Helicidae

Blacket, Mark J., Shea, Michael, Semeraro, Linda & Malipatil, Mallik B., 2016, Introduced Helicidae Garden Snails in Australia: Morphological and Molecular Diagnostics, Species Distributions and Systematics, Records of the Australian Museum 68 (3), pp. 99-116 : 102-103

Helicidae species present in Australia

In the present study three Helicidae species were verified as being currently established in Australia: C. aspersum , C. apertus , T. pisana . A fourth species, E. vermiculata , became locally established twice, in NSW and Tasmania, but now appears locally extinct in both locations. No evidence for any additional species in Australia referred to in previous literature (see above and Table 1) were found. Indeed, reference collection specimens were not located in the present study to support previous literature records for E. vermiculata from northern Tasmania (Petterd & Hedley, 1909) or for O. lactea from NSW ( Smith, 1992). It appears likely that previous NSW records of O. lactea were actually misidentified E. vermiculata (Shea, unpublished data) and that E. vermiculata was formerly known from northern Tasmania (K. Bonham, pers. comm.), but is not represented in reference collections. A number of other exotic Helicidae species are regularly intercepted at the nation’s border (e.g., Table 3), with more than 900 interceptions occurring between 2002 and 2015, including at least 14 different Helicidae species (L. Watson, pers. comm.); however, none of these are known to have led to additional Helicidae species becoming established in Australia. Images, and adult shell sizes, of some exotic species commonly misidentified or intercepted at the border are shown in Fig. 4 .

Morphological identification of Helicidae in Australia

Most native terrestrial snail species are small, subglobose, and not domestic in habit ( Kershaw, 1991; Smith, 1992; Stanisic et al., 2010). An up-to-date family key for eastern Australia is available to aid in identification ( Stanisic et al., 2010). A number of introduced species of Hygromiidae and Bradybaenidae are morphologically and ecologically similar to species of Helicidae ( Stanisic et al., 2010) . Bradybaenidae is currently represented by a single species in Australia, the Asian Trampsnail Bradybaena similaris (illustrated in Stanisic et al., 2010). Hygromiidae is a large Western Palearctic family with numerous species now established in Australia (e.g., Smith, 1992; Stanisic et al., 2010). Hygromids vary widely in shell shape, but their shells do not usually possess a reflected lip or have a differentiation between the lip edge and the columella, the external soft body is similar in appearance to Helicidae but usually has a narrower foot ( Stanisic et al., 2010). Other more detailed descriptions of diagnostic Helicidae / Hygromiidae characters are outlined in Schileyko (2005, 2006), and a large number of potential exotic species are covered by Welter-Schultes (2012).

Some native snails, including many species of Camaenidae , which is one of the largest families in Australia and the dominant group in the tropics, could potentially be confused with Helicidae snails in being both globose and large in size ( Stanisic et al. 2010). Species of Camaenidae differ from Helicidae / Hygromiidae in not possessing a dart sac and in having an eversible “head wart” (which emits an attractant pheromone) situated between the two superior tentacles ( Stanisic et al., 2010).

Specimens of the four Helicidae Garden Snail species collected from Australia, that are larger than c. 10 mm in diameter (specimens smaller than this often have fewer whorls and variable coloration), can be identified using the diagnostic images presented here ( Figs 2 , 5–7 ) and the following key:

Figures

Figure 2. Images of live Brown (C. aspersum) and Green (C. apertus) Garden Snails. (A) Brown adult, Knoxfield Vic.; (B) Green adult, Cobram Vic.; (C) Brown adult, Knoxfield Vic. (left) and Green adult, Cobram Vic. (right); (D) Brown juvenile, Knoxfield (left ×1) and Cobram (right ×2) [note: these three specimen identifications (VAITC 3071–3073) were confirmed through DNA barcoding in the present study]; (E) Green Juvenile, Cobram Vic.; (F) Green epiphragm, Cobram Vic. Image credits: A–E, Andrew Henderson (DEDJTR); F, Gordon Berg (DEDJTR).

Figure 4. Some exotic species of Helicidae commonly misidentified and/or intercepted at the Australian border. (A) Helix pomatia (AM C22156), SW=30–50 mm;(B) Cepaea nemoralis (AM C166354), SW=18–25 mm; (C) Arianta arbustrorum (AM unregistered England), SW = 18–25 mm; (D) Otala lactea (AM unregistered, Portugal), SW = 30–40 mm. (Images are adults, not shown to same scale). Image credits: A–D, Des Beechey (AM).

Figure 5. Shell variation axial–aperture view,Helicidae Garden Snails inAustralia:(A) Brown (Cornu)

Figure 6. Shell variation lateral–spire view, Helicidae Garden Snails inAustralia:(A) Brown (Cornu); (B) Green (Cantareus); (C) (formerly present) Chocolate Banded (Eobania) and (D) White (Theba). Scale bar = 5 mm; adults above line, juveniles below; specimen collection locations indicated in Table 2.

Figure 7. Shell variation lateral–umbilicus view, Helicidae Garden Snails in Australia: (A) Brown (Cornu); (B) Green (Cantareus); (C) (formerly present) Chocolate Banded (Eobania) and (D) White (Theba). Scale bar = 5 mm; adults above line, juveniles below; specimen collection locations indicated in Table 2.