Mangrove horseshoe crab

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Mangrove horseshoe crab
Carcinoscorpius rotundicauda (mangrove horseshoe crab).jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Order: Xiphosura
Family: Limulidae
Genus: Carcinoscorpius
Pocock, 1902
Species:
C. rotundicauda
Binomial name
Carcinoscorpius rotundicauda
(Latreille, 1802)
Synonyms
  • Limulus rotundicaudaLatreille, 1802

The mangrove horseshoe crab (Carcinoscorpius rotundicauda), also known as the round-tailed horseshoe crab, [2] is a species of horseshoe crab, a chelicerate arthropod found in tropical marine and brackish waters of India, Bangladesh, and Southeast Asia. It may also occur in Sri Lanka, Myanmar and the Philippines, but confirmed records are lacking. [3] It is the only species in the genus Carcinoscorpius. [4]

Contents

The biology, ecology and breeding patterns of C. rotundicauda and the two other Asian horseshoe crab species, Tachypleus gigas and Tachypleus tridentatus , have not been as well documented as those of the North American species Limulus polyphemus . All four extant species of horseshoe crabs are anatomically very similar, but C. rotundicauda is considerably smaller than the others and the only species where the cross section of the tail (telson) is rounded instead of essentially triangular. [5]

Evolutionary history

Horseshoe crabs are commonly known by biologists around the world as a living fossil because they have remained practically unchanged in terms of shape and size for millions of years. Although their physiology has changed over the years, their typical three piece exoskeleton, consisting of a prosoma, opisthosoma, and telson, has remained since the mid-Paleozoic era. [6] Fossils of horseshoe crabs that have been dated to over 400  million years ago look almost identical to those species that are still alive today. [7] The long existence of this body plan suggests its success. The three Asian species of horseshoe crabs form their own clade, and it is estimated that they diverged from the American species between 135  million years ago to 436  million years ago. [8] [6]

Anatomy

Mangrove horseshoe crab in Bako National Park, Malaysia Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda) (6707310189).jpg
Mangrove horseshoe crab in Bako National Park, Malaysia

The basic body plan of a horseshoe crab consists of three parts: the prosoma, the opisthosoma and the tail (telson). The prosoma is the large, dome-shaped frontal part at the carapace. The smaller rear carapace with spines on the edge is the opisthosoma. The rear extension that looks like a spike is the telson, which is commonly described as the tail. [9] Uniquely among the horseshoe crabs, the cross section of the tail of the mangrove horseshoe crab is rounded. It is essentially triangular in the other species. [5] [10] The tail is used to turn itself right side up when overturned. [7]

The mangrove horseshoe crab is the smallest of the four living species of horseshoe crabs. [5] Like the other species, females grow larger than males. On average in Peninsular Malaysia, females are about 30.5–31.5 cm (12.0–12.4 in) long, including a tail that is about 16.5–19 cm (6.5–7.5 in), and their carapace (prosoma) is about 16–17.5 cm (6.3–6.9 in) wide. In comparison, the average for males is about 28–30.5 cm (11.0–12.0 in) long, including a tail that is about 15–17.5 cm (5.9–6.9 in), and their carapace is about 14.5–15 cm (5.7–5.9 in) wide. [11] There are significant geographic variations in the size, but this does not follow a clear north–south or east–west pattern. Those from West Bengal in India average somewhat smaller than those from Peninsular Malaysia, with a carapace width of about 16 cm (6.3 in) and 14 cm (5.5 in) in females and males respectively. Elsewhere it averages even smaller, with the smallest reported from the Balikpapan and Belawan regions in Indonesia where the carapace width of females is about 13 cm (5.1 in) and in males 11 cm (4.3 in). [10] The largest females of the species may reach up to 40 cm (16 in) in length, including the tail. [5]

