Amphidromus

{{Short description|Genus of land snails}} {{Good article}} {{Use dmy dates|date=October 2020}} {{Automatic taxobox |image = Amphidromus roseolabiatus.png |image_caption = The species ''Amphidromus roseolabiatus'' has dextral shell coiling. |image2 = Amphidromus fuscolabris.png |image2_caption = The species ''Amphidromus fuscolabris'' has sinistral shell coiling. |display_parents = 3 |taxon = Amphidromus |authority = Albers, 1850<ref>15px Albers J. C. (1850). ''Die Heliceen nach natürlicher Verwandtschaft: systematisch georduct'': 138.</ref> |type_species = ''Helix perversa'' |type_species_authority = (Linnaeus, 1758) |subdivision_ranks = Species |subdivision = See text |diversity_link = List of Amphidromus species |diversity = Over 270 species |diversity_ref = <ref name="Sutcharit 2015">{{Cite journal| doi = 10.3897/zookeys.492.8641| pmid = 25878542| pmc = 4389215| issn = 1313-2970| issue = 492| pages = 49–105| last1 = Sutcharit| first1 = Chirasak| last2 = Ablett| first2 = Jonathan| last3 = Tongkerd| first3 = Piyoros| last4 = Naggs| first4 = Fred| last5 = Panha| first5 = Somsak| title = Illustrated type catalogue of Amphidromus Albers, 1850 in the Natural History Museum, London, and descriptions of two new species| journal = ZooKeys| access-date = 2017-07-08| date = 2015-03-30| url = https://zookeys.pensoft.net/articles.php?id=5002| doi-access = free}}</ref><ref name="Inkhavilay 2017"/> |synonyms = * ''Amphidromus (Amphidromus)'' Albers, 1850· accepted, alternate representation * ''Amphidromus (Goniodromus)'' Bülow, 1905· accepted, alternate representation * ''Amphidromus (Syndromus)'' Pilsbry, 1900· accepted, alternate representation * ''Amphidronus'' Albers, 1850 (incorrect subsequent spelling) * ''Bulimus (Amphidromus)'' Albers, 1850 (original rank) * ''Goniodromus'' Bülow, 1905 * ''Syndromus'' Pilsbry, 1900 }}

'''''Amphidromus''''' is a genus of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the family Camaenidae.

The shells of ''Amphidromus'' are relatively large, from {{convert|25|mm|in|abbr=on}} to {{convert|75|mm|in|abbr=on}} in maximum dimension, and particularly colorful. During the 18th century, they were among the first Indonesian land snail shells brought to Europe by travelers and explorers. Since then, the genus has been extensively studied: several comprehensive monographs and catalogs were authored by naturalists and zoologists during the time period from the early 19th to the mid 20th centuries. Modern studies have focused on better understanding the evolutionary relationships within the group, as well as solving taxonomic problems.

The genus ''Amphidromus'' is unusual in that it includes species that have dextral shell-coiling and species that have sinistral shell-coiling. In addition, some species within this genus (such as ''Amphidromus janus'' (L. Pfeiffer, 1854))are particularly notable because their populations simultaneously include individuals with left-handed and right-handed shell-coiling. This is an extremely rare phenomenon, and very interesting to biologists. Studies focused on the soft anatomy of ''Amphidromus'' are scattered and fragmentary. Information on the internal anatomy is known only from a few species, and no larger, comparative morphological study has ever been carried out.

Species in the genus ''Amphidromus'' are arboreal — in other words, they are tree snails. However, more detailed information on their habits is still lacking. The general feeding habits of these snails are unknown, but a few species are known to feed on microscopic fungi, lichens or terrestrial algae. ''Amphidromus'' themselves are preyed upon by birds, snakes, and probably also by smaller mammals such as rats.

== Taxonomy and history == [[File:Carl Eduard von Martens (1831-1904).jpg|thumb|upright|German zoologist Eduard von Martens (1831–1904) published the first comprehensive monograph on the genus ''Amphidromus'' in 1867, and many of his concepts are still in use.<ref name="Laidlaw 1961"/>]]

The generic name is derived from the ancient Greek words ''{{lang|el|amphí}}'' ({{lang|el|ἀμφί}}), meaning "on both sides", and ''{{lang|el|drómos}}'' ({{lang|el|δρόμος}}), meaning "running", alluding to the different chiralities of the shells.<ref name=Brown1954>{{cite book |last1=Brown |first1=Roland W. | author-link=Roland W. Brown | title=Composition of Scientific Words: A manual of methods and a lexicon of materials for the practice of logotechnics |year=1977 |orig-date=1st Pub. 1954 |publisher=Smithsonian Institutional Press | location=Washington, D.C. | isbn=978-0-87474-286-2 | oclc=4495758 |via=Internet Archive |url=https://archive.org/details/compositionofsci00brow |access-date=27 August 2025}}</ref> The shells of ''Amphidromus'' are relatively large, and quite colorful; considerable numbers of them were among the first Indonesian land snail shells brought back to Europe by travelers and explorers during the 18th century. Comparatively speaking, malacologists have gathered a much smaller number of specimens.<ref name="Laidlaw 1961"/>

Several species and forms were described before 1800, most of them with inadequate locality data. At least two names — ''Amphidromus laevus'' (Müller, 1774) and the form ''A. perversus'' f. ''aureus'' Martyn, 1784 – still (as of 2017) have not yet been reported from a precise locality. During the first half of the nineteenth century, many species and varieties were named, again usually with poor locality data. Not until Eduard von Martens (1867) published his monograph<ref>15px Martens E. von (1867). ''Die Preussische Expedition nach Ost-Asien''. Zoologischer Theil. '''2''': xii, 447 pp., 22 plates.</ref> was there an attempt to cover the entire complex of species within this genus. The 1867 monograph contained considerable information both on the variation within the genus, and on the problems of the geographic distribution of the species. Many concepts that originated with von Martens are still (as of 2017) in use.<ref name="Laidlaw 1961"/>

