Recent from talks
Contribute something
Nothing was collected or created yet.
Ranina ranina
View on Wikipedia
| Ranina ranina | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Brachyura |
| Family: | Raninidae |
| Genus: | Ranina |
| Species: | R. ranina
|
| Binomial name | |
| Ranina ranina | |
| Synonyms[1] | |
| |

Ranina ranina, also known as the Huỳnh Đế crab,[2] (red) frog crab or spanner crab,[3] is a species of crab[4] found throughout tropical and subtropical habitats.[5] It is often fished for its meat.[6]
Description
[edit]It may grow up to 15.0 centimetres (5.9 in) long, and may weigh up to 900 grams (2.0 lb).[7] The carapace is wider at the front, reddish brown in color, with ten white spots.[5] Ranina ranina is mainly nocturnal, and remains buried in the sand during the day.[3] Ranina ranina is easily distinguished from other crab species in its habitat due to its red carapace and elongated midsection.[7]
Distribution and ecology
[edit]Spanner crabs inhabit coastal waters along the east coast of Australia, from Yeppoon in Queensland to the North coast of New South Wales. There is also a population to the north of Perth in Western Australia.[7] Ranina ranina is abundant in the coastal waters of south-western Mindanao, Philippines. These crabs are also found in the eastern coast of Africa, across the Indian Ocean to Indonesia, Japan and Hawaii and Vietnam.[8]
Ranina ranina inhabits depths of 10–100 metres (33–328 ft) on sandy-smooth substrata in which they bury themselves from where they attack small bottom-dwelling fish.[9] When waiting for prey, Ranina ranina will cover itself with sand, but leave its eye and mouthparts sticking out to help detect its food.[3] Offshore areas within this range in a subtropical or tropical environment serves as a habitat for Ranina ranina, but they must have ample sand for Ranina ranina to flourish, as covering themselves in sand is instrumental in their method of catching prey. The Ranina Ranina crab is a popular species of crab that gets fished, in Australia, 96% of the female crab doesn’t get fished. In one location during spawning season, the decrease in females being hunted doesn’t apply. Meaning that the specific area of Tallows Beach is the focus of spawning migration.
Fishery
[edit]The species is commercially exploited over much of its range, but the largest fishery is in Australia, where the annual commercial catch an estimated at 3,592 tonnes (7,919,000 lb).[5][10] In Queensland, only adults above 100 mm (3.9 in) carapace length may be landed.[11] In the Philippines in 2008, prices for Ranina ranina were around 200–300 pesos per kilogram.[5] Ranina ranina populations have been surveyed to avoid overfishing and are currently stable.[12]
Although Ranina ranina is a target of commercial fishing operations, little is known about the species' biology, population dynamics and ecology.[11] Attempts have been made to grow Ranina ranina in captivity, but have so far been met with little success.[3]
Culinary use
[edit]Ranina ranina is a regional specialty in some regions of the Philippines where it is known as curacha. It is generally eaten steamed as halabos, or cooked in coconut milk as ginataan. A notable variant of the latter is the curacha Alavar of Zamboanga City.[13][14]
In Vietnam the species is named as "Huỳnh Đế crab", literally means "emperor crab". The names refer to the fact that R. ranina is one of the favorite high-ranked cuisine of historical Vietnamese monarchs.[15] It is the delicacy harvested in the provinces Bình Định and Quảng Ngãi, and is hailed "monarch of all the crab".[16]
References
[edit]- ^ "Ranina ranina". WoRMS. World Register of Marine Species. Retrieved 6 October 2024.
- ^ Crustacean diversity in Vietnam's coral reef
- ^ a b c d Phyu Phyu Than; Taizo Sakata; Kazuhisa Hamada; Keinosuke Imaizumi (1999). "Characteristics of dominant microflora in aquaculture tanks of juvenile red frog crab, Ranina ranina" (PDF). Memoirs of the Faculty of Fisheries: 1–6.
- ^ S. L. Slattery; A. L. Ford & S. M. Nottingham (1992). "Cooking methods for spanner crabs Ranina ranina (L) and their effect on cadmium residues". Food Australia. 44 (5): 206–210.