Uncommon for chelicerates, horseshoe crabs have two compound eyes. The main function of these compound eyes is to find a mate. In addition, they have two median eyes, two rudimentary lateral eyes, and an endoparietal eye on their carapace and two ventral eyes located on the underside by the mouth. Scientists believe the two ventral eyes aid in the orientation of the horseshoe crab when swimming. [5] Each individual has six pairs of appendages. The first pair, the chelicerae, are relatively small and placed in front of the mouth. They are used to place food in it. The remaining five pairs of legs are placed on either side of the mouth and are used for walking/pushing. These are the pedipalps (first pair) and the pusher legs (remaining four pairs). [5] [10] Most of the appendages have straight, scissor-like claws, but in males the first and second pair of walking legs have strongly hooked "scissors", which are used for grasping the female during mating. [10] Located behind their legs are book gills. These gills are used for propulsion to swim and to exchange respiratory gases. [5]

Distribution and habitat

This species occurs only in Asia around the Indo-West Pacific region where the climate is tropical or subtropical. [12] These horseshoe crabs can be found to exist throughout southeast Asia in shallow waters with soft, sandy bottoms or extensive mud flats. The mangrove horseshoe crab is benthopelagic, spending most of its life close to or at the bottom of a body of their brackish, swampy water habitat, such as mangroves. [12] This is the habitat for which it gains its common name: mangrove horseshoe crab. Scientists have studied the distribution of mangrove horseshoe crabs in Hong Kong specifically. The researchers noted their abundance on the beaches of Hong Kong before the sharp decline in population over the past ten years. In the study, they found an uneven distribution of the horseshoe crabs throughout Hong Kong, with a greater abundance found in the western waters. They predict this unevenness is due to the estuarine hydrography in the western waters, influenced by the Pearl River. They also found that T. tridentatus can coexist in the same habitat as the mangrove horseshoe crab. [13]

Diet

Mangrove horseshoe crabs are selective benthic feeders, feeding mainly on insect larvae, small fish, oligochaetes, small crabs and thin-shelled bivalves. [14] Lacking jaws, it grinds up the food with bristles on its legs and places it in its mouth using its chelicerae. The ingested food then enters the cuticle-lined oesophagus and then the proventriculus. The proventriculus is made up of a crop and a gizzard. The crop can expand to fit the ingested food, while the gizzard grinds the food into a pulp. [5] Studies have found that mangrove horseshoe crabs have a strong preference for insect larvae over the other organisms on which it also feeds. [14]

Mating biology

In the spring, horseshoe crabs migrate from the deeper water to the shallow, muddy areas. Nesting usually follows the cycle of the high tide of the full and new moons. During the mating period, the males will follow and cling to the backs of their potential mates using modified prosomal appendages for long periods of time before the egg-laying has occurred. Horseshoe crab species with low spawning densities and 1:1 sex ratios, such as the mangrove horseshoe crab, are found to be monogamous. In addition, the female does not choose her mate. Males find their female mates with the use of visual and chemoreceptive signals. [15] Once a mate is found, the female digs a hole and lays the eggs while the male externally fertilizes them. Once the eggs are laid, the male and female go back to the ocean, and the eggs develop on their own. [15] Their eggs are large, and after a couple weeks, the eggs hatch into miniature versions of the adults. The females lay about 3500 of them.[ citation needed ]

Mangrove horseshoe crabs in Singapore breed from August to April. Juveniles grow about 33% bigger each time they molt, and it takes the juveniles about five molts to grow from 2 centimetres (0.79 in) to adult size. [16]

Use by humans

Mangrove horseshoe crabs caught in Chonburi, Thailand Carcinoscorpius rotundicauda (Chonburi).jpg
Mangrove horseshoe crabs caught in Chonburi, Thailand

Thousands of the horseshoe crabs are caught by local fishermen. [17] While the crabs have very little flesh, their roe is prized as a delicacy, in Thailand most commonly served as a salad called yam khai maeng da (ยำไข่แมงดา). [18]

There have occasionally been cases of food poisonings or even deaths after consuming the crabs as they were misidentified as another horseshoe crab species, Tachypleus gigas. Unlike larger T. gigas, C. rotundicauda is known to often contain lethal tetrodotoxin. [19]

Related Research Articles

<span class="mw-page-title-main">Chelicerata</span> Subphylum of arthropods

The subphylum Chelicerata constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids, as well as a number of extinct lineages, such as the eurypterids and chasmataspidids.