In 1896, Hugh Fulton<ref>Fulton H. (1896). "A list of the species of ''Amphidromus'', Albers, with critical notes and descriptions of some hitherto undescribed species and varieties". ''Annals and Magazine of Natural History'' (6)'''17''': 66–94, plates 5–7.</ref> organized 142 specific and varietal names into eighteen species groups containing a total of 64 species. When Henry Augustus Pilsbry's 1900 monograph ''Manual of Conchology''<ref name="Pilsbry 1900">15px Pilsbry H. A. (1900). ''Manual of Conchology, structural and systematic, with illustrations of the species. Second series: Pulmonata''. [https://archive.org/details/manualofconcholo13tryorich Volume 13]. Australasian Bulimulidae: ''Bothriembryon'', ''Placostylus''. Helicidae: ''Amphidromus''. 253 pp., 72 plates, [https://archive.org/stream/manualofconcholo13tryo#page/184/mode/2up page 184].</ref> appeared, the number of species in the genus ''Amphidromus'' had increased to 81, and these were placed in nineteen groups. Pilsbry's study has remained the only illustrated monograph of the genus, and it is still considered indispensable for any serious study of the genus.<ref name="Laidlaw 1961"/>

Since 1900, the major taxonomic studies on ''Amphidromus'' have been faunistic (a study of the fauna of some territory or area) in scope. The papers of American malacologist Paul Bartsch (1917, 1918, 1919)<ref>15px Bartsch P. (1917). "The Philippine land snails of the genus ''Amphidromus''". ''U. S. Nat. Mus. Bull.'' '''100'''(1), part 1: 1–47, 22 plates.</ref><ref>15px Bartsch P. (1918). "The land snails of the genus ''Amphidromus'' from the islands of the Palawan Passage". ''Jour. Washington Acad. Sci.'' '''8'''(11): 361–367.</ref><ref>15px Bartsch P. (1919). "Critical remarks on Philippine Island land shells". ''Proc. Biol. Soc. Washington'' '''32''': 177–184.</ref> on the Philippine species, Bernhard Rensch (1932)<ref>{{in lang|de}} Rensch B. (1932). "Die Mollusken Fauna der Kleinen Sunda-Inseln, Bali, Lombok, Sumbawa, Flores und Sumba". ''Zool. Jahrb., Syst.'' '''63''': 1–130, 3 plates.</ref> on the Lesser Sunda Islands forms, and Tera van Benthem Jutting (1950, 1959)<ref name="Jutting 1950">van Benthem Jutting T. (1950). "Critical studies of the Javanese pulmonate land-shells of the families Helicarionidae, Pleurodontidae, Fruticicolidae and Streptaxidae". ''Treubia'' '''20'''(3): 381–505, 107 figs.</ref><ref>van Benthem Jutting T. (1959). "Catalogue of the non-marine Mollusca of Sumatra and of its satellite islands". ''Beaufortia'' '''7'''(83): 41–191, 1 plate, 11 figs.</ref> on Javan and Sumatran populations are especially comprehensive. Potentially the most valuable<ref name="Laidlaw 1961"/> contribution is that of Curt Haniel (1921),<ref name="Haniel 1921">{{in lang|de}} Haniel C. (1921). "Variationsstudie an Timoresischen ''Amphidromus'' Arten". ''Zeits. Induct. Abstamm. und Vererbungsl.'' '''25'''(1–2): 88 pp., 5 plates.</ref> who discussed the variation within ''A. contrarius'' and ''A. reflexilabris'' on Timor; the variations in color and form were well illustrated in a series of color plates.

Literature published after 1900 contains many scattered descriptions of new color forms and subspecies. Of the 309 names in the nomenclatural list, 111 (35.9%) were published after Pilsbry (1900). Adolf Michael Zilch (1953)<ref>{{in lang|de}} Zilch A. M. (1953). "Die Typen und Typoide des Natur-Museums Senckenberg. 10: Mollusca, Pleurodontidae (1)". ''Archiv für Molluskenkunde'' '''82'''(4–6): 131–140, plates 22–25.</ref> listed type specimens in the Senckenberg Museum, and illustrated many previously unfigured species. Frank Fortescue Laidlaw & Alan Solem (1961) recognized 74 species by name, and considered that material from the Banda Islands probably represented an undescribed species. Eleven of the species recognized by Laidlaw & Solem were described after the appearance of Pilsbry's monograph. However, several species recognized by Pilsbry have subsequently been subordinated to subspecific or varietal status, and a few names have been transferred to incertae sedis, since they are based on hundred-year-old references that have not been substantiated by more recent collectors. In fact, the study by Laidlaw & Solem (1961) forms a supplement to Pilsbry's monograph with his extensive plates, and many of Laidlaw & Solem's conclusions concerning the relationships of color forms described as species were taken not so much from new samples, but from the extent of variation that was outlined by Haniel (1921) in his pioneer study.<ref name="Laidlaw 1961"/>

===Characterization=== Species in the genus ''Amphidromus'' usually have smooth, glossy, brightly colored, elongate or conic, dextrally or sinistrally coiled shells. The shells are moderately large, ranging from {{convert|25|mm|in|abbr=on}} to {{convert|70|mm|in|abbr=on}} in maximum dimension, having from 6 to 8 convex whorls. Their color pattern is usually monochromatic yellowish or greenish, but can be variegated. The aperture is oblique or ovate in shape, without any teeth or folds, and with the aperture height ranging from two-fifths to one-third of total shell height. The peristome is expanded and/or reflected, and is sometimes thickened. The columella may be straight or recurved, and the parietal callus is weak to well-developed, and the umbilicus may be open or closed. The radula is spatulate, has cusped teeth arranged in rows, usually with a monocuspid central tooth and bicuspid or tricuspid lateral teeth. The jaw is thin and weak, with low flat ribs. The pallial region is sigmurethrous, with a very long, narrow kidney. The genitalia are that of typical camaenids, with a long seminal receptacle, a short penis with low insertion of the retractor muscle, and a short or long epiphallic caecum (flagellum and appendix). The spermatophores have a pentagonal outline in cross-section. ''Amphidromus'' are typically arboreal animals.<ref name="Laidlaw 1961"/><ref name="Sutcharit 2006" />

