Chaetozone malmgreni, 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 : 522-524

publication ID

https://doi.org/ 10.11646/zootaxa.3919.3.5

publication LSID

lsid:zoobank.org:pub:743AF37E-54B4-4BCB-A3E8-93092F779A20

DOI

https://doi.org/10.5281/zenodo.5664940

persistent identifier

https://treatment.plazi.org/id/9A3E87FE-EB74-FFC8-D2F7-FED3FB4AF91B

treatment provided by

Plazi

scientific name

Chaetozone malmgreni
status

sp. nov.

Chaetozone malmgreni View in CoL new species

Figures 11–12 View FIGURE 11 View FIGURE 12

Chaetozone setosa: Blake 1996: 274 View in CoL –276, Fig. 8.1. Not Malmgren 1867.

Material examined. Oregon, Clapsop County, off Tillamook Head, Sta. SMG 1937, Scallops Island, 45°53.6ʹN, 124°11.9ʹW, 109 m, 0.1 m 2 Smith-McIntyre grab, coll. 7 Nov 1981, A.G. Carey, Jr. holotype (LACM-AHF Poly 6542), one paratype (LACM-AHF Poly 6543).

Description. A large species, two complete specimens; holotype largest, 25 mm long, 2.5 mm wide for 106 setigers; paratype 18 mm long, 1 mm wide for 82 setigers. Color in alcohol light tan to brown, lacking any distinctive body pigment. Body long, arched dorsally, with shallow, narrow, mid-dorsal groove along entire length of body ( Figs. 11 View FIGURE 11 A, 12A), most prominent in anterior setigers, but reemphasized in far posterior segments by overlap of setae and membranes of dorsal cinctures; venter flattened, with deep prominent mid-ventral groove ( Fig. 12 View FIGURE 12 B) continuing along entire body through cinctured posterior segments ( Fig. 11 View FIGURE 11 F).

Prostomium long, narrow, pointed on anterior end ( Figs. 11 View FIGURE 11 A–B, 12B, D); eyes absent; nuchal organs elongated slits on posterior margin of prostomium ( Fig. 11 View FIGURE 11 B); peristomium with large anterior inflated buccal region followed by two narrow annulations, second annulation interpreted as an achaetous segment bearing a pair of dorsal tentacles and a pair of branchiae positioned laterally ( Fig. 11 View FIGURE 11 A–B). Subsequent setigers with branchiae dorsal to notosetae ( Figs. 11 View FIGURE 11 A–B, 12D); anterior branchiae thicker than those of middle segments.

Setiger 1 of approximately same size as preceding achaetous segment and following segments; podial lobes reduced to inconspicuous ridges in anterior setigers, becoming inflated and conspicuous in middle setigers, greatly enlarged with elevated ridges in posterior setigers on deeply cinctured segments bearing conspicuous armature ( Fig. 12 View FIGURE 12 A–C); 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. 11 View FIGURE 11 F, 12A–C); small, ciliated organ present between ventral-most notopodial spine and dorsal-most neuropodial spine ( Fig. 11 View FIGURE 11 E); notopodial spines directed ventrally, neuropodial spines directed dorsally.

Noto- and neurosetae from setiger 1 all capillaries, numbering about 6–7 per fascicle; each seta thickened, with short fibrils usually apparent along broadest edge; these capillaries remaining thick and long until far posterior setigers. Acicular spines first present from setigers 20–35 in neuropodia and 40–45 in notopodia, numbering 2–3 at first, accompanied by an equal number of thickened capillaries; neuropodial spines numbering 8–9 per fascicle and notopodial spines numbering 7–8 per fascicle in far posterior setigers, spines forming complete setal cinctures with up to 17 spines on a side ( Fig. 9 View FIGURE 9 F); spines accompanied by alternating thin capillaries ( Fig. 11 View FIGURE 11 F); spines blunttipped, slightly curved, with weak node or notch at point of emergence from podial lobe ( Fig. 11 View FIGURE 11 E); spines with thick borders and fine internal striations.

Last few cinctured setigers narrowing to pointed posterior end ( Fig. 12 View FIGURE 12 A–C); pygidium with terminal anus and small flattened ventral lobe ( Figs. 11 View FIGURE 11 C–D, 12C).

Methyl Green staining pattern. Stain imparts distinct pattern on prostomium, peristomium, and anterior parapodia ( Fig. 12 View FIGURE 12 D). Anterior tip of prostomium unstained, then with transverse band, then clear again; peristomium lightly stained, but with deeper stain on dorsal surface of last achaetous ring. Anterior parapodia deeply stained laterally, with bands extending across venter and sometimes dorsum.

Remarks. Chaetozone malmgreni n. sp. is characterized by having one large and one narrow achaetous peristomial ring followed by another narrow achaetous segment that bears both the tentacles and first pair of branchiae. In addition, this species has deep dorsal and ventral grooves and a distinct MG staining pattern. Other species having the dorsal tentacles and first pair of branchiae on a single achaetous segment include C. lunula Blake, 1996 from northern California, C. corona Berkeley & Berkeley, 1941 , from southern California, C. allanotai Blake, 2006 from deep-water offshore California, and C. michellae Magalhães & Bailey-Brock, 2013 from Hawaii. C. lunula , however, has the peristomium shifted posteriorly so that the dorsal tentacles and first pair of branchiae are at the level of setiger 1; further differences with C. malmgreni n. sp. are that the ventral-most neuropodial acicular spine of C. lunula is typically bidentate and the pygidium has a terminal cirrus. C. corona differs from all Chaetozone species in North America in having neuropodial acicular spines beginning on setiger 1. C. allanotai belongs to a group of species having a distinct type of acicular spine where the fine tip curves back and fuses with the shaft. C. michellae has a deep dorsal groove along the entire body, whereas C. malmgreni has both a shallow dorsal groove and a deep ventral groove along the body; the two species have very different MG staining patterns.

There is also some similarity between C. malmgreni n. sp. and C. anasima Doner & Blake, 2006 and C. hystricosa Doner & Blake, 2006 , both described from New England waters. However, both of these species have indistinct annulations on the peristomium and the exact origin of the tentacles and first pair of branchiae are vague. Etymology. The species is named for Dr. A. J. Malmgren, who described the first species of Chaetozone , C. setosa , in his classic work on polychaetes from Greenland, Spitsbergen, Iceland, and Scandinavia in 1867.

Distribution. Known only from continental shelf sediments, offshore Oregon, 109 m.

Kingdom

Animalia

Phylum

Annelida

Class

Polychaeta

Order

Terebellida

Family

Cirratulidae

Genus

Chaetozone

Loc

Chaetozone malmgreni

Blake, James A. 2015
2015
Loc

Chaetozone setosa:

Blake 1996: 274
1996
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