Tropical Natural History 13(1): 53-57, April 2013 2013 by University

Short Note First Record on Chiral Dimorphic Population of Amphidromus inversus annamiticus (Crosse and Fischer, 1863) from

CHIRASAK SUTCHARIT*, PIYOROS TONGKERD AND SOMSAK PANHA

Animal Systematics Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand

* Corresponding author. E-mail: [email protected] Received: 25 October 2012; Accepted: 27 December 2012

In nature, the vast majority of living found, this subspecies has been assumed to gastropod species occur in either the dextral be monomorphically dextral for shell (clockwise shell coiling, >90%) or sinistral coiling6,17. Although sinistral coiled shell (counterclockwise shell coiling) form1,2. specimens have been recorded in the Although comparatively rare, sinistral literature, they are not unequivocal and have species, populations or individuals appear in inaccurate locality records14. Here, the first various occasions, such as mutant precise record for over a hundred years on individuals within dextral species, related chirally dimorphic populations of A. sinistral species within otherwise dextral inversus annamiticus is presented, along genera, or as entirely sinistral genera or with additional notes on their reproductive families1-4. However, over the dimorphic biology and ecology. chirality of dextral and sinistral individuals In October 2010, a survey in occurring in the same population is northeastern Thailand along the Thai- extremely rare in gastropods1-4. The border discovered a peculiar Southeast Asian endemic tree snail genus population of A. inversus from Nam Yuen Amphidromus are exceptional and remark- district, Ubonratchathani Province in the able cases as they mostly exist as chirally lower Mekong basin. The species design- polymorphic populations5-8. The genus is nation was determined by comparison with regarded as a good model in evolutionary the type specimen, and examination of studies, and many of the papers focused on genitalia, and these indicated the typical A. the chirality of snails over the last decade inversus annamiticus5,6. Voucher specimens have been based on members of this genus (CUMZ 4921 – CUMZ 4925) are housed in of snails8-13. Chulalongkorn University, Museum of Currently, the genus Amphidromus is Zoology, Bangkok. comprised of about 90 nominal species of The habitat of the A. inversus annami- which the prominent character other than ticus population at Nam Yuen was a mixed their colorful shell and arboreal habit is the deciduous forest along a nature trail presence of dimorphic shell coiling5,6,14,15. (approximately 200 m long and 10 m wide) Since from more than 2,200 specimens from parallel with a cascade stream. Both juvenile 16 localities of A. inversus annamiticus and adult snails were found on tree trunks, (Crosse and Fischer, 1863)16 from Thailand branches or climbers of various tree species, only a dextral (clockwise) shell coiling was such as Mangifera indica L. and Artocarpus 54 TROPICAL NATURAL HISTORY. 13(1), APRIL 2013 heterophyllus Lam., and so they appear not tion on the biology and ecology of this to be tree species-specific. Some snails were subspecies are still largely unknown. also found under the roof of a small cottage Normally, members of Amphidromus are nearby to the stream. nocturnal being active at night time, Both empty shells (2 dextral and 2 but they also appear at day time in high sinistral) and living snails (21 dextral, 14 humidity conditions, especially after heavy sinistral) were observed and collected (Fig. rain. Most behaviors are accordingly easily 1A, B). Measurement of the adult shells observed at night, and include their feeding, yielded a shell height range from 45 to 55 mating, egg laying and nesting. mm, and shell width range from 35 to 40 Only five intrachiral copulating pairs mm. The shell morphology was as in the (dextral x dextral) of A. inversus annami- typical A. inversus annamiticus, except they ticus were observed, where the snails were slightly larger, with the presence of displayed a face-to-face mating pattern3,18 black varices, a dark brown streak, rose- with their coiling axis almost at right angles pink colored spire with a black suprasutural to each other (Fig. 1C). This is slightly band, and dark apex5,6,14-16. The living snails different from the interchiral matings possessed a brown to brownish body and (dextral x sinistral) of A. inversus albulus were usually covered with a light brown Sutcharit and Panha, 200619, in which the reticulated skin (Fig. 1C, D). The foot was mating pairs are reported to perform at an greyish to brownish; head black; upper acute angle of coiling axis2,8,18. The tentacles blackish with yellowish tips; lower copulating process was prolonged, lasting tentacles, head and mouthpart were brown more than 6 to 9 hours for complete to light brown; and a pale cream mantle exchange of spermatophores. With respect cavity. The male and female genital systems to egg laying, A. inversus annamiticus did and radula morphology were exactly similar not create an egg nest, as seen in A. to that described in Sutcharit and Panha atricallosus atricallosus (Gould, 1843), but (2006)6. rather they laid egg clusters (~60-120 eggs) The known range of A. inversus annami- under loose-bark or small holes in tree ticus in Thailand is therefore not only the trunks or branches, similar to that reported offshore islands in the Gulf of Thailand, but for A. inversus albulus8,18. The details of egg is extended to the northeastern mainland development and post-hatched juveniles, as regions of high plateau (0 - 350 m amsl) and well as their growth and survival rates, in mountainous characteristics. The whole the local environment are still unavailable. distribution range of the subspecies is then Members of Amphidromus, including A. from northeastern Thailand to southern inversus annamiticus, are arboreal and , Cambodia and south of Vietnam, with spend their entire life on trees of up to more the southernmost limit being at Koh Samui than 10 m height (Fig. 1E-G). Snails feed on Islands, Suratthani, Thailand5,6,14-17. microscopic flora on the tree trunks, In Thailand, A. inversus annamiticus are branches or leaves, and leave distinctive mainly found inhabiting islands5,6,17, perhaps grazing trails which are easily to identify as since the suitable mainland habitats were Amphidromus. These grazing trails can also mostly invaded by farmers for agricultural be observed on artificial structures, such as purposes, and, if so, then the species seems concrete walls or electric poles (Fig. 1E). to be vulnerable. However, basic informa- SUTCHARIT ET AL. – CHIRAL DIMORPHIC POPULATION OF AMPHIDROMUS 55

