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Ovalipes catharus

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Ovalipes catharus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Suborder: Pleocyemata
Infraorder: Brachyura
Family: Ovalipidae
Genus: Ovalipes
Species:
O. catharus
Binomial name
Ovalipes catharus
(White in White and Doubleday, 1843)
Synonyms[1]
  • Portunus catharus White in White and Doubleday, 1843

Ovalipes catharus, commonly known as the paddle crab, swimming crab, or Māori: pāpaka,[2] is a species of crab in the family Ovalipidae.[1][3] They are found in shallow, sandy-bottomed waters around the coasts of New Zealand, the Chatham Islands, and uncommonly in southern Australia.[4][5][6] They are opportunistic and versatile feeders active mostly at night, preying predominantly on molluscs and crustaceans.[7][8] They are also highly prone to cannibalism both as part of their regular diet and as part of their mating behaviour.[7][9] Their paddle-shaped rear legs and streamlined carapace allow them to swim rapidly to capture prey and to burrow in the sand in order to escape predation.[10] Their mating season is in winter; the male carries the female until she moults, after which the two mate and the female moves into deeper waters to disperse her larvae.[11]

The paddle crab has been targeted by commercial fisheries since the 1970s, although the amount caught has dramatically decreased since a peak in the late 1990s.[8] Their population is expected to be increasing,[8] although ecologists have raised concerns that the paddle crab could become outcompeted by Charybdis japonica, an invasive species with a similar size, diet, and habitat.[12] O. catharus is present in Māori culture, both as an artistic motif and as a traditional source of food.[13]

Description

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Rear view of Ovalipes catharus swimming with its rear, paddle-shaped legs raised and its walking legs spread out laterally. Set against a teal, watery background.
O. catharus use their paddle-shaped rear legs to swim.[14]

O. catharus has an oval-shaped, streamlined, and slightly grainy carapace with five teeth to either side of the eyes and four teeth at the front.[4][10][15] It is overall sandy grey with orange-red highlights and dotted with small, brown spots.[4][15] Its carapace has two large, maroon eye-spots at the rear and two smaller ones near the front.[4][16] Its underside is white, and its rear legs – which are flattened and function as swimming paddles[14] – have a purplish tinge.[4]

Mature paddle crabs can reach carapace widths ranging from >100 mm (3.9 in) up to a reported 150 mm (5.9 in).[8] Individuals from shallow waters, 0.1–0.5 metres (4–20 in) deep, have a carapace width of only 10–15 millimetres (0.4–0.6 in), while those from 5–15 m (16–49 ft) are 100–140 mm (3.9–5.5 in) wide.[17] Its left chela is smaller than its right.[18]

It has a long period of larval development with eight zoeal stages. The zoea is transparent or blackish, later develops red chromatophores, and then turns black when it moults into a megalopa.[19] The zoea features a prominent dorsal spine and similarly prominent rostral spine; neither are present in its megalopal form, whose carapace is entirely smooth.[19]

Taxonomy

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O. catharus was described in 1843 by zoologist Adam White, originally placed into the genus Portunus.[15] They are colloquially known as the paddle crab, the swimming crab, or Māori: pāpaka.[2] The following cladogram shows the relationship between O. catharus and the other extant species of Ovalipes:[20][a]

Ovalipes
     
     

Ovalipes georgei

     
     
     
     
     

Ovalipes australiensis

     

Ovalipes punctatus

     

Ovalipes elongatus

     

Ovalipes trimaculatus

     

Ovalipes catharus

     
     
     
     
     

Ovalipes ocellatus

     

Ovalipes stephensoni

     

Ovalipes floridanus

     
     

Ovalipes iridescens

     

Ovalipes molleri


Distribution and habitat

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O. catharus is native to New Zealand, where it can be found from Stewart Island to Northland and in the Chatham Islands.[21][14] They are also uncommon on the southern coast of Australia, where they're known as far west as the state of South Australia and as far east as Port Phillip Bay in Victoria.[4][5][19] They live along sandy-bottomed coastal waters, generally at depths of <10 m (33 ft) in estuaries and the subtidal zone,[21][6][22] and they move into the intertidal zone during the evening or the night in order to feed.[8] Although they generally stick to shallow waters, they can be found at depths of up to 100 m (330 ft),[21] and their larvae can be found in deeper waters, up to at least 700 m (2,300 ft).[8] They have been observed to be highly migratory.[8] Anecdotal information suggests a dramatic population increase since the 1970s.[8]

