Micropsectra radialis Goetghebuer 1939

Micropsectra radialis Goetghebuer, 1939

Material examined: 2 larvae, Norway, Svalbard, Nordenskioldland, Solryggen, Skartjørne, N77.96194° E13.82041°, 50 m, 0 7.viii.2008, T. Ekrem & K. Hårsaker; 1 larva Norway, Svalbard, Kapp Linné, Søndre Borgdam, N78.07055° E13.79345°, 35m, 08.viii.2008, leg. T. Ekrem & K. Hårsaker.

Diagnostic characters. Micropsectra radialis can be separated from other described Micropsectra larvae by having a short antennal pedestal (70–80 µm) including a short spur; antennal segment 2 about ¼ length of segment 1; labral seta SII pectinate; labral lamella with <30 teeth; posterior parapod with more than 100 claws in 2–3 rows.

Description (n = 3). Head capsule (Fig. 9) light yellowish-brown with darker posterior margins, mandibular teeth and mentum. Live individuals light red. Total length c. 10 mm.

Head capsule length c. 430 µm, width c. 350 µm; AR 2.2–2.5, 2.3; AHR c. 0.18; AAR c. 0.49; antennal pedestal 70–84, 78 µm long with short, triangular spur (Fig. 22); antenna with segments 1–2 well sclerotized, segments 3–5 pigmented, antennal seta placed at about 2/3 length of antennal segment 1; lengths of antennal segments (in µm): 157–163, 159; 40–46, 43; 12; 6; 6; Lauterborn organs small, on 60 µm long pedicels; LOR c. 2.4; SII simple or slightly pectinate; chaetae plumose, pectinate; chaetulae simple; S3 simple. Pecten epipharyngis consisting of three scales with parallel sided, blunt teeth (Fig. 23); premandible with 2 robust apical teeth and one small basal tooth, middle tooth broadest, brush well developed (Figs 23–24). Mentum (Fig. 25) about 120 µm wide; median tooth with lateral notches, tooth becomes rounded appearance in worn menta, somewhat paler than lateral teeth; ventromental plates 155 µm wide, slightly more curved laterally, with obvious striation along whole length; MVR c. 0.76; Mandible (Fig. 26) with 3 inner teeth, one apical tooth, one dorsal tooth; pecten mandibularis slightly convex; postoccipital arch broad, rounded, plate not developed.

Body. Anterior parapods with long, simple spines; posterior parapod with more than 100 simple hooks in two– three rows (Fig. 14); second lateral setae of segments 2–7 simple or split in two branches; anal segment with 4 anal tubules, c. 180 µm long; procercus with one short and one long dorsal seta, with 5 short (c. 600 µm) and 3 long (c. 1000 µm) anal setae.