Mercuria baudoniana ( Gassies, 1859 )

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 : 232-235

Mercuria baudoniana ( Gassies, 1859)

( Fig. 3 F-K; Table 2)

Bythinia [sic] baudoniana Gassies, 1859: 289-290 ; 1867: 129-130, pl. 1, fig. 7.

Amnicola lanceolata Paladilhe, 1869: 228 , pl. 19, figs 8, 9 [separatum: 105, pl. 5, figs 8, 9].

ORIGINAL INDICATIONS OF THE TYPE LOCALITIES. — Bythinia [sic] baudoniana : “Habite: les fossés de la grande Lande voisine des prés salés, au Teich.” — Amnicola lanceolata : “L’ A. lanceolata habite les environs de Saint-Jean-de-Luz (Basses-Pyrénées)”.

MATERIAL EXAMINED. — France. (i) Landes, Le Teich [UTM XQ54] ( MNHN / 6 syntypes, label: “ Bythinia Baudoniana var. major GASS. Le Taich [sic]”). — (ii) Pyrénées-Atlantiques, Saint-Jean-de-Luz [UTM XP00] ( MHNG-BGT 5437/ 1 syntype of Amnicola lanceolata Paladilhe, 1869 ).

LECTOTYPES. — Bythinia [sic] baudoniana , MNHN-IM-2000-32542; H: 5.70 mm, D: 3.15 mm, 5.75 whorls (here designated). — Amnicola lanceolata, MHNG-BGT 5473/1 (orig. fig.); H: 4.70 mm, D: 2.65 mm, 5.6 whorls (here designated).

DISTRIBUTION AND ECOLOGY. — Reported only from the type localities in Landes and Pyrénées-Atlantiques. At Le Teich in ditches of saline meadows, sympatric with Planorbiidae and Lymnaeidae ( Anisus spirorbis and Omphiscola glabra ; cf. Gassies 1859: 290).

DESCRIPTION

Shell

Elongated conical with pointed apex and straight sidelines; last whorl about 57-59% of total height of shell; umbilicated; 5.38 [5.0-5.75] whorls [n = 4], 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, basal margin and columellar edge simple, palatal, basal and columellar margin not even slightly thickened.

Measurements

See Table 2.

Operculum

According to Gassies (1859: 290) “opercule corné, mince, d’un beau rouge orange, à spire complète”.

Animal

External features: “gris enfumé, presque noir sous le pied dont les bords sont plus pâles; tentacules filiformes, blanchâtres, gélatineux, yeux très-noirs situés à la base postérieure,mufle proboscidiforme, noir, ridé transversalement en dessus; mâchoire, cornée, rougeâtre, arquée légèrement” ( Gassies 1859: 289).

Anatomy

Unknown.

DIFFERENTIATING FEATURES

M. baudoniana can be distinguished from M. bayonnensis and M. sarahae by a more elongated shape of its shell. This is reflected by a ratio H: D (height: diameter of shell) of 1.61- 1.67 in M. baudoniana , whereas in M. s. sarahae it is 1.54 and in M. bayonnensis 1.38-1.46.

REMARKS

As regards the attribute “ var. major ” on the label of the syntypes of Bythinia [sic] baudoniana , a varietas “ major” has never been described by Gassies. Thus, this attribute is regarded as a mere descriptive term which later has been abandoned in the description.

Gassies (1859: 290 and 1867: 130) mentions as measurements of the shell of his Bythinia [sic] baudoniana “Haut. 8-12 mill. Diamètre 6-7 mill.” which neither applies to the syntypes nor to the figure given by Gassies (1867: pl. 1, fig. 7), having a height of about 6 mm. Further, the figured shell, showing a concentrically ringed operculum is in clear contradiction to the description “à spire complète”.

There is a sample with three empty shells in the collection Pascal ( MNHN-PAS), received from de Folin, which might be regarded as syntypes ; de Folin’s label reads: “ Amnicola similis var. Baudoniana Gassies ex auctore ipso Le Teich Gironde”. However, these three shells belong to M. bayonnensis . Remarkably, all these three shells are empty, whereas the lectotype and the five paralectotypes show operculum and dried animals. It is open to question whether de Folin himself added “Le Teich” bona fide.

Paladilhe’s description of his Amnicola lanceolata was very probably based on a single specimen from Bourguignat’s collection since it is possible to identify this specimen with Paladilhe’s figures disregard of the fact that the label refers to these figures. But as Paladilhe indicated a variation in the number of whorls it cannot be excluded that he had further specimens at his disposal. Therefore we prefer to designate the specimen from Bourguignat’s collection as Lectotype.

Topotypes of Amnicola lanceolata have not yet been recollected. From the biotope described by Gassies for his M. baudoniana it might, however, be concluded that this species inhabits or inhabited in the environment of Saint-Jean-de-Luz water bodies which may occasionally fall to dryness. For further investigations it is worth mentioning that before 1971, Boeters saw a sample in Bérillon’s collection (MHNB-BER) with a label reading “ Amnicola lanceolata Ruisseau près le parc aux huitres St Jean de Luz vieille route du Boucau [district of Bayonne]”.

Since the shells of the types of Bythinia [sic] baudoniana are covered by a brownish coat, at a glance they might be taken as shells of a species of Pseudamnicola ; however, at least one shell has spotwise lost its cover and shows the milky colour characteristic of Mercuria .

Figures

FIG. 3. — A-E, Mercuria bayonnensis (Locard, 1894): A, lectotype of Bythinia [sic] bayonnensis, France, Pyrénées-Atlantiques, Lac de la Négresse près Bayonne (Biarritz) (MHNG-BGT 4943a); B, C, France, Pyrénées-Atlantiques, Biarritz, source dans la falaise, leg. Letellier 1949 (MNHN); B, cleaned; C, specimen with camouflage, front view and back view; D, E, paralectotype (?) of Bythinia [sic] baudoniana Gassies, 1859 (MNHN-PAS ex de Folin), allegedly: Gironde, Le Teich; E, de Folin’s label [“ex auctore ipso”]; F-K, Mercuria baudoniana (Gassies, 1859); F-H, syntypes of Bythinia baudoniana, France, Gironde, Le Teich, fossés de la Grande Lande voisins des près salés (MNHN); F, lectotype (MNHN-IM-2000-32542); G, paralectotype; H, Gassies’ label; I-K, lectotype of Amnicola lanceolata (Paladilhe, 1869), France, Pyrénées-Atlantiques, Saint-Jean-de-Luz (MHNG-BGT 5437); J, K, Bourguignat’s labels on the tube of the holotype. Scale bar: 3 mm. All reproductions of labels in this and the following figures are in natural size.