Kirkegaardia cristata, 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: 42-44

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Kirkegaardia cristata

new species

Kirkegaardia cristata   new species

Figure 20 View FIGURE 20

Material Examined. Northeastern Pacific , Puget Sound, Case Inlet, Sta. 47, Rep. 1, 0 1 April 1993, 47.23300°N, 122.84984°W, 20 m, coll. MSMP, holotype (LACM-AHF Poly 8935). GoogleMaps  

Description. Holotype only specimen, mostly complete, 7.25 mm long, 0.4 mm wide across thorax, with 60 setigerous segments. Color in alcohol, light tan.

A slender, threadlike species, with narrow, tapering pre-setigerous region and thoracic region only slightly wider than peristomium ( Fig. 20 View FIGURE 20 A). Pre-setigerous region 1.6x as long a wide; as long as first 13 thoracic setigers ( Fig. 20 View FIGURE 20 A). Prostomium triangular, tapering to narrow rounded apex ( Fig. 20 View FIGURE 20 A); eyes absent; slit-like nuchal organs present on posterior lateral margins. Peristomium only slightly longer than wide; smooth with three lateral grooves posterior to prostomium producing four weakly developed annulations ( Fig. 20 View FIGURE 20 A); prominent dorsal ridge extending along peristomium from posterior margin of prostomium to posterior end of peristomium, then continuing as narrow bead-like ridge within mid-dorsal thoracic channel ( Fig. 20 View FIGURE 20 A). Dorsal tentacles on posterior margin of peristomium; first pair of branchiae lateral to tentacles between peristomium and anterior border of setiger 1 ( Fig. 20 View FIGURE 20 A); second pair of branchiae on setiger 1 dorsal to notosetae on posterior margin of segment overlying mid-dorsal channel; subsequent thoracic branchiae in same location ( Fig. 20 View FIGURE 20 A); anterior abdominal branchiae mostly missing, but appear to also be located on dorsum.

Thoracic region with 14–15 setigers, all narrow, first 10 thoracic setigers crowded, 11x wider than long, next five setigers 7x wider than long ( Fig. 20 View FIGURE 20 A). Subsequent anterior and middle abdominal setigers longer, 2.1x as wide as long ( Fig. 20 View FIGURE 20 B); posterior abdominal setigers becoming oval, moniliform ( Fig. 20 View FIGURE 20 C); last 1–2 narrow; pygidial segment absent. Thoracic region with venter swollen, rounded; anterior abdominal segments with prominent ventral groove; groove absent in posterior abdominal segments. Thoracic region with parapodia dorsally elevated overlying mid-dorsal channel continuing as narrow dorsal ridge ( Fig. 20 View FIGURE 20 A).

Dorsally elevated parapodia of thoracic region shifting to lateral position in abdominal segments ( Fig. 20 View FIGURE 20 B–C). Parapodia narrow ridges from which setae project; thoracic setae consisting of long simple capillaries with smooth margins, numbering 6–7 per notopodium and 8–9 per neuropodium; anterior abdominal setae similar but fewer in number with 4–5 in both noto- and neuropodia; neurosetae becoming shorter and broader; setae of posterior abdominal segments increasing to 5–6 in notopodia and 6–8 in neuropodia; denticulate noto- and neurosetae observed only with light microscopy in posterior abdominal setigers from about setiger 45 with denticles visible at 400x. Denticles of noto- and neurosetae similar, short, minutely pointed ( Fig. 20 View FIGURE 20 D–E). Denticles of notosetae directed ventrally, with denticles of neurosetae directed dorsally, vis-à-vis.

Methyl Green stain. Ventral surface of last 5–6 thoracic segments staining intensely as a large patch. Etymology. From the Latin, crista, for crest or ridge, referring to the mid-dorsal ridge or keel that starts on the peristomium and continues within the mid-dorsal channel.

Remarks. Kirkegaardia cristata   n. sp. belongs to a large group of 12 species that have the parapodia dorsally elevated and overlying a distinct mid-dorsal channel. Within this group, K. cristata   n. sp. belongs to a smaller subgroup including K. annulosa   , K. kladara   n. sp., and K. hampsoni   n. sp. that have a mid-dorsal ridge along the entire mid-line of the peristomium. K. cristata   n. sp. differs from all of these species in having four distinct annular rings on the peristomium instead of 0–2. In addition, K. kladara   n. sp. has the first branchiae arising from setiger 1 instead of posterolateral to the tentacular cirri on the peristomium as in K. cristata   n. sp. and the other two species. Although all four species have a prominent MG pattern on the venter of the peristomium, K. annulosa   and K. hampsoni   n. sp. have patches of stain on the peristomium that is entirely lacking in both K. cristata   n. sp. and K. kladara   n. sp.

Distribution. Known only from the Puget Sound, Washington, in ca. 20 m.