== Shell description ==

The shells of ''Amphidromus'' are relatively large, from one to three inches high, and colorful. ''Amphidromus'' has an elongate-conic or ovate-conic helicoid shell of 5 to 8 whorls. The shell may be thin and fragile, or very heavy and solid, with no known correlation of shell structure with distribution or habitats.<ref name="Laidlaw 1961"/>

===Shell coiling=== {{Main|Gastropod shell#Chirality in gastropods}} In some species within this genus, the shell coils invariably to the right, and in many others just as invariably to the left. However, a significant number of species in this genus are "amphidromine"; this term means that both left- and right-handed shell coiling are found within the same population. One could say they are "polymorphic" for the direction of shell coiling, but because there are only two possible types of shell coiling, they are described as "dimorphic" in coiling. The two types of shell coiling occur in some species in approximately equal numbers, other species have a distinct predominance of one phase. There is as yet no information on the heredity of this character in ''Amphidromus''.<ref name="Laidlaw 1961"/>

Because almost all other species of amphidromine gastropods, such as ones within the genera ''Partula'' and ''Achatinella'', have already become extinct,<ref name="Sutcharit 2007"/> the genus ''Amphidromus'', containing over 110 species, is uniquely useful for the study of the evolution of asymmetry in animals,<ref name="Sutcharit 2007"/> and this is why the conservation of this genus is of essential importance to biologists. <gallery mode=packed heights=160px> File:Amphidromus floresianus shell 2.png|In ''A. floresianus'', subgenus ''Syndromus'', shell coiling is normally sinistral. Scale bar 10 mm. File:Amphidromus perversus natunensis shell 2.png|Shells in the amphidromine species ''A. perversus'' can be dextral, as shown here. File:Amphidromus perversus natunensis shell 3.png|But shell coiling in ''A. perversus'' can also be sinistral, as shown here. File:Amphidromus perversus shell.jpg|Abapertural view of a sinistral shell (left), and apertural view of a dextral shell (right) of ''A. perversus'' </gallery>

===Shell shape and sculpture=== [[File:Amphidromus atricallosus leucoxanthus 01.JPG|thumb|''Amphidromus atricallosus leucoxanthus'' has a shell form that is typical for the genus ''Amphidromus'': it is moderately convex and smooth.]] The whorls of the shell of species of ''Amphidromus'' are moderately convex and, with only a few exceptions, are smooth or have a faint sculpture of growth lines. However, a sculpture of moderately heavy oblique radial ribs has appeared at least four separate times in the genus, and can be seen in the following species: ''Amphidromus costifer'' Smith from Binh Dinh Province in Vietnam; ''A. begini'' Morlet from Cambodia; ''A. heccarii'' Tapparone-Canefri from Celebes; and the ''A. palaceus''-''A. winteri'' complex from Java and Sumatra. Correlated with the ribbing is a light, monochrome coloration, and a thin shell with a large aperture and a flaring lip. Many solid shells in other species do show a slight roughening of the surface, but this is very different from the ribbed sculpture mentioned above.<ref name="Laidlaw 1961"/>

The aperture is generally large, varying from about two-fifths to one-third the height of the shell, often within the same population. Usually the lip is at least somewhat expanded, and in forms such as ''A. reflexilabris'' Schepman and ''A. winteri'' (Pfeiffer) var. ''inauris'' Fulton, the lip can only be called flaring. In ''A. perversus'' (Linnaeus) and most other thick-shelled species, the lip is internally thickened, forming a "roll" in its expansion, and has a very heavy parietal callus. In thin-shelled species, the lip is usually a simple reflected edge. The umbilical area can be partially open, nearly closed, or sealed. This feature sometimes provides a useful criterion for specific identification. The angle of the parietal wall varies, but no precise information on this has been compiled.<ref name="Laidlaw 1961"/>

Generally the whorls of the shell increase rather regularly in size, however, species which are probably closely related, such as ''A. sinistralis'' (Reeve) and ''A. heccarii'' Tapparone-Canefri, can have quite different degrees of whorl increment. No attempt has been made to express these differences meristically, since most of the available material was inadequate for statistical treatment. Actual dimensions of the shell vary greatly both within and between species. The minimum adult size is about 21 mm high, the observed maximum about 75 mm. There is not much variation in adult size within species: only a few species, notably ''A. maculiferus'', ''A. sinensis'' and ''A. entobaptus'', have a variation in adult size that is greater than seven or eight millimeters in total.<ref name="Laidlaw 1961"/>

===Shell coloration=== [[File:Amphidromus everetti 01.JPG|thumb|''Amphidromus everetti'' shell is brightly colored, a feature which is typical of arboreal snails in general.]] [[File:Amphidromus perversus butoti infraviridis shell.png|thumb|90px|right|The dark varix on this ''Amphidromus perversus'' shell marks a resting stage.]] The single most major aspect of shell variation within the genus is the color patterning. In general, many arboreal snails are brightly colored, obvious examples being the bulimulid genera ''Drymaeus'' and ''Liguus'', the cepolid ''Polymita'', and the camaenid ''Papuina''. However, ''Polymita'', ''Liguus'' and ''Amphidromus'' are particularly noted for their color variations. The basic ground color of ''Amphidromus'' appears to be yellow, and this color is usually (except for ''Amphidromus entobaptus'') confined to the surface layers of the shell, since worn specimens appear to be nearly devoid of color. In some species the background color is whitish, and a few have dark background colors. The apical whorls are pale, purple, brown, or black, and this sometimes varies within a population (as in ''A. quadrasi''). A few species, for example ''A. schomburgki'', have a deciduous green periostracum.<ref name="Laidlaw 1961"/>

