| Polybius henslowii | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Brachyura |
| Family: | Polybiidae |
| Genus: | Polybius Leach, 1820 |
| Species: | P. henslowii |
| Binomial name | |
| Polybius henslowii Leach, 1820 | |
Polybius henslowii is a species of crab, the only species in the genus Polybius. It is a capable swimmer and feeds in open water in the north-east Atlantic Ocean and western Mediterranean Sea.
The carapace of P. henslowii is almost circular, 48 millimetres (1.9 in) wide and 40 mm (1.6 in) long. The first pair of pereiopods (walking legs) carry claws, and the remaining four pairs are flattened with fringed edges. [1] This contrasts with other members of the family Portunidae, which have only the last pair of legs adapted for swimming. [2] P. henslowii is red-brown on the upper surface, and paler beneath. [1]
Polybius is found in the north-east Atlantic Ocean from the British Isles to Morocco, and in the western Mediterranean Sea. Very abundant swarms have been found along the coasts off Galicia (Spain) [3] and off Portugal. [4] Rare specimens have been caught in the North Sea east of Shetland, and in the Skagerrak. [1] Its range has expanded into the southern North Sea, possibly as a result of climate change. [5] It can be found on sandy or gravelly sediments at depths of up to 500 metres (1,600 ft). [2]
Polybius henslowii is a capable swimmer, and can be found swimming near the ocean surface, where it feeds on a mixture of squid, fish, and other crustaceans, including specimens of the same species. [6] Indeed, P. henslowii has been observed to form pelagic swarms. These swarms are mostly composed of females, excluding that aggregations are for mating, while they might be related to feeding. [6] When they swim inshore, along the coastal upwelling areas of Galicia (NW Spain), they rely more on benthic prey, such as polychaetes and detritus [6] and are influenced by terrestrial organic matter coming from the rivers. [7]
In Galicia (NW Spain), P. henslowii is an important food source for the yellow-legged gull, Larus michahellis . [8] In summer, loggerhead turtles (Caretta caretta) off North Africa feed almost exclusively on P. henslowii. [9]
Polybius henslowii was first described by William Elford Leach in 1820, as the only species in his new genus Polybius. [10] Although a number of other species were added to the genus over time, they have all since been split off into new genera such as Liocarcinus , Necora and Macropipus . [10] The genus name "Polybius" may be in reference to the Greek historian Polybius; the specific epithet henslowii honours John Stevens Henslow, Professor of Botany at Cambridge University, [11] who had collected the specimens used by Leach from a herring fisherman in North Devon in 1817. [12] This was the first of several species that were named in Henslow's honour. [12] Common names for the species include "sardine swimming crab" [11] and "Henslow's swimming crab". [8]
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail-like abdomen, usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers on each arm. They first appeared during the Jurassic period, around 200 million years ago.
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and distantly related to auks, and even more distantly to waders. Until the 21st century, most gulls were placed in the genus Larus, but that arrangement is now considered polyphyletic, leading to the resurrection of several genera. An older name for gulls is mews, which is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse, and French mouette, and can still be found in certain regional dialects.
Krill(Euphausiids) are small and exclusively marine crustaceans of the order Euphausiacea, found in all the world's oceans. The name "krill" comes from the Norwegian word krill, meaning "small fry of fish", which is also often attributed to species of fish.
Cheloniidae is a family of typically large marine turtles that are characterised by their common traits such as, having a flat streamlined wide and rounded shell and almost paddle-like flippers for their forelimbs. They are the only sea turtles to have stronger front limbs than back limbs. The six species that make up this family are: the green sea turtle, loggerhead sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle and the Kemp's ridley sea turtle.
Ghost crabs are semiterrestrial crabs of the subfamily Ocypodinae. They are common shore crabs in tropical and subtropical regions throughout the world, inhabiting deep burrows in the intertidal zone. They are generalist scavengers and predators of small animals. The name "ghost crab" derives from their nocturnality and their generally pale coloration. They are also sometimes called sand crabs, though the name refers to various other crabs that do not belong to the subfamily.
The loggerhead sea turtle is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons than the females.
