Polybius henslowii
| Polybius henslowii | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Crustacea |
| Class: | Malacostraca |
| Order: | Decapoda |
| Infraorder: | Brachyura |
| Family: | Portunidae |
| 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.
Description
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]
Distribution
Polybius is found in the north-east Atlantic Ocean from the British Isles to Morocco, and in the western Mediterranean Sea. 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.[3] It can be found on sandy or gravelly sediments at depths of up to 500 metres (1,600 ft).[2]
Ecology and behaviour
Polybius henslowii is a capable swimmer, and can be found swimming near the ocean surface, where it feeds on sardines, squid and other animals.[2] P. henslowii has been observed to form pelagic swarms. These swarms are mostly composed of males, and are thought to be related to the reproductive cycle.[1]
In Galicia (NW Spain), P. henslowii is an important food source for the yellow-legged gull, Larus michahellis.[4] In summer, loggerhead turtles (Caretta caretta) off North Africa feed almost exclusively on P. henslowii.[5]
Taxonomy
Polybius henslowii was first described by William Elford Leach in 1820, as the only species in his new genus Polybius.[6] 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.[6] 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,[7] who had collected the specimens used by Leach from a herring fisherman in North Devon in 1817.[8] This was the first of several species that were named in Henslow's honour.[8] Common names for the species include "sardine swimming crab"[7] and "Henslow's swimming crab".[4]
References
- 1 2 3 4 "Zooplankton and Micronekton of the North Sea". Marine Species Identification Portal. Retrieved February 12, 2012.
- 1 2 3 Andrew Hosie (2009). "Polybius henslowii. Henslow's swimming crab". Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme. Plymouth: Marine Biological Association of the United Kingdom. Retrieved February 12, 2012.
- ↑ J. A. Lindley, G. Beaugrand, C. Luczak, J.-M. Dewarumez & R. R. Kirby (2010). "Warm-water decapods and the trophic amplification of climate in the North Sea". Biology Letters 6 (6): 773–776. doi:10.1098/rsbl.2010.0394. PMC 3001376. PMID 20554562.
- 1 2 Ignacio Munilla (1997). "Henslow's swimming crab (Polybius henslowii) as an important food for yellow-legged gulls (Larus cachinnans) in NW Spain" (PDF). ICES Journal of Marine Science 54 (4): 631–634. doi:10.1006/jmsc.1997.0249.
- ↑ O. Ocaña, A. G. de los Rios y los Huertos & A. Brito (2005). "The crab Polybius henslowii (Decapoda: Brachyura) as a main resource in the loggerhead turtle (Caretta caretta) diet from North Africa". Revista de la Academia Canaria de Ciencias 17 (4): 103–116.
- 1 2 Peter Davie & Michael Türkay (2012). "Polybius". World Register of Marine Species. Retrieved February 12, 2012.
- 1 2 R. W. Ingle (1997). Crayfishes, Lobsters, and Crabs of Europe: an Illustrated Guide to Common and Traded Species. Springer. p. 140. ISBN 978-0-412-71060-5.
- 1 2 Stuart Max Walters, Max Walters & Elizabeth Anne Stow (2001). "Appendix 4. Eponymous taxa". Darwin's Mentor: John Stevens Henslow, 1796–1861. Cambridge University Press. pp. 285–288. ISBN 978-0-521-59146-1.