Mercuria anatina ( Poiret, 1801 )

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 : 239-241

Mercuria anatina ( Poiret, 1801)

( Figs 6 K-P, 7A-G; Table 5)

Bulimus anatinus Poiret, 1801: 47 .

Paludina anatina – Garnier in Picard 1841: 301.

Pseudamnicola confusa – Adam 1940: 1.

Mercuria confusa – Gittenberger et al. 1998: 82. — Boeters 1998: 25 [partim], 50, pl. F, figs 6-10, 60, pl. N, fig. 6.

ORIGINAL INDICATIONS OF THE TYPE LOCALITIES. — [1] “L.[ieu] n.[atal] Les environs de Paris? [2] La variété A se trouve à l’embouchure de la Somme.”

MATERIAL EXAMINED. — The Netherlands. (i) Zuid-Holland, Oude Maas at Hoogvliet [right side of Oude Maas SW Rotterdam] [UTM ET95] ( BOE 0133 ), leg. Backhuys 30.X.1965; (ii) Biesbosch [SE Dordrecht] [UTM FT24] ( BOE 0271 animals and 3186 shells), leg. Butot 1959; (iii) Spijkenisse [left side of Oude Maas SW Rotterdam] [UTM ET95] ( BOE 1477 ), leg. Boeters 9.V.1970; (iv) “ Zuid Holland, Goudswaard , rietpoel in de uiterward” [reed puddle in foreland of dam] [UTM ET94]; NN leg. 26.V.1960 ( RMNH MOL 124 746/30 ex collection Delta Instituut) .

Belgium. Anvers (Antwerpen) r[ive] g[auche], “fossé eaux saumâtre” [UTM ES97] ( BOE 3203), leg. Giltay 2.IV.1927.

IDENTIFICATION. — Frauenfeld’s collection comprises one single shell which he obtained from Charpentier who received it from Férussac fils ( NMW-FRD 92601; label: “ anatina Orig. Ex. v[on] Charp[entier]” ( Fig. 6K ). However, we hesitate to base our understanding of the species on this putative syntype since we have not been able to find any Mercuria -Population which convincingly matches the character combination of this specimen (a check with Pseudamnicola was also negative). Especially the shell does not show an aperture as outlined below as characteristic of M. anatina . Also the inflated second whorl does neither fit Mercuria nor Pseudamnicola , it is best interpreted as an anomaly of growth. Nevertheless, the predominantly milky colour of the shell and the whitish surrounding of the umbilicus in combination with the chestnut-reddish operculum are characters which clearly speak for the belonging to Mercuria .

A strong support for the identification of Bulimus anatinus as belonging to Mercuria is the figure given by Draparnaud (1805: pl. 1, figs 24, 25). The shell figured there under the name Cyclostoma anatinum doubtlessly belongs to Mercuria . This specimen was considered by Kadolsky (2011: 70 legend of fig. 2A; 71 right column) to represent another possible syntype of Poiret’s Bulimus anatinus .

Mercuria anatina has never been reported from “Les environs de Paris”, except for Poiret and with reservation. As regards the “embouchure de la Somme”, Cucherat (in litt. 15.IV.2002) and later on in X.2002 G. and M. Falkner have made attempts to recollect the snail, but without any success. In Kadolsky’s opinion the supposed origin of M. anatina in northern France is incorrect. “Les environs de Paris?” has to be treated as erroneous (2011: 71 left column) and Picard’s record of M. anatina from the other type locality, i.e. “baie de Somme, à l’embouchure de cette rivière” (Garnier in Picard 1841: 302), concerned rather Peringia ulvae (Pennant, 1777) . Kadolsky refers to Garnier’s statement (in Picard 1841: 302) “tentacles grey with a black circle at their extremities” [“tentacules gris avec un cercle noir à l’extrémité”] which applies to P. ulvae (see e.g., Seifert 1935: 233, fig. 1). This, however, overlooks Garnier’s decription of the operculum as of dark brown [“d’un brun foncé”]. This feature is characteristic of Mercuria species , whereas in P. ulvae the operculum is yellowish in its center and colourless towards its periphery ( Meyer & Möbius 1872: 37) or the operculum is horny ( Fretter & Graham 1978: 123). Thus Garnier’s description might cover two different species, but without any doubt M. anatina as one of them. Further, Garnier described the last whorl as “légèrement caréné” and the aperture of the shell as “ovale, presqu’arrondie à droite, un peu rétrécie vers la haut”. This slight keel of the last whorl and correspondingly slight flattening of the right border of the aperture in frontal view is not shown by M. sarahae distributed in North-West France, but by Mercuria living in neighboured Belgium and the Netherlands; see Adam (1940: 3, fig. 1) for Belgium and Boeters (1998: 60, fig. N6) for the Netherlands. This encourages us to base the following description of M. anatina not only on Poiret’s (1801) and Garnier’s (in Picard 1841) publications, but also on material from Belgium and the Netherlands.