<span class="mw-page-title-main">Amplexus</span> Type of mating behavior exhibited by some externally fertilizing species

Amplexus is a type of mating behavior exhibited by some externally fertilizing species in which a male grasps a female with his front legs as part of the mating process, and at the same time or with some time delay, he fertilizes the eggs, as they are released from the female's body. In amphibians, females may be grasped by the head, waist, or armpits, and the type of amplexus is characteristic of some taxonomic groups.

<span class="mw-page-title-main">Atlantic horseshoe crab</span> Species of arthropod

The Atlantic horseshoe crab, also known as the American horseshoe crab, is a species of horseshoe crab, a kind of marine and brackish chelicerate arthropod. It is found in the Gulf of Mexico and along the Atlantic coast of North America. The main area of annual migration is Delaware Bay along the South Jersey Delaware Bayshore.

<i>Eurypterus</i> Extinct genus of sea scorpions

Eurypterus is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens.

<span class="mw-page-title-main">Horseshoe crab</span> Order of arthropods

Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arachnids such as spiders, ticks, and scorpions.

<span class="mw-page-title-main">Xiphosura</span> Order of marine chelicerates

Xiphosura is an order of arthropods related to arachnids. They are more commonly known as horseshoe crabs. They first appeared in the Hirnantian. Currently, there are only four living species. Xiphosura contains one suborder, Xiphosurida, and several stem-genera.

<i>Slimonia</i> Extinct genus of arthropods

Slimonia is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Slimonia have been discovered in deposits of Silurian age in South America and Europe. Classified as part of the family Slimonidae alongside the related Salteropterus, the genus contains three valid species, S. acuminata from Lesmahagow, Scotland, S. boliviana from Cochabamba, Bolivia and S. dubia from the Pentland Hills of Scotland and one dubious species, S. stylops, from Herefordshire, England. The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow.

<i>Tachypleus</i> Genus of horseshoe crab relatives

Tachypleus is a genus of south, southeast and east Asian horseshoe crabs in the family Limulidae.

<i>Tachypleus tridentatus</i> Species of arthropod

Tachypleus tridentatus, commonly known as the Chinese horseshoe crab, Japanese horseshoe crab, or tri-spine horseshoe crab, is a species of horseshoe crab found in Southeast and East Asia, with records from China, Indonesia, Japan, South Korea, Malaysia, the Philippines, Taiwan, and Vietnam. It is found in coastal marine and brackish waters, and tolerates colder temperatures than the other Asian horseshoe crabs, although juveniles still need water warmer than 22 °C (72 °F) to moult.

<i>Mixopterus</i> Extinct genus of arthropods

Mixopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Mixopterus have been discovered in deposits from Late Silurian age, and have been referred to several different species. Fossils have been recovered from two continents; Europe and North America.

<i>Onychopterella</i> Extinct genus of arthropods

Onychopterella is a genus of predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Onychopterella have been discovered in deposits from the Late Ordovician to the Late Silurian. The genus contains three species: O. kokomoensis, the type species, from the Early Pridoli epoch of Indiana; O. pumilus, from the Early Llandovery epoch of Illinois, both from the United States; and O. augusti, from the Late Hirnantian to Early Rhuddanian stages of South Africa.

<i>Legrandella</i> Extinct genus of chelicerate

Legrandella is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Legrandella was regarded as part of the clade Prosomapoda. Fossils of the single and type species, L. lombardii, have been discovered in deposits of the Devonian period in Cochabamba, Bolivia.

<i>Pasternakevia</i> Extinct genus of chelicerate

Pasternakevia is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Pasternakevia was regarded as part of the clade Planaterga. Fossils of the single and type species, P. podolica, have been discovered in deposits of the Silurian period in Podolia, Ukraine.

