''Ranina ranina'', also known as the Huỳnh Đế crab, (red) frog crab or spanner crab, is a species of

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

found throughout tropical and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...

habitats. It is often fished for its meat, and is the only known species in its genus.

Description

It may grow up to long, and may weigh up to . The

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

is wider at the front, reddish brown in color, with ten white spots. ''Ranina ranina'' is mainly

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, and remains buried in the sand during the day. ''Ranina ranina'' is easily distinguished from other crab species in its habitat due to its red carapace and elongated midsection.

Distribution and ecology

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. ''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.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. ''Ranina ranina'' inhabits depths of on sandy-smooth substrata in which they bury themselves from where they attack small bottom-dwelling fish.Sydney Fish Market, “Species information: Spanner Crab” (2013) www.sydneyfishmarket.com When waiting for prey, ''Ranina ranina'' will cover itself with sand, but leave its eye and mouthparts sticking out to help detect its food. 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

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 .Queensland Fisheries (2010) “Stock Status of Queensland's Fisheries Resources 2009-10” Queensland Australia: Queensland Department of Employment, Economic Development and Innovation. 65 In Queensland, only adults above

length may be landed. In the Philippines in 2008, prices for ''Ranina ranina'' were around 200–300 pesos per

kilogram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...

. ''Ranina ranina'' populations have been surveyed to avoid

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

and are currently stable.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. Although ''Ranina ranina'' is a target of commercial fishing operations, little is known about the species' biology, population dynamics and ecology. Attempts have been made to grow ''Ranina ranina'' in captivity, but have so far been met with little success.

Culinary use

''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. 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. It is the delicacy harvested in the provinces Bình Định and Quảng Ngãi, and is hailed "monarch of all the crab".

References

{{DEFAULTSORT:crab, spanner

spanner crab ''Ranina ranina'', also known as the Huỳnh Đế crab, (red) frog crab or spanner crab, is a species of crab found throughout tropical and subtropical habitats. It is often fished for its meat, and is the only known species in its genus. Desc ...

Marine fauna of Eastern Australia Edible crustaceans Commercial crustaceans