Five-fingered handwheels
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Five-fingered handwheels ( Bipes biporus ) |
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| Bipes biporus | ||||||||||||
| ( Cope , 1894) |
The five-fingered handwheel , also five-limbed handwheel ( Bipes biporus ) is a small, peculiar looking reptile from the genus of the handwheel . The five-fingered handwheel is reminiscent of a large earthworm with two mole-like hands, has no other limbs and crawls or digs through the sandy soil of its semi-desert-like habitats.
features
Five-fingered hand rooting are on average 19-21 cm, maximum up to 24 cm long. They have a worm-like body with regular cross rings and a scaling of small, smooth horny shields. In specimens> 15 cm, the body and tail are white on the back and on the abdomen, in smaller specimens pale pink. While their hind legs have receded, they have a stubby pair of arms in front with well-developed, longer-clawed hands. The number of fingers distinguishes the five-fingered handwheel from other handwheels. However, in rare cases the four-finger handwheel can also have five fingers. On the other hand, the number of pore-like skin openings in front of the anal gap (pre-anal pores) is a reliable determinant. With the five-fingered handwheel there are always only two, with the other two species of the genus Bipes at least six. The eyes sit quite far forward on the bluntly rounded head and are very small; the sense of sight is reduced. There are no ear openings. The tongue is two-pointed and can be stuck out.
Way of life
The five-fingered hand digger is, like all representatives of the genus hand digger, adapted to a digging way of life. The animals spend most of their time in self-dug tunnels in the ground. In the early morning they stay in corridors close to the surface of the earth. When the temperature rises in the course of the day, they withdraw into lower-lying corridors or into corridors in shady areas. They are rarely found on the earth's surface.
nutrition
Five-fingered hand rooters feed on insects and other invertebrates , especially ants and termites .
Reproduction
Five-fingered hand burrows are oviparous . The females become sexually mature at the age of about 45 months, with a body length of about 18.5 cm. The reproductive rhythm appears to follow a two-year cycle. A clutch comprises 1–4 (on average 2.15) eggs. The eggs are usually laid in July and the young hatch in September with a body length of 9-10 cm.
It is noteworthy that in large-scale censuses in the distribution area about twice as many adult females as males were found. It is not known whether this discrepancy in the distribution of the sexes is species-specific, caused by an increased mortality rate in male individuals, or a systematic error in sampling.
Predators
Little is known about potential predators of the five-fingered hand rooters. Coral otters , which are known to eat hand-rooting, do not occur in the distribution area of the five-fingered hand-rooting. There is a single known case in which a five-fingered handwheel was eaten by a spotted night snake ( Hypsiglena torquata ). In general, however, the selection pressure from predators seems to be rather low. This can also be seen in the number of individuals with a tail thrown off for defense. In the case of Bipes biporus , only 2.7% of the specimens examined showed signs of a shed tail. In the case of the other representatives of the genus, the proportion was significantly higher at 10.2% ( Bipes canaliculatus ) and 17.0% ( Bipes tridactylus ).
distribution
The occurrence of the species is limited to the southwestern part of the Baja California peninsula . The distribution area essentially coincides with the extent of the Vizcaíno desert in the north and the Magdalena plain in the south. Both areas are characterized by loose, sandy soils with shrub growth.
Research history
The species was first described by Edward Drinker Cope in 1894 and initially assigned to its own genus ( Euchirotes ). Later the species was placed in the genus Bipes together with the three-fingered handwheel ( Bipes tridactylus ) and the four-fingered handwheel ( Bipes canaliculatus ) .
Web links
- Bipes biporus inthe IUCN 2013 Red List of Threatened Species . Listed by: Hollingsworth, B. & Frost, DR, 2007. Retrieved February 1, 2014.
- Bipes biporus in Reptile Database (English)
- Front view of a Handwühle (English)
Individual evidence
- ^ TCH Cole: Dictionary of animal names: Latin-German-English, German-Latin-English. 2nd edition, 974 pp., Springer Verlag, 2015. ISBN 978-3-662-44241-8 (reading sample)
- ↑ a b c d e f g h i Th. J. Papenfuss: The Ecology and Systematics of the Amphisbaenian Genus Bipes. In: Occasional Papers of the California Academy of Sciences , No. 136, 42 pp., 1982. (digitized version)
- ↑ a b L. L. Grismer: Amphibians and Reptiles of Baja California, Including Its Pacific Islands and the Islands in the Sea of Cortés. 413 pp., University of California Press, 2002. ISBN 0-520-22417-5 (reading sample)
- ↑ M. Kearney: Diet in the Amphisbaenian Bipes biporus. In: Journal of Herpetology , Vol. 37, No. 2, pp. 404-408, 2003 (abstract)
- ↑ ED Cope: On the Genera and Species of Euchirotidæ. In: The American Naturalist , Vol. 28, pp. 436–437, 1894. (digitized version )
- ^ L. Stejneger & Th. Barbour: A Check List of North American Amphibians and Reptiles. 125 pp., Harvard University Press, 1917. (digitized version)