Continuous zonal patterns can take the form of whitish subsutural bands (''A. similis''), heavy subperipheral pigmentation (''A. perversus'' var. ''infraviridis''), subsutural color lines (''A. columellaris''), broad spiral color bands (''A. metabletus'', ''A. webbi''), or narrow spiral bands (''A. laevus''). Interrupted zonation can consist of the interruption of bands into spots in (''A. maculatus''); highly irregular splitting of zones (''A. perversus'' vars. ''sultanus'' and ''interruptus''); formation of oblique radial streaks which run parallel to (in ''A. inversus'') or cross (in ''A. latestrigatus'') the incremental growth lines; or almost every conceivable combination and variation of these factors. Often the pattern will change radically from the apex to the body whorl (in ''A. quadrasi'' vars.). The aperture, parietal callus, columella, lip, and umbilical region are variously marked with pink, brown, purple, white, or black. Haniel (1921)<ref name="Haniel 1921"/> includes several color plates which clearly demonstrate the extent of color variation within two species of the ''Syndromus'' type. ''A. perversus'' and ''A. maculiferus'' of the subgenus ''Amphidromus'' are equally variable, whereas species such as ''A. inversus'' and ''A. similis'' are almost uniform in coloration.<ref name="Laidlaw 1961"/>

In shells of most of the species in the subgenus ''Amphidromus'', resting stages are marked by the deposition of a brown or black radial band called a varix. This appears to be rare in the subgenus ''Syndromus'', although the shell of ''A. laevus'' does show evidence of interruption of the spiral banding after a resting phase.<ref name="Laidlaw 1961"/>

===Species recognition=== Species recognition is based on combinations of minor structural variations in the shape, aperture, whorl contour, umbilical region, and color pattern. It appears to be the case that many species have a stable color pattern, while other species seem to vary tremendously. Adequate unselected field samples will enable a better understanding of the relative stability or variability of particular species in single localities.<ref name="Laidlaw 1961"/>

== Anatomy == Information concerning the soft anatomy of ''Amphidromus'' is widely scattered and fragmentary. The most complete account is that of Arnold Jacobi (1895)<ref>{{in lang|de}} Jacobi A. (1895). "Anatomische Untersuchungen an Malayischen Landschnecken". ''Arch. Naturg.'' '''61''': 293–318, plate 14.</ref> on specimens from Great Natuna (Natuna Islands) and Djemadja (Anamba Islands). Unfortunately, although it is clear that anatomical differences exist in the two species Jacobi dissected, unfortunately we do not know which forms he worked on, because he had incorrectly identified his material. In his paper he referred to the two species as ''Amphidromus chloris'' and the ''interruptus'' phase of ''A. perversus''. However, that is not possible, because in reality ''Amphidromus chloris'' is a species found only in the Philippine Islands, and the ''interruptus'' phase of ''A. perversus'' is not present in the Natuna Islands.<ref name="Laidlaw 1961"/>

Carl Arend Friedrich Wiegmann (1893, 1898)<ref>15px {{in lang|de}} Wiegmann C. A. F. (1863). "Beitrage zur Anatomie der Landschnecken des Indischen Archipels". In: Weber (1863). ''Zool. Ergeb. Reisen Indischen Arch.'' '''3''': 112–259, plates 9–16.</ref><ref>15px {{in lang|de}} Wiegmann C. A. F. (1898). "Landmollusken (Stylommatophoren)". ''Zootomischer Teil. Abhl. Sencken. Naturf. Gesell.'' '''24'''(3): 289–557, plates 21–31. [https://archive.org/stream/landmolluskensty00wieg#page/514/mode/2up/ 514]-527.</ref> discussed portions of the anatomy of ''A. adamsii'', ''A. porcellanus'', ''A. contrarius'', and ''A. sinistralis''. Walter Edward Collinge (1901, 1902)<ref>Collinge W. E. (1901). "Note on the anatomy of ''Amphidromus palaceus'', Mouss". ''Jour. Malac.'' '''8'''(2): 50–52, plate 4.</ref><ref>Collinge W. E. (1902). "On the non-operculated land and fresh-water molluscs collected by members of the "Skeat Expedition" in the Malay Peninsula, 1899–1900". ''Op. cit.'' '''9'''(3): 71–95, plates 4–6.</ref> briefly noted features of ''A. palaceus'' and ''A. parakensis'' (reported as ''A. perversus''). Haniel (1921)<ref name="Haniel 1921"/> dissected ''A. contrarius'' and ''A. reflexilabris'', and Bernhard Rensch published a few scattered notes in his various faunistic surveys. A few earlier notes are mentioned in Pilsbry (1900).<ref name="Laidlaw 1961"/><ref name="Pilsbry 1900"/>