<i>Weinbergina</i> Extinct genus of chelicerate

Weinbergina is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Fossils of the single and type species, W. opitzi, have been discovered in deposits of the Devonian period in the Hunsrück Slate, Germany.

<i>Tachypleus gigas</i> Species of arthropod

Tachypleus gigas, commonly known as the Indo-Pacific horseshoe crab, Indonesian horseshoe crab, Indian horseshoe crab, or southern horseshoe crab, is one of the four extant (living) species of horseshoe crab. It is found in coastal water in South and Southeast Asia at depths to 40 m (130 ft).

<span class="mw-page-title-main">Slimonidae</span> Extinct family of eurypterids

Slimonidae is a family of eurypterids, an extinct group of aquatic arthropods. Slimonids were members of the superfamily Pterygotioidea and the family most closely related to the derived pterygotid eurypterids, which are famous for their cheliceral claws and great size. Many characteristics of the Slimonidae, such as their flattened and expanded telsons, support a close relationship between the two groups.

<i>Paleomerus</i> Extinct genus of arthropods

Paleomerus is a genus of strabopid, a group of extinct arthropods. It has been found in deposits from the Cambrian period. It is classified in the family Strabopidae of the monotypic order Strabopida. It contains two species, P. hamiltoni from Sweden and P. makowskii from Poland. The generic name is composed by the Ancient Greek words παλαιός (palaiós), meaning "ancient", and μέρος (méros), meaning "part".

<i>Armases cinereum</i> Species of crab

Armases cinereum, also known as the squareback marsh crab or wharf crab, is a species of crab in the family Sesarmidae. The wharf crab is a small crab that is dark brown to muddy in color, which allows it to blend in with its usual surroundings. It is found on the Atlantic southeastern coast, down into the Gulf of Mexico. It is an omnivore and is prevalent in marshy coastal environments along the Southwestern Atlantic.

<i>Camanchia</i> Extinct genus of chelicerate

Camanchia is a genus of synziphosurine, a paraphyletic group of fossil chelicerate arthropods. Camanchia was regarded as part of the clade Prosomapoda. Fossils of the single and type species, C. grovensis, have been discovered in deposits of the Silurian period in Iowa, in the United States. Alongside Venustulus, Camanchia is one of the only Silurian synziphosurine with fossil showing evidence of appendages.

