Caecum cf. semilaeve Carpenter, 1857

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 cf. semilaeve Carpenter, 1857

Caecum semilaeve Carpenter, 1857: 319, pl. 33, figs 1526. Type locality: Mazatlán [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 & Absalão, 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 Absalão 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; Absalão and Gomes 2001). Caecum semilaeve is a species described as similar to C. liratocinctum ( Carpenter 1855-1857) and its type locality is Mazatlán, 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).

Figures

Figure 7. A-F Caecum pulchellum A, C, E, F specimen ZSM-Mol- 20090485 B, D juvenile specimen ZSM-Mol- 20200118 A, B light microscopic pictures C, D SEM scans E close-up of mucro and F microsculpture H-K C. donmoorei, specimen USNM 1618844 H-K C. regulare, specimen ZSM-Mol- 20100321, juvenile H light microscopic picture I SEM scans J close-up of mucro and K microsculpture L-T C. cf. teres and C. cf. strangulatum L specimen ZSM-Mol- 20200033, juvenile specimen with larval shell still attached M, N, Q, S specimen ZSM-Mol- 20200032, juvenile M light microscopic picture N SEM scan Q close-up of mucro and S microsculpture O, P, R, T C. cf. strangulatum, specimen ZSM-Mol- 20200038, juvenile O light microscopic picture P SEM scan R close-up of mucro and T microsculpture U-X C. cf. semilaeve, specimen ZSM-Mol- 20200034 U Light microscopic picture V SEM scan W close-up of mucro and X microsculpture. Scale bars: 10 µm (F, S, T, W, X); 20 µm (J, K, Q, R); 50 µm (E); 100 µm (H, I, L-P, U, V); 200 µm (A-D).