DISTRIBUTION AND ECOLOGY. — No French locality is known where the species still lives. It has been reported in France from the surrounding of Paris with reservation, from the Somme and from the basin of the Escaut. In Belgium in the river Escaut at Anvers (Schelde at Antwerpen, Adam 1940; recently not refound, Bruyne & Geene 1998: 102). In the Netherlands in the delta areas of the rivers Rhine and Maas; Gittenberger et al. 1998 (figs 130, 131) give maps of distribution. Biotope: Tide areas of rivers; see Butot (1960), Hartog (1960: 72, fig. 3 with tide limits) and Bruyne & Geene (1998); salt concentration indicated as 0.3-3.0 ‰ ( Bruyne & Geene 1998: 101) or 0.5-5.4 ‰ ( Gittenberger et al. 1998: 82).

DESCRIPTION

Shell and operculum

Shell with 4.5-4.75 whorls ( BOE 0133).

Measurements

See Table 5.

In view of the fact that the identification of this species cannot be based with certainty on type material, Poiret’s and Garnier’s descriptions are given:

Poiret 1801: “Coquille presque conique, un peu aigue; ouverture arrondie. 4 tours et demi de spire. Diam. près de 2 millim. Haut. environ 3 millim.Testa subconica, subacuta; apertura subrotunda. Long. 2 lin. Diam. 1 lin.

[La variété] A. Le même un peu plus grand à 5 tours de spire. A. Idem major, anfractibus quinque.”

Garnier 1841: “Long. 2 à 5 m [sic], Larg. 1 à 2 1/2. Coquille très-petite, allongée, blanche où d’un jaune-pâle quand elle est dépouillée de l’enveloppe verdâtre dont elle est recouverte; la spire est composée de six tours et non de sept à huit suivant de M. Deshayes [1832: 693], ou de quatre demi-tours, comme le dit Draparnauld [sic] [1805: 37]; elle est très-finement striée longitudinalement, à suture peu marquée, le dernier tour légèrement caréné; bord simple, épais, blanchâtre; l’ouverture est ovale, presqu’arrondie à droite, un peu rétrécie vers le haut, avec les bords presque continus; ombilic formant une fente très-peu profonde, mais perfaitement visible; l’opercule est d’un brun-foncé, cornée et très-mince.”

Variability

In the Netherlands SE Dordrecht in the Biesbosch with remarkably depressed spire (cf. Boeters 1998: 50, fig. F8); ratio hight of aperture: total height of shell c. 56% compared to c. 49% at other Dutch localities.

Animal

External characters. In the following Garnier’s description of the animal is supplemented by anatomical data of a Dutch sample ( BOE 0271 ). “Animal gris, rayé de noir; tête noirâtre, avec la trompe très allongée et violette; tentacules gris avec un cercle noir à l’extrémité; yeux noir, pédonculés, situés à la base externe; plan locomoteur coupé carrément à l’extrémité antérieure, arrondie postérieurement, large et blanchâtre” ( Garnier 1841: 302). Pallial tentacle not seen ; remarkably the ctenidium shows only 16 gill filaments (1♂; BOE 0271 ). Radula figured by Adam (1940: 4, fig. 2A) .

Male copulatory organ. Penis blackish, appendix like an elliptical disc ( Boeters 1998: 50, fig. F9).

Female genital tract. Bursa copulatrix and one receptaculum seminis ( Boeters 1998: 50, fig. F10). It is noticeable that the receptaculum flanks the bursa and is not embedded as usual in the angle formed by the insertion of the pedunculus into the bursa.

DIFFERENTIATING FEATURES

M. anatina in our present perception can be distinguished from M. sarahae in that the shell of the latter one shows a well rounded and not flattened aperture. The male genitalia of M. sarahae shows a bulge which is missing in M. anatina .

REMARKS

For the sake of correctness a sample of a species of Mercuria in the collection Locard ( MNHN-LOC /5, Fig. 6 N-O) should be mentioned since it had been collected at a locality between the Somme and Paris. Its label reads “ Amnicola similis Oise ”. The Oise is a northern tributary of the Seine downriver of Paris and is quite near to the river system of the Escaut where historical occurrences are reported by Potiez & Michaud (1838: 254) from the Hainaut, Douai and Valenciennes, to which Norguet (1872: 282 [Separatum p. 22]) added Cambrai. As Norguet, who uses the generic name Bythinia , discriminates between leachii and similis , it can be taken for sure, that his indications really concern a species of Mercuria . However, the shells from the Oise do not show an aperture as characteristic of M. anatina in our understanding (see Fig. 6N ). Further, in the Netherlands, Belgium and Northeast France Mercuria lives exclusively in tide areas of rivers. If our understanding that the distribution of M. anatina extends from the Netherlands across Belgium to Northeast France should be incorrect, rather the sample from the Oise represents M. anatina , the species living in the Netherlands and Belgium would have to be described as a new representative of Mercuria .

The findings upstream of the tide area of the Escaut and the alledged occurrence of M. anatina in the “Oise” ( MNHN- LOC/5) as a contributary river of the Seine are to be confirmed. A confirmation would mean that the species invades rivers also upstream of their tide areas. Further, Poiret’s first indication “Les environs de Paris” would gain importance.

The locality of Calais as given by Locard (1882: 225) results from a printing error and should read “Le Palais”; cf. under M. sarahae vindilica .

Figures

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.