Mercuria sarahae ( Paladilhe, 1869 )

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 : 235-239

Mercuria sarahae ( Paladilhe, 1869)

This species, distributed in northwestern France, comprises two subspecies, that is the nominate subspecies and Mercuria sarahae vindilica ( Paladilhe, 1870) .

Mercuria sarahae sarahae ( Paladilhe, 1869) ( Figs 4 , 6 A-G; Table 3)

Amnicola sarahae Paladilhe, 1869: 233 , pl. 19, figs 12, 13 [separatum: 109, pl. 5, figs 12, 13].

ORIGINAL INDICATION OF THE TYPE LOCALITY. — “[…] vit dans l’Erdre et la Loire aux environs de Nantes.”

MATERIAL EXAMINED. — France. (i-iii) Calvados , (i) ( SMF 142038 /13 and 244634/22; NMW/2 and NMW/9 both ex Terver and paralec - totypes of Amnicola confusa Frauenfeld, 1863 ); (ii) Blainville [-sur- Orne] [UTM XV95] ( MNHN-PAS/5 ex de Folin [2]); (iii) Caen [UTM XV95] ( MNHN-PAS/5 ex de Folin [3], de Folin’s label: “ Amnicola similis Drap. var. Bord de l’Orne sous les cours Caffarelli”. — Loire-Atlantique, (iv) “Erdre à Nantes” [UTM XT13] ( MHNG-BGT 54591 / 1 lectotype; PPSUM2 -PAL/ 2 syntypes); (v) Loire upstream of Nantes, Thouaré-sur-Loire [UTM XT13] ( SMNS-FAL and BOE 1478 animals and 2415 shells), leg. G. and M. Falkner 26.V.1999 .

LECTOTYPE. — MHNG-BGT 5459 /1 (orig. fig.) (here designated).

DISTRIBUTION AND ECOLOGY. — Calvados (Orne at Caen), Morbihan (“marais dunaire à Pénestin” [UTM WT36]; Pasco in litt.), Loire-Atlantique (Loire and Erdre as its tributary at Nantes). Biotope: Tide area of rivers, in the Loire together with Potamopyrgus antipodarum (Gray, 1843) .

DESCRIPTION

Shell

Conical with pointed apex and straight sidelines; last whorl striatulate and of about 48-54% of total height of shell; umbilicated; of transparent milky colour; 4.7-5.0 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 3.

Operculum

Reddish, nucleus even more intensely coloured.

Animal

External characters. Pallial tentacle not seen. Black pigment to be found merely on the mantle at its border and in the neighbourhood of the intestine and the gill. Ctenidium with 25 (1 ♀) and 21 gill filaments (1 ♂).

Male copulatory organ. Penis blackish pigmented, of about the same length as the appendix. Appendix with a lateral bulge like an abutment for the penis.

Female genital tract. Bursa copulatrix and one receptaculum seminis.

DIFFERENTIATING FEATURES

Versus M. s. vindilica : The nominotypical subspecies cannot be distinguished by conchological or anatomical characters, however, M. s. vindilica does not live on the mainland of France but on the Belle-Île and, further, does it not inhabit the tide areas of rivers but lives in springs.

Versus M. baudoniana : in M. s. sarahae the spire of shell is less elongated and more conical such that the last whorl forms about 48.1 to 53.7% (n = 4) of the total height of the shell and not merely about 38.0 to 46.2% (n = 5 syntypes of M. baudoniana ).

Versus M. bayonnensis : in M. s. sarahae at least the last two whorls are striatulate (as at Thouaré-sur-Loire), however, in M. bayonnensis these whorls are more or less smouth (as at Bidart and Biarritz), except for some irregularities of growth. Further, the male copulatory organ of M. s. sarahae shows a comparatively pronounced indication of a bulge (compare Figures 4 and 7 ).

Versus M. anatina : in M. s. sarahae the angle of the aperture is fairly rounded and not rather narrow leading over to the palatal border shoulder-like; border of the angle not only straight but sometimes even slightly broadened. Male copulatory organ smaller than in M. anatina , penis shaped rather vermiform, not wedge-like, appendix with a lateral bulge like an abutment for the penis, which is missing in M. anatina .

REMARKS

As already mentioned for M. bayonnensis , since this species and M. s. sarahae can clearly be distinguished by anatomical characters, but not in any case by their shell, we must leave it open to question to which species records from the interjacent regions belong, except for M. baudoniana . Reference is made to the last paragraph of the chapter Taxa uncertain.

Mercuria sarahae vindilica ( Paladilhe, 1870) ( Figs 5 A-F, 6H-J; Table 4)

Amnicola vindilica Paladilhe, 1870: 189 [no figs; separatum: 23]; 1874: 1-38, pl. 3, figs 1, 2.

ORIGINAL INDICATION OF THE TYPE LOCALITY. — “[…] de Belle- Isle-en-Mer (Vindilis des anciens), où elle a été recueillie près de Palais (village principal de l’île)”.

MATERIAL EXAMINED. — France. (i-ii) Morbihan , (i) (locus typicus; destroyed) “font[aine] près le Palais” [UTM VT84] ( MHNG-BGT 5479 / 1 syntype, becomes Lectotype); (ii) Belle-Île-en-Mer [UTM VT84] ( MNHN-PAS/2 ex de Folin [10]). — (iii) Locmaria, outflow of a captured spring [UTM VT93]( BOE 1448 animals and 2418 shells), leg. Boeters VII.1994 .

LECTOTYPE. — MHNG-BGT 5479 /1 (here designated).

