Lysilla

Londoño-Mesa, Mario H. & Carrera-Parra, Luis F., 2005, Terebellidae (Polychaeta) from the Mexican Caribbean with description of four new species, Zootaxa 1057, pp. 1-44 : 3

Lysilla sp.

Figures 1 A–C

Material examined: Mexican Caribbean: ECOSUR­TERE13 (1) R/V “Edwin Link”, sta. 2785, Punta Gavilan, Quintana Roo (18°21’N 87°47’W), 25 Aug. 1990.

Description: Specimen incomplete, broken in two pieces, with 26 segments; 11 mm long, thorax 5 mm long, 2.6 mm wide ( Figure 1 A). Dorsum not clearly segmented, but after staining, segments are differentiated. Tentacles of two sizes, the longest are thin, distally swollen; the shortest are stout. Tentacular membrane inconspicuously divided into lobes. Eyespots absent. Upper lip with folded free edge, formed by thin membrane. Lower lip swollen, with papillae only visible by staining. Lower lip projected toward the ventral shields. No lateral lappets. Nephridial papillae from segment 5 to 9, situated near the bases of notopodia, each as a low ring with pale center. Ventral shields thin, short, with midventral groove. Both sides of the shields with glandular tissues, more obvious after staining, from segment 2 to 11. Ventral abdominal region with a middle deep groove from segment 13. Parapodia from segment 2, with smooth capillary chaetae. Each fascicles with chaetae diminishing in length towards the ventral side ( Figure 1 B). Thorax with 10 long notopodia ( Figure 1 C).

Discussion: Lysilla sp. resembles Lysilla sp. A Kritzler, 1984 (Gulf of Mexico), by having a trilobed tentacular membrane; the two species differ because Lysilla . sp. has five pairs of nephridial papillae, 10 thoracic chaetigers, smooth capillary chaetae, and a well developed lower lip, while Lysilla sp. A lacks nephridial papillae, has 13 thoracic chaetigers, faintly hispid chaetae, and a inconspicuous lower lip. These specimens represent an undescribed species, but the condition of the materials precludes its description.

Distribution: Mexican Caribbean.

Figures

FIGURE 1. Lysilla sp. A. Ventral view; B. Chaetiger from segment 4; C. Parapodia from segment 8. Polycirrus holthei sp. nov. D. Dorsal view; E. Ventral view; F. Chaetae pinnate from segment 2; G. Thoracic uncini from segment 8 (0.02 mm); H. Abdominal uncini from segment 14. Scale bars: A, D, E, 1 mm; B 0.05 mm; C, 0.5 mm; F, G, H, 0.02 mm.