Double sneak
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Moorish networm ( Blanus cinereus ) |
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| Gray , 1844 |
The double sneaks (Amphisbaenia), also called ring snakes , worm sneaks or ring lizards , are a group of highly specialized, relatively small, scaled crawfish (Squamata) that look like earthworms . Its scientific name is derived from Amphisbaena (ἀμφίσβαινα, 'the one going in two directions'), a mythical snake with a head at each end. He refers to the fact that in animals it is sometimes impossible to tell at first glance at which end of the body the head is. The German common name "Doppelschleiche" also expresses this.
Occurrence
Most of the over 190 species (as of 2017) live in Africa , South America and on the islands of the Caribbean , Florida and in the south of Baja California . The genus Blanus lives in the Mediterranean area. The 30 cm long Moorish networm ( Blanus cinereus ) lives on the Iberian Peninsula . The Turkish networm lives in Rhodes , Kos , Cyprus , western Turkey , Lebanon , Syria and northern Iraq .
Since they are rare and have a burrowing way of life, little is known other than their anatomy.
Appearance and anatomy
Double creeps are the scaled crawfish most adapted to an underground way of life. All but the two-footed double-creeps (Bipedidae) are legless. The scales have disappeared apart from remains on the head. The animals are surrounded by a tough, diagonally ringed skin sac, which can lead to confusion with earthworms . The elongated body is round, the front and back of the same thickness.
Four different head shapes can be distinguished: rounded, shovel-shaped, dorsally keeled and chisel-shaped. * The mouth is small, the lower jaw is shorter. The animals dig with the help of their strong skull, which is inserted into the ground like a drill head . Each of the head shapes listed at the beginning seems to be associated with a specific grave style. The nostrils point backwards so that no soil can enter. The tail is also short and blunt, or pointed.
Double sneaks do not crawl like snakes or sneaking by twisting the body sideways, but rather stretched to adapt to the movement in narrow burial tunnels. As with earthworms, pulse-like wave movements run through the body. They can only crawl relatively slowly, but equally forwards and backwards.
Amphisbaenians breathe with the enlarged left lung (the right is reduced), as opposed to the snakes and almost all snake-like lizards (except the Zwergteju generic Bachia ) in which the left lung function and size instead is reduced. They are usually 20 to 30 centimeters tall. The red double worm ( Amphisbaena alba ) from South America and Monopeltis capensis from Africa are 50 to 70 centimeters long.
Reproduction
Like all scaled reptiles, male double snakes have two hemipenes as mating organs. Most species lay eggs, often in termite burrows, and some species are also viviparous.
nutrition
Ringworms eat worms , millipedes , insects and their larvae, and many tropical species mainly feed on ants and termites . The Moorish networm also has a preference for ants.
Tribal history
Double creeps have been found in fossil records from the Paleocene . The affiliation of older finds to this group is not considered certain. Sineoamphisbaena from the Upper Cretaceous of the Gobi Basin, originally identified as an early double worm, is assigned to the purely fossil squamate family Polyglyphanodontidae in more recent studies . Investigations using the molecular clock method suggest that the group originated in the Cenozoic , long after the break-up of the ancient continent of Pangea . The first double snakes lived in North America and they have probably spread three times over oceans, possibly drifting on driftwood, to other continents, first from North America to Europe, then from North America to Africa and finally from Africa to South America. So far, all fossil finds of double snakes come only from the northern continents (North America, Europe and Asia). With Blanus antiquus from the Middle Miocene of southern Germany, they also represent a Central European species. Today, however, their distribution area extends mainly to the southern continents of Africa and South America.
Systematics
External system
Due to their special anatomy and way of life, the double snakes were traditionally listed alongside snakes (Serpentes) and lizards (Sauria, Lacertilia) as a subordinate of the order Squamata ( scale creeps ). At the end of the 20th century, with the increasing influence of cladistics on zoological systematics, it became clear, however, that such a profound subdivision of scaly creepers is actually not justified because both snakes and double-creeping are subgroups of lizards and the lizards themselves are not Form a closed, natural group ( Paraphylum ). Despite their resemblance to snakes, the double snakes are not closely related to them.
Exactly what position the double creeps occupy within the scale creepers was not exactly clarified until the end of the 20th century. In some cases a position within the Skink-like (Scincomorpha), i.e. H. a closer relationship with skinks (Scincidae), real lizards (Lacertidae), belt tails (Cordylidae) and rail lizards (Teiidae) than likely.
