Semiodera villalobosi, Salazar-Vallejo, 2012

Salazar-Vallejo, Sergio I., 2012, 3562, Zootaxa 3562, pp. 1-62 : 41-42

Semiodera villalobosi n. sp.

Figure 16

Type material. Northwestern Caribbean Sea , Chinchorro Bank. Holotype ( ECOSUR 142 ) and paratype ( ECOSUR 143 ), SW off Chinchorro Bank, RV Edwin Link, Sta. 2782 (18°34.41' N, 87°26.89' W), calcareous rock, 290.3 m depth, 23 Aug. 1990, E. Escobar, L. Soto & J.L. Villalobos, coll. (paratype complete, 18 mm long, 2 mm wide, cephalic cage slightly damaged, 14 mm long, 49 chaetigers).

Additional material: Northwestern Caribbean Sea , Chinchorro Bank. Four specimens ( ECOSUR 1769 ), two complete, an anterior fragment and the other without posterior end, partially dried-out, E off Cancun, RV Edwin Link, Sta. 2792a (21°16.44' N, 84°30.5' W), calcareous rock, 123.5 m depth, 28 Aug. 1990, E. Escobar, L. Soto & J.L. Villalobos, coll. (complete specimens 11–16 mm long, 1.2–1.8 mm wide, cephalic cage 12–13 mm long, 46–48 chaetigers). One specimen ( ECOSUR 1770 ), complete, E off Cancun, RV Edwin Link, Sta. 2792b (21°16.44' N, 84°30.5' W), calcareous rock, 139 m depth, 28 Aug. 1990, E. Escobar, L. Soto & J.L. Villalobos, coll. (20 mm long, 2 mm wide, cephalic cage 12 mm long, 50 chaetigers; dissected for anterior end features) .

Description. Holotype (ECOSUR-0000) white, cylindrical, tapering posteriorly ( Fig. 16A); 15 mm long, 3 mm wide, cephalic cage 15 mm long, 50 chaetigers. Tunic thin, without sediment; body papillae digitate, arranged in a single row per segment.

Anterior end observed in a non-type specimen (ECOSUR). Cephalic hood short, margin smooth. Prostomium low lobe, dark-brown eyes, coalescent. Caruncle not visible, not projected dorsally; palps keels or lips not visible.

Branchiae cirriform, sessile on branchial plate, decreasing in size laterally, about 12 filaments; two larger, distal filaments, other filaments progressively smaller. Nephridial lobes not seen. Palps as long as, and 2–3 times thicker than branchiae. Palps and branchiae with tips yellowish (paratype with 8 branchial filaments of different lengths exposed).

Cephalic cage chaetae as long as body length, or five times longer than body width. Chaetigers 1–2 involved in the cephalic cage. Cephalic cage chaetae arranged in short lateral and ventral rows on each chaetiger; eight noto- and 4–6 neurochaetae per bundle.

Anterior dorsal margin of first chaetiger with two large lobes, separated by a longitudinal cleft, each lateral lobe with two small papillae ( Fig. 16C) (fused in paratype). Anterior chaetigers with long papillae restricted to chaetal lobes in first two chaetigers. Chaetigers 1–2 of about the same length, chaetiger 3 longer. Sand cemented anterior shield oval, barely projected posteriorly beyond chaetiger 5 ( Fig. 16B), continued laterally and ventrally, but only covering up to chaetiger 3 ventrally ( Fig. 16C, D). Particles larger dorsally. Chaetal transition from cephalic cage to body chaetae gradual; pseudocompound hooks in chaetigers 4–6. Simple falcate neurohooks from chaetiger 7. Gonopodial slits in chaetiger 5, transverse short slightly darker cushion (duplicated in chaetigers 5–6 in paratype; not duplicated in other specimens).

Parapodia poorly developed; only chaetigers 1–2 with projected lobes and long papillae; others with chaetae emerging from the body wall. Parapodia lateral, neuropodia ventrolateral.

Median notochaetae arranged in transverse tufts. Notochaetae of median chaetigers multiarticulate capillaries, as long as 1/5–1/6 body width, 2–3 per fascicle, each notochaetae with short articles basally, difficult to be detected or missing, median and distal regions with long articles ( Fig. 16G). Neurochaetae multiarticulate capillaries in chaetigers 1–3; pseudocompound neurohooks in chaetigers 3–6, two per fascicle, decreasing in size posteriorly. Falcate neurohooks from chaetiger 7, arranged in transverse rows, 3–4 in first few chaetigers, thereafter up to 7 per bundle in median region ( Fig. 16F), gradually decreasing to one per bundle in far posterior chaetigers.

Posterior end tapering; pygidium conical,, terminal anus, without anal cirri.

Etymology. The species name is to honor Dr. José Luis Villalobos-Hiriart, a famous Mexican carcinologist in recognition of his fine studies on tropical American crustaceans and especially because he participated in the Edwin Link expedition to Chinchorro. The samples collected during this Expedition are included in this paper.

Variation: The specimens were 11–20 mm long, 1.2–3.0 mm wide, cephalic cage 12–15 mm long, and had 46–50 chaetigers. The relative size of the cephalic cage is remarkably large in comparison with other adult species of Semiodera .

Remarks. Semiodera villalobosi n. sp., resembles S. glynni n. sp. because both have a poorly developed dorsal shield, 3–4 neurohooks per bundle, and first falcate neurohooks from chaetiger 7. They differ regarding the extension of the dorsal shield and by the number of transverse rows of papillae; S. villalobosi has a shield extended laterally and ventrally and a single row of papillae, whereas S. glynni has a shield restricted to the dorsal surface and three rows of papillae.

This species was collected during the RV Edwin Link expedition to the Chinchorro Bank, Northwestern Caribbean Sea; some of the published results include mollusks ( González 1998), caridean shrimps (Escobar- Briones & Villalobos-Hiriart 2003) and amphipods ( Winfield & Escobar-Briones 2007).

Distribution. Apparently restricted to the Northwestern Caribbean Sea region, in rocky substrates at 123–290 m depth.