Nature - PBS". 10 June 2008. 
  31. ^ The Blood Harvest The Atlantic, 2014.
  32. ^ Carmichael, R.H.; Shin, M.L.; Cheung, S.G. (Eds.) (2015). Changing Global Perspectives on Horseshoe Crab Biology, Conservation and Management. Springer International Publishing. 
  33. ^ Chesler, Caren. "Medical Labs May Be Killing Horseshoe Crabs". Scientific American. Scientific American. Retrieved 2018. 
  34. ^ Chesler, Caren. "The Blood of the Crab". Popular Mechanics (13 April 2017). Retrieved 2017. 
  35. ^ Chesler, Caren (June 9, 2016). "Medical Labs May Be Killing Horseshoe Crabs". Scientific American. Retrieved . 
  36. ^ "Horseshoe crab". SC DNR species gallery. Archived from the original on March 31, 2016. Retrieved . 
  37. ^ ?. "Vol.56 ". . Archived from the original on 2003-08-13. Retrieved . 
  38. ^ "Red knots get to feast on horseshoe crab eggs". Environment News Service. March 26, 2008. Retrieved . 
  39. ^ "Critter Class Hodge Podge (Horseshoe crabs and Wooly Bears)" (PDF). The Wildlife Center. October 26, 2011. Retrieved . 
  40. ^ "Conservation". ERDG. Retrieved . 

Further reading

External links


  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

Horseshoe_crab
 



 

Top US Cities

Like2do.com was developed using defaultLogic.com's knowledge management platform. It allows users to manage learning and research. Visit defaultLogic's other partner sites below:
PopFlock.com : Music Genres | Musicians | Musical Instruments | Music Industry
NCR Works : Retail Banking | Restaurant Industry | Retail Industry | Hospitality Industry