Chaetozone

Key to 21 species of Chaetozone from the Northeastern Pacific and North American Arctic and Subarctic

(Reference code: 1, Blake 1996; 2, Blake 2006; 3, this paper. Note: Chaetozone gracilis Moore, 1923 and C. armata Hartman, 1963, both redescribed in Blake [1996] are rare species not included in this key; both lack posterior cinctures and may belong to other genera. MG = Methyl Green).

1A. Paired dorsal tentacles on posterior margin of peristomium shifted posteriorly over anterior setigerous segments.......... 2

1B. Paired dorsal tentacles on posterior margin of peristomium or anterior achaetous segment, not shifted posteriorly over setiger- ous segments......................................................................................... 4

2B. Dorsal tentacles shifted dorsally over setiger 1............................................................... 3

2B. Dorsal tentacles shifted dorsally over setigers 4‒7; with distinct MG staining pattern......................... C. bansei 1

3A. With distinct achaetous segment preceding setiger 1, bearing first pair of branchiae; all spines in posterior cinctures unidentate; no MG staining pattern..................................................................... C. careyi n. sp. 3

3B. Without distinct achaetous segment preceding setiger 1, first pair of branchiae on setiger 1; ventral-most spine in posterior neu- ropodia of cinctures bidentate; with distinct MG staining pattern......................................... C. lunula 1

4A. Posterior noto- and neuropodial spines with sharply pointed with recurved tip extending posteriorly and fused with shaft form- ing blunt tip.......................................................................................... 5

4B. Posterior noto- and neuropodial spines sharply pointed or blunt, not with recurved tip............................... 7

5A First pair of branchiae on setiger 1; no MG pattern............................................... C. commonalis 1

5B. First and second pair of branchiae both on setiger 1........................................................... 6

6A. Posterior spines from posterior third of body, or about setiger 65 in neuropodia and setiger 70 in neuropodia; dorsal longitudi- nal groove absent; with thin ridge along ventral midline; posterior cinctures well developed, with 26‒29 spines on a side, over-

lapping at dorsal midline of each cincture; MG staining prostomium and peristomium, but with clear unstained curved dorsal band between at posterior margin of prostomium.................................................... C. allanotai 2 6B. Posterior spines from middle body segments, or setigers 30‒40 in neuropodia and 40‒45 in notopodia; shallow dorsal groove from anterior through middle segments, absent posterior segments; ventral groove in middle segments; posterior cinctures well developed, with 20‒23 spines on a side; MG on tip of prostomium and last two peristomial rings...... C. camasetosa n. sp. 3

7A. With distinct achaetous segment between peristomium and setiger 1, may be partially fused to setiger 