- ^ a b c d Oliver D. Tito & Jonalyn P. Alanano (2008). "Some aspects of fisheries and biology of spanner crab (Ranina ranina, Linnaeus) in Maluso, Basilan Province, Philippines" (PDF). Memoirs of the Faculty of Fisheries: 40–48.
- ^ Peter K. L. Ng; Danièle Guinot & Peter J. F. Davie (2008). "Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world" (PDF). Raffles Bulletin of Zoology. 17: 1–286. Archived from the original (PDF) on 2011-06-06. Retrieved 2010-01-05.
- ^ a b c "Spanner crab Ranina ranina". Fishing and Aquaculture. New South Wales Department of Primary Industries. 2005. Retrieved January 4, 2009.
- ^ Juliana C. Baylon & Oliver D. Tito (2012) “Natural diet and feeding habits of the red frog crab (Ranina ranina) from southwestern Mindanao, Philippines” Philip. Agric. Scientist Vol. 95 No. 4, 391–398.
- ^ Sydney Fish Market, “Species information: Spanner Crab” (2013) www.sydneyfishmarket.com
- ^ Queensland Fisheries (2010) “Stock Status of Queensland's Fisheries Resources 2009-10” Queensland Australia: Queensland Department of Employment, Economic Development and Innovation. 65
- ^ a b J. M. Kirkwood; I. W. Brown; S. W. Gaddes; S. Hoyle (2005). "Juvenile length-at-age data reveal that spanner crabs (Ranina ranina) grow slowly". Marine Biology. 147 (2): 331–339. doi:10.1007/s00227-005-1574-0. S2CID 85319322.
- ^ J. McGilvray, I. Brown, E. Jebreen & D. Smallwood (2006) Fisheries Long Term Monitoring Program Summary of spanner crab (Ranina ranina) survey results: 2000-2005. Department of Primary Industries and Fisheries, Queensland, QI06095, Brisbane, Australia.
- ^ Clavite, Harold E. "Homecoming: Food and country". Philippine Information Agency. Retrieved 13 April 2019.
- ^ "Halabos na Curacha". Panlasang Pinoy Meaty Recipes. Retrieved 13 April 2019.
- ^ Huỳnh đế - đệ nhất cua biển giá "chát" vẫn được chuộng
- ^ "Cua huỳnh đế". 10 February 2012.
External links
[edit]
Media related to Ranina ranina at Wikimedia Commons
Data related to Ranina ranina at Wikispecies
Ranina ranina
View on GrokipediaTaxonomy
Scientific classification
Ranina ranina is the accepted binomial name for this species of crab, originally described by Carl Linnaeus as Cancer ranina in the 10th edition of Systema Naturae published in 1758.[3][7] The taxonomic hierarchy places Ranina ranina within the following classification:| Rank | Taxon |
|---|---|
| Kingdom | Animalia |
| Phylum | Arthropoda |
| Subphylum | Crustacea |
| Class | Malacostraca |
| Order | Decapoda |
| Suborder | Pleocyemata |
| Infraorder | Brachyura |
| Superfamily | Raninoidea |
| Family | Raninidae |
| Genus | Ranina |
| Species | ranina |
Common names and etymology
Ranina ranina is known by various common names across its range in the Indo-Pacific region. In Australia, it is commonly referred to as the spanner crab, a name highlighting its distinctive claw structure used in fisheries. In Hawaii, it is called the Kona crab or red frog crab, reflecting local harvesting traditions in deeper waters. In Vietnam, the species bears the name Huỳnh Đế crab, translating to "emperor crab," owing to its status as a prized delicacy with high market value. Throughout the broader Indo-Pacific, it is often termed the red frog crab, emphasizing its widespread recognition in marine ecosystems.[1][12][13][14] The genus name Ranina derives from the Latin word "rana," meaning frog, alluding to the crab's elongated and frog-like body form that distinguishes it within the Raninidae family. The species epithet "ranina" reinforces the frog association in its binomial nomenclature established by Linnaeus in 1758. This etymological choice underscores the taxonomic emphasis on morphological traits reminiscent of amphibians.[13] Historically, Ranina ranina has been described under several synonyms in early taxonomic works. Prior to its current classification, it was named Cancer ranina by Linnaeus in 1758, a pre-Linnaean combination within the broad genus Cancer. Later, Lamarck assigned it as Ranina serrata in 1801, based on serrated features observed in specimens, though this is now considered a junior synonym. Additional junior synonyms include Ranina dentata (Milne Edwards, 1837) and Ranina cristata (Desjardins, 1835). These nomenclatural shifts reflect evolving understandings of brachyuran crab systematics.[13][8] Cultural naming variations add layers to its regional identity. In Taiwan, Ranina ranina holds symbolic significance in Chinese traditions, viewed as a bearer of blessings due to its reddish hue evoking prosperity and good fortune; it is incorporated into offerings during festivals and rituals. This cultural reverence elevates its role beyond ecology, intertwining it with local folklore and marine heritage in areas like the South Penghu Marine National Park.[15]Description
