Mercuria meridionalis ( Risso, 1826 )

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 : 244-249

Mercuria meridionalis ( Risso, 1826)

( Figs 9 D-H, 10, 11A-C; Table 7)

Bithynia meridionalis Risso, 1826: 100 , pl. 3, fig. 28.

Mercuria confusa – Boeters 1971: 175 [partim].

Mercuria similis – Giusti 1979: 7, figs 4c1-4c4. Erroneous determination.

ORIGINAL INDICATION OF THE TYPE LOCALITY. — “[…] de l’Europe méridionale et particulièrement de celles des environs de Nice et des Alpes Maritimes” (title of the book) and “Fossés aquatiques. App.[arition] Printemps”.

MATERIAL EXAMINED. — France. (i)-(iii) Bouches-du-Rhône , Région Étang de Berre : (i) between Port-de-Beau-Rivage and Mauran, Merveille, “ruisselets se jettant dans l’étang” [UTM FJ62] ( BOE 0315 /shells), leg. Berner 25.X.1967; (ii) outflow of a spring below road from La Fare-les-Oliviers to Saint-Chamas between Mas Suriane and Mas Meyroux [UTM FJ62] ( BOE 3205 ex 0262), leg. Boeters 28.IX.1969; (iii) Source-du-Canet South of road from La Fare-les-Oliviers to Saint-Chamas [UTM FJ62] ( BOE 0263 ), leg. Boeters 28.IX.1969. — (iv) Var, Draguignan, Foux-de-Draguignan [UTM KP92] ( BOE 0302 ex Meier-Brook), leg. Berner V.1930; ( BOE 2151 /animals and 2414/shells ex 0261) , leg. Boeters 27.IX.1969. — (v)-(viii) Alpes-Maritimes: (v) Nice? [UTM LP53] ( MNHN-RIO / 4 syntypes of Bithynia meridionalis Risso 1826 ); (vi) “marais des Environs de Nice ” [UTM LP53] ( MNHN/204 ), leg. Risso; (vii) “Fossés du Var près Nice ” [UTM LP53] ( MNHN); (viii) Nice [UTM LP53] ( MNHN/22 ex Caziot; MNHN-LOC/5 ; MNHN-PAS/4 ex de Folin [11]; SMF 119945 /20 and 266447/3) .

TYPES. — France, Alpes-Maritimes , Nice? MNHN-RIO/4 shells and 4 preparations of rehydrated soft parts; original historical label: “ Bythinia [sic] Meridionalis Risso ”. Lectotype MNHN- IM-2000-32539 [ H: 4.35 mm, D: 3.05 mm, 5.0 whorls] and 3 paralectotypes MNHN-IM-2000-32540 preselected by Giusti in 1998 (here designated).

IDENTIFICATION. — In the Mediterranean coastal area two species of Mercuria can be distinguished, M. similis with a whip-like penis and the species in question with a wedge-like penis. From the west to the East, M. similis is distributed in the departments Pyrénées- Orientales, Aude, Hérault, Gard and Bouches-du-Rhône, but does not reach the Étang-de-Berre, whereas the species in question lives farther East, nowadays in the department Bouches-du-Rhône at the shore of the Étang-de-Berre, and at least in the department Var. From two paralectotypes of Bithynia meridionalis from presumably Nice, male soft parts have been isolated by Giusti, one of them in such a good condition that the wedge-like penis can be seen (see Fig. 12).

DISTRIBUTION AND ECOLOGY. — In the department Alpes-Maritimes likely to be extinct. In the department Var collected live at one single locality (Foux-de-Draguignan) and in the department Bouches-du- Rhône live at two localities (shore of Étang-de-Berre).

In the department Alpes-Maritimes, fossés at the destroyed mouth of river Var, accompanied by Valvata sp. , Bithynia sp. and Belgrandia varica (J. Paget, 1854) . A portable case of a Trichoptera-larva with several specimens of Mercuria meridionalis glued living on it, with Belgrandia varica and a taxonomically problematic Valvata sp. , collected by G. de Mortillet in 1851 (MNHN) shows the former richness of those lost biotopes ( Fig. 9 G-H).

Caziot (1910: 471) described the occurrence of Mercuria in the destroyed “Fossés aquatiques” at Nice, as follows: “Espèce très commune dans tous les fossés de la rive gauche du Var, près de son embouchure”. These “fossés” were the “fossés de Californie”, ditches or side-brooks with runnig water, indicated by by Caziot (1910: 474, 476) also for “ Valvata piscinalis ” (O. F. Müller, 1774) , “ Valvata depressa ” C. Pfeiffer, 1821 and “ Neritina fluviatilis niciensis Caziot, 1910 ”.

In the departments Var and Bouches-du-Rhône in springs and their outflow, in the Foux-de-Draguignan sometimes amphibious; temperature 21° C (one single determination; BOE 0262).

In the department Var sympatric with Theodoxus sp. , Corrosella astierii ( Dupuy, 1851) (the generic allocation follows Delicado et al. 2015: 414) and Belgrandia marginata (Michaud, 1831) (all BOE 2151).

In the department Bouches-du-Rhône occasionally sympatric with Theodoxus sp. (BOE 0263), Potamopyrgus antipodarum (Gray, 1843) (BOE 0263) and Pseudamnicola (P.) chamasensis Boeters, 2000 (BOE 0262). For further information on former or recent biotopes in Bouches-du-Rhône and for accompanying molluscs see Coutagne (1881: 23).