Diet

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The off-white shell of a lone specimen of Paphies australis sitting on a background of grey pebbles
Bivalves such as Paphies australis are a significant portion of the paddle crab's diet.[7]

The diet of paddle crabs consists predominantly of molluscs (especially of genus Paphies) and crustaceans, but they also feed on fish, bristle worms, and occasionally algae.[7][8][14] Large O. catharus tend to feed less frequently but on larger animals such as decapods and teleosts, while smaller ones prey frequently on smaller, softer crustaceans such as amphipods, isopods, opossum shrimp, and hooded shrimp.[14] A major portion of their diet is cannibalizing other members of O. catharus which are either smaller than them or have lost their shell during the winter moulting season.[7][14]

The flattened hind legs and streamlined body shape of the crab allow them to swim rapidly and catch faster prey,[14][10] and they have relatively small chelae which are well-suited to handling small molluscs.[23] Its chelae are dimorphic; the left is used for cutting while the right is used for crushing.[18]

Predators and other interactions

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A video of Ovalipes catharus retreating backward into loose, pebbly sand on the seabed, fully covering itself from back to front over a period of 6.5 seconds. The video is shot from the front at an angle of about 45 degrees to the right relative to where the crab is facing. Brownish seaweed is visible in the foreground of the shot.
O. catharus burrow in the seabed to escape predation.[10]

Predators of the paddle crab include spiny dogfish,[24] snapper (Pagrus auratus), rig (Mustelus lenticulatus),[25], groper (Polyprion oxygeneiosis), Hector's dolphin,[26] and the invasive crab species Charybdis japonica.[12] Younger individuals are prone to being cannibalized,[7][14] and all paddle crabs are vulnerable to cannibalism during moulting.[14] Commercial fisheries additionally target the paddle crab.[8] In order to escape predation, O. catharus creates temporary burrows in soft sand using their paddles, taking only several seconds to completely submerge itself.[10]

O. catharus do not appear to be typically parasitized by nematodes or barnacles.[22] Instead, the overwhelming majority of them[b] are hosts to the ctenosome bryozoan Triticella capsularis, which forms a fur of up to almost 10 mm (0.4 in) thick on their underside after their final moult.[27][22] It is only found on O. catharus,[27] and it is speculated to be an obligate symbiont of the crab.[22] O. catharus does not appear to be affected by parasites present in the invasive C. japonica, which tends to be sympatric with the paddle crab and is heavily parasitized by serpulids.[22]

Mating and reproduction

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O. catharus reach sexual maturity within the first year of benthic life, and females produce clutches of eggs from early spring to late summer.[28][14] It is not known how many clutches can be fertilised from one insemination, but females have been observed to produce up to four or five without re-mating.[14][11] In one clutch the female crabs produce between 82,000 and 683,000 eggs, but like in other crabs, a very large proportion of these are lost to disease or predation.[11] Fecundity is also heavily influenced by carapace width and body mass, with larger and heavier crabs having higher fecundity.[11] Larvae develop synchronously and are released in large numbers by vigorous waving of the female's body, which disturbs their egg cases and causes them to break out.[11] Females mostly release their larvae at night and when releasing they stand on their dactyli before extending themselves as far as possible. They then angle themselves up and begin flexing their abdomen to release large clouds of larvae.[11] Females have also been observed to preen the egg mass during development. Higher temperatures have been observed to prolong the breeding season, increase growth rates, and cause them to obtain sexual maturity sooner.[14] This causes slight differences in mating times between populations of O. catharus living at different locations in the wild.[14]

Mating behaviours

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Males and females meet in shallow sheltered bays during winter, which is July to August in New Zealand. The time is also variable between populations with some mating as early as May and some as late as November. Males often attract mates by creating a rasping sound, by rubbing their legs together vigorously.[13][11]

In these shallow bays, they mate when the females moult. Male crabs can only mate with soft post-moult females, so they begin to carry female crabs under their bodies up to 8 days prior to the females moulting.[11] Once the female has moulted, she depends entirely on the male for protection, and he will even assist with the moulting process by using his legs to remove parts of the female's old carapace. Once moulting is complete they will mate for between 12 and 36 hours and even up to four days.[11] After mating the female is released and the females move onto spawning grounds deeper in the water, of which the location is not known, and the males move to foraging grounds.[14]