Morphology
Ranina ranina exhibits a distinctive body form that differs markedly from the typical brachyuran crabs, characterized by a frog-like appearance due to its elongated and narrow structure with a vermilion shell. This overall shape includes a carapace that is longitudinally ovate, wider along the anterior third and narrowing to a waist-like posterior, with the abdomen clearly visible from the dorsal view. The carapace features red-orange coloration and setaceous surfaces, with short setae lining the frontal and lateral margins as well as a dorsal setal field posterior to the fronto-orbital spines. Twelve uneven white spots are present across the upper third of the carapace, more prominent in larger individuals.[16] Sexual dimorphism is evident in several features. The rostrum is narrower and longer in males, while shorter and broader in females. Males have a squarish fronto-anterior margin and setal lining on the chelipeds, which is absent in females; the male abdomen is narrow and triangular with invaginations in the third and fourth pleomeres, whereas females have a broader, rounded abdomen adapted for egg carrying.[16][4] The rostrum is a large, straight, thick, and flattened projection, forming an acute triangle bounded by symmetrical lateral rostral teeth. Projecting forward from the carapace, it contributes to the species' elongated profile.[16] The appendages are adapted with flattened structures, including robust pereiopods 2–5 featuring semi-flat dactyls and short horns such as bifid and trifid orbital spines. The chelipeds, or first pereiopods, bear pincer-like chelae that are large and flat, equipped with multiple spines on the dactyl for feeding. The carapace is slightly longer than wide, supporting these appendages in a configuration suited to the species' morphology.[16][17] Regarding internal features relevant to morphology, the second maxilla includes a scaphognathite that extends into the gill chamber and is thinly lined with setae, aiding in basic respiratory anatomy.[16]Size and coloration
Ranina ranina adults typically attain a carapace length of 10–17.5 cm, with males reaching a maximum of 17.5 cm and females 12 cm; maximum body weights are up to 900 g for males and 400 g for females.[1] Sexual dimorphism is evident in carapace breadth, with males possessing broader structures, while females exhibit wider abdomens adapted for carrying eggs.[4][18] The coloration of R. ranina features a distinctive bright red-orange carapace, often described as vermilion in living specimens, with small white spots on the anterior surface. This vivid hue is unique among many decapod crustaceans and serves as a key identifying trait.[4][19] Growth in R. ranina proceeds through successive molting stages, resulting in incremental size increases, as documented in populations from the Andaman Sea. Studies there reveal allometric growth patterns, with males exhibiting faster growth rates than females, leading to the observed size disparities in adults.[20]Distribution and habitat
Geographic range
Ranina ranina is widely distributed across the tropical and subtropical regions of the Indo-Pacific Ocean, extending from the Red Sea and East Africa eastward to Hawaii, northward to Japan, and southward along the east coast of Australia from Queensland to New South Wales.[21][22][12] The species is particularly abundant in several key areas, including the east coast of Australia where it supports significant populations from Yeppoon in Queensland to Nowra in New South Wales, the Hawaiian Islands as a major commercial hub, the Andaman Sea off Thailand, South Penghu Marine National Park in Taiwan, and southwestern Mindanao in the Philippines.[2][23][4] Ranina ranina primarily occupies depths between 10 and 100 meters, with occasional records exceeding 100 meters in sandy substrates.[24][25][21] As of 2025, the geographic distribution of R. ranina appears stable, with no documented major expansions or contractions in its range.[22]Habitat preferences
