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Milax gagates (Draparnaud, 1801)
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Species name:
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Milax gagates (Draparnaud, 1801)
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Taxon name:
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Limax gagates Draparnaud, 1801
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Originally described in:
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Draparnaud, J. P. R. 1801. Tableau des mollusques terrestres et fluviatiles de la France. - pp. [1-2], 1-116. Montpellier, Paris. (Renaud; Bossange, Masson & Besson).
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Distribution:
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Originally from Morocco to Tunisia and S Spain to S France and Balearic Islands, perhaps native in Canary Islands, introduced between Portugal and Galicia, Atlantic coastlands of France to Belgium, British Isles, and almost worldwide (Australia, Tasmania, New Zealand, Japan, Pacific islands, South Africa, Atlantic islands)
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Diagnosis:
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Slug evenly dark grey to black except somewhat lighter sides, no pigment spots. Mantle relatively large (35-40 % of body length), with distinct grooves, keel prominent between mantle and posterior end, skin sculpture weak, 16-17 grooves between keel and pneumostome. Sole with blackish lateral zones and lighter medial zone.
Penis rounded, half as long as epiphallus, epiphallus slightly widened and truncated (as if cut off) at its end, vas deferens short (usually not longer than epiphallus), opens asymmetrically at truncated end of epiphallus, atrium short, not widened, accessory gland consisting of several elongate glands, connected to atrium by some 20 short coiled tubular ducts. Stimulator narrow, conical, slightly flattened, at its end with some papillae.
The stimulator of Milax nigricans has more papillae, situated at its base and not near its free end.
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Size:
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Up to 50 mm long (preserved 25-30 x 6-8 mm), eggs 2 x 1.5 mm
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Biology:
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Mostly in cultivated areas, often in coastal vicinity, also in forests and shrublands, natural meadows, preferably close to water, hides under stones, moist ground litter and in soil cavities. Feeds on fresh herbs, occasionally (W British areas) noxious to gardens and crops (carrots and potatoes).
Copulation in Britain from spring to autumn, during copulation both slugs cling together so closely that no everted genitalia are visible. Self-fertilization is also possible. In France 45-60 eggs (diameter 3 mm) are laid in October. Under laboratory conditions the first eggs are laid 5-15 days after copulation, at one time some 15 eggs are laid, this can be repeated various times, in total not more than 100 eggs are laid by an individual. Juveniles (4 mm long) hatch after 25-40 days, maturity is reached after 18-20 months (4-5 months under laboratory conditions). 15-30 days after egg-laying the slugs die.
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Threatened:
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In Britain always local except in Cornwall.
Endangered in Rheinland-Pfalz.
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Family:
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Milacidae
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Higher group:
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Gastropoda
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Comments:
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Has often been confounded with Milax nigricans. Literature records are only reliable if description and drawing of the stimulator was provided.
References: Germain 1930: 107, Wiktor 1987: 202, Falkner 1990: 184, Vogt et al. 1994: 177, Manganelli et al. 1995: 20, Turner et al. 1998: 284, Kerney 1999: 149, Quintana Cardona 2006 (Menorca, introduced), Beckmann 2007: 84 (Mallorca, Menorca, Cabrera, Ibiza, Formentera), Welter-Schultes 2012: 432 (range map).
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