Sexual cannibalism

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Sexual cannibalism has been frequently observed in O. catharus, and it is directed by males towards females. This sexual cannibalism occurs when the female is soft-shelled after moulting during the mating process.[9] Male crabs protect the females they mate with from being cannibalised, but unreceptive females or those that have mated with other crabs are in danger of being cannibalised.[9] This is most likely done to maximize the number of eggs fertilised by his sperm.[29] Some examples of males cannibalising females they have mated with have also been observed.[9] This sexual cannibalism is not about mate choice or adaptation and is instead more opportunistic.[30][31][32] In one example, male crabs that had not cannibalised female crabs all accepted frozen squid afterwards, while very few males that had cannibalised female crabs accepted frozen squid afterwards. This indicates that hunger could be a part of the cause behind the cannibalism, and male crabs just take the opportunity to feed while the females are vulnerable in their soft-shelled state. Unlike in other examples of sexual cannibalism, size was not shown to have an effect on whether cannibalism occurred.[9][30] Sexual cannibalism in O. catharus is very prevalent, with a study on the diet of the crab detecting it in almost every location tested.[7] Part of the prevalence of O. catharus in its own diet could be due to males consuming each other during the breeding season, as the smaller males guarding females do not have protection themselves from cannibalism and can sometimes be mistaken for females.[9]

Relation to humans

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O. catharus is a common motif in Māori art, with designs being incorporated into weaving patterns, tā moko, and the designs of wharenui and whare wānanga (houses of learning). The crabs are known to be a traditional food source, but researchers in the early Colonial period did not record much about harvesting traditions.[13]

Commercial fisheries have targeted targeted paddle crabs since the late 1970s, mostly to the east of the North Island and the north of the South Island.[14][8] Catch is sold both locally in New Zealand and overseas to Japan.[33] The paddle crab is known for having meat with both good flavor and texture.[14] The amount of paddle crabs landed generally increased until the late 1990s, reaching a peak at 519 t (1,144,000 lb) in 1998–99, at which point it began generally decreasing for the next two decades, reaching an average of 16.6 t (37,000 lb) annually from the five-year period of 2017–2022.[8]

They are known for their aggression on beaches, often pinching swimmers in New Zealand.[13][4]

Notes

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  1. ^ Ovalipes itself sits within the monogeneric family Ovalipidae.[3]
  2. ^ 97.4% of O. catharus surveyed from six sites were hosts to Triticella capsularis.[22]

