Mercuria similis ( Draparnaud, 1805 )

Boeters, Hans D. & Falkner, Gerhard, 2017, The genus Mercuria Boeters, 1971 in France (Gastropoda: Caenogastropoda: Hydrobiidae). West-European Hydrobiidae, Part 13, Zoosystema 39 (2), pp. 227-261 : 241-244

Mercuria similis ( Draparnaud, 1805)

( Figs 8 A-G, 9A-C; Table 6)

Cyclostoma simile Draparnaud, 1805: 34 , pl. 1, fig. 15.

Amnicola confusa Frauenfeld, 1863: 1029 .

Mercuria confusa – Boeters 1971: 178, 179, fig. 10.

Mercuria emiliana – Boeters 1988: 208: figs 92, 93; 210: figs 118, 125; 211; pl. 3, fig. 34. — Clanzig & Bertrand 2001: 45, fig. 1.

Mercuria similis – Boeters & Falkner 2000: 37. — Girardi 2004: 83-86 [partim]; fig. 1A-C, E-F.

ORIGINAL INDICATIONS OF THE TYPE LOCALITIES. — Cyclostoma simile : “ France ” (title of the book). — Amnicola confusa : “Gallia mer. [idionalis]”, restricted by Lectotype designation ( Boeters 1971: 175).

MATERIAL EXAMINED. — France. (i) Gallia mer.[idionalis] ( NMW- FRD/ 1 neotype of Cyclostoma simile , also lectotype of Amnicola confusa and NMW / 1 paralectotype of Amnicola confusa ). — (ii)-(iv) Pyrénées-Orientales: (ii) Salses [UTM DH94] ( MNHN-PAS /4 ex de Folin [6] and MNHN-PAS /5 ex de Folin [7]; (iii) Salses, Font Estramar [UTM DH94] ( BOE 0281, 0513 and 2167 ex 281b), leg. Meier-Brook 9.VI.1963 and leg. Boeters 7.IX.1972 and 4.IX.1980; (iv) Salses, ditch at Font Dame [UTM DH94] ( BOE 3208 ex 0999), leg. Boeters 4.IX.1980. — (v)-(vi) Aude, Port-la-Nouvelle [UTM EH06]: (v) ( BOE 2607), collection unknown; (vi) brackish [?] ponds at the foot of limestone rocks ( BOE 1193), leg. de Winter 19.VI.1979. — (vii)-(ix) Hérault: (vii) Vic-la-Gardiole, La Robine [UTM EJ61] ( BOE 3200), leg. Boeters 4.VI.2011; (viii) Montpellier ( NMW 92604/ 6 paralectotypes of Amnicola confusa , label: “ Paludina similis Drap. var. major ”). — (ix) Cette [modern spelling: Sète] [UTM EJ50] ( MNHN), leg. Paladihe. — (x)-(xi) Gard, between Saint-Gilles and Aigues-Mortes: (x) Étang de Scamandre [UTM FJ03] ( BOE 0534), leg. Vala & Monod 12.V.1973; (xi) area of the Syndicat Mixte Camargue Gardoise (Centre du Scamandre) ( BOE 3197), leg. Boeters 1.VI.2011. — (xii)-(xiii) Bouches-du-Rhône: (xii) Aigues-Mortes [UTM EJ92]( MNHN); (xiii) Stes-Maries-de-la-Mer [UTM FJ11] ( SMNS-FAL and BOE 2612, NMW 108871/10), leg. G. and M. Falkner 15.VI.2002).

NEOTYPE. — France, “Gallia mer.[idionalis]” ( NMW-FRD; the lectotype of Amnicola confusa has been designated as neotype of Cyclostoma simile ; Boeters & Falkner 2000).

IDENTIFICATION. — The distribution boundary of M. similis and M. meridionalis runs between the delta of the Rhône and the Étang de Berre. M. similis lives in the French Mediterranean coastal area from the Pyrénées up to the delta of the Rhône. Contrary to M. similis , M. meridionalis lives or lived, respectively, in the French Mediterranean coastal area from the Étang de Berre up to the mouth of the Var at Nice. The restricted type locality of Amnicola similis “Gallia mer. [idionalis]”. which is identical with that of Amnicola confusa , would cover both areas. However, since Draparnaud lived in Montpellier, it is assumed that his description of Cyclostoma simile was based on material collected in the Hérault, in the surrounding of Montpellier. Potiez & Michaud (1838: 254) give the following information on the provenance and identity of Draparnaud’s material: “La coquille qui vit à Cette (Hérault), et qui a servi de type à Draparnaud, est bien différente de celles que l’on rencontre dans le Périgord, en Belgique, et dans les autres parties de la France; elle est plus courte, plus solide, et sa couleur est d’un vert tendre tirant sur le blanc; la suture est moins prononcée.”

A thorough reassessment of the handwriting on the label of the similis - neotype revealed that it stems from Dupuy (see Fig. 9B ). The only sample of authentic M. similis (under the name Hydrobia similis ) known to Dupuy at the time when he wrote his Histoire, was that collected by de Boissy in “les environs de Montpellier” ( Dupuy 1851: 553). As Dupuy considered still in 1849 the Material collected by Mouton near Grasse as specifically distinct, it is most likely, that he gave under the name similis specimens from Montpellier to his exchange partners. This coincides with our decision to consider the Mercuria from the Étang de Scamandre as conspecific with the neotype of Cyclostoma simile ( Boeters & Falkner 2000: 39) . Although we admit that with our present knowledge we cannot distinguish with absolute certainty between M. similis and M. meridionalis on conchological characters only, the circumstances clearly speak for an origin of the neotype from the Montpellier region. The distance of the centres of Montpellier and Sète (former spelling: Cette) is about 25 km, but suitable biotopes where the species can be expected to live or to have lived and which can be attributed either to Sète or to the environs of Montpellier can be found at distances of about 10 km bordering the same lagonary system.

