Tandonia sowerbyi (Férussac, 1823)
T. sowerbyi is a synanthropic species that is probably introduced to most of its current range (Wiktor 1987).
M. gagates, T. budapestensis.
External: Variable body coloration: brown-yellow to orangish to grayish; dark pigment in skin grooves forming reticulated patterns on body and dark streaks on sides of mantle; dark head and tentacles; strong keel along entire dorsum, making body vaguely triangular in cross-section; weak skin wrinkles; yellow to orange keel and orange foot fringe (when alive; cream after preservation); pale sole; thick, yellow mucus (Quick 1960; Wiktor 1987, 1996).
Internal: Internal shell 5 x 3 mm; vas deferens 2x epiphallus length; cylindrical epiphallus widest at its base, and with small papillae inside; cylindrical penis with folds in muscular interior; interior papilla at constriction ~between epiphallus and penis; one retractor muscle and two retentor muscles on epiphallus; lobe-shaped internal structure in atrium between spermatheca duct and penis; long, tubular oviduct; spermatheca long to rounded, with duct 1/2-1/3 its length; short vagina with long accessory glands around it; atrium as long as wide, with longitudinal folds inside; 13 mm long spermatophore forming a hook with minute spines at its wide end, a bare middle section, and with fan-shaped spines at its narrow end (Quick 1960; Kerney & Cameron 1979; Wiktor 1987, 1996).
Differs from M. gagates: body colors, less abrupt end to keel, less flat when contracted, stickier and yellow mucus, spermatheca duct starts closer to the atrium and spermatheca narrows toward its apex, epiphallus widens rather than narrows at its apex. Differs fromT. budapestensis: wider body and pale sole (Quick 1960).
Eggs: 4 x 3.5 mm, translucent, amber; ~12 per clutch (Quick 1960).
Juveniles: 8 mm long at hatching, with strong and light keel; black specks on body and sometimes a dark midline on the mantle (Quick 1960).
70 mm long extended (Quick 1960); preserved: 60 mm long, 16 mm wide, mantle 18 mm long (Wiktor 1996).
Probably began in the seaside Mediterranean region, such as Greece (Wiktor 1996).
Probably non-native to: synanthropic habitats in Europe, in Ireland, the UK, Netherlands, Austria, France, Belgium, the former Yugoslavia, Italy, Spain, Portugal, and N Africa (Quick 1960; Wiktor 1987, 1996).
Non-native to: South America, New Zealand (Quick 1960).
Lowlands and foothills; often synanthropic, inhabiting open and shrubby habitats, gardens, cropland, and waste disposal sites; takes shelter under rocks and dead wood (Quick 1960; Wiktor 1996).
Pest of carrot and potato (Quick 1960).