Caecum cooperi S. Smith, 1860

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

Caecum cooperi S. Smith, 1860

Caecum cooperi S. Smith, 1860: 154-155. Type locality: northern part of Gardiner’s Bay, four or five fathoms [United States].

Caecum costatum A. E. Verrill, 1872: 283, pl. 6, fig. 6, Caecum smithi Cooper, 1872.

Material examined.

French Antilles • 1 (Fig. 6F-I ); Guadeloupe; 16.3558, -61.5965; depth 2 m; 24 May 2012; MNHN KARUBENTHOS exped.; Stat. GS32; GenBank: MT704297, MT731713; MNHN-IM-2019-32.

Shell morphology.

Shell opaque, with whitish diffuse patterns. Size> 2 mm, tube narrow and elongated, curvature increasing towards posterior end (Fig. 6F, G ). Septum flat, triangular shaped, strongly pointed mucro (Fig. 6H ) similar to mucro in C. imbricatum . Prominent and conspicuous shell ornamentation, minimum of 20 longitudinal strings of beads, more pronounced towards aperture (Fig. 6I ).

Remarks.

Our molecular species delimitation separates C. cooperi and C. imbricatum into two independent evolving sister species (see Figs 3 , 4 ). This is supported by (minor) morphological differences such as a finer but more pronounced bead-like ornamentation in C. cooperi in comparison to flattened squarish and less frequent longitudinal pattern. The included barcodes and distinguishing diagnostic features should help to overcome previous taxonomic uncertainty suggestive of synonymy (see C. imbricatum sensu Moore (1972: 888, fig. 6)). The putative synonymy of C. insularum Moore, 1969 and C. imbricatum (compare C. imbricatum sensu Tunnell et al. (2010: 144) = C. insularum sensu Moore (1970: 370, fig. 1A, B) needs to be tested by molecular data, ideally based on material recollected from the type localities.

Figures

Figure 3. Optimal ML tree of the concatenated 28 S rRNA, 16 S rRNA and COI genes partitioned by genes and COI codon positions. Bootstrap values (below nodes) of the ML analysis are shown for values> 80 % and posterior probability support (above nodes) of the BI analysis are shown for values> 0.95. Specimens previously classified as Meioceras are indicated in yellow color. Smooth, translucent specimens, lacking diagnostic features and summarized in the ' Caecum glabrum - like complex' are indicated in blue. C. = Caecum, M. = Meioceras, MOTU I / MOTU II = molecular operational taxonomic unit within the ' Caecum glabrum - like complex'. Figured specimens are all to the same scale. Scale bar: 1 mm.

Figure 4. Molecular based species delimitation of Central American Caecidae. Guide tree used for PTP and bPTP based on the optimal likelihood tree of the concatenated three-marker dataset. Color codes indicate our preliminary species hypothesis derived from the phylogenetic tree. Color bars reflect the species delimitation suggested by the four consulted species delimitation programs (including ML and Bayesian implementation for PTP and single and multiple threshold for GMYC). Bars are missing where no sequence data obtained.

Figure 6. A-E Caecum heptagonum A specimen USNM 1618866 juvenile specimen with larval shell still attached B-E specimen ZSM-Mol- 20200030, juvenile specimen already resembling closely the adult form B light microscopic picture C SEM scan D close-up of mucro and E microsculpture F-I C. cooperi, specimen MNHN-IM- 2019 - 32 F light microscopic picture G SEM scan H close-up of mucro and I microsculpture whole specimen and close-up of mucro and microsculpture J-M C. debile, specimen MNHN-IM- 2019 - 27 J light microscopic picture K SEM scan L close-up of mucro and M microsculpture N-Q C. striatum, specimen ZSM-Mol- 20100322 N light microscopic picture O SEM scan P close-up of mucro and Q microsculpture R-U C. clathratum, specimen MNHN-IM- 2019 - 17 R light microscopic picture S SEM scan T close-up of mucro and U microsculpture. Scale bars: 10 µm (D, E, I, Q); 20 µm (H, M, P, U); 100 µm (A, B, C, L, N, O, T); 200 µm (F, G, J, K whole specimen); 300 µm (R, S).