The slow worm (Anguis fragilis) is a reptile native to western Eurasia. It is also called a deaf adder, a slowworm,[2][3] a blindworm, or regionally, a long-cripple and hazelworm. These legless lizards are also sometimes called common slowworms. The "blind" in blindworm refers to the lizard's small eyes, similar to a blindsnake (although the slowworm's eyes are functional).
Slow worms are semifossorial[4] (burrowing) lizards, spending much of their time hiding underneath objects. The skin of slow worms is smooth with scales that do not overlap one another. Like many other lizards, they autotomize, meaning that they have the ability to shed their tails to escape predators. While the tail regrows, it does not reach its original length. In the UK, they are common in gardens and allotments, and can be encouraged to enter and help remove pest insects by placing black plastic or providing places to shelter such as piles of logs, corrugated iron sheets or under tiles.[5] On warm days, one or more slow worms can often be found underneath these heat collectors. One of the biggest causes of mortality in slow worms in suburban areas is the domestic cat, against which it has no defence.[6]
Slow worms have been shown to be a species complex, consisting of 5 distinct but similar species.
Taxonomy
Distribution of species of European slow worms
Anguis fragilis was traditionally divided into two subspecies (A. f. fragilis and A. f. colchica), but they are now classified as separate species:[7][8]
Anguis fragilissensu stricto (found in western Europe, northern Europe and western Balkans) and
Anguis colchica (found in eastern Europe, eastern Balkans and in western Asia).
Three more species were later distinguished from A. fragilis:
Slow worms have an elongated body with a circular cross-section without limbs and reach a maximum length of up to 57.5cm.[9] Most adult animals are between 40 and 45cm long, with up to 22cm on the head and trunk section and the rest on the tail.[10] There is no visible neck. The tail, which ends in a horny tip, is continuous with the trunk and is often slightly longer. Slow worms exhibit caudal autotomy, the severing of the tail when it is pulled by predators.[11] When regrown the tail only grows back to a short stub, probably because loss of the tail does not sufficiently impact the species' locomotion, foraging and defence abilities to necessitate full and rapid regeneration.[12]
The skin surface consists of smooth, round-to-hexagonal scales which overlap like roof tiles and are roughly the same shape on the dorsal and ventral surfaces of the body. There are several longitudinal rows running along the underside. In total, the trunk has 125 to 150 transverse scale rows and the tail has another 130 to 160 rows. Under the scales there are bony plates (osteoderms), so that slow worms crawl much more stiffly and clumsily than snakes. The scaling of the head is similar to that of snakes. The ear openings are mostly completely hidden under the scales. The relatively small eyes have movable, closable eyelids (these are fused in snakes) and round pupils. The rather short tongue is broad, bilobed and does not end in fine tips. To lick, i.e. to absorb odorous substances, slow worms have to open their mouths slightly, as they lack the gap in the upper lip that snakes possess. The pointed, sometimes loosely fixed teeth are curved backwards; there are 7 to 9 teeth in the premaxilla, 10 to 12 in the maxilla and 14 to 16 in the lower jaw.[13]
Close-up of the head of a slow worm
Reproduction
Juvenile slow worm, paperclip for size comparison
In Central Europe, the mating season of the species is usually between late April and June. The males often wrestle violently around the females, although in most populations they are in the majority. The opponents try to push each other to the ground, bite each other and wrap themselves tightly around each other. When mating, the female is bitten in the head or neck region, while the male introduces his two hemipenes into the female's cloaca. Copulation can take several hours. Sometimes females mate with other males later. The gestation period of the females lasts 11 to 14 weeks, and subsequently, between mid-July and the end of August, and sometimes even later, they usually give birth to between eight and twelve young (extreme values: 2 to 28). Slow worms are ovoviviparous; at birth, the 7 to 10cm long young animals are in a very thin, transparent egg shell, which they pierce immediately afterwards. They initially weigh less than a gram and still have a remnant of the yolk.[14] Juvenile slow worms have a contrasting color scheme and pattern. The top of the body is silvery-white to golden yellow, while the sides and underside are black.
Size and longevity
Adult slow worms grow to be about 50cm (20") long, and are known for their exceptionally long lives; the slow worm may be the longest-living lizard, living about 30 years in the wild and up to at least 54 years in captivity (this record is held by a male slow worm that lived at the Copenhagen Zoo from 1892 until 1946, the age when first obtained is unknown).[15][16] The female often has a stripe along the spine and dark sides, while the male may have blue spots dorsally. Juveniles of both sexes are gold with dark brown bellies and sides with a dark stripe along the spine.
These reptiles are largely nocturnal and do not bask in the sun like other reptiles, but choose to warm themselves indirectly underneath objects such as rocks which have been warmed by the sun. They can often be found in long grass and other damp environments[22] In a 2009 study of a Danish population, the diet of the slow-worm was found to include slugs, snails, earthworms, caterpillars and pill millipedes.[23]
The slow worm is assumed to be non-native in Ireland, possibly arriving in the 1900s. Due to their secretive habits they are difficult to observe and have only been sighted in parts of County Clare, mainly in the Burren region.[26][27][28]
Evolutionary history
Members of the genus Anguis, to which the slow worm belongs, first appeared in Europe during the Mammal Paleogene zone 14, between 43.5 and 41.2 million years ago, corresponding to the Lutetian stage of the Eocene.[29] Remains assigned to the Anguis fragilisspecies complex are known from the late Miocene onwards.[30]
Gallery
A slow worm
A slow worm close
Slow worm in turquoise color
A slow worm moving through grass. This individual is a juvenile, as evinced by its golden colouration.