References

  1. ↑ World Conservation Monitoring Centre (1996). "Carcinoscorpius rotundicauda". IUCN Red List of Threatened Species . 1996: e.T3856A10123044. doi: 10.2305/IUCN.UK.1996.RLTS.T3856A10123044.en . Retrieved 15 November 2021.
  2. ↑ "Identification guide". Horseshoe Crab monitoring site. Retrieved 27 June 2018.
  3. ↑ Vestbo, Stine; Obst, Matthias; Fernandez, Francisco J. Quevedo; Intanai, Itsara; Funch, Peter (May 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 .
  4. ↑ Myers, P.; Espinosa, R.; Parr, C. S.; Jones, T.; Hammond, G. S.; Dewey, T. A., eds. (2023). "Carcinoscorpius". Animal Diversity Web. University of Michigan Museum of Zoology. Retrieved 21 January 2023.
  5. 1 2 3 4 5 6 7 8 "About the Species". The Horseshoe Crab. Retrieved 26 June 2018.
  6. 1 2 Rudkin, D. M.; Young, G. A. (2009). "Horseshoe Crabs – an Ancient Ancestry Revealed". In Tanacredi, John T.; Botton, Mark L.; Smith, David (eds.). Biology and Conservation of Horseshoe Crabs . pp.  25–44. doi:10.1007/978-0-387-89959-6_2. ISBN   978-0-387-89958-9.
  7. 1 2 Kelvin K. P. Lim; Dennis H. Murphy; T. Morgany; N. Sivasothi; Peter K. L. Ng; B. C. Soong; Hugh T. W. Tan; K. S. Tan & T. K. Tan (2001). Peter K. L. Ng & N. Sivasothi (eds.). "Mangrove horseshoe crab, Carcinoscorpius rotundicauda, family Limulidae". A Guide to Mangroves of Singapore 1. Guide to the Mangroves of Singapore. Singapore Science Centre.
  8. ↑ Prashant Shingate; Vydianathan Ravi; Aravind Prasad; Boon Hui Tay & Byrappa Venkatesh (2020). "Chromosome-level genome assembly of the coastal Horseshoe Crab (Tachypleus gigas)". Molecular Ecology Resources. Wiley Online. 20 (6): 1748–1760. doi:10.1111/1755-0998.13233. PMID   32725950. S2CID   220853600.
  9. ↑ Helen M. C. Chiu & Brian Morton (2003). "The morphological differentiation of two horseshoe crab species, Tachypleus tridentatus and Carcinoscorpius rotundicauda (Xiphosura), in Hong Kong with a regional Asian comparison". Journal of Natural History . 37 (19): 2369–2382. doi:10.1080/00222930210149753. S2CID   84286729.
  10. 1 2 3 4 Koichi Sekiguchi; Carl N. Shuster Jr (2009). "Limits on the Global Distribution of Horseshoe Crabs (Limulacea): Lessons Learned from Two Lifetimes of Observations: Asia and America". In Tanacredi, John T.; Botton, Mark L.; Smith, David (eds.). Biology and Conservation of Horseshoe Crabs . Springer. pp.  5–24. ISBN   978-0-387-89959-6.
  11. ↑ 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 .
  12. 1 2 "Carcinoscorpius rotundicauda, mangrove horseshoe crab". SeaLifeBase. 2010. Retrieved April 23, 2011.
  13. ↑ Helen M. C. Chiu & Brian Morton (1999). "The distribution of horseshoe crabs (Tachypleus tridentatus and Carcinoscorpius rotundicauda) in Hong Kong". In Brian Morton (ed.). Asian Marine Biology. Vol. 16. Hong Kong University Press. pp. 185–196. ISBN   978-962-209-520-5.
  14. 1 2 H. Zhou & Brian Morton (2004). "The diets of juvenile horseshoe crabs, Tachypleus tridentatus and Carcinoscorpius rotundicauda (Xiphosura), from nursery beaches proposed for conservation in Hong Kong". Journal of Natural History . 38 (15): 1915–1925. doi:10.1080/0022293031000155377. S2CID   84518612.
  15. 1 2 Jennifer H. Mattei; Mark A. Beekey; Adam Rudman & Alyssa Woronik (2010). "Reproductive behavior in horseshoe crabs: does density matter?" (PDF). Current Zoology . 56 (5): 634–642. doi: 10.1093/czoolo/56.5.634 . Archived from the original (PDF) on 2011-09-27. Retrieved 2011-06-01.
  16. ↑ Lesley Cartwright-Taylor; Julian Lee & Chia Chi Hsu (2019). "Population structure and breeding pattern of the mangrove horseshoe crab Carcinoscorpius rotundicauda in Singapore". Aquatic Biology . 8: 61–69. doi: 10.3354/ab00206 .
  17. ↑ Bibhuti Pati (June 24, 2008). "Horseshoe crabs galloping towards extinction". Merinews. Archived from the original on October 5, 2012. Retrieved June 1, 2011.
  18. ↑ "~Horseshoe Crab Egg Salad Recipe, ยำไข่แมงดา~". 2013-01-28.
  19. ↑ Kanchanapongkul, J.; Krittayapoositpot, P. (June 1995). "An epidemic of tetrodotoxin poisoning following ingestion of the horseshoe crab Carcinoscorpius rotundicauda". The Southeast Asian Journal of Tropical Medicine and Public Health. 26 (2): 364–367. ISSN   0125-1562. PMID   8629077.
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