Kirkegaardia neotesselata, Blake, James A., 2016

Blake, James A., 2016, Kirkegaardia (Polychaeta, Cirratulidae), new name for Monticellina Laubier, preoccupied in the Rhabdocoela, together with new records and descriptions of eight previously known and sixteen new species from the Atlantic, Pacific, and Southern Oceans, Zootaxa 4166 (1), pp. 1-93 : 32-34

Kirkegaardia neotesselata new species

Figures 14 , 15 A–C

Tharyx annulosus: Maciolek et al. 1987 : Appendix D-2 (In part, Sta. 11). Not Hartman (1965).

Material examined. Western North Atlantic, Offshore New England, Georges Bank, continental slope south Cape Cod , US North Atlantic ACSAR Program, Cruse 2, R/V Oceanus, Sta. 11, Rep. 2, 0 4 May 1985, coll. G. Hampson , WHOI, Chief Scientist, 40°01.28′N, 70°55.09′W, 250 m, holotype and 7 paratypes (USNM 1407135– 6).

Description. Holotype, complete, 10 mm long, 0.26 mm wide across thoracic segments for about 75 setigers; however an exact segment count not possible due to worms being enclosed in tube materials ( Fig. 15 A–C). Body elongate, cylindrical throughout, with body segments wider than long in thoracic and anterior abdominal segments, becoming longer posteriorly, with some appearing oval or moniliform in shape; segments becoming narrow and crowded in far posterior segments forming an expanded posterior end terminating in a simple pygidium with terminal anus and single ventral lobe ( Fig. 14 B).

Pre-setigerous area somewhat bullet-shaped, 1.5x as long as wide; prostomium short, triangular, and narrowing to a pointed tip ( Fig. 14 A); nuchal organs at posterior-lateral margin; eyes absent. Peristomium with three lateral grooves producing up to four annular rings only apparent laterally ( Fig. 14 A); dorsum elevated, with mid-dorsal ridge along most of peristomium, continuing along mid-dorsal thoracic groove ( Fig. 14 A). Peristomium ending at anterior border of setiger 1, with demarcation clearly evident; dorsal tentacles arising from posterior margin ( Fig. 14 A). First pair of branchiae on setiger 1, dorsal to notosetae ( Fig. 14 A).

Thoracic region with about 10 setigers, but overall nature of anterior end obscured on several specimens due to tightly adhering tube material; channel between parapodia with a narrow mid-dorsal ridge present, continuing from peristomium and extending for 6–7 setigers, then merging with mid-dorsum and disappearing ( Fig. 14 A).

Parapodia weakly defined with only low tori from which setae arise. Notosetae long, slender, simple capillaries in anterior setigers, numbering about 6–8 per fascicle, some becoming thicker in mid-body segments, none with serrations or denticles; thoracic neurosetae short simple capillaries numbering 5–8 per fascicle in thoracic segments, becoming wider basally, with serrated edges present on setae of anterior abdominal segments (setigers 11–12) continuing to near posterior end ( Fig. 14 C); noto- and neurosetae of posterior setigers reduced to 2–4 per fascicle.

Methyl Green stain. Stain is retained on the prostomium and as stripes on the venter of posterior thoracic and anterior abdominal segments on the anterior border of each segment; these stripes generally encircle each segment up the lateral and dorsal most sides of each parapodium involved. No stain is retained on the peristomium, anterior thoracic segments, or the expanded posterior section.

Etymology. The epithet neotesselata is derived the Latin, neo for new and tessellatus for a mosaic and is derived from the name of its Pacific congener, K. tesselata , due to its having a similar tessellated tube structure.

Remarks. Eight specimens similar to K. tesselata from California were found in a sample from off New England in upper continental slope depths. The specimens were all enclosed by filamentous tube materials through which branchiae projected in groups at intervals along the body ( Fig. 15 A–C). This tube structure is similar in appearance to the tessellated or tattered tubes reported by Hartman (1960) and Blake (1996) for K. tesselata from offshore California. However, the tube material of the New England specimens is a hardened substance within which the worms are compressed and twisted upon preservation and from which they are difficult to extract; whereas, the tube material of K. tesselata is soft and pliable such that worms are easily removed intact. Further, careful inspection of these New England specimens revealed a species having a different morphology despite the similar appearing tube.

The most obvious morphological difference is that the parapodia of thoracic segments are elevated sufficiently high to produce a low mid-dorsal channel that is not evident in K. tesselata . The peristomium of K. neotesselata n. sp. is incised with three lateral grooves producing up to four annulated rings; in contrast, K. tesselata has a smooth peristomium with no evidence of annular rings. In addition, the peristomium has a mid-dorsal ridge that continues posteriorly as a mid-dorsal thoracic ridge within the dorsal channel. A mid-thoracic ridge is also present in K. tesselata , but it is not within a mid-dorsal thoracic channel. Finally, a MG staining pattern has not been observed for K. tesselata ; in K. neotesselata n. sp., however, the prostomium stains and stripes are present on the venter of posterior thoracic and anterior abdominal segments.

Locally off New England, K. neotesselata n. sp. is most closely related to K. baptisteae , which has also been found to have tessellated tubes. However, the tubes of K. baptisteae are soft and pliable as in K. tesselata and not the tougher tube material of K. neotesselata n. sp. Additionally, K. baptisteae has denticulated notosetae instead of lacking them, has no dorsal peristomial or thoracic ridge and while the parapodia are enlarged into prominent shoulders, the mid-dorsum is actually domed or elevated rather than weakly depressed.

Biology. These specimens were removed from a sample containing K. annulosa and specimens of Aphelochaeta spp. It is likely that additional records of K. neotesselata will be found in similar samples. The tough, closely adhering tubes readily separate this species from other cirratulids in the same samples.

Distribution. New England upper continental slope, 250 m.

Figures

FIGURE 14. Kirkegaardia neotesselata n. sp.: A, anterior end, dorsal view; B, posterior end, left ventrolateral view; C, denticulated neuroseta. (paratypes, USNM 1407136).

FIGURE 15. Kirkegaardia neotesselata n. sp.: A – C, photomicrographs of paratypes (USNM 14307136) within tessellated tubes; head of animal at the top. — Kirkegaardia sp. A, D, photomicrograph of specimen within tessellated tube, anterior end to the right (MCZ 35293).