Mercuria maceana ( Paladilhe, 1869 )

Miller, Jonathan P., Delicado, Diana, García-Guerrero, Fernando, Khalloufi, Noureddine & Ramos, Marian A., 2023, Morphology and taxonomic assessment of eight genetic clades of Mercuria Boeters, 1971 (Caenogastropoda, Hydrobiidae), with the description of five new species, European Journal of Taxonomy 866 (1), pp. 1-63 : 26-29

Mercuria maceana ( Paladilhe, 1869)

Figs 15–16

Amnicola maceana Paladilhe, 1869: 103 .

Mercuria maceana – Bank & Neubert 2017: 16.

Revised diagnosis

Shell ovate-conic; aperture obliquely broad ovate; periostracum yellowish to pale grey; protoconch microsculpture granulated; central radular tooth formula 3-C-3/1-1.

Type material (not examined)

Syntypes SPAIN • 1 spec. (sex unknown); Barcelona, C’an Tunis ; MHNG-MOLL-105438/2 • 1 spec. (sex unknown); same collection data as for preceding; MHNL 45013950 • 1 spec. (sex unknown); same collection data as for preceding; UM.PDL.006 ( Breure & Audibert 2017).

Type locality

C’an Tunis, Barcelona, Spain. The type locality of this species in the original description “récoltée à Antunez, près de Barcelone” refers to a series of local geographic names for a private property: C’an Tunis, Casa Antúnez, Camp de la Bota, Llano del Llobregat. These names have been written either conserving the original language, Catalan, sometimes using the Spanish form, or even using other local names for the same place.

Material examined

SPAIN • 30 specs; Barcelona, C’an Tunis ; MNCN 15.05/7009 • 30 specs; same collection data as for preceding; MZB 77-8445 , MZB 77-8107 .

Description

SHELL. Ovate-conic, whorls 4–5, height 3.9–5.2 mm, width 3–3.8 mm ( Fig. 15A–E ); periostracum yellowish to pale grey; protoconch of 1.5 whorls, ca 350 µm wide, nucleus ca 200 µm wide ( Fig. 16A ); protoconch microsculpture granulated ( Fig. 16B–C ); teleoconch whorls convex, separated by a deep suture; body whorl large, convex, occupying about two-thirds of the total shell length; aperture obliquely broad ovate, complete; inner lip thicker than outer lip; aperture margin slightly reflexed; umbilicus narrow, not covered by the inner lip ( Fig. 15A–E ).

RADULA. Length intermediate, ca 800 µm long (35% of total shell length), containing about 63 rows of teeth. Central tooth formula 3-C-3/1-1, central cusp V shaped, cutting edge slightly concave ( Fig. 16D ). Lateral tooth formula (3)4-C-4(3), central cusp V shaped and slightly longer than the central tooth one. Inner marginal teeth with 12–14 cusps; outer marginal teeth with 12–14 cusps ( Fig. 16E–F ). Radular data were compiled from a dry specimen (MZB 77-8445) collected from the type locality.

Ecology and distribution

This species is only known from the type locality, C’an Tunis (Casa Antúnez), Catalonia, Spain. The type locality has likely disappeared due to extensive alterations (e.g., construction, pollution) of the area as a result of port works conducted in the Barcelona harbour and the industrial zone in the 1980s and the construction work carried out for the 1992 Olympic Games (Jordi Corbella and Francesc Uribe pers. com.). Recent surveys conducted around Barcelona did not yield live specimens.

Remarks

Mercuria maceana is only known from its type locality, which has been destroyed over the past few decades. Specimens of this species have not been found in the nearby areas, suggesting that the species is extinct (IUCN category EX). The shells and dry specimens of M. maceana deposited in the Zoological Museum of Barcelona were examined to delineate the morphological variation presented by the species and to support its recognition. Our PCA based on shell shape differentiated this species ( Fig. 3 ). Accordingly, M. maceana differs from M. egarensis sp. nov. by its shorter and more globose or subglobose shell and is more similar to the Moroccan species M. targouasensis . Based on the characters observed on the radulae, M. maceana cannot be distinguished from M. similis or M. egarensis . We were unable to study other anatomical features due to the lack of ethanol-preserved material.

Figures

Fig. 15. Shells and operculum of Mercuria maceana (Paladilhe, 1869) from C’an Tunis, Barcelona, Spain. A–E. Shells. F. Operculum, inner side. G. Operculum, outer side.

Fig. 16. Protoconch (A–C) and radula (D–F) of Mercuria maceana (Paladilhe, 1869) from C’an Tunis, Barcelona, Spain. A. Protoconch nucleus. B. Details of the protoconch. C. Protoconch microsculpture. D. Overview of radular teeth rows. E–F. Detailed view of the lateral and inner teeth.

Fig. 3. Principal components analysis plot for species of Mercuria Boeters, 1971 based on 21 coordinates (9 landmarks and 12 semilandmarks). Each dot on the plot represents the consensus of the shape of each of the sampled populations. Warp grid deformations (TPS) show expansion (in red colour) and contraction (in blue) of the shell shape.