DESCRIPTION

Shell

Conical with pointed apex and straight sidelines (as for M. similis ); last whorl about 49-53% of total height of shell; umbilicated; of transparent milky colour; 4.67 [4.5-5.0] (n = 3) 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 7.

Operculum

Colour of horn up to weak chestnut-reddish.

Animal

External characters. Pallial tentacle present. Except for a weak band on the snout, head and ommatophores pigmentless; mantle with the exception of its skirt, and visceral hump not brownish but blackish. Ctenidium with 22-24 gill filaments ( Boeters 1971: 178 and fig. 6, ♂).

Male copulatory organ. Penis short and wedge-like, not extending beyond its appendix, both of about the same length; socket of the copulatory organ in its inactive state with transversal folds, immediately in front of the appendix

Fig. 10 . — Continuation. Mercuria meridionalis ( Risso, 1826) : F, G, ♂, France, Bouches-du-Rhône, between La-Fare-les Oliviers and Saint-Chamas, Sourcedu-Canet ( BOE 0263 ) ; F, shell with partially retracted animal; G, head with copulatory organ exposed through slit in mantle; H -L, France, Var , Draguignan, La Foux-de-Draguignan ( BOE 2151 ex 0261) ; H, ♂: shell partially broken away and mantle slitted to expose copulatory organ ; I -J, ♂: copulatory organ (dorsal and ventral view); K -L, ♀; K, shell with partially retracted animal; L, body lumen opened to show renal oviductus with receptaculum seminis (rs1) and bursa copulatrix surrounded by intestinal section. Abbreviations: bc, bursa copulatrix; in, intestine; op, operculum; pe, penis; pl, pedal lobe; ro, renal oviductus; rs1, single receptaculum seminis. Scale bars: 1 mm.

with a dorsal thickening; appendix like a disk with a lateral bulge; area of the furcation of penis and appendix blackish ( Fig. 11D ; Boeters 1971: 178, fig. 7; Giusti 1979: 7, figs 4c2 and 4c4).

Female genital tract. Bursa copulatrix and one receptaculum seminis ( Boeters 1971: 178, fig. 8; Giusti 1979: 7, fig. 4c3).

DIFFERENTIATING FEATURES

Versus M. similis: Penis does not extend beyond appendix as in M. similis . Mercuria meridionalis prefers running waters whereas M. similis is also known from stagnant water bodies.

REMARKS

Draguignan is already of record in the Collection Dupuy (Toulouse).

Bérenguier (1882: 42-44) gave a detailed description of the Foux-de-Draguignan and listed Amnicola compacta Paladilhe, 1869 and Amnicola anatina as from Trans[-en-Provence]. One should know that the Foux is situated South-East of Draguignan immediately in front of Trans-en-Provence.

A photograph of a shell of this species from Le Muy about 8 km far from Draguignan can be found in Germain (1931: pl. 17, fig. 496). We have not checked whether M. meridionalis still lives there.

For records of Mercuria from the Alpes-Maritimes which we could not definitely attribute to M. meridionalis see discussion under Bithinia [sic] moutonii Dupuy, 1849 , first paragraph of the chapter “Taxa uncertain”.

Figures

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.

FIG. 10. — Mercuria meridionalis (Risso, 1826): A-C, France, Nice (?) (MNHN-RIO, paralectotypes, MNHN-IM-2000-32540); A, B, 2 ♂: 2 shells, one of them belongs to the soft parts of Fig. 13C; C, ♂, double magnification compared to shells: view of soft parts showing copulatory organ, head and foot [Giusti separated soft parts of 1 ♀ and 2 ♂ from the shells of 3 paralectotypes but did not attribute each soft body to its shell; he stated only that the female soft body belongs to the largest shell; thus the figured ♂ soft body belongs to one of the two smaller shells of Fig. 13A, B; D, E, ♂, France, Bouches-du-Rhône, at road from La Fareles-Oliviers to Saint-Chamas between Mas Suriane and Mas Moyroux (BOE 3205 ex 0262); D, shell; E, copulatory organ exposed through slit in mantle (shell partially removed). Abbreviations and scale bars, see continuation page 21.

FIG. 11. — A-C, Mercuria meridionalis (Risso, 1826), France, Var, Foux de Draguignan, leg. Boeters 27.IX.1969, BOE 2414 ex 0261 (A, B); BOE 2151 ex 0261 (C); A, ♀; B, ♂; C, ♂, pallial tentacle, copulatory organ and pedal lobe clearly to be seen; D, E, Mercuria sp., presumable topotypes of Bithinia [sic] moutonii Dupuy, 1849; D, France, Alpes-Maritimes, Cannes (i.e. Mandelieu-la-Napoule [Népoule sensu Dupuy]), ♀ (MNHN-LOC); E, France, Var, Grasse (MNHN-JOU); F, Mercuria corsensis n. sp. France, Corse-du-Sud, Bonifacio, Couvent de la Trinité, leg Boeters IX.1979 (holotype MNHN-IM-2000-31951 ex BOE 0916); G-H, Mercuria zopissa (Paulucci, 1882), Italy, Sardinia, Monte dei Sette Fratelli, leg Giusti, Topotypes ex SMF 252038/7; G, globular shell; H, slender shell; I-J, Pseudamnicola emiliana (Paladilhe 1869); I, Neotype ex Topotype; France, Hérault, ruisseau [d’eaux douces] près de Balaruc (MNHN-IM-2000-32541 ex de Folin); J, de Folin’s label [“determ. par Paladilhe”, handwriting de Folin]. Scale bars: A, B, D-I, 3 mm; C, 1 mm.