Uncovering the shell game with barcodes: diversity of meiofaunal Caecidae snails (Truncatelloidea, Caenogastropoda) from Central America Author Egger, Christina SNSB-Zoologische Staatssammlung Muenchen, Muenchhausenstr. 21, 81247 Munich, Germany & CCMAR, Campus de Gambelas, Universidade do Algarve, 8005 - 139 Faro, Portugal https://orcid.org/0000-0002-6678-2549 christinaegger@gmx.de Author Neusser, Timea P. LMU Munich, Biocenter, Dept. II, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany Author Norenburg, Jon Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA Author Leasi, Francesca Department of Biology, Geology and Environmental Science. University of Tennessee at Chattanooga. 615 McCallie Ave. Chattanooga, TN 37403, USA Author Buge, Barbara Museum national d'Histoire naturelle, 55 Rue Buffon, 75231 Paris, France Author Vannozzi, Angelo Independent researcher, Via M. L. Longo 8, Rome, Italy Author Cunha, Regina L. CCMAR, Campus de Gambelas, Universidade do Algarve, 8005 - 139 Faro, Portugal Author Cox, Cymon J. CCMAR, Campus de Gambelas, Universidade do Algarve, 8005 - 139 Faro, Portugal Author Joerger, Katharina M. SNSB-Zoologische Staatssammlung Muenchen, Muenchhausenstr. 21, 81247 Munich, Germany text ZooKeys 2020 968 1 42 http://dx.doi.org/10.3897/zookeys.968.52986 journal article http://dx.doi.org/10.3897/zookeys.968.52986 1313-2970-968-1 4296306E51B94873AB6F4B475194CA98 0ABFD46F13B65EEE97867BC2166A59E3 Caecum cf. semilaeve Carpenter, 1857 Caecum semilaeve Carpenter, 1857: 319, pl. 33, figs 1526. Type locality: Mazatlan [Mexico]. Material examined. Panama • 1 juv.; Achotines; 7.6207 , -80.0013 ; depth 12 m; 29 Feb 2016; USNM Achotines 2016 exped.; Stat. PA14; DNA voucher; DNA bank: r462p2f2t91; GenBank: MT704282, MT731716; ZSM-Mol-20200028. • 1 juv. (Fig. 7U-X ); Achotines; 7.6349, -79.9968; depth 10 m; 6 Mar 2016; USNM Achotines 2016 exped.; Stat. PA23a; DNA voucher; DNA bank: r462p8f2t91; GenBank: MT704285, MT731719; ZSM-Mol-20200034. Shell morphology. Shell very thin, delicate and highly translucent, glossy (Fig. 7U ). Size 1.0 mm long, 0.5 mm wide. Tube gradually narrowing towards posterior end and evenly curved. Septum blistered, entirely below posterior tube end (Fig. 7W ). Posterior end fringed and in specimen ZSM-Mol-20200034 still connected partly with mucro indicating a recent shedding of transitional septum. Mucro with elongated, rounded tip, only slightly extending from tube (Fig. 7W ). Aperture bordered by very tiny sharp lip, otherwise fragile (Fig. 7X ). Shell surface smooth, no sculpture visible apart from regular growth lines. Shell covered by organic layer (periostracum). Remarks. The examined shells all belong to juveniles due to their fragile character and the unfinished aperture. Therefore, it will be critical to reassess these observations based on mature shell structures, as sculpturing is known to be variable during development (see e.g., C. metamorphosicum S. Lima, Santos & Absalao , 2013 in Lima et al. 2013 ). The specimens investigated here build and shed transitional septa as described by Pizzini et al. (1998) . Specimens that show a similar mucro are Caecum lineicinctum de Folin, 1880 (compare Absalao and Gomes 2001 : 10, figs 1, 2), C. liratocinctum Carpenter, 1857; however, both occur in the Western Atlantic ( de Folin 1880 ; Moore 1972 ; Lightfoot 1992a ; Absalao and Gomes 2001 ). Caecum semilaeve is a species described as similar to C. liratocinctum ( Carpenter 1855-1857 ) and its type locality is Mazatlan , Mexico, Eastern Pacific, thus with geographic proximity to the localities of our investigated specimens (Achotines, Panama, eastern Pacific). We therefore assign our material to C. semilaeve . However, identification remains uncertain without having observed the manifestations of the shell sculpture as described for C. semilaeve in later developmental stages (compare syntypes C. elongatum var. semilaeve NHMUK 1857.6.4.1526).