地瓜上的蝸牛

Yen-Chen Lee¹ & Wen-lung Wu²

1.      Department of Life Science National Taiwan Normal University

2.      Research Center of Biodiversity , Academia Sinica.

Received Oct. 23, 2006; accepted Dec. 25, 2006

Abstract

In 2000 an unknown large Ariophantid species was found in Pingtung County . The shell morphology is very similar to native species Petalochlamys formosana (Schmacker et Boettger, 1891). But the soft part is quite different. In this paper we will describe its taxonomy, ecology, food, morphology, anatomy and effect on the environment of Taiwan .

Materials and Methods

The snails were collected and recorded its locality. The specimens were brought to the laboratory, well relaxed and immersed in boiling water, than dissected to exam its reproductive system. Measured the following morphometric items: shell length (SL), shell width (SW), apertural length (APL) and apertural width (APW).

Results

Taxonomy:

Family Ariophantidae Godwin-Austen, 1888

Subfamily Macrochlamydinae Godwin-Austen, 1888

Genus Macrochlamys Benson, 1832 in Gray, 1847

Species hippocastaneum Godwin-Austen, 1918

Ecology: This species was first found in 2000 in Pingtung. It may import to Taiwan before 2000 with rose from India . In 2004, it can be found in Taichung , Shinju, Taipei . In 2005, it had spread to Yilan and Hualian. This species can be easily found in public garden, wasteland near urban area, traffic island and vegetable farm. The population size is more than 10 individuals per square meter, observe on a wasteland of Nei-hu District Taipei in 2005. According to the distributing data, the species seems transgress local dispersal filter. It is widespread and dominant, consensus to stage V of invasive species definition (Colautti & MacIsaac, 2004).

Food: they feed carrot, sweet potato in laboratory. In field, they feed almost all herbaceous plants, even defoliations.

Shell: globosely conoid, finely perforate, polished; no sculpture except unclear growth striae, quite smooth and glassy; color yellowish brown; spire conic, apex blunt, suture impressed, whorl 5-6, rather rapidly increasing, rounded on the periphery; aperture broadly lunate, nearly vertical; peristome thin, columellar margin thin, scarcely reflected near umbilicus.(Fig. 1A )

Reproductive system: Penial sheath (PS) well developed, with a volute structure at the epiphallus (EP) site terminal. Epiphallus is slender than penial sheath. Penial appendix (PA) as wide as epiphallus. Vas deferens (VD) slender separates from the connection between penial appendix and epiphallus, extends and connects at outer wall of oviduct (OV) at the distal end of brown color prostatic gland (PG). Vagina (VA) short and large in diameter, divding clavate shaped spermatheca (SP) from its posterior. Dart (DT) gently swell toward the dart sac (DS) site and contracted at the junction between dart and dart sac. Dart sac slender and 3 times long as dart length. (Fig. 3)

Discussion

Macrochlamys hippocastaneum is very similar to native species Petalochlamys formosana (Schmacker et Boettger, 1891) (Fig. 1B) in shell morphology. P. formosana increased its whorl width rapider than the former. The body whorl width is 3 times of penultimate whorl in P. formosana. In M. hippocastaneum, body whorl width is 2 times of penultimate whorl. Besides, the aperture width of M. hippocastaneum is half wide of shell width. The aperture width of P. formosana is larger than half wide of shell width. The former with slender gray-yellow mantle lop (Fig. 2), but P. formosana with wide expand mantle lop, which has black spot on it.

There is no report about agricultural loss cause by M. hippocastaneum till now. By the reasons of polyphagia of this species and the huge population size, this species is a potentially destructive pest such as Pomacea canaliculata (Apple snail). To reduce the huge loss in horticultural and agricultural industry of Taiwan , an effective quarantine system should be established to control the invasive species.

Acknowledgments

The authors wish to appreciate Mr. Wen-Der Chen for their generous donations of the specimen shells.

References

Colautti, R. I. & MacIsaac, H. J. 2004. A neutral terminology to define invasive species. Diversity and Distributions 10: 135–141.

Godwin-Austen, H.H. 1918. Zoological results of the Abor expedition, 1911-12. Records of the Indian Museum 8: 581-600.