Chaetozone spinosa Moore 1903

Chaetozone spinosa Moore, 1903

Chaetozone spinosa Moore, 1903: 468–470, pl. 26, figs. 73–74; Imajima & Hartman 1964: 297–298; Blake 1996: 300–303, figs. 8.13–8.14; Blake 2006: 54, fig. 6E–I.

Material examined. Off Peru, Peru-Chile Trench, SEPBOP, R / V Anton Bruun Cr. 17, Sta. 663-C, 13°44ʹS, 77°33ʹW, Menzies trawl, 4100 m, 2 specimens (USNM 1490777).

Descriptive remarks. Chaetozone spinosa is a deep-sea species previously known from off Japan and northern California (Blake 1996, 2006). The two incomplete specimens from the Peru-Chile Trench are smaller than those from off California but agree well with the descriptions presented in those two papers. A brief description follows.

In this species, the body is thickest anteriorly and broadly flattened dorsally (Blake 2006: Fig. 6E). The prostomium is short, triangular, and fused with and mostly indistinguishable from the peristomium. The prostomium and peristomium together form a large, heart-shaped head that is distinctly set off from a reduced segment 1 (Blake 2006: Fig. 6 E–F). Segment 1 lies between the peristomium and setiger 1 and is visible both dorsally and laterally (Blake 2006: Fig. 6F); the first pair of branchiae arise on this reduced segment as apparently do the tentacles.

Setiger 1 is larger than following ones, bearing a pair of branchiae located dorsal to notochaetae. Setae of anterior segments include capillaries; long natatory capillaries are present on the two specimens here. The noto- and neurosetal fascicles of capillaries nearly merge laterally, with little space between them. Neuropodial acicular spines are present from setigers 21–25 (per Blake 2006), but in the present smaller specimens they occur from setiger 12–13; notopodial acicular spines occur from setiger 29 in the larger specimen.

General remarks. The two specimens, while incomplete, are well preserved and retain the form of the unusual pre-setal “head” that dominates the anterior end and provides ready recognition for this species. The narrow achaetous segments between the “head” and setigerous segments are as previously described.

Chaetozone spinosa is a deep-sea species; the present specimens from the Peru-Chile Trench represent its deepest record and most southern location.

Distribution. Off Japan, 280 m; off California, ca. 2000–3100 m; Peru-Chile Trench, 4100 m.