Kirkegaardia kladara Blake, 2016, new species

Kirkegaardia kladara new species

Figures 10 D, 11

Tharyx sp. 4: Blake et al. 1987: C-2; Hilbig 1994: 941.

Material examined. Western North Atlantic, off Cape Lookout, North Carolina, U.S. South Atlantic ACSAR Program Cruise 1, R/ V Columbus Iselin Sta. 1, Rep. 2, 11 November 1983, 34°16.36′N, 75°45.50′W, 640 m, coll. J.A. Blake, Chief Scientist, holotype (USNM 1407164); Cruise 2, R/V Cape Hatteras, Sta. 2, Rep. 3, 27 March 1984, 34°14.56′N, 75°43.35′W, 1000 m, coll. J.A. Blake, Chief Scientist, 1 paratype (USNM 1407165).

Description. An elongate, thin, fragile species; holotype complete, 24 mm long, 0.3 mm wide with about 95 setigers; paratype incomplete, 4.36 mm long, 0.23 mm wide across thorax, for 19 setigers. Body of holotype covered with closely adhering silt particles. Color in alcohol, light tan with no pigment.

Pre-setigerous region 1.8x as long as wide. Prostomium narrow, rounded on anterior margin, continuing as a narrow peristomial ridge or dorsal crest to anterior border of setiger 1 (Fig. 11 A); eyes absent; nuchal organs not observed. Peristomium elongate, narrow, about 1.6x as long as wide; smooth, without obvious annulations (Fig. 11 A). Dorsal tentacles arising on posterior part of peristomium with first pair of branchiae posterior to tentacles on setiger 1 at posterior margin overlying mid-dorsal groove (Fig. 11 A). Subsequent branchiae in same position on following thoracic setigers. Branchiae of thoracic segments dorsal and posterior to notosetae at border with middorsal channel; thereafter, parapodia shifting to lateral position in abdominal segments (Fig. 11 B–C); branchiae not observed in far posterior segments.

Thoracic region with 7–9 setigerous segments, each about 3x as wide as long (Fig. 11 A); abdominal segments increasing in length and decreasing in width to about 2.5x as long as wide, each more or less cylindrical with parapodia at posterior end (Fig. 11 B); thoracic parapodia dorsally elevated over mid-dorsal surface forming shallow dorsal groove extending from end of peristomium posteriorly to about setiger 7 where dorsal groove ends (Fig. 11 A); contained dorsal ridge extends to about setiger 5, continuing on setigers 5–7 as low elevated mid-dorsal mounds between parapodia (Fig. 11 A). Body without ventral groove or ridge. Far posterior segments becoming short again, wider than long, greatly expanded posterior end terminating in pygidium with narrow pointed ventral lobe (Fig. 11 C).

Parapodia reduced to low mounds from which setae project; thoracic setae consisting of long simple capillaries numbering 5–6 per notopodium and 6–8 per neuropodium; anterior abdominal noto- and neurosetae transitioning to broader capillaries with broad bases and fine denticles along margin from setigers 10–12 (Fig. 11 D–E); abdominal notosetae 2–4 per notopodium; neurosetae 4–6 per neuropodium; denticles minute, pointed teeth directed lateral to main axis of shaft (Fig. 11 D–E) visible at 400– 1000x. Notosetae with denticles directed ventrally and denticles of neurosetae directed dorsally, vis-à-vis.

Methyl Green stain. Tip of prostomium lightly retaining stain; peristomium not staining. Distinctive pattern on middle and posterior thoracic segments consisting of diffuse turquoise speckles anteriorly and larger, darker turquoise speckles posteriorly (Fig. 10 D); stain extends laterally up the sides of the parapodia, but does not enter the mid-dorsal channel. Posteriorly, individual parapodia at the posterior edge of each abdominal segment stain Green (Fig. 10 D); no mid-ventral stain retained.

Etymology. The species name kladara is from the Greek, kladaros for brittle or easily broken, referring to the thin, fragile nature of this species.

Remarks. Kirkegaardia kladara n. sp. has only rarely been collected most likely because of the thin, fragile nature of the body and high probability of damage during sample processing. K. kladara n. sp. belongs to the K. dorsobranchialis - heterochaeta group of 12 species in having the thoracic parapodia elevated and producing a middorsal channel between them. Of these, K. kladara n. sp. is one of four species having a peristomium with a dorsal ridge extending along its entire length. K. kladara n. sp. differs from K. annulosa and the others in this group of four by having the first pair of branchiae arising from setiger 1 instead of lateral to the dorsal tentacles on the peristomium. Furthermore, the short, rounded prostomium that is continuous with the mid-dorsal peristomial ridge differs from these species and other species of the genus Kirkegaardia. Other details are presented in the Remarks for K. annulosa (see above).

Distribution. Kirkegaardia kladara was collected only from samples taken in muddy sediments along the continental slope off Cape Lookout, North Carolina, in depths of about 640–1000 m. The species was not identified on the nearby Cape Hatteras shelf or in the companion surveys off the U.S. Mid- and North Atlantic slopes.