DISTRIBUTION AND ECOLOGY. — Pyrénées-Orientales, Aude, Hérault, Gard and Bouches-du-Rhône. Stagnant waters as of, for example, ditches and coastal lakes (étangs) within the delta of the Rhône river. In the outflow of large karstic springs such as La Robine at Vic-la-Gardiole and Font Estramar at Salses. Immediately downstream of the large spring basin of La Robine in its section of the outflow free of vegetation but still in front of its section flanked by reeds, on the underside of stones as far as they are not sunk into mud. In both karstic springs together with Semisalsa sp. , in the Font Estramar also together with Theodoxus sp. and Belgrandia cf. gibba ( Draparnaud, 1805) . In the étang de Scamandre sympatrically with Semisalsa scamandri ( Boeters, Monod & Vala, 1977) (the generic allocation follows Kroll et al. 2012: 1521), and a representative of the Planorbiidae between Phragmites communis , also on Chara sp. and Cladophora sp. ; salinity 0.4-0.5%, pH 7.5-8 ( Boeters et al. 1977: 48).

DESCRIPTION

Shell

Shape of shell: conical with pointed apex and straight sidelines, umbilicated; of transparent milky colour; 4.55 [4.50-4.75] (n = 4) whorls, swollen and very convex, respectively, separated by a deep suture; last whorl towards aperture neither ascending nor descending; aperture obliquely broad ovate, a little narrowed above; peristome continuous, usually touching the shell wall over a short distance, outer margin simple, basal margin and columellar edge faintly reflexed, columellar edge slightly thickened.

Measurements

See Table 6.

Operculum

Yellowish with chestnut-brown nucleus.

Animal

External characters. Pallial tentacle present. Snout at least with a blackish band; blackish pigmentation of the ommatophores can be missing; visceral hump more or less black-cloudy to brownish. Ctenidium with 21 gill filaments (1♂ ex BOE 0513 ) and 22 gill filaments (1♀ ex BOE 0534 ) .

Male copulatory organ. Penis extends clearly beyond its appendix; area of their furcation blackish ( Boeters 1988: 210, fig. 118; Girardi 2004: 86, fig. 2A, B).

Female genital tract. Bursa copulatrix and one receptaculum seminis ( Boeters 1988: 210, fig. 125; Girardi 2004: 86, fig. 2A, B).

DIFFERENTIATING FEATURES

Versus M. meridionalis : other than in M. meridionalis , penis extends beyond appendix. Contrary to M. meridionalis slow running or even stagnant waters as those of ditches or étangs are preferred.

REMARK

The fact that M. similis inhabits in France the coastal area from the Basses-Pyrénées to Bouches-du-Rhône leads to the question whether this species lives also in Spanish coastal areas. Reference is made to Amnicola maceana Paladilhe, 1869 from “Antunez, près de Barcelone” which might be a synonym of M. similis (cf. photograph of a syntype in Boeters 1988: pl. 3, fig. 16).

Figures

FIG. 8. — Mercuria similis (Draparnaud, 1805): A-E, France, Gard, between Saint-Gilles and Aigues-Mortes, Étang de Scamandre (BOE 0534); A, shell; B, C, ♂ head and foot with copulatory organ exposed through slit in mantle, dorsal (B) and ventral view (C); D, E, ♀; D, shell (partially broken away); E, body lumen opened to show renal oviductus with receptaculum seminis (rs1) and bursa copulatrix surrounded by intestinal section (partially removed);F, G, France,Pyrénées- Orientales, Salses, Fontaine-de-Salses: Font Estramar; F, BOE 2167 ex 0281b, shell; G, ♂, BOE 0513, shell partially broken away and mantle slitted to expose copulatory organ. Abbreviations: bc: bursa copulatrix; in, intestine; op, operculum; pe, penis; ro, renal oviductus; rs1, single receptaculum seminis; wc, wall of mantle cavity. Scale bar: 1 mm.

FIG. 9. — A-C, Mercuria similis (Draparnaud, 1805): A, "Gallia mer.[idionalis]", most likely Montpellier (NMW-FRD/1 neotype of Cyclostoma simile: lectotype of Amnicola confusa (cleaned);B, Dupuy’s label;C, France,Bouches-du-Rhône,Saintes-Maries-de-la-Mer,ditch NW of the village,leg.G.and M. Falkner 15.VI.2002 (Coll. P. GlÖer); D-H, Mercuria meridionalis (Risso, 1826): D, E, syntypes of Bithynia meridionalis, France, Alpes-Maritimes, most likely Nice (MNHN-RIO); D, lectotype ♀ (MNHN-IM-2000-32539); E, paralectotype (MNHN-IM-2000-32540), ♂; F, France, Alpes-Maritimes,Nice, large ♀ (MNHN ex Caziot); G, H, portable case of a Trichoptera-larva with several specimens of Mercuria meridionallis, Belgrandia varica (J. Paget, 1854), and a taxonomically problematic Valvata sp., glued living on it, Fossés du Var près Nice, leg. G. de Mortillet 1851 (MNHN); H, de Mortillet’s label. Scale bars: 3 mm.