Chaetozone pugettensis, Blake, James A., 2015

Blake, James A., 2015, New species of Chaetozone and Tharyx (Polychaeta: Cirratulidae) from the Alaskan and Canadian Arctic and the Northeastern Pacific, including a description of the lectotype of Chaetozone setosa Malmgren from Spitsbergen in the Norwegian Arctic, Zootaxa 3919 (3), pp. 501-552 : 524-527

Chaetozone pugettensis new species

Figures 13–14

Material examined. Washington, Puget Sound, San Juan Islands, Decatur Island, Puget Sound Environmental Monitoring Program ( PSEMP) Spatial Survey, R/V Kittiwake Sta. 753, coll. 89 Jul 2012, 48°30.1315ʹN, 122°49.4996ʹW, grab, 9 m, silt and clay, holotype (LACM-AHF Poly 6544), 17 paratypes (LACM-AHF Poly 6545).

Description. A moderate-sized species, holotype and larger paratypes 12–13 mm long, 0.9–1.0 mm wide across anterior fourth of body, with 85–90 setigers. Color in alcohol light tan to brown, lacking any distinctive body pigment. Body with narrow crowded segments for two-thirds of body, without any prominent swelling or anterior enlargement ( Fig. 14 C–D); dorsal groove absent or weakly developed anteriorly ( Fig. 13 A), emphasized in far posterior segments by overlap of dorsal cinctures ( Figs. 13 A, 14F); venter flattened, with deep prominent midventral groove continuing along entire body through cinctured posterior segments ( Fig. 14 B, D).

Prostomium broadly triangular, narrowing anteriorly to bluntly rounded tip ( Figs. 13 A, 14A–B); eyes absent; nuchal organ at posterior lateral margin, consisting of narrow slit, sometimes weakly pigmented ( Fig. 13 B). Peristomium with two large rings, both overlain dorsally by an inflated ridge or crest extending posteriorly to level of setiger 1; these peristomial rings followed by narrow achaetous segment having a similar shape as setiger 1. Dorsal tentacles arising from groove at posterior end of second large peristomial ring ( Figs. 13 A–B, 14A); first pair of branchiae arising posterior to tentacles on posterior margin of achaetous segment; achaetous segment approximately same size as subsequent setigers, sometimes with a lateral furrow ( Figs. 13 A–B, 14A); second pair of branchiae arising dorsal to notosetae on first setiger immediately posterior to achaetous segment 1 ( Figs. 13 A, 14A); subsequent setigers with branchiae dorsal to notosetae; branchiae of anterior setigers thicker than those in middle segments.

Setiger 1 of approximately same size as preceding achaetous segment and subsequent setigers; podial lobes reduced to inconspicuous ridges in anterior setigers; becoming inflated and conspicuous in middle setigers and greatly enlarged with elevated ridges in posterior setigers, with conspicuous armature; posterior segments separated by deeply cut intersegmental furrows and with highly elevated membranous podial lobes from which spines and capillaries emerge, forming full cinctures ( Figs. 13 C, 14E); notopodial spines directed ventrally, neuropodial spines directed dorsally ( Fig. 14 F).

Noto- and neurosetae from setiger 1 all capillaries, numbering 8–10 per fascicle; each seta thickened, with fibrils usually apparent along broadest edge; these capillaries remaining thick and long until far posterior setigers; long natatory-like capillary setae not observed; acicular spines first present from about setigers 50–53 in neuropodia and 60 in notopodia, or the posterior one-third of the body on specimens with 85‒90 setigers; spines numbering 2–3 at first, accompanied by an equal number of thickened capillaries; in far posterior setigers notopodial spines numbering 8–9, and neuropodial spines numbering 9–10, formed into complete setal cinctures, with spines alternating with thin capillaries ( Fig. 13 D–F) with up to 19 spines on a side; spines blunt-tipped, slightly curved, with weak node or notch at point of emergence from podial lobe; with thick borders and fine internal striations ( Fig. 14 G–H).

Last few cinctured setigers tapering to narrow posterior end; pygidium with terminal anus and small flattened ventral plate or disk ( Figs. 13 C, 14E).

Methyl Green staining pattern. No distinct pattern.

Remarks. Chaetozone pugettensis n. sp. closely resembles the type species, C. setosa in the nature of the two large peristomial rings, overlaid dorsally by an inflated and sometimes bulbous dorsal ridge or crest; the form and placement of the achaetous segment anterior to setiger 1; position of the dorsal tentacles and first pair of branchiae; and the number and structure of the posterior spines. Both species also have the noto- and neuropodial acicular spines from the posterior third of the body and both have weakly developed dorsal grooves and well-developed ventral grooves along the body. C. pugettensis n. sp. differs from C. setosa in that the type species exhibits long natatory-like capillaries on most body segments including among the posterior spines whereas no specimens of C. pugettensis n. sp. in the present collection have been observed with these setae. Another important difference is that C. setosa has a distinct MG staining pattern, whereas C. pugettensis n. sp. has none.

Etymology. This species is named for its collection in the Puget Sound, offshore Decatur Island.

Distribution. Puget Sound, in silt and clay, shallow water, 9 m.

Figures

FIGURE 13. Chaetozone pugettensis n. sp. A, anterior end, dorsal view; B, anterior end, right lateral view; C, posterior end, dorsal view; D, posterior parapodium, anterior view; E, detail of posterior notopodial acicular spines and capillaries; F, detail of posterior neuropodial acicular spines and capillaries. (All paratypes LACM-AHF Poly 6545).

FIGURE 14. Chaetozone pugettensis n. sp. Photomicrographs: A, anterior end, dorsal view; B, anterior end, ventral view; C, entire animal; D, anterior end, right lateral view; E, posterior end showing elevated parapodia with spines and pygidial segment; F, posterior parapodium, anterior view; G, detail of posterior notopodial acicular spines and capillaries; H, detail of posterior neuropodial acicular spines and capillaries. (All paratypes LACM-AHF Poly 6545; all stained with Shirlastain A).