References

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  1. ^ a b De Grave, Sammy (10 April 2022). "Ovalipes catharus (White in White & Doubleday, 1843)". WoRMS. World Register of Marine Species. Retrieved 28 October 2024.
  2. ^ a b Moorfield, John C. "pāpaka". Te Aka Māori Dictionary. Retrieved 5 March 2022.
  3. ^ a b Poore, Gary C.B.; Ahyong, Shane T. (2023). Marine Decapod Crustacea: A Guide to Families and Genera of the World. CRC Press. pp. 695–696. ISBN 978-1-4863-1178-1.
  4. ^ a b c d e f g Wilkens, Serena L.; Ahyong, Shane T. (2015). Coastal Crabs: A Guide to the Crabs of New Zealand (PDF) (First ed.). NIWA. pp. 3–5, 43.
  5. ^ a b O'Hara, Tim; Barmby, Victoria (May 2000). Victorian Marine Species of Conservation Concern: Molluscs, Echinoderms and Decapod Crustaceans (Report). Victoria Department of Natural Resources and Environment. p. 45. ISBN 0-7311-4561-5 – via ResearchGate.
  6. ^ a b Richards, R.N. (1992). The structure and function of the gills of the New Zealand paddle crab: Ovalipes catharus (Master of Sciences thesis). University of Canterbury. doi:10.26021/13400.
  7. ^ a b c d e f g Wear, Robert G.; Haddon, M. (1987-01-27). "Natural diet of the crab Ovalipes catharus (Crustacea, Portunidae) around central and northern New Zealand". Marine Ecology Progress Series. 35: 39–49. doi:10.3354/meps035039. ISSN 0171-8630. JSTOR 24825007.
  8. ^ a b c d e f g h i j k l Fisheries Assessment Plenary May 2023 Volume 2 – Paddle Crabs (PAD) (Report). Fisheries New Zealand. 21 June 2023.
  9. ^ a b c d e f Haddon, Malcolm (1995). "Avoidance of Post-Coital Cannibalism in the Brachyurid Paddle Crab Ovalipes catharus". Oecologia. 104 (2): 256–258. doi:10.1007/BF00328590. JSTOR 4221102. PMID 28307362.
  10. ^ a b c d e McLay, C.L.; Osborne, T.A. (1985). "Burrowing behaviour of the paddle crab Ovalipes catharus (White, 1843) (Brachyura: Portunidae)". New Zealand Journal of Marine and Freshwater Research. 19 (2): 125–130. doi:10.1080/00288330.1985.9516078. ISSN 0028-8330.
  11. ^ a b c d e f g h i Haddon, Malcolm (1994). "Size ‐ fecundity relationships, mating behaviour, and larval release in the New Zealand paddle crab, Ovalipes catharus (White 1843) (Brachyura: Portunidae)". New Zealand Journal of Marine and Freshwater Research. 28 (4): 329–334. doi:10.1080/00288330.1994.9516622. ISSN 0028-8330.
  12. ^ a b Fowler, Amy E.; Muirhead, Jim R.; Taylor, Richard B. (September 2013). "Early Stages of A New Zealand Invasion By Charybdis Japonica (A. Milne-Edwards, 1861) (Brachyura: Portunidae) from Asia: Behavioral Interactions with A Native Crab Species". Journal of Crustacean Biology. 33 (5): 672–680. doi:10.1163/1937240X-00002177. JSTOR 43835684.
  13. ^ a b c d Vennell, Robert (5 October 2022). Secrets of the Sea: The Story of New Zealand's Native Sea Creatures. HarperCollins Publishers Ltd. pp. 78–83. ISBN 978-1-77554-179-0. LCCN 2021388548. Wikidata Q114871191.
  14. ^ a b c d e f g h i j k l m n o p Osborne, T. A. (1987). Life history and population biology of the paddle crab, Ovalipes catharus (PhD thesis). University of Canterbury. doi:10.26021/6494.
  15. ^ a b c White, Adam; Doubleday, Edward (1843). "List of Annulose Animals hitherto recorded as found in New Zealand, with the Descriptions of some New Species". In Dieffenbach, Ernest (ed.). Travels in New Zealand; with Contributions to the Geography, Geology, Botany, and Natural History of that Country. Vol. II. John Murray. p. 265 – via the Internet Archive.
  16. ^ Naylor, J.R.; Webber, W.R.; Booth, J.D. (2005). A guide to common offshore crabs in New Zealand waters (PDF) (Report). New Zealand Ministry of Fisheries. p. 24. ISSN 1176-9440. New Zealand Aquatic Environment and Biodiversity Report No. 2.
  17. ^ "Biology and Ecology of Ovalipes catharus" (worksheet). Bay of Plenty Polytechnic. Archived from the original on 20 August 2011. Adapted from “Form 7 Biology Animal Study” by Paul Furneaux of Otumoetai College.{{cite web}}: CS1 maint: postscript (link)