Characters such as the long, narrow kidney with reflexed ureter and closed secondary ureter, the penial complex with distinct penis, which is continuous with the epiphallus, epiphallic caecum (a flagellum and an appendix), unbranched gametolytic duct, lack of vaginal accessory organs, and the basic condition of the nervous and retractor muscle systems support the inclusion of ''Amphidromus'' in the family Camaenidae.<ref name="Sutcharit 2006" /> This group of snails occur in a wide variety of habitats in the tropics of Eastern Asia and Australasia, and is one of the most diverse families in the clade Stylommatophora.<ref name="Cuezzo2003">{{cite journal|last1=Cuezzo|first1=M.G.|title=Phylogenetic analysis of the Camaenidae (Mollusca: Stylommatophora) with special emphasis on the American taxa|journal=Zoological Journal of the Linnean Society|date=2003|volume=138|issue=4|pages=449–476|doi=10.1046/j.1096-3642.2003.00061.x|doi-access=free|hdl=11336/101199|hdl-access=free}}</ref> Though Laidlaw & Solem (1961) provided no more additional details on the anatomy of ''Amphidromus'', subsequent studies by distinct authors, e.g., Bishop (1977)<ref name="Bishop 1977">{{cite journal|last1=Bishop|first1=M.J.|title=Anatomical notes on some Javanese ''Amphidromus'' (Pulmonata: Camaenidae)|journal=Journal of Conchology|date=1977|volume=29|pages=199–205}}</ref> and Solem (1983),<ref name="Solem 1983" /> have demonstrated that the reproductive system can provide valuable data for species recognition.<ref name="Laidlaw 1961"/> <gallery mode=packed-hover heights=200px caption="Reproductive systems isolated through dissection"> File:Amphidromus areolatus reproductive system.png|''Amphidromus areolatus''; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens File:Amphidromus flavus reproductive system.png|''Amphidromus flavus''; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens File:Amphidromus fuscolabris reproductive system.png|''Amphidromus fuscolabris''; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens File:Amphidromus roseolabiatus reproductive system.png|''Amphidromus roseolabiatus''; '''ap''' – appendix; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens File:Amphidromus syndromoideus reproductive system.png|''Amphidromus syndromoideus''; '''ap''' – appendix; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens File:Amphidromus xiengensis reproductive system.png|''Amphidromus xiengensis''; '''at''' – atrium; '''e''' – epiphallus; '''fl''' – flagellum; '''fo''' – free oviduct; '''gd''' – gametolytic duct; '''gs''' – gametolytic sac; '''ov''' – oviduct; '''p''' – penis; '''pr''' – penial retractor muscle; '''v''' – vagina; '''vd''' – vas deferens </gallery>

== Diversity and phylogeny ==

<div>{{cladogram|style=width:400px;font-size:90%;line-height:85%|cladogram= {{clade |label1='''''Amphidromus''''' |1={{clade |1={{clade |1={{clade |1={{clade |1={{clade |1=''A. inversus'' |2=''A. givenchyi'' }} |2=''A. schomburgki'' }} |2={{clade |1={{clade |1=''A. atricallosus'' var. ''laidlawi'' |2=''A. atricallosus leucoxanthus'' }} |2=''A. atricallosus atricallosus'' |3={{clade |1={{clade |1=''A. atricallosus perakensis'' |2=''A. palaceus'' }} |2=''A. perversus naturnensis'' }} |4=''A. martensi'' |5=''A. similis'' }} }} |2={{clade |1={{clade |1={{clade |1={{clade |1=''A. adamsii'' |2=''A. pictus'' }} |2=''Amphidromus'' sp. }} |2=''A. semitessallatus'' }} |2={{clade |1={{clade |1={{clade |1=''A. xiengensis'' |2=''A. flavus'' }} |2={{clade |1={{clade |1=''A. areolatus'' |2=''A. xiengensis'' }} |2={{clade |1=''A. porcellanus'' |2=''A. xiengensis'' }} }} }} |2={{clade |1=''A. semitessellatus'' |2=''A. areolatus'' }} }} }} }} |2=''A. glaucolarynx'' }} }}|caption=Phylogeny and relationships of ''Amphidromus'' according to Sutcharit et al. (2007)<ref name="Sutcharit 2007"/> }} </div>

Prior to 1900, the similarity in shape of the shell of ''Amphidromus'' to that of South American tree snails in the family Bulimulidae had misled taxonomists. However, the dissections made by Wiegmann and Jacobi clearly showed that the inner anatomical features of ''Amphidromus'' were the same as those of the Asian-Indonesian Camaenidae, and that the resemblance of the shell of ''Amphidromus'' to that of bulimulids was merely an example of parallelism.<ref name="Laidlaw 1961"/>

;Subgenera and species {{Main|List of Amphidromus species}}

Laidlaw and Solem (1961) recognized 75 species in the genus ''Amphidromus'', and placed another seven names under ''incertae sedis''. In 2010, 87 species in the genus ''Amphidromus'' were recognized.<ref name="Sutcharit 2007"/><ref name="Chan Tan Abbas 2008">Chan S.-Y., Tan S.-K. & Abbas J. B. (2008). "On a new species of ''Amphidromus'' (''Syndromus'') (Gastropoda: Pulmonata: Camaenidae) from Rotti Island, Indonesia". ''Occasional Molluscan Papers'' '''1''': 1–5. [http://web.singnet.com.sg/~chansy2/download/2008omp1-5.pdf PDF] {{webarchive|url=https://web.archive.org/web/20110724040713/http://web.singnet.com.sg/~chansy2/download/2008omp1-5.pdf |date=24 July 2011 }}, [https://archive.org/download/OnANewSpeciesOfAmphidromussyndromusgastropodaPulmonataCamaenidae_575/2008omp1-5.pdf Internet Archive]</ref><ref name="Chan 2008 from Sumba">Chan S.-Y. & Tan S.-K. (2008). "On a new species of ''Amphidromus'' (''Syndromus'') (Gastropoda: Pulmonata: Camaenidae) from Sumba Island, Indonesia". ''Occasional Molluscan Papers'' '''1''': 6–10. [http://web.singnet.com.sg/~chansy2/download/2008omp6-10.pdf PDF] {{webarchive|url=https://web.archive.org/web/20110724040608/http://web.singnet.com.sg/~chansy2/download/2008omp6-10.pdf |date=24 July 2011 }}, [https://archive.org/details/OnANewSpeciesOfAmphidromussyndromusgastropodaPulmonataCamaenidae_859 Internet Archive]</ref><ref name="Laidlaw 1961"/> Species within the genus ''Amphidromus'' are divided into two subgenera, as in the following list:<ref name="Sutcharit 2007">{{cite journal | last1=Sutcharit | first1=C. | last2=Asami | first2=T. | last3=Panha | first3=S. | title=Evolution of whole-body enantiomorphy in the tree snail genus Amphidromus | journal=Journal of Evolutionary Biology | volume=20| issue=2 |pages=661–672 | doi=10.1111/j.1420-9101.2006.01246.x | year=2007 | pmc=1920546 | pmid=17305832}}</ref>

