Chaetozone hystricosa Doner & Blake, 2006

Blake, James A., 2022, New species and records of Caulleriella, Chaetocirratulus and Chaetozone (Annelida, Cirratulidae) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 5113 (1), pp. 1-89 : 71

Chaetozone hystricosa Doner & Blake, 2006

Figure 36

Chaetozone setosa Blake et al. 1998b : C-1 (in part). Not Malmgren, 1867.

Chaetozone hystricosus Doner & Blake, 2006: 69–71 , Fig. 3 , 5A, F .

Chaetozone hystricosa: Blake & Levesque 2017: 573 .

Material examined. (8 specimens) Northeastern United States, MWRA Harbor & Outfall Monitoring Program: Boston Harbor, Sta. T-05A: Rep. 2, 05 Aug. 2009, 42°20.38’N, 70°57.64’W, 17.5 m (2, MCZ 161948 ) .— Massachusetts Bay, 1997 August Survey , Sta. FF-04, Rep. 1, Aug 1997, 42°17.30′N, 70°25.50′W, 87 m (3, MCZ 1619490 ) ; Sta. FF-04: Rep. 2, 14 Aug. 2002, 42°17.30′N, 70°25.50′W, 90 m, 3 specimens on SEM stub ( MCZ 161950 ) .

Description. A moderately sized species, adults with 70–80 setigers, 9–15 mm long and up to 0.45 mm wide. Body long, dorsum rounded, venter flattened with mid-ventral groove ( Fig. 36A ); body segments generally short and crowded anteriorly and less so in posterior cinctured setigers bearing numerous acicular spines. Color in alcohol light tan, lacking any distinctive body pigment.

Pre-setiger region long, narrow, smooth, about as long as first seven setigers ( Fig. 36A ). Prostomium elongate, pointed anteriorly ( Fig. 36A–B ); eyespots absent; ciliated oval nuchal organs present on posterior lateral border with peristomium just anterior to oral opening ( Fig. 36B , inset). Peristomium smooth, lacking any grooves or annular rings, merging seamlessly with prostomium anteriorly and setiger 1 posteriorly ( Fig. 36A–B ); dorsal surface with elongate dorsal crest ( Fig. 36B ); dorsal tentacles arise anterior to setiger 1 with first pair of branchiae lateral and posterior to tentacles ( Fig. 36A–B ). Second pair of branchiae dorsal to notosetae on setiger 1; subsequent branchiae arise in similar position ( Fig. 36A–B ).

Anterior parapodia low rounded lobes from which setae emerge; noto- and neurosetae from setiger 1 all capillaries, 7–10 per fascicle in notopodia and 5–7 in neuropodia; capillaries of anterior setigers with fringe of fibrils along one edge ( Fig. 36G ). Long, thin natatory-like capillaries present along body, not associated with sexual maturity ( Fig. 36C–E ). Acicular spines from about setiger 40–45 in neuropodia and setiger 45–50 in notopodia. Posterior cinctured segments with deep intersegmental furrows separating highly elevated membranous podial lobes from which spines and capillaries emerge ( Fig. 36D–F ). In most posterior cinctured setigers, acicular spines 6–7 per fascicle in noto- and neuropodia with 12–14 spines on a side, with narrow dorsal and ventral gaps between fascicles ( Fig. 36D–E ); spines accompanied by alternating, long, thin capillaries ( Fig. 36H ); acicular spines curved, thickened, with blunt tips ( Fig. 36H ).

Pygidium a simple flattened lobe ventral to anal opening ( Fig. 36D–E ).

Methyl green staining. No pattern.

Remarks. Locally, Chaetozone hystricosa is readily recognized by the long, smooth pre-setiger region where there are no annular rings on the peristomium, which is merged almost seamlessly with both the prostomium and setiger 1. The long, narrow dorsal peristomial crest was not noted in the original description.

Globally, the only species of Chaetozone with a smooth, non-annulated pre-setiger region similar to that found in C. hystricosa , a continental shelf species, are two species from abyssal depths: Chaetozone reticulata Blake, 2018 from the Weddell Sea, Antarctica in 3111 m and Chaetozone truebloodi Blake, 2019 from the equatorial Pacific Ocean in 4880 m. Neither of the two deep-sea species, however, have a dorsal peristomial crest and the prostomium of both species is relatively short and rounded apically instead of being long, narrow, and acutely pointed. In addition, these two species have fewer posterior spines, up to 9 or 11 on a side, instead of 12–14 as in C. hystricosa .

Distribution. Northeastern United States, Boston Harbor to Massachusetts Bay, 15– 90 m.

Figures

FIGURE 3. Chaetocirratulus gayheadius. Holotype (LACM AHF-Poly 0564): A, anterior end, ventral view; B, anterior end, dorsal view; C, posterior end, dorsolateral view. Paratypes (LACM AHF-Poly 0565): D, 8-setiger post-larva, left lateral view; E, 7-setiger post-larva, right lateral view. B–C, E, dark spots denote MG stain; D, stippled areas denote MG stain.

FIGURE 5. Chaetocirratulus gayheadius. Juveniles from Sta. Ch 105-B, (LACM AHF-Poly 12721): A, 19-setiger juvenile, right lateral view; B, 28-setiger juvenile, right lateral view; C, 31-setiger juvenile, left lateral view; D, 34-setiger juvenile, right lateral view; E, 17-setiger juvenile, right lateral view; F, 27-setiger juvenile, left lateral view; G, 29-setiger juvenile, ventral view; H, neuropodial acicular spines and capillaries; I, detail of acicular spine. All stained with Shirlastain A.

FIGURE 36. Chaetozone hystricosa. SEMS, (MCZ 161950): A, anterior end, right lateral view; B, anterior end, left lateral view, inset of nuchal organ (not to scale); C, mid-body segments, lateral view; D, posterior segments and pygidium, lateral view; E, posterior segments and pygidium, dorsal view; F, two far posterior setigers with acicular spines and capillaries, lateral view; G, capillary notoseta from an anterior setiger; H, neuroacicular spines and capillaries from a far posterior setiger.