Meioceras nitidum (Stimpson, 1851)

Egger, Christina, Neusser, Timea P., Norenburg, Jon, Leasi, Francesca, Buge, Barbara, Vannozzi, Angelo, Cunha, Regina L., Cox, Cymon J. & Joerger, Katharina M., 2020, Uncovering the shell game with barcodes: diversity of meiofaunal Caecidae snails (Truncatelloidea, Caenogastropoda) from Central America, ZooKeys 968, pp. 1-42 : 1

Meioceras nitidum (Stimpson, 1851)

Caecum nitidum Stimpson, 1851 in Stimpson (1851a): 112. Type locality: Florida.

Caecum lermondi Dall, 1924: 7; Caecum rotundum de Folin, 1868: 49, pl. 5, fig. 2; Meioceras bitumidum de Folin, 1869: 9, fig. 4; Meioceras carpenteri de Folin, 1869: 8, 9, fig. 3; Meioceras cingulatum Dall, 1892: 302, pl. 16, figs 6, 7; Meioceras contractum de Folin, 1874: 213, t. 2, pl. 4, fig. 7; Meioceras coxi de Folin, 1869: 13, fig. 9; Meioceras crossei de Folin, 1869: 11, 12, fig. 7; Meioceras deshayesi de Folin, 1869: 11, fig. 6; Meioceras elongatum de Folin, 1881: 17, pl. 1, fig. 9; Meioceras fischeri de Folin, 1870: 188, pl. 26, figs 3, 4; Meioceras imiklis de Folin, 1870: 189, pl. 26, figs 5, 6; Meioceras leoni Bérillon, 1874: 251, pl. 5, fig. 3; Meioceras moreleti de Folin, 1869: 10, fig. 5; Meioceras subinflexum de Folin, 1869: 165, pl. 23, fig. 8; Meioceras undulosum de Folin, 1869: 12, fig. 8.

Material examined.

French Antilles • 1 (Fig. 5A-D ); Martinique, Anse Noir; 14.528, -61.088; depth 6 m; 6 Sep 2016; MNHN Madibenthos exped.; Stat. AB102; GenBank: MT704298, MT731714; MNHN-IM-2013-72087a • 1; same collection data as for preceding; GenBank: MT704299, MT731715; MNHN-IM-2013-72087b.

Shell morphology.

Shell translucent, glossy. Light brown zig-zag pattern covering entire shell in rings with irregular white dorsal patches (Fig. 5A ). Bulbous tube, tapering towards aperture and posterior end. Maximum width at about one third of shell length. Slightly more bowed towards aperture. Septum flat, with triangular, pointed mucro (Fig. 5C ). No sculpture or microsculpture diagnostic features (Fig. 5D ).

Remarks.

Meioceras and in particular " M. nitidum " has a complex taxonomic history involving at present 16 synonyms and several reallocations between Meioceras and Caecum ( MolluscaBase 2019). Vannozzi (2017) highlighted the problems with the ambiguous type specimen of M. nitidum ( Stimpson 1851a), which encouraged multiple novel descriptions (e.g., Carpenter 1858-1859; De Folin and Périer 1867), nowadays recognized as synonyms. Our two investigated specimens from Martinique are consistent with the meagre original description by Stimpson (1851a) based on specimens from Florida and several redescriptions based on material from the Caribbean and southern America, now all accepted as M. nitidum ( M. nitidum see Bandel 1996: 99, pl. 5, figs 1-7; M. contractum see de Folin and Périer 1875: pl. 9, fig. 7). Our specimens differ morphologically from several " M. nitidum " specimens from Central American waters all of which were described as a different species in the past but later synonymized with M. nitidum acknowledging intraspecific variability (i.e., M. elongatum , holotype accessible through the online catalogue of the MNHN (MNHN-IM-2000-32923) and M. subinflexum (see de Folin and Périer 1867: pl. 23, fig. 8). Molecular comparison of specimens spanning the morphological and geographical range is needed to clarify the species status and distribution of the species.

Figures

Figure 5. A-D Meioceras nitidum, specimen MNHN-IM- 2013 - 72087 A light microscopic picture B SEM scan C SEM close-up of mucro and D microsculpture E M. cubitatum, specimen USNM 1618851 F, G C. cf. corrugulatum, specimen USNM 1618861 F light microscopic picture G light microscopic close-up of microstructure H MOTU II, specimen USNM 1618853 I-L MOTU I, specimen ZSM-Mol- 20200039 I light microscopic picture J SEM scan K SEM close-up of mucro and L microsculpture M C. glabrum, specimen ZSM-Mol- 20200096 N C. glabellum auctt. non Adams, specimen ZSM-Mol- 20200074 O-R C. invisibile sp. nov., holotype ZSM-Mol- 20100320 O light microscopic picture P SEM scan Q SEM close-up of mucro and R microsculpture. Scale bars: 10 µm (R); 20 µm (C, K, L, Q); 50 µm (D, E) 100 µm (I, J, O, P); 200 µm (A, B, M, N).