* Subgenus ''Amphidromus'' Albers, 1850

Originally described as ''Helix perversus'' by Linnaeus in 1758, ''Amphidromus perversus'' is the type species of the genus ''Amphidromus'', by the subsequent designation of Eduard von Martens (1860).<ref>von Martens E. (1860). ''Die Heliceen'' 2nd ed., p. 184.</ref> Species in the subgenus ''Amphidromus'' are amphidromine (left-handed and right-handed snails occur within the population) with a few exceptions. Four dextral taxa are: ''A. givenchyi'', ''A. protania'', ''A. schomburgki dextrochlorus'' and ''A. inversus annamiticus''; and one sinistral: ''A. atricallosus classiaris''.<ref name="Sutcharit 2007"/> These species usually have shells which have ht following characteristics: they are large (height often exceeding {{convert|35|mm|in|abbr=on}}); they have a height/width ratio of less than 1.85; and a shell color which is yellowish or greenish. Anatomically they have a long epiphallus and flagellum, and an appendix is usually present.<ref name="Laidlaw 1961"/><ref name="Sutcharit 2006" />

* Subgenus ''Syndromus'' Pilsbry, 1900<ref name="Pilsbry 1900"/>

All but two species within the subgenus ''Syndromus'' are sinistral. The exceptions are the amphidromine ''A. glaucolarynx'' and the dextral ''A. kuehni''.<ref name="Chan 2008 from Sumba"/> The type species of the subgenus ''Syndromus'' is ''A. contrarius'' Müller, 1774, by the subsequent designation of Adolf Michael Zilch (1960).<ref>Zilch A. M. (1960). ''Gastropoda, Euthyneura. Handb. Palaozool.'' (6)'''2'''(4): 601–834, figs. 2112–2515. page 623.</ref> Species in the subgenus ''Syndromus'' have smaller shells (height usually less than {{convert|35|mm|in|abbr=on}} and height/width ratio greater than 1.85), with variable color pattern. They also have a short epiphallus and flagellum, lacking an appendix.<ref name="Laidlaw 1961"/><ref name="Sutcharit 2006"/> A third possible subgenus, ''Goniodromus'' Bülow, 1905 (type species ''Amphidromus büllowi'' Fruhstorfer, 1905),<ref>Bülow (1905). ''Nachr. d. Malak. Gesell.'' '''37''': 83.</ref> is also cited in the literature, though its subgeneric status is yet to be confirmed.<ref name="Sutcharit 2006">{{cite journal | last1=Sutcharit | first1=C. | title=Taxonomic review of the tree snail Amphidromus Albers, 1850 (Pulmonata: Camaenidae) in Thailand and adjacent areas: subgenus ''Amphidromus''| journal=Journal of Molluscan Studies | volume=72 | pages=1–30 | year=2005 | doi=10.1093/mollus/eyi044 | doi-access=free }}</ref>

;Phylogeny Molecular analyses of partial sequences of 16S rDNA of 18 distinct species carried out by Sutcharit and colleagues (2007)<ref name="Sutcharit 2007"/> indicate that ''Amphidromus'' is a monophyletic group. In their study, different cladograms obtained through distinct methods such as maximum parsimony, neighbor joining and maximum likelihood were congruent among themselves. Though the topology obtained for the subgenus ''Amphidromus'' was fairly consistent with current taxonomy, the phylogeny of sinistral ''Syndromus'' species showed no such correspondence. Also according to their results, enantiomorphy seems to be the ancestral state of shell coiling in the genus ''Amphidromus'', which is contrary to the general expectation of dextrally coiled shells as an ancestral condition.<ref name="Sutcharit 2007"/>

Despite being morphologically identical, some specimens supposedly belonging to three species, namely ''Amphidromus semitessellatus'', ''A. xiengensis'' and ''A. areolatus'', apparently had polyphyletic origins of mtDNA haplotypes. This resulted in the same species simultaneously appearing in distinct clades along the topology: for instance, ''A. areolatus'' can be found in two different clades in Sutcharit and colleague's (2007) cladogram, clustered respectively with ''A. xiengiensis'' and also with ''A. semitesselatus''. According to the authors, these results could be explained by convergent and polymorphic shell color patterns (e.g., the shells of the specimens had very similar colors and shape, though the mtDNA markers showed significant differences). Alternatively, they could also be the result of introgressive hybridization or ancestral polymorphism of mtDNA. In any case, analyses of phylogeography using other markers (nuclear markers or other mtDNA markers) or additional morphological characters would still be necessary to further clarify these issues.<ref name="Sutcharit 2007"/>

=== Fossil history === Currently, no reliable pre-human fossil occurrences of ''Amphidromus'' have been recorded. Tera van Benthem Jutting (1932)<ref>van Benthem Jutting T. (1932). "On prehistoric shells from Sampoeng Cave (central Java)". ''Treubia'' '''14'''(1): 103–108, 5 figs.</ref> reported finding several specimens of ''A. filozonatus'' which had been eaten in prehistoric times by natives, in Sampoeng Cave, central Java; and a few years later (van Benthem Jutting, 1937, pp. 92–94)<ref>van Benthem Jutting T. (1937). "Non-marine Mollusca from fossil horizons in Java with special reference to the Trinil fauna. Zool. Meded., 20: 83–180, pis. 4–12.</ref> the same author reported a single specimen of ''A. palaceus'' from the Trinil Beds of Java. Neither record predates human occupancy, and therefore these shed no light on the pre-human history of ''Amphidromus''.<ref name="Laidlaw 1961"/>

== Ecology == [[File:Meghalaya Abode of the Clouds India Nature in Laitmawsiang Landscape.jpg|thumb|upright|250px|Meghalaya, in India, is one of the many places where ''Amphidromus'' species can be found.]] [[File:Amphidromus roseolabiatus 3.png|right|thumb|Aestivating ''Amphidromus roseolabiatus'' inside sterile fronds of stag horn ferns, ''Platycerium''.]] thumb|Pair of ''Amphidromus'' (''Syndromus'') sp. Red arrows shows protruded vaginal stimulator pilaster (vsp), which may be a stimulating organ.<ref name="Inkhavilay 2017">{{Cite journal| doi = 10.5852/ejt.2017.330| issn = 2118-9773| volume = | issue = 330| last1 = Inkhavilay| first1 = Khamla| last2 = Sutcharit| first2 = Chirasak| last3 = Panha| first3 = Somsak| title = Taxonomic review of the tree snail genus Amphidromus Albers, 1850 (Pulmonata: Camaenidae) in Laos, with the description of two new species| journal = European Journal of Taxonomy| date = 2017-06-13| doi-access = free}}</ref>

