Jpn，J，Environ，Entomol，Zool、25（4）：153－154（2014） 環動昆 第 25 巻 第 4 号：153－154（2014） Notes species are known to use as a lifeline while hanging (Langlois, 1965; Gordon, 2010). The banana Ariolimax spp. can suspend themselves from a slime cord to Use of a mucus thread as a lifeline in the descend to the ground (Gordon, 2010). The most striking Lehmannia valentiana (Férussac) example is the giant garden slug, maximus (L.), (: ) which mates in the air hanging by a mucus thread (Langlois, 1965). However, use of mucus threads has rarely been reported in slugs, although several shell-bearing gastropods Kazuo Yamazaki dangle from rocks possibly using mucus threads for hibernation (Breure, 2011). This report describes the slug

Lehmannia valentiana (Férussac) (Mollusca: Gastropoda) Osaka City Institute of Public Health and hanging from a leaf using its mucus thread in central Japan. Environmental Sciences 8-34 Tojo-cho, Tennoji, Osaka 543-0026, Japan Study site and Methods (Received : September 30,2014; Accepted : October,17,2014) In a house garden in Abeno-ku, Osaka City, west-central Japan, a L. valentiana slug was observed in the ナメクジ類は粘液を命綱に用いて垂下することがあ evening on June 30, 2014. The photo of hanging behaviour るが、その野外観察は難しく報告例はいまだ少ない。 of the slug was taken with a digital camera (Ricoh, CX4), 本報では、大阪市においてチャコウラナメクジが、湿 and the descent distance and the time required for the 度の高い夏季の夕刻に、粘液糸により約 23cm 下の葉へ descent were measured using a tape measure and a watch, 垂下し着地したことを記録した。この行動の適応的意 respectively. 義と侵入生物学上の問題点について指摘した。 Results and Discussion

Abstract A L. valentiana slug (ca. 30 mm in length) was seen Slugs are known to use mucus thread for hanging down, leaning from the leaf of a morning glory Ipomoea tricolor but this behavior is difficult to observe in the field and thus (ca. 2 m above the ground) at 18:35 in the house garden. has rarely been reported. In this note, it was reported that The slug then hung using a caudal mucus thread with its the slug Lehmannia valentiana (Férussac) hung using a head down (Fig. 1), and landed on another leaf ca. 23 cm mucus thread and landed on a leaf ca. 23 cm beneath in the beneath it in ca. 1 min. The mucus thread separated from evening of humid summer in Osaka City, central Japan. The the lower leaf just after landing, but it dried and was seen adaptive significance and invasion problems associated with swaying in the wind from the upper leaf the following this behaviour were suggested. morning. Use of a thread as a lifeline is a well-known behaviour Keywords: Lehmannia valentiana, lifeline, mucus for spiders and caterpillars. These threads are sufficiently strong to support their weight, and therefore they can use three-dimensional space efficiently (Osaki, 1996; Sugiura Introduction and Yamazaki, 2006). Although this slug uses a mucus thread only for descending, unlike spiders and caterpillars Slugs (Mollusca: Gastropoda) leave a trail of mucus that can climb up the thread, it may be able to swiftly when travelling using their ventral foot. This mucus is one escape from enemies and land on lower sites or on the of the reasons slugs and other gastropods thrive on land, and ground where it is more humid. it has many functions, including prevention of desiccation The slug L. valentiana, which originated from the (South, 1992), smooth locomotion (Denny, 1980), defence Iberian District, is an invasive alien species in Japan that against predators and parasites (Pakarinen, 1994), and trail infests vegetables, fruits, and ornamental plants (Kurozumi, making (Cook, 1992). In addition, a small number of slug 2002), and acts as an intermediate host of the zoonosis

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- 153 - 山崎一夫 agent Angiostrongylus cantonensis (Chen) (Noda et al. Breure, A. S. H. (2011) Dangling shells and dangerous 1987). This slug has invaded various areas around the world, spiders: malacophagy and mimicry in terrestrial including China, North and South America, and New gastropods. Folia Conchyliologica 7: 7–13. Zealand (e.g., Barker 1999; Wiktor et al. 2000; Forsyth Cook, A. (1992) The function of trail following in the 2001; Gutiérrez Gregoric 2013). The slug inhabits lowland pulmonate slug, Limax pseudoflavus. Anim. Behav. 43: residential areas, farms, and coastal districts, and is active 813–821. throughout the year with its breeding season from late Denny, M. (1980) The role of gastropod pedal mucus in autumn to early spring (Udaka and Numata, 2008). The use locomotion. Nature 285: 160–161. of mucus threads in this slug may be related to its Forsyth, R.G. (2001) First records of the European land slug invasiveness, and it may be inadvertently transported via Lehmannia valentiana in British Columbia, Canada. plant nurseries, cargo and trading ships, and airplanes. For Festivus 33: 75–78. example, L. valentiana could enter trading ships when Gordon, S. G. (2010) Secret World of Slugs and Snails. docked in port by mucus-threading from a nearby tree and Sasquatch Books, Seattle. be transported to new areas. Further studies are needed Gutiérrez Gregoric, D. E., A. A. Beltramino, R. E. Vogler, regarding the use of mucus threads in various slug species M. G. Cuezzo, V. Núñez, S. R. Gomes, M. Virgillito around the world, from both basic and applied perspectives. and S. E. Miquel (2013) First records of four exotic slugs in Argentina. Amer. Malac. Bull. 31: 245–256. Kurozumi, T. (2002) Lehmannia valentiana. In “Handbook of Alien Species in Japan” (The Ecological Society of Japan, ed.), pp.164, Chijin-shokan, Tokyo. Langlois, T. H. (1965) The conjugal behavior of the introduced European Giant Garden Slug, Limax maximus L., as observed on South Bass Island, Lake Erie. Ohio J. Sci. 65: 298–304. Noda, S. R. Uchikawa, T. Mori and A. Sato (1987) A survey of Angiostrongylus cantonensis in the port side areas of Kagoshima city and Makurazaki city, Kagoshima prefecture. Jpn. J. Parasitol. 36: 100–102. Osaki, S. (1996) Spider silk as mechanical lifeline. Nature 384: 419. Pakarinen, E. (1994) The importance of mucus as a defence against carabid beetles by the slugs Arion fasciatus and Deroceras reticulatum. J. Mollusc. Stud. 60: 149-155. South, A. (1992) Terrestrial Slugs: Biology and Control. Chapman and Hall, Oxford. Fig. 1 . Lehmannia valentiana hanging from a Sugiura, S. and K. Yamazaki (2006) The role of silk threads leaf using a mucus thread. Upper and lower arrows indicate the mucus thread and slug, respectively. as lifelines for caterpillars: pattern and significance of The mucus thread continues above from the upper lifeline-climbing behaviour. Ecol. Entomol. 31: 52–57. frame of the photo. Scale bar: 10 mm. Udaka, H. and H. Numata (2008) Short-day and low-temperature conditions promote reproductive

maturation in the terrestrial slug, Lehmannia References valentiana. Comp. Biochem. Physiol. A 150: 80–83.

Wiktor, A., C. De-Ni and W. Ming (2000) Barker, G. M. (1999) Naturalised terrestrial Stylommatophoran slugs of China (Gastropoda: (Mollusca: Gastropoda). Fauna of Pulmonata) – prodromus. Folia Malacol. 8: 3–35. New Zealand 38: 1–253.

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