FIGURE 1. Shells and living snails of A. inversus annamiticus; (A, B, D) from Nam Yuen district, Ubonratchathani (June 2010), (C) from Samui Island, Suratthani (June 2007) and (E-G) from Chaiya district, Suratthani (May 2012). A, B. Dextral and sinistral shells (CUMZ 4922). C. Mating pair of D x D, photo taken from the field, 1-2 hours after rain. D. Living sinistral snail (shell height 48 mm). E. Juvenile snail grazing micro-flora on an electric pole (height about 1.5 m). F. Juvenile snail hiding in a small hole in a mango tree Mangifera indica L. G. Snail, on the top left, on the trunk of a Jackfruit tree (Artocarpus heterophyllus Lam.) at about 5 m height.

56 TROPICAL NATURAL HISTORY. 13(1), APRIL 2013

Snails, collected as eggs or juveniles, species. However, there is still no direct were reared and observed in captivity in evidence to confirm these suggestions or terrarium conditions but they never reached their applicability to A. inversus annami- adult size despite the provision of artificial ticus specifically. diets and some vegetables20. However, It seems that the survival of A. inversus collected adults were observed to form annamiticus is dependent to a fair degree on copulation pairs in captivity and egg-laying good habitat conditions, and that they may was observed. Eggs hatched within 10 to 15 survive in a fragmented habitat as long as days, and newborn snails were fed on the sufficient suitable trees remain as these above artificial diet supplemented with snails can be found in anthopogenic cuttlebones. After hatching, the juvenile habitat5. However, populations have been snails initially grew very well (shell height found to exhibit a low genetic diversity and reach about 10 to 15 mm within three likely inbreeding23. Habitat loss by weeks), but thereafter the growth rate deforestation and natural disasters will became quite slow and later the snails likely be the main causes of extinction of showed signs of abnormal development snails on those islands. including shell deformation and subsequ- ently died at a maximum shell height of 20- ACKNOWLEDGEMENTS 30 mm. No information on the natural enemies of We are grateful to P. Bouchet and V. A. inversus annamiticus is currently Héros (MNHN, Paris); J. Ablett and F. available, with very little on members of Naggs (NHM, London); T. Backeljau Amphidromus in general. There have been (RBINS, Brussels); R. Janssen (SMF, some field observations of A. inversus Frankfurt) for their kind permission and albulus and A. atricallosus temasek Tan, help in studying of type materials. We are Chan and Panha, 201121 in Singapore, where also indebted to the ASRU Members, it was reported that the snails were predated Chulalongkorn University for field upon by some rodent species8,11,22. From assistance. This project was funded and interviews with local people at Koh Samui award from the Plant Genetic Conservation Island and the broken shells we found, we Project under the Royal Initiation of Her suspect that squirrels and rats predate upon Royal Highness Princess Maha Chakri A. inversus annamiticus. Likewise, corres- Sirindhorn, the Darwin Initiative Project pondence with bird specialists and (no. 14-653), the TRF Senior Research examination of the dropped-food of Scholar 2012-2015 (RTA5880001), and the hornbills, and the observation of shell NRU Project FW0646A-56. Thanks also to remnants at the sacrificing stones of the blue R. Butcher from the PCU Unit, Faculty of whistling thrush, tend to suggest that land Science, Chulalongkorn University for his snails, including unidentified Amphidromus critical reading of the manuscript. spp. are one of the major food sources of these birds (Panha, personal observation). In LITERATURE CITED addition, local herpetologists have stated that a group of arboreal snail-eating snakes 1. Asami, T. 1993. Genetic variation and evolution (Pareas spp.) are expected to be a of coiling chirality in snails. Forma. 8: 263–276. significant predator of Amphidromus SUTCHARIT ET AL. – CHIRAL DIMORPHIC POPULATION OF AMPHIDROMUS 57

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