Pista cf. quadrilobata (Augener, 1918)

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 : 29-31

Pista cf. quadrilobata (Augener, 1918)

Figures 8 A–E

Nicolea quadrilobata Augener, 1918:532 , Pl.6, fig.183, Pl. 7, fig. 226–227, text­fig. 90. Pista quadrilobata Day, 1967:740 , figs. 36.8a–e.

Material examined: Mexican Caribbean: ECOSUR TERE­21 (2) QR4 Playa Aventuras (20°20’15.5’’N 87°20’31.7’’W), 21 Mar. 1992, in coralline rock, 2m.

Description: Complete specimen, body dark on preserved material, with 77 segments, 12 mm long; thorax 3.5 mm long, 0.5 mm wide ( Figures 8 A–B). Tentacles short. Tentacular membrane dorsally reduced and well developed laterally, with ventral margins. Eyespots small, placed laterally on the tentacular membrane arranged in rows of 5–6 eyespots. Upper lip long and folded, free edge, projecting forwards; lower lip swollen and conspicuous. Three pairs of lateral lappets, on segments 1–3; first pair not covering tentacular membrane, well developed ventrally; second and third pairs dorsally reduced, projecting ventrolaterally; third pair covering dorsal part of second pair; lappets not forming branchial cavity. Two pairs of branchiae, branched, on segments 2 and 3, branchia with long stalk, ending with digitate tips; first pair longer than the second one, extending forwards beyond upper lip. With two pair of white nephridial papillae, on segments 5 and 6, inserted dorsal to notopodia, as long as notopodia. Eighteen ventral shields, starting from segment 2, anterior shields rectangular, beyond segment 5 square, placed in a depressed ventral region. Abdomen with midventral groove. Thorax with 17 pairs of notopodia from segment 4. Notochaetae of two sizes, long chaetae twice as long as the short chaetae, straight, distally bilimbate, limb on one side broader than the other; short chaetae curved, distally bilimbate, with both limbs equal­sized ( Figure 8 C). Neuropodia from segment 5, uncini arranged in single rows on segments 5–10, in double rows on segments 11–20, in face to face position, in single row from segment 21 until pygidium. Uncini from segment 5 with dental formula MF:3:3:2–3:1–2 ( Figure 8 D), with rounded upper subrostrum, well developed subrostral process, without appendix; concave lower subrostrum; short anterior process, without filament; basis curved near to anterior process and straight before well developed posterior process, with long filament; short occipitium, concave in the lower region and straight in the upper region, ending in a toothed capitium. Uncini from segment 8 ( Figure 8 E) and posterior body similar to those from segment 5, but with short posterior process. Pygidium small, reduced, without anal papillae. Tube made off small white coarse sand attached to a weak membrane; 1 mm wide.

Var ia t io n: The total number of segments in all specimens complete revised varies from 61 to 81 segments.

Remarks: These specimens resemble P. quadrilobata (Augener, 1918) from southwestern Africa, because of the presence of eyespots, uncini from first three neuropodia with long posterior process (manubrium) and by the absence of branchial cavity. Day (1967) indicated that uncini on the first pair of neuropodia have a long occipitium and a posterior process, but in the specimen from the Mexican Caribbean they have a short occipitium. Furthermore, these specimens have three pairs of lateral lappets, the second and the third reduced, while in the African specimens, only the second pair is dorsally reduced. Kritzlers (1984) records are closer to the African forms than to Mexican Caribbean specimens for having the second pair of lateral lappet dorsally reduced. We consider doubtful that Mexican specimens belong to P. quadrilobata because of the reasons above, but it is necessary to compare material from both localities to determine whether this material represent P. quadrilobata or not.

Distribution: Mexican Caribbean.

Figures

FIGURE 8. Pista cf. quadrilobata: A. Lateral view; B. Ventral view; C. Chaetae from segment 15; D. Uncinus from segment 5; E. Uncinus from segment 8. Terebella verrilli: F. Ventral view; G. Anterior end in dorsal view with nephridial tube; H. Chaetae from segment 10; I. Chaeta from segment 10; J. Chaetae from segment 50; K. Uncini from segment 10. Scale bars: A, B 1 mm; C, D, E, I, J 0.02 mm; F 1 mm; G 0.5 mm; H 0.05 mm; K 0.01 mm.