DESCRIPTION

Shell

Conical with pointed apex and straight sidelines; last whorl about 45-47% of total height of shell; umbilicated; of transparent milky colour; 4 1/2 whorls, swollen and very convex, respectively, separated by a deep suture; last whorl shortly in front of aperture occasionally descending on shell wall; 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 broadened, palatal, basal and columellar edge slightly thickened.

Measurements

See Table 4.

Operculum

Coloured like horn, utmost yellowish, not reddish.

Animal

External characters. Pallial tentacle not seen. Strongly pigmented black; position of the different glands of the pallial oviductus and of the intestine towards the stomach cannot be seen through the mantle and the body wall. Ctenidium with 23 (1 ♀) and 24 gill filaments (1 ♂).

Male copulatory organ. Penis and appendix like forefinger and thumb, appendix with a slight indication of a bulge; penis blackish (1♂).

Female genital tract. Bursa copulatrix plus one receptaculum seminis.

DIFFERENTIATING FEATURES

The more or less pronounced bulge in the penial appendix discriminates this subspecies (as well as M. s. sarahae ) from all congeners of the Atlantic slope. M. s. vindilica is ecologically specialised to springs and does not inhabit the tide zone of rivers where M. s. sarahae lives.

Paladilhe himself distinguished Mercuria s. vindilica from M. baudoniana only in the following way: “On la distinguera de l’ Amn.lanceolata par sa spire moins élancée; son dernier tour plus ventru, non détaché près de l’ouverture; son ouverture non saillante en dehors, moins anguleuse, plus régulièrement arrondie et bien moins oblique.”

DISTRIBUTION AND ECOLOGY. — Morbihan (Belle-Île-en-Mer). In springs; at Locmaria together with a representative of the Lymnaeidae .

REMARKS

It is assumed that the “font[aine]” mentioned on the label of the lectotype (MHNG-BGT 5479) refers to a nowadays completely sealed spring in the parc of Le Palais.

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Figures

FIG. 4. — Mercuria sarahae sarahae (Paladilhe,1869),France,Loire-Inférieure,Thouaré-sur-Loire,river Loire (BOE 1478 ex SMNS-FAL);A-C, ♂; A, shell; B, C, head and foot with copulatory organ exposed through slit in mantle, ventral (B) and dorsal view (C); D, E (♀); D, shell; E, body lumen opened to show renal oviductus with receptaculum seminis (rs1) and bursa copulatrix surrounded by intestinal section (partially removed). Abbreviations: bc, bursa copulatrix; fp, fecal pellet; in, intestine; op, operculum; pe, penis; ro, renal oviductus; rs1, single receptaculum seminis. Scale bar: 1 mm.

FIG. 6. — A-G, Mercuria sarahae sarahae (Paladilhe, 1869): A, lectotype of Amnicola sarahae, France, Loire-Atlantique, Loire près de Nantes (MHNG-BGT 5459); B-D, France,Loire-Atlantique,Thouaré-sur-Loire,bras mort de la Sauterelle,leg.G. and M.Falkner 26.V.1999 (SMNS-FAL);B, ♂; C, ♀; D, excessively grown specimen [überwüchsig]; E-G, France, Calvados,Blainville-sur-Orne (MNHN-PAS ex de Folin);E, ♂; F, ♀; G, de Folin’s label;H-J, Mercuria sarahae vindilica (Paladilhe, 1870): H, France, Morbihan, Belle-Île-en-Mer, shell cleaned (MNHN-PAS ex de Folin, “déterminée par Paladilhe”); I, J, lectotype of Amnicola vindilica, France, Morbihan, Belle-Île-en-Mer, fontaine près Le Palais (MHNG-BGT 5479); J, Bourguignat’s label; K-M; Mercuria (or Pseudamnicola) sp.: K, questionable syntype of Bulimus anatinus Poiret, 1801 (NMW-FRA); L, M, labels of the questionable syntype; L, Frauenfeld’s label; M, Sturany’s label (handwriting of Sturany’s calligrapher Matzka and of Sturany himself); N-P, Mercuria anatina (?) (Poiret, 1801); N, O, France, Oise, northern tributary of the Seine downriver of Paris (MNHN-LOC); O, Locard’s label; P, the Netherlands, Zuid-Holland,Oude Maas at Hoogvliet [right side of Oude Maas SW Rotterdam], leg. Backhuys 30.X.1965 (BOE 0133). Scale bar: 3 mm.

FIG. 7. — Mercuria anatina (Poiret, 1801): A-F, the Netherlands, Biesbosch (BOE 0271); A, B, ♂; A, shell with partially retracted animal; B, head with copulatory organ exposed through slit in mantle; C, D, ♂: head with copulatory organ, dorsal (C) and ventral view (D); E, F,♀; E, shell; F, body lumen opened to show renal oviductus with receptaculum seminis (rs1) and bursa copulatrix surrounded by intestinal section (partially removed); G, the Netherlands,Oude Maas at Hoogvliet (BOE 0133): shell. 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. 5. — Mercuria sarahae vindilica (Paladilhe,1870), France, Morbihan, Locmaria [Belle-Île-en-Mer] (BOE 1448); A, B, ♂; A, shell; B, head and foot with copulatory organ exposed through slit in mantle; C, D, ♂: head with copulatory organ, ventral (C) and dorsal view (D); E, F (♀); E, shell; F, body lumen opened to show renal oviductus with receptaculum seminis (rs1) and bursa copulatrix surrounded by intestinal section (partially removed). Abbreviations: bc, bursa copulatrix; in, intestine; op, operculum; pe, penis; ro, renal oviductus; rs1, single receptaculum seminis. Scale bar: 1 mm.