=== Distribution === The genus ''Amphidromus'' ranges from eastern India, in south-western Asia (limited to the north by the Himalayas), to northern Australia (limited eastward by Weber's Line).<ref name="Sutcharit 2006" /><ref name="Solem 1983">{{cite journal|author-link=Alan Solem |last1=Solem |first1=A |year=1983 |title=First record of ''Amphidromus'' from Australia with anatomical note on several species (Mollusca: Pulmonata: Camaenidae) |journal=Records of the Australian Museum |volume=35 |issue=4 |pages=153–166 |doi=10.3853/j.0067-1975.35.1983.315 |doi-access=free }}</ref> ''Amphidromus'' species are found in localities as follows: from the Garo Hills and Khasi Hills of Meghalaya in northeastern India; throughout Burma, Malay Peninsula, Thailand, Laos, Cambodia, Vietnam, Indonesia as far east as the Sulawesi, Banda Islands, Timor and the Tenimber Islands (but not on Ceram, Buru, Halmahera, Batjan Island, the Obi Islands, the Aru and Kei Islands or the Talaud Archipelago and some Celebesian satellite islands); in the southern Philippines, notably Mindanao and the Balabac, Palawan;<ref name="Laidlaw 1961"/> and in northern Australia (solely represented by ''Amphidromus cognatus'').<ref name="Solem 1983"/>

=== Habitat and feeding habits === ''Amphidromus'' species are arboreal land snails. Further information concerning the habits and mode of life of the species of ''Amphidromus'' is almost non-existent, however, these snails have generally been collected while they were crawling on trees or shrubs. The diet of ''Amphidromus'' is unknown, but ''Amphidromus atricallosus perakensis'' is thought to feed on microscopic fungi, lichens or terrestrial algae.<ref name="Laidlaw 1961"/><ref name="Lok 2008">Lok A. F. S. L. & Tan S. K. (2008). "A review of the Singapore status of the green tree snail, ''Amphidromus atricallosus perakensis'' Fulton, 1901 and its biology". ''Nature in Singapore'' [http://rmbr.nus.edu.sg/nis/bulletin2008.html '''1'''] {{Webarchive|url=https://web.archive.org/web/20110219132834/http://rmbr.nus.edu.sg/nis/bulletin2008.html |date=19 February 2011 }}: 225–230. [http://rmbr.nus.edu.sg/nis/bulletin2008/2008nis225-230.pdf PDF] {{Webarchive|url=https://web.archive.org/web/20110606042102/http://rmbr.nus.edu.sg/nis/bulletin2008/2008nis225-230.pdf |date=6 June 2011 }}</ref>

=== Life cycle === Despite the great diversity within this genus, as of 2017, comprehensive life-history studies of ''Amphidromus'' species are still lacking; only a few observations of behavior of species within the genus exist, and these observations are scattered throughout the literature. A study by Eugen Paravicini (1921)<ref>Paravicini E. (1921). "Die Eiablage zweier Javanischer Landschnecken". ''Archiv für Molluskenkunde'' '''53''': 113–116, plate 2.</ref> described egg-laying behaviour in ''Amphidromus palaceus'' var. ''pura'' at Palimanan, West Java. According to Paravicini's observations, in October, 1920, locals from West Java brought in two "nests" containing snails that had just begun depositing their eggs; one snail had folded the exterior leaves of a young bamboo shoot and gummed them together into a pointed cornet. The shoot hung vertically with the narrow end pointed upward, and the wide opening below.<ref name="Laidlaw 1961"/> The upper part of the sack was filled with eggs when collected. The snail descended slowly, rotating around its longitudinal axis, and deposited eggs until the entire cavity was filled up. If a crack in the basket exposed eggs to the air, they quickly dried up. Two days after capture, egg-laying was finished, and the snail closed the opening by folding over more leaves. Probably four days were spent in egg-laying, since the cavity was half filled at the start of observations. A second nest of similarly folded mango leaves contained 234 eggs. The volume of eggs in each case greatly exceeded the size of the snail, indicating that the eggs must be encapsulated just before deposition. The capsules were very thin, and dried quickly upon any exposure to the air. October marked the start of the rainy season and probably this is the normal breeding period. Eggs of ''A. porcellanus'' were reported by van Benthem Jutting (1950, p. 493)<ref name="Jutting 1950"/> to have started hatching only ten days after being laid. Similar nest-building habits have been reported for other species, but no complete study of a life cycle has been published. Up until 1961, no information was available on the cycle of activity, longevity, rate of growth, etc.<ref name="Laidlaw 1961"/>

Schilthuizen et al. (2005) described the spatial structure of a population of ''A. inversus'' in Malaysia.<ref>{{cite journal | last1=Schilthuizen | first1=M | last2=Scott | first2=B J | last3=Cabanban | first3=A S | last4=Craze | first4=P G | title=Population structure and coil dimorphism in a tropical land snail | journal=Heredity | volume=95 | issue=3|pages=216–220 | year=2005 | pmid=16077741 | doi=10.1038/sj.hdy.6800715 | doi-access=free }}</ref> Schilthuizen et al. (2007) found that there is sexual selection in mating with snails of the opposite chirality.<ref name="Schilthuizen 2007"/> This means that the left-handed snails mate more often with right-handed snails than they do with snails of the same coiling. Additionally there are anatomical adaptations of the spermatophore and of the female part of the reproductive system for the success of these matings.<ref name="Schilthuizen 2007"/>

