Chaetozone careyi Blake, 2015, new species

Chaetozone careyi new species

Figures 7–8

Chaetozone setosa: Carey et al. 1984: 99, 103. Not Malmgren 1867. Chaetozone sp. Goldsmit et al. 2014, Table 1 S.

Material examined. Alaskan Arctic, Beaufort Sea, coll. off Pitt Point, 20 May 1976, 71°19ʹN, 152°38.5ʹW, 55 m, 0.1 m 2 Smith-McIntyre grab, Bell 205 helicopter, Sta. PPB-55, coll. A.G. Carey Jr., holotype (LACM-AHF Poly 6537), 1 paratype (LACM-AHF-Poly 6538); Beaufort Sea, coll. off Narwhal Island, 28 Aug 1976, 70°24.3ʹN, 147°29.2ʹW, 10 m, 0.1 m 2 Smith-McIntyre grab, R/V Aluminak Sta. NIB-15, coll. P.A. Montagna, 10 paratypes (LACM-AHF-Poly 6539).— Canadian subarctic, Hudson Strait, Deception Bay, Quebec, coll. Jésica Goldsmit, Sta. 4B, 0 2 Aug 2012, 62°13.187ʹN, 74°52.187ʹW, intertidal, in sand, 5 specimens (CMNA 2014-0015); Sta. 3D, 0 2 Aug 2012, 62°30.137ʹN, 74°48.614ʹW, 6.7 m, in sand and silt, 2 specimens (CMNA 2014-0016).

Description. A moderate-sized species, holotype complete, 11 mm long, 0.6 mm wide across thoracic region, with 118 setigerous segments; most paratypes complete, smaller than holotype; Deception Bay specimens of similar size, up to 11 mm long, 0.8 mm wide, for 90 setigers. Body relatively sleek in appearance, not expanded in anterior region, consistent in width along most of body, narrowing in far posterior setigers. Dorsal surface of body with weak longitudinal groove (Fig. 8 A), venter with distinct groove along entire length of body (Fig. 8 B). Color in alcohol light tan with no body pigment.

Prostomium triangular, acutely pointed on anterior margin (Figs. 7 A, 8A); eyes absent; nuchal organs not pigmented, narrow slits at posterior lateral margin of prostomium; peristomium elongate, with 3–4 rings (Fig. 7 A); peristomium extending dorsally over achaetous segment 1; dorsal tentacles arising over segment 2 (setiger 1) (Figs. 7 A, 8A); first pair of branchiae arising from achaetous segment 1; second pair of branchiae arising from segment 2 (setiger 1) lateral to paired medial dorsal tentacles and dorsal to notosetae; branchiae continuing on subsequent setigers (Fig. 7 A, 8A).

Anterior noto- and neurosetae all simple capillaries arranged in single rows of 5–6 notosetae and neurosetae; capillaries increasing to 6–8 per noto- and neuropodium in middle body segments. Some middle body parapodia with natatory-like capillary setae.

Neuropodial acicular spines first present from setigers 60–65, or about posterior one-third of body; notopodial acicular spines from about setiger 90 or near posterior end; spines single at first, then increasing to 5–7 in notopodia and 7–10 in neuropodia; spines forming distinct cinctures in posterior segments, with moderately developed elevated membranes and up to 17 spines on a side (Figs. 7 C, 8D). All acicular spines in cinctured segments alternating with long, thin capillaries; each spine thickened basally, curved, and tapered to blunt tip (Figs. 7 D, 8E).

Pygidium with elongate ventral lobe (Figs. 7 B, 8C).

Methyl Green staining pattern. No pattern.

Remarks. The characteristic that most defines C. careyi n. sp. is a shift in the position of the paired dorsal tentacles posteriorly over the first setiger and posterior to the first pair of branchiae. In most species of Chaetozone, including the other species described in this paper, the tentacles arise posteriorly on the peristomium but well anterior to the first branchiae and any of the setigerous segments. The situation in C. careyi n. sp. is similar to but not as extreme as that in C. bansei Blake, 1996, where the first tentacles are shifted posteriorly to setigers 4–7. C. careyi n. sp. and C. bansei are also similar in the cinctured posterior setigers, shape of the acicular spines, and the nature of the pygidium. However, C. careyi n. sp. further differs from C. bansei in lacking thickened anterior capillaries and a MG staining pattern, which is characteristic of C. bansei. In addition, in C. bansei the neuropodial acicular spines begin on setigers 28–29 or the anterior third of the body, whereas in C. careyi n. sp. they begin on setigers 60–65 or near the posterior third of the body; notoacicular spines begin about setiger 80 in C. bansei and setiger 90 in C. careyi n. sp. Originally described from shallow shelf depths offshore San Francisco, California, C. bansei ranges north to at least off Oregon (Blake unpublished), whereas C. careyi n. sp. appears to be limited to the North American Arctic and subarctic.

In correspondence and among the notes and illustrations left by Dr. Mary E. Petersen, was data on specimens of a species of Chaetozone from the Aleutian Islands, Dutch Harbor, Alaska coll. 30 September 1980, from shallow water grab samples provided by the University of Alaska, Fairbanks. These specimens were attributed to C. bansei by Dr. Petersen and were noted to have the dorsal tentacles shifted posteriorly over an anterior setiger and with the neuroaciculars from the posterior third of the body instead of the anterior third in C. bansei. This information agrees well with the characters of C. careyi n. sp. described here.

Biology and Ecology. The data from the Beaufort Sea project is only available in a report to the U.S. government (Carey et al. 1984). From this, C. careyi (as C. setosa) was part of an assemblage dominated by a suite of polychaetes including Capitella sp., Chone cf. murmanica Lukasch, 1910, Prionospio cirrifera Wirén, 1883, and Pholoe minuta (Fabricius, 1780).

Etymology. This species is named for Dr. Andrew (Drew) G. Carey, Oregon State University, Corvallis, Oregon, benthic ecologist and friend. Dr. Carey’s surveys in the Alaskan Arctic and in deep-sea habitats inspired several students, some of whom have developed their own careers in benthic ecology and taxonomy.

Distribution. Known from the Beaufort Sea, Alaska, to Hudson Strait, Canada, in shallow depths; Aleutian Islands; intertidal to 55 m.