Hemilepistus reaumuri
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| Species: | H. reaumuri
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| Hemilepistus reaumuri (H. Milne-Edwards, 1840) [Note 1]
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Hemilepistus reaumuri is a species of woodlouse that lives in and around the deserts of North Africa and the Middle East, "the driest habitat conquered by any species of crustacean".[2] They occur at great population densities and fulfil an important rôle in the desert ecosystem. They live in burrows, each containing a family group, and recognise their family members using pheromones.
Distribution
Hemilepistus reaumuri is found in the steppes, semideserts and deserts of North Africa, and the Middle East, and occasionally on the margins of salt lakes.[3] It is most closely associated with loess soils in the Sahara Desert and Negev Desert,[4] although its range extends from eastern Algeria to western Syria.[1] It has been found at population densities of up to 480,000 individuals per hectare, which is equivalent to a biomass of 19.2 kg/ha; desert mammals are estimated to have a combined biomass of 39.9 kg/ha.[5] It sometimes rests under stones on in crevices of rocks.[4]
Life cycle
Hemilepistus reaumuri is the only species of Hemilepistus to have developed parental care of its offspring,[2] and it is only because of this development that the species can survive in the desert.[6] It is monogamous, and, unusually, both parents tend the young.[6] H. reaumuri can spend up to ten months of the year returning to the surface to forage, which is far longer than species which do not dig burrows, such as Armadillidium vulgare or Armadillo officinalis.[4]
The colonies are quiescent during the winter, and young individuals emerge in February and March to establish new burrows.[7] Sheltered sites below bushes are chosen, although larger males will often try to pair with a female who has already established a burrow, sometimes ousting her male partner.[7] They have no specialised digging equipment, and the excavation is a slow process, taking place only in early spring.[3] The first 3–5 centimetres (1.2–2.0 in) are dug by a single woodlouse, which then stops to guard the new burrow. Eventually, it will allow one other woodlouse of the opposite sex to enter, and they then engage in a ritual which often lasts for hours, before copulation.[3] The females bears 50–100 live young, typically in May. The young remain in the burrow for 10–20 days, being provided with food by their parents. On leaving the burrow, they are wary of other families, and adults may catch other adults' offspring and feed them to their own, but do not normally attack their own children.[3] Members of each social group recognise each other using pheromones.[4]
Ecology
Burrows
H. reaumuri can only escape the heat of the desert by constructing a burrow, which is time-consuming and energetically costly. One parent must therefore guard the burrow while the other forages for food.[6] Although they will forage at temperatures as high as 35 °C (95 °F),[7] these woodlice retreat to their burrow when the temperature is too high.[4] They are also unable to tolerate air with a relative humidity below 6%, which often occurs in the hottest months at depths of up to 30 centimetres (12 in) in the desert soil, and the burrows are therefore dug at least 40–50 cm (16–20 in) deep.[4] The entrances to the burrows are about 1 cm (0.39 in) wide, and there may be up to 20 burrows per square metre in favourable areas.[7]
Predators
Up to 70% of the diet of the scorpion Scorpio maurus may be made up of H. reaumuri.[8]
Feeding
Hemilepistus reaumuri has a significantly higher biomass than other herbivores in the Negev Desert, making it an important part of herbivore–omnivore food chains.[4] They spend the day provisioning their burrows with leaf material from the surface of the desert. Their faeces accumulates on the surface, and forms a "faecal embankment", similar to a levee, which demarcates the extent of the home territory of the colony in the burrow.[7] The bulk of the water intake of Hemilepistus reaumuri is by taking up water vapour from saturated air and by eating damp sand. Water loss is minimised by the rectal epithelium, which absorbs water, ensuring that the faeces is drier than the food the animal consumed.[9]
H. reaumuri differs from other desert woodlice in a number of respects. It is crepuscular, while other species are nocturnal. Apart from at the highest temperatures, it is also positively phototactic (is attracted to sunlight), while other species are negatively phototactic (move away from bright light).[4]
Taxonomic history
Hemilepistus reaumuri was illustrated in volume 21 of the Description de l'Égypte, researched during Napoleon's campaign in Egypt and Syria of 1798–1801, and dedicated to René Antoine Ferchault de Réaumur. The section on Crustacea was begun by Marie Jules César Savigny but finished by Jean Victoire Audouin after Savigny's healtth deteriorated. The species was not given a formal scientific name, however, until Henri Milne-Edwards did so in 1840, calling it Porcellio reaumuri.[1] Although initially placed in the genus Porcellio, it was later moved to Hemilepistus,[1] which was created by G. H. A. Budde-Lund in 1879 as a subgenus of Porcellio, but raised to the rank of genus by Karl Wilhelm Verhoeff in 1930.[10]
External links
- Description de l'Égypte
- "Roly-Poly Lifestyles" by Marilyn Schotte
Media related to Hemilepistus reaumuri at Wikimedia Commons
Notes
- ^ The authority is often cited as "(Audouin, 1826)" or "(Audouin & Savigny, 1826)". See the section on taxonomic history for an explanation.
References
- ^ a b c d Helmut Schmalfuss (2003). "World catalog of terrestrial isopods (Isopoda: Oniscidea) – revised and updated version" (PDF). Stuttgarter Beiträge zur Naturkunde, Serie A. 654: 1–341.
- ^ a b Rod Preston-Mafham & Ken Preston-Mafham (1993). "Crustacea. Woodlice, crabs". The Encyclopedia of Land Invertebrate Behavior. MIT Press. p. 161. ISBN 9780262161374.
- ^ a b c d K. Eduard Linsenmair (1974). "Some adaptations of the desert woodlouse Hemilepistus reaumuri (Isopoda, Oniscoidea) to desert environment" (PDF). Verhandlungen der Gesellschaft für Ökologie. 4: 183–185.
- ^ a b c d e f g h Fred Punzo (2000). "Life histories: individual case studies". Desert arthropods: life history variations. Springer. pp. 105–156. ISBN 9783540660415.
- ^ James T. Markwiese, Randall T. Ryti, Mark M. Hooten, Daniel I. Michael & Ihor Hlohowskyj (2000). "Toxicity bioassays for ecological risk assessment in arid and semiarid ecosystems". In George W. Ware (ed.). Volume 168. Reviews of Environmental Contamination and Toxicology. Springer. pp. 43–98. ISBN 9780387951386.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b c Tristram Wyatt (October 8, 1987). "How habitat leads to mothercare". New Scientist. 116 (1581): 50–53.
- ^ a b c d e James T. Costa (2006). "Other social arthropods. Arachnids, centipedes, millipedes, and crustaceans". The Other Insect Societies. Belknap Press Series. Harvard University Press. pp. 667–716. ISBN 9780674021631.
- ^ David Ward (2009). The Biology of Deserts. Biology of Habitats. Oxford University Press. ISBN 9780199211470.
- ^ Colin Little. "Crustaceans and the evolution of the arthropods". The Colonisation of Land: Origins and Adaptation of Terrestrial Animals. Cambridge University Press. pp. 63–106. ISBN 9780521252188.
{{cite book}}: Unknown parameter|Year=ignored (|year=suggested) (help) - ^ Ghasem M. Kashani, Alireza Sari & Shidokht Hosseinie (Ostavani) (2010). "Terrestrial isopods of the subgenus Hemilepistus (Hemilepistus) Budde-Lund, 1879 (Isopoda: Oniscidea) from Iran" (PDF extract). Zootaxa. 2549: 54–68.