=== Predators === Predators of ''Amphidromus'' snails include the red-crowned barbet ''Megalaima rafflesii'',<ref>Wee J. (2006). "Red-crowned barbet feeding on snail". http://besgroup.talfrynature.com/2006/06/01/red-crowned-barbet-feeding-on-a-snail/ {{Webarchive|url=https://web.archive.org/web/20110613074807/http://besgroup.talfrynature.com/2006/06/01/red-crowned-barbet-feeding-on-a-snail/ |date=13 June 2011 }}. Accessed 9 May 2010.</ref> and probably other bird species.<ref name="Lok 2008"/> Asian snakes in the genus ''Pareas'' are known to feed on ''Amphidromus'' species by removing the soft parts from the shells.<ref name="Danai2016">{{cite journal|last1=Danaisawadi|first1=P.|last2=Asami|first2=T.|last3=Ota|first3=H.|last4=Sutcharit|first4=C.|last5=Panha|first5=Somsak|title=A snail-eating snake recognizes prey handedness|journal=Scientific Reports|date=5 April 2016|volume=6|issue=1|article-number=23832|doi=10.1038/srep23832|pmid=27046345|pmc=4820687|bibcode=2016NatSR...623832D}}</ref><ref name="Sutcharit 2006" /> Many shells of ''Amphidromus'' were found in the den of a rat in Malaysia.<ref name="Schilthuizen 2007">{{cite journal | last1=Schilthuizen | first1=M. | last2=Craze | first2=P. G. | last3=Cabanban | first3=A. S. | last4=Davison | first4=A. | last5=Stone | first5=J. | last6=Gittenberger | first6=E. | last7=Scott | first7=B. J. | title=Sexual selection maintains whole-body chiral dimorphism in snails | journal=Journal of Evolutionary Biology | volume=20| issue=5 |pages=1941–1949 | year=2007|doi=10.1111/j.1420-9101.2007.01370.x | pmid=17714311 | pmc=2121153}}</ref>

== See also == * Asymmetry * Chirality (mathematics) * Symmetry in biology

== References == This article incorporates public domain text from the reference.<ref name="Laidlaw 1961">15px Laidlaw F. F. & Solem A. (1961). [https://archive.org/details/landsnailgenusam414laid "The land snail genus ''Amphidromus'': a synoptic catalogue"]. ''Fieldiana Zoology'' '''41'''(4): 505–720.</ref> {{Reflist}}

== Further reading == * {{cite journal|last1=Craze|first1=Paul G.|last2=Bin Elahan|first2=Berjaya|last3=Schilthuizen|first3=Menno | title=Opposite shell-coiling morphs of the tropical land snail ''Amphidromus martensi'' show no spatial-scale effects|journal=Ecography|volume=29|issue=4|pages=477–486|year=2006 | doi=10.1111/j.0906-7590.2006.04731.x |url=http://sro.sussex.ac.uk/id/eprint/2148/1/Craze%2C_bin_Elahan_%26_Schilthuizen_2006.pdf}} * {{cite journal | last1 = Dharma | first1 = E. | year = 2008 | title = Penerapan sistem pakar dalam perancangan program identifikasi jenis siput-pohon ''Amphidromus'' di Indonesia. Part 1 | journal = Berita Solaris | volume = 11 | issue = 2| pages = 12–16 }} * Dumrongrojwattana P., Mutchacheep S. & Senapin R. (2006). "Identification of 7 Thai arboreal snails genus ''Amphidromus'' Alber, 1850 by using morphometrics technique (Pulmonata: Camaenidae)". ''The Proceeding of 44th Kasetsart University Annual Conference, 30 Jan – 2 Feb 2006, Subject Science'': 7 pp. Kasetsart University, Bangkok. * {{cite journal | last1 = Goldberg | first1 = R. L. | last2 = Severns | first2 = M. | year = 1997 | title = Isolation and evolution of the ''Amphidromus'' in Nusa Tenggara | url = http://www.conchologistsofamerica.org/articles/y1997/9706_Gold&Seve.asp | journal = American Conchologist | volume = 25 | issue = 2 | pages = 3–7 | access-date = 26 September 2019 | archive-url = https://web.archive.org/web/20171125153452/http://www.conchologistsofamerica.org/articles/y1997/9706_Gold%26Seve.asp | archive-date = 25 November 2017 }} * {{cite journal | last1 = Panha | first1 = S. | author-link4 = John B. Burch | last2 = Sutcharit | first2 = C. | last3 = Tongkerd | first3 = P. | last4 = Burch | first4 = J. B. | year = 2001 | title = Morphogeography of an endemic tree snail genus ''Amphidromus'' of Thailand (Pulmonata: Camaenidae) | journal = Of Sea and Shore | volume = 24 | issue = 2| pages = 106–113 }} * {{cite journal | doi=10.2108/zsj.24.189 | last1=Prasankok | first1=P | last2=Ota | first2=H | last3=Toda | first3=M | last4=Panha | first4=S | title=Allozyme variation in the camaenid tree snails ''Amphidromus atricallosus'' (Gould, 1843) and ''A. inversus'' (Müller, 1774). | journal=Zoological Science | volume=24 | issue=2 | pages=189–97 | year=2007 |pmid=17409732| hdl=2433/108565 | s2cid=3470462 | hdl-access=free }} * {{cite journal | last1 = Severns | first1 = M. | year = 2003 | title = A quick explanation of ''Amphidromus'' | journal = Of Sea and Shore | volume = 25 | issue = 4| pages = 228–231 }} * {{cite journal | last1 = Severns | first1 = M. | year = 2006 | title = A new species and a new subspecies of ''Amphidromus'' from Atauro Island, East Timor (Gastropoda, Pulmonata, Camaenidae) | journal = Basteria | volume = 70 | pages = 23–28 | title-link = Atauro Island }}

== External links == {{Commons category|Amphidromus}}

Category:Amphidromus Category:Taxonomy articles created by Polbot Category:Taxa named by Johann Christoph Albers