Profilicollis is a genus of acanthocephalan parasites of crustaceans. The status of the genus Profilicollis has been debated, and species placed in this genus were formerly included in the genus Polymorphus. However, research on the morphology of the group and their use of hosts has concluded that Profilicollis and Polymorphus should be regarded as distinct genera, and species previously described as Polymorphus altmani are now referred to as Profilicollis altmani in taxonomic and biological literature. Profilicollis parasites infect decapod crustaceans, usually shore crabs, as intermediate hosts, and use many species of shorebirds as definitive (final) hosts.
Ocypode ceratophthalmus, the horned ghost crab or horn-eyed ghost crab, is a species of ghost crab. It lives in the Indo-Pacific region ; from the coast of East Africa to the Philippines and from Japan to the Great Barrier Reef. They also occur in the Pacific Islands to as far east as Polynesia and Clipperton Island. As their common name implies, O. ceratophthalmus possess eyestalks extending beyond the eyes into long points, which are longer in adults, and shorter in juveniles. The crabs have a box-shaped body, 6–8 centimetres (2.4–3.1 in) across the carapace, with a darker markings towards the rear in the shape of an H. The outer edges of the eye-sheaths are also sharp and broadly triangular and distinctly pointing sideways in larger individuals. O. ceratophthalmus can run at speeds of up to 2.1 metres per second (6.9 ft/s).
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Alitta succinea is a species of marine annelid in the family Nereididae. It has been recorded throughout the North West Atlantic, as well as in the Gulf of Maine and South Africa.
Xantho is a genus of crabs in the family Xanthidae, containing five extant species, all restricted to the north-east Atlantic Ocean and Mediterranean Sea, although Xantho granulicarpis is not universally recognised as a separate species from Xantho hydrophilus:
Grimothea planipes, also known as the pelagic red crab, red crab, or tuna crab, is a species of squat lobster from the eastern Pacific Ocean.
Munida rugosa, commonly known as the rugose squat lobster or plated lobster, is a species of decapod crustacean found in the north east Atlantic Ocean and the Mediterranean Sea.
Dyspanopeus sayi is a species of mud crab that is native to the Atlantic coast of North America. It has also become established outside its native range, living in Swansea Docks since 1960, the Mediterranean Sea since the 1970s, the North Sea since 2007 and the Black Sea since 2010. It can reach a carapace width of 20 mm (0.8 in), and has black tips to its unequal claws. It feeds on bivalves and barnacles, and is in turn eaten by predators including the Atlantic blue crab, Callinectes sapidus. Eggs are produced from spring to autumn, the offspring reach sexual maturity the following summer, and individuals can live for up to two years. The closest relative of D. sayi is D. texanus, which lives in the Gulf of Mexico; the two species differ in subtle features of the genitalia and the last pair of walking legs.
Around 65 species of crab occur in the waters of the British Isles. All are marine, with the exception of the introduced Chinese mitten crab, Eriocheir sinensis, which occurs in fresh and brackish water. They range in size from the deep-water species Paromola cuvieri, which can reach a claw span of 1.2 metres, to the pea crab, which is only 4 mm (0.16 in) wide and lives inside mussel shells.
Libinia dubia, the longnose spider crab, is a species of crab in the family Epialtidae. It is found in shallow waters on the eastern coast of North America.
Planes minutus is a species of pelagic crab that lives in the North Atlantic Ocean. It is typically less than 10 mm (0.4 in) long across the back, and is variable in colouration, to match its background. It may have been the crab seen by Christopher Columbus on Sargassum weed in the Sargasso Sea in 1492.
Portunus sayi, the sargassum swimming crab, is a species of pelagic crab in the family Portunidae. It is found in the western Atlantic Ocean and the Caribbean Sea where it makes its home among floating mats of Sargassum seaweed. It was named in honour of the American naturalist Thomas Say.
Ocypode convexa, commonly known as the golden ghost crab, or alternatively the western ghost crab or yellow ghost crab, is a species of ghost crabs endemic to the coast of Western Australia, from Broome to Perth. They are relatively large ghost crabs, with a carapace growing up to 45 mm (1.8 in) long and 52 mm (2.0 in) wide. They are easily recognisable by their golden yellow colouration. Like other ghost crabs they have box-like bodies with unequally sized claws. They also have large eyestalks with the cornea occupying most of the bottom part.
Chelonibia testudinaria is a species of barnacle in the family Chelonibiidae. It is native to the Atlantic Ocean, Mediterranean Sea and Gulf of Mexico where it lives as a symbiont on sea turtles, being particularly abundant on the loggerhead sea turtle.