According to the latest molecular biological investigations, the double snakes are the sister group of the real lizards and with them they form a taxon called Lacertibaenia . The thesis is supported by the discovery of Cryptolacerta , a small lizard from the Messel Pit , whose skeletal anatomy is characterized by a mixture of lizard and double-sneak features.
A very comprehensive molecular genetic investigation of the relationships between the scallops (44 nucleus genes each from 161 squamate taxa and 10 outer group taxa), the results of which were published at the end of 2012, confirmed the close relationship between real lizards and double sneaks, but also provided indications of a possible paraphylyia of double snakes : In the cladogram of the maximum likelihood analysis, Rhineura floridana (Rhineuridae) stood outside a common clade of lizards and the other representatives of double snakes. The Bayesian analysis, however, revealed monophyletic double creeps with the lizards as a sister group (see following cladogram).
| Scale reptiles (Squamata) |
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Internal system
The double creeps are currently (as of 2014) divided into six families:
- Florida twin snakes (Rhineuridae). Only one species, the Florida double sneak ( Rhineura floridana ) lives in northern Florida up to Lake Okeechobee in the Everglades National Park . It systematically faces all other double sneaks as a sister group.
- Actual double snakes (Amphisbaenidae). 11 to 16 genera, distribution in Africa, South America and the Caribbean islands.
- Pointed-toothed double sneaks (Trogonophidae). Four genera ( Agamodon , Diplometopon , Pachycalamus , Trogonophis ) with a total of six species in Africa and the Middle East.
- Dual Foot amphisbaenians (Bipedidae). The only genus, the hand- digging ( Bipes ) with three kinds, have small forelimbs transformed into digging tools. You live in western Mexico.
- Cadeidae . A genus ( Cadea ) occurring in Cuba with two species ( Cadea blanoides and Cadea palirostrata ).
- Blanidae . A genus ( Blanus ) occurring in the Mediterranean region with seven species, including the Moorish networm ( Blanus cinereus ).
The families Blanidae and Cadeidae were only established in 2004 and 2008, respectively.
The following cladogram clarifies the relationships within the double creeps:
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According to this hypothesis, the Florida double-creeps, as completely legless forms with a grave head, have the most basal position in the cladogram, and the Bipedidae, which have front legs and a skull that is not very much transformed into a dig, belong to the more strongly derived taxa. This implies that, if the hypothesis is correct, the development of the head ditch and the reduction of the forelegs must have taken place independently of one another at least three times within the double creeps: in the Florida double creeps, the real and pointed tooth double creeps as well as in the Cadeids and Blanids.
Remarks
- *These shape designations are not used uniformly in the literature. The term “spade-shaped” is used for both shovel-like and chisel-like head shapes. For example, Dalophia's head shape is sometimes referred to as shovel-shaped and sometimes as spade-shaped, while the head shape of the chisel- headed Diplometopon is also referred to as spade-shaped.
literature
- Nicolas Vidal, Anna Azvolinsky, Corinne Cruaud, S. Blair Hedges: Origin of tropical American burrowing reptiles by transatlantic rafting. Biology Letters, Vol. 4, No. 1, 2008, pp. 115-118, doi : 10.1098 / rsbl.2007.0531 .
- Wolfgang Böhme : Squamata, scale reptiles. In: W. Westheide, R. Rieger (Ed.): Special Zoology. Part 2. Vertebrate or skull animals. Spektrum, Munich 2004, ISBN 3-8274-0307-3 , pp. 377-398.