Ranina ranina inhabits open sandy or muddy bottoms on continental shelves, where it burrows into unconsolidated sediments just beneath the surface, often with eyes and antennae protruding. This species avoids rocky reefs, coral rubble, and dense muddy clay, showing a clear preference for soft, burrowable substrates that facilitate its sedentary lifestyle. Depths typically range from 10 to 100 meters, though records extend to 200 meters in some areas.[26][1][22] The crab thrives in warm temperate to tropical waters across the Indo-Pacific, with bottom temperatures generally between 20°C and 30°C (mean approximately 27.4°C). Salinity levels in its preferred habitats fall within 30-35 ppt, consistent with fully marine conditions that support optimal larval survival and development from 27 to 34 ppt. These environmental parameters align with the species' distribution in shelf waters adjacent to coral reefs but not within them.[1][27] Populations of Ranina ranina are typically solitary or occur at low densities, with patchy distributions estimated at around 1,460 individuals per hectare in high-density patches, though catch rates vary seasonally and geographically. The species favors soft sediment areas over structured habitats, resulting in low co-occurrence with reef-associated biota beyond occasional proximity to seagrass or coral beds.[26][28][29] Key adaptations include burrowing behavior, where individuals spend over 95% of their time buried, emerging primarily at night to evade predators such as large fish and turtles. This is aided by semi-shovel-like pereiopods for rapid digging (average burial time of 31.2 seconds) and the ability to halt heart activity for at least 20 minutes while buried, using the cor frontale to maintain haemolymph circulation. Nocturnal activity and sand camouflage further enhance survival in these soft-bottom environments.[26][28][22]Ecology and life history
Reproduction and development
Ranina ranina reproduces sexually through internal fertilization, with males transferring spermatophores to females during mating, allowing for egg storage and multiple broods per season in some populations. Breeding is seasonal in tropical regions, with peak gonad maturation and spawning occurring from November to February in the Andaman Sea off Thailand, coinciding with cooler water temperatures that favor embryonic development. In the southwestern Philippines, reproductive activity is year-round but with ovigerous females most abundant during the same November–February period, suggesting a broad pattern of synchronized breeding across its range.[30][31] Females are fecund, carrying 74,600 to 354,084 eggs beneath the abdomen in a brood pouch formed by the abdomen and thoracic sternum, with larger individuals producing more eggs; for example, the relationship between fecundity (F) and carapace length (CL) in Thai populations is approximated by F = 5.1151 CL^{4.4939}. Sexual maturity is attained at carapace widths of 7.22 cm for females and 7.44 cm for males in the Andaman Sea, though smaller ovigerous females as small as 6.19 cm have been recorded in Philippine waters. Females may produce at least two egg batches per breeding season from a single mating, enhancing reproductive output.[30][31][30] Eggs are brooded externally until hatching, after which planktonic zoea larvae are released into the water column. Larval development includes seven or eight zoeal stages followed by a megalopa stage, with the full progression from zoea I to megalopa taking 36–62 days under laboratory conditions at 25–28°C. Unlike some advanced brachyurans with abbreviated larval phases, R. ranina exhibits a typical decapod larval cycle, though the megalopa settles to the benthos relatively soon after formation, limiting long-distance dispersal compared to many portunid crabs.[31][5] Post-settlement growth follows the von Bertalanffy model, which describes length at age t aswhere is the asymptotic length, K is the growth coefficient, and is the hypothetical age at zero length. In eastern Australian populations, parameters are estimated as cm, K = 0.23 year^{-1}, and for males, and cm, K = 0.29 year^{-1}, and for females, indicating slower growth in males despite larger maximum size.[32] These parameters imply that juveniles reach maturity sizes (around 7–10 cm carapace length) in 2–4 years, with overall lifespan estimated at 5–10 years based on modeled age distributions.[32]