Anguidae refers to a large and diverse family of lizards native to the Northern Hemisphere. Common characteristics of this group include a reduced supratemporal arch, striations on the medial faces of tooth crowns, osteoderms, and a lateral fold in the skin of most taxa. The group is divided into two living subfamilies, the legless Anguinae, which contains slow worms and glass lizards, among others, found across the Northern Hemisphere, and Gerrhonotinae, which contains the alligator lizards, native to North and Central America. The family Diploglossidae was also formerly included. The family contains about 87 species in 8 genera.
Slowworms are a small genus (Anguis) of snake-like legless lizards in the family Anguidae. The genus has several living species, including the common slowworm, the eastern slowworm, the Greek slowworm, the Peloponnese slowworm, and the Italian slowworm. There are also known fossil species.
Ophisaurus is a genus of superficially snake-like legless lizards in the subfamily Anguinae. Known as joint snakes, glass snakes, or glass lizards, they are so-named because their tails are easily broken; like many lizards, they have the ability to deter predation by dropping off part of the tail, which can break into several pieces, like glass. The tail remains mobile, distracting the predator, while the lizard becomes motionless, allowing eventual escape. This serious loss of body mass requires a considerable effort to replace, and can take years to do so. Despite this ability, the new tail is usually smaller than the original.
The sheltopusik, also commonly called Pallas's glass lizard, the European legless lizard, or the European glass lizard, is a species of large glass lizard found from Southern Europe to Central Asia.
Langford Heathfield is a 95.4 hectare biological Site of Special Scientific Interest at Langford Budville, 3 km (1.9 mi) north west of Wellington in Somerset, notified in 1966.
The eastern glass lizard is a species of legless lizard in the family Anguidae and the longest and heaviest species of glass lizards in the genus Ophisaurus, endemic to the Southeastern United States. It is 1 of 4 glass lizard species in the eastern United States. The streamlined, legless species is often confused with snakes. Glass lizards differ from snakes as they possess a moveable eyelid and an external ear opening, both of which are absent in snakes. Snakes also have flexible jaws while lizards do not. Ventralis comes from the Latin "venter" meaning belly; this is in reference to the snake-like movement.
In the 10th edition of Systema Naturae, Carl Linnaeus described the Amphibia as:
Animals that are distinguished by a body cold and generally naked; stern and expressive countenance; harsh voice; mostly lurid color; filthy odor; a few are furnished with a horrid poison; all have cartilaginous bones, slow circulation, exquisite sight and hearing, large pulmonary vessels, lobate liver, oblong thick stomach, and cystic, hepatic, and pancreatic ducts: they are deficient in diaphragm, do not transpire (sweat), can live a long time without food, are tenatious of life, and have the power of reproducing parts which have been destroyed or lost; some undergo a metamorphosis; some cast (shed) their skin; some appear to live promiscuously on land or in the water, and some are torpid during the winter.
Pedioplanis lineoocellata, known commonly as the common sand lizard, the ocellated sand lizard, and the spotted sand lizard, is a species of lizard in the family Lacertidae. The species is endemic to Southern Africa. There are three recognized subspecies.
Anguis veronensis, commonly known as the Italian slow worm or Italian slowworm, is a European lizard species in the family Anguidae. The slow worm is distributed throughout Italy and in southeastern part of France.
Anguis colchica, the eastern slowworm, is a species of lizard in the family Anguidae found in eastern Europe and Asia. It is easily confused with the common slowworm, due to their physical similarities, and the proximity of their distribution.
↑ The "slow-" in slowworm is distinct from the English adjective slow ("not fast"); the word comes from Old English slāwyrm, where slā- means 'earthworm' or 'slowworm' and wyrm means "serpent, reptile". ( "Slowworm". The American Heritage Dictionary of the English Language. Houghton Mifflin Harcourt. 2017.)
↑ Wolfgang Böhme: A record-sized specimen of the western slow worm (Anguis fragilis). In: Zeitschrift für Feldherpetologie. Bd. 19, Nr. 1, 2012, ISSN0946-7998, S. 117–118.
↑ Dieter Glandt: Die Amphibien und Reptilien Europas. Alle Arten im Porträt. Quelle & Meyer Verlag, Wiebelsheim 2015, ISBN978-3-494-01581-1, S. 322–327.
↑ Bryant SV, Bellairs ADA. 1967. Tail regeneration in the lizards Anguis fragilis and Lacerta dugesii. Zoological Journal of the Linnean Society 46 (310): 297-305.
↑ Barr JI, Boisvert CA, Bateman PW. 2021. At what cost? Trade-offs and influences on energetic investment in tail regeneration in lizards following autotomy. Journal of Developmental Biology 9(4): 53.
↑ Rainer Günther, Wolfgang Völkl: Blindschleiche – Anguis fragilis Linnaeus, 1758. In: Rainer Günther (Hrsg.): Die Amphibien und Reptilien Deutschlands. Gustav Fischer, Jena u. a. 1996, ISBN3-437-35016-1, S. 617–631.
↑ Heribert Wolfbeck, Klemens Fritz: Blindschleiche, Anguis fragilis Linnaeus, 1758. In: Hubert Laufer, Klemens Fritz, Peter Sowig: Die Amphibien und Reptilien Baden-Württembergs. Ulmer, Stuttgart 2007, ISBN978-3-8001-4385-6, S. 619–632.
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