- Carl Gans, Ricardo Montero: An Atlas of Amphisbaenian Skull Anatomy. P. 621-738 in: Carl Gans, Abbot S. Gaunt, Kraig Adler (eds.): Biology of the reptilia. Vol. 21, Morphology I: The skull and appendicular locomotor apparatus of Lepidosauria. Contributions to Herpetology, Vol. 24. Society for the Study of Amphibians and Reptiles, Ithaca (NY) 2008, ISBN 978-0-9169-8477-9 ( online )
Individual evidence
- ^ Amphisbaenia in The Reptile Database
- ↑ Collective of authors: The Encyclopedia of Animals. National Geographic Germany, Hamburg 2012, ISBN 978-3-8669-0246-6 , p. 370
- ^ A b Nicholas R. Longrich, Jakob Vinther, R. Alexander Pyron, Davide Pisani, Jacques A. Gauthier: Biogeography of worm lizards (Amphisbaenia) driven by end-Cretaceous mass extinction. Proceedings of the Royal Society Series B, May 2015, volume 282, issue 1806 DOI: 10.1098 / rspb.2014.3034
- ↑ Xiao-Chun Wu, Donald B. Brinkman, Anthony P. Russell: Sineoamphisbaena hexatabularis , an amphisbaenian (Diapsida: Squamata) from the Upper Cretaceous redbeds at Bayan Mandahu (Inner Mongolia, People's Republic of China), and comments on the phylogenetic relationships of the Amphisbaenia. Canadian Journal of Earth Sciences, Vol. 33, No. 4, 1996, pp. 541-577, doi : 10.1139 / e96-042 (alternative full-text access : wormlizard.org PDF 6.3 MB).
- ↑ a b Johannes Müller, Christy A. Hipsley, Jason J. Head, Nikolay Kardjilov, André Hilger, Michael Wuttke, Robert R. Reisz: Eocene lizard from Germany reveals amphisbaenian origins. Nature , Vol. 473, pp. 364-367, doi : 10.1038 / nature09919 .
- ↑ H. Hermann Schleich: New reptile finds from the Tertiary of Germany: 3rd first record of double sneaks ( Blanus antiquus sp. Nov.) From the Middle Miocene of southern Germany. Munich Geoscientific Treatises Series A: Geology and Paleontology. Vol. 4, 1985, pp. 1–16 ( sample page with images including the holotype ( memento of the original from September 24, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link accordingly Instructions and then remove this note. 79 kB).
- ^ Richard Estes, Kevin de Queiroz, and Jacques Gauthier: Phylogenetic Relationships within Squamata. In: Richard Estes, Gregory Pregill (Eds.): Phylogenetic Relationships of the Lizard Families: Essays Commemorating Charles L. Camp. Stanford University Press, Stanford (CA) 1988, pp. 219-281
- ↑ Wolfgang Böhme: Squamata, Schuppenkriechtiere. 2004 (see literature ), p. 393.
- ^ Gerhard Mickoleit: Phylogenetic systematics of vertebrates. Publishing house Dr. Friedrich Pfeil, Munich 2004, ISBN 3-89937-044-9 , p. 309.
- ↑ Nicolas Vidal, S. Blair Hedges: The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genes. Comptes Rendus Biologies. Vol. 328, No. 10-11, 2005, pp. 1000-1008, doi : 10.1016 / j.crvi.2005.10.001 .
- ^ John J. Wiens, Carl R. Hutter, Daniel G. Mulcahy, Brice P. Noonan, Ted M. Townsend, Jack W. Sites Jr., Tod W. Reeder: Resolving the phylogeny of lizards and snakes (Squamata) with extensive sampling of genes and species. Biology Letters. Vol. 8, No. 6, 2012, pp. 1043-1046, doi : 10.1098 / rsbl.2012.0703 ( Supplementa , inter alia with tree of Bayesian analysis).
- ↑ a b Maureen Kearney, Bryan L. Stuart: Repeated evolution of limblessness and digging heads in worm lizards revealed by DNA from old bones. Proceedings of the Royal Society B. Vol. 271, 2004, pp. 1677-1683, doi : 10.1098 / rspb.2004.2771 , PMC 1691774 (free full text).
- ^ A b Nicolas Vidal et al .: Origin of tropical American burrowing reptiles. 2008 (see literature ).
- ↑ G. John Measey, Krystal A. Tolley: A molecular phylogeny for sub-Saharan amphisbaenians. African Journal of Herpetology. Vol. 62, No. 2, 2013, doi: 10.1080 / 21564574.2013.824927
- ↑ Gans & Montero: An Atlas of Amphisbaenian Skull Anatomy. 2008 (see literature ), p. 699
- ↑ JA Maisano, M. Kearney, T. Rowe: Cranial anatomy of the spade-headed amphisbaenian Diplometopon zarudnyi (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography. Journal of Morphology. Vol. 267, No. 1, 2006, pp. 70-102, doi: 10.1002 / jmor.10388 .