  18. ^ a b Davidson, Robert J. (November 1986). "Mussel selection by the paddle crab Ovalipes catharus (White): Evidence of flexible foraging behaviour". Journal of Experimental Marine Biology and Ecology. 102 (2–3): 281–299. doi:10.1016/0022-0981(86)90182-6.
  19. ^ a b c Wear, Robert G.; Fielder, D. R. (1985). The marine fauna of New Zealand: Larvae of Brachyura (Crustacea, Decapoda). New Zealand Oceanographic Institute Memoir 92. pp. 50–52. ISBN 0-477-06722-0. ISSN 0083-7903 – via the Internet Archive.
  20. ^ Parker, Andrew R.; Mckenzie, David R.; Ahyong, Shane T. (22 May 1998). "A unique form of light reflector and the evolution of signalling in Ovalipes (Crustacea: Decapoda: Portunidae)". Proceedings of the Royal Society B: Biological Sciences. doi:10.1098/rspb.1998.0371.
  21. ^ a b c Gust, Nick; Inglis, Graeme J. (March 2006). "Adaptive multi-scale sampling to determine an invasive crab's habitat usage and range in New Zealand". Biological Invasions. 8 (2): 339–353. doi:10.1007/s10530-004-8243-y – via ResearchGate.
  22. ^ a b c d e f Miller, Aroha; Inglis, Graeme J.; Poulin, Robert (2006). "Comparison of the ectosymbionts and parasites of an introduced crab, Charybdis japonica, with sympatric and allopatric populations of a native New Zealand crab, Ovalipes catharus (Brachyura: Portunidae)". New Zealand Journal of Marine and Freshwater Research. 40 (2): 369–378. doi:10.1080/00288330.2006.9517428. ISSN 0028-8330.
  23. ^ Davidson, Robert J. (1987). Natural food and predatory activity of the paddle crab, Ovalipes catharus: A flexible forager (Master of Science thesis). University of Canterbury. pp. 2–15. doi:10.26021/6041.
  24. ^ Hanchet, Stuart (September 1991). "Diet of spiny dogfish, Squalus acanthias Linnaeus, on the east coast, South Island, New Zealand". Journal of Fish Biology. 39 (3): 313–323. doi:10.1111/j.1095-8649.1991.tb04365.x.
  25. ^ King, Ken J.; Clark, Malcolm R. (1984). "The food of rig (Mustelus lenticulatus) and the relationship of feeding to reproduction and condition in Golden Bay". New Zealand Journal of Marine and Freshwater Research. 18 (1): 29–42. doi:10.1080/00288330.1984.9516026. ISSN 0028-8330.
  26. ^ Miller, Elanor J.; Lalas, Chris; Dawson, Stephen M.; Ratz, Hultrun; Slooten, Elisabeth (August 2012). "Hector's dolphin diet: The species, sizes and relative importance of prey eaten by Cephalorhynchus hectori, investigated using stomach content analysis". Marine Mammal Science. 29 (4): 606–628. doi:10.1111/j.1748-7692.2012.00594.x – via ResearchGate.
  27. ^ a b Gordon, Dennis P.; Wear, Robert G. (1999). "A new ctenostome brozoan ectosymbiotic with terminal-moult paddle crabs (Portunidae) in New Zealand". New Zealand Journal of Zoology. 26 (4): 373–380. doi:10.1080/03014223.1999.9518200.
  28. ^ Armstrong, James H. (1988). "Reproduction in the paddle crab Ovalipes catharus (Decapoda: Portunidae) from Blueskin Bay, Otago, New Zealand". New Zealand Journal of Marine and Freshwater Research. 22 (4): 529–536. doi:10.1080/00288330.1988.9516323. ISSN 0028-8330.
  29. ^ Buskirk, Ruth E.; Frohlich, Cliff; Ross, Kenneth G. (May 1984). "The Natural Selection of Sexual Cannibalism". The American Naturalist. 123 (5): 612–625. doi:10.1086/284227. JSTOR 2461241.
  30. ^ a b Prenter, John; MacNeil, Calum; Elwood, Robert W. (March 2006). "Sexual cannibalism and mate choice". Animal Behaviour. 71 (3): 481–490. doi:10.1016/j.anbehav.2005.05.011.
  31. ^ Schneider, Jutta M. (2014). "Sexual Cannibalism as a Manifestation of Sexual Conflict". Cold Spring Harbor Perspectives in Biology. 6 (11): a017731. doi:10.1101/cshperspect.a017731. PMC 4413240. PMID 25213095.
  32. ^ Zuk, Marlene (5 December 2016). "Mates with Benefits: When and How Sexual Cannibalism Is Adaptive". Current Biology. 26 (23): R1230–R1232. doi:10.1016/j.cub.2016.10.017. PMID 27923131.
  33. ^ Jester, Rozalind J.; Rhodes, Lesley L.; Beuzenberg, Veronica (January 2009). "Uptake of paralytic shellfish poisoning and spirolide toxins by paddle crabs (Ovalipes catharus) via a bivalve vector". Harmful Algae. 8 (2): 369–376. doi:10.1016/j.hal.2008.08.002. ISSN 1568-9883.
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