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Growth and development

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Horseshoe crab "trilobite" larvae

Growth from egg[1]

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Females are about 20–30% larger than males.[2] The smallest species is C. rotundicauda and the largest is T. tridentatus.[3] On average, males of C. rotundicauda are about 30 centimetres (12 inches) long, including a tail (telson) that is about 15 cm (6 in), and their carapace (prosoma) is about 15 cm (6 in) wide.[4] Some southern populations (in the Yucatán Peninsula) of L. polyphemus are somewhat smaller, but otherwise this species is larger.[2]

In the largest species, T. tridentatus, females can reach as much as 79.5 cm (31+1⁄4 in) long, including their tail, and up to 4 kg (9 lb) in weight.[5] 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.[6][7]

The juveniles grow about 33% larger with every molt until reaching adult size.[8] Atlantic horseshoe crabs molt in late July.[citation needed]

The larvae molt six times during the first year and annually after the first 3 or 4 years.[9]

Reproduction

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Horseshoe crabs mating
Horseshoe crab eggs

During the breeding season (spring and summer in the Northeast US, year-round in warmer locations or when the full moon rises), horseshoe crabs migrate to shallow coastal waters.[10] There they spawn on beaches and salt marshes.[11]

When mating, the smaller male clings to the back or opisthosoma of the larger female using specialized pedipalps.[10] This typically leaves scars, allowing younger females to be easily identified.[12] Female horseshoe crabs can lay between 60,000 and 120,000 eggs in batches of a few thousand at a time.[13] After being laid, the eggs are typically fertilized in between 20 to 30 minutes.[13] Procreation is done by both the main and additional "satellite males".[10] Satellite males surround the main pair and may have some success fertilizing eggs.[10] In L. polyphemus, the eggs take about two weeks to hatch with shore birds eating many of them in the process[10]

Natural breeding of horseshoe crabs in captivity has proven to be difficult.[14] 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.[14] However, it's not known with certainty what the animals sense in the sand, how they sense it, or why they only mate in its presence.[14]

Artificial insemination and induced spawning have been done on a relatively large scale in captivity, and eggs and juveniles collected from the wild are often raised to adulthood in captivity.[15][16] To preserve and ensure the continuous supply of horseshoe crabs, a breeding center was built in Johor, Malaysia where the crabs are bred and released back into the ocean in the thousands once every two years.[17] It is estimated to take around 12 years before they are suitable for consumption.[17]

References

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Citations

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  1. ^ Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D. (2004). Invertebrate zoology : a functional evolutionary approach. Internet Archive. Belmont, CA : Thomson-Brooks/Cole. p. 559. ISBN 978-0-03-025982-1.
  2. ^ a b Zaldívar-Rae J, Sapién-Silva RE, Rosales-Raya M, Brockmann HJ (2009). "American horseshoe crabs, Limulus polyphemus, in México: open possibilities". In J.T. Tanacredi, M.L. Botton, D.R. Smith (eds.). Biology and Conservation of Horseshoe Crabs. Springer. pp. 97–113. ISBN 9780387899589.
  3. ^ "About the Species". The Horseshoe Crab. Archived from the original on 12 February 2007. Retrieved 26 June 2018.
  4. ^ Srijaya TC, Pradeep PJ, Mithun S, Hassan A, Shaharom F, Chatterji A (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.
  5. ^ Manca A, Mohamad F, Ahmad A, Sofa MF, Ismail N (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.
  6. ^ "Horseshoe Crab (Limulus polyphemus)". WAZA. Archived from the original on 3 July 2017. Retrieved 26 June 2018.
  7. ^ Jawahir AR, Samsur M, Shabdin ML, Rahim KA (2017). "Morphometric allometry of horseshoe crab, Tachypleus gigas at west part of Sarawak waters, Borneo, East Malaysia". AACL Bioflux. 10 (1): 18–24.
  8. ^ Cartwright-Taylor L, Lee J, Hsu CC (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. Archived (PDF) from the original on 2020-08-01. Retrieved 2020-01-27.
  9. ^ "Molt". The Horseshoe Crab. Archived from the original on 2019-06-02. Retrieved 2019-06-02.
  10. ^ a b c d e "Facts About Horseshoe Crabs and FAQ". Florida Fish and Wildlife Conservation Commission. Archived from the original on 4 June 2023. Retrieved 19 January 2020.
  11. ^ Sasson, Daniel A; Chabot, Christopher C; Mattei, Jennifer H; Brunson, Jeff F; Hall, Fletcher K; Huber, Jeanette H; Kasinak, Jo-Marie E; McShane, Cole; Puckette, Paul T; Sundin, Gary; Kingsley-Smith, Peter R; Kendrick, Michael R (April 2024). "The American horseshoe crab ( Limulus polyphemus ) spawns regularly in salt marshes". Frontiers in Ecology and the Environment. 22 (5). Bibcode:2024FrEE...22E2738S. doi:10.1002/fee.2738. ISSN 1540-9295.
  12. ^ "The Horseshoe Crab, limulus polyphemus: 200 Millions Years of Existence, 100 Years of study". 2002. Archived (PDF) from the original on 11 November 2020. Retrieved 3 February 2020.
  13. ^ a b Mohamad Faizul Mat Isa (16 January 2021). "Belangkas : Potensi dan Masa Depan" [Horseshoe crabs: their potential and future]. Utusan Borneo (in Malay). Archived from the original on 17 January 2023. Retrieved 17 January 2023 – via Universiti Putra Malaysia.
  14. ^ a b c Funkhouser D (April 15, 2011). "Crab love nest". Scientific American. 304 (4): 29. Bibcode:2011SciAm.304d..29F. doi:10.1038/scientificamerican0411-29.
  15. ^ Chen Y, Lau CW, Cheung SG, Ke CH, Shin PK (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.
  16. ^ Carmichael RH, Brush E (2012). "Three decades of horseshoe crab rearing: A review of conditions for captive growth and survival". Reviews in Aquaculture. 4 (1): 32–43. Bibcode:2012RvAq....4...32C. doi:10.1111/j.1753-5131.2012.01059.x.
  17. ^ a b "Horseshoe crab business still a hit despite pandemic". The Star. 13 December 2020. Archived from the original on 23 April 2021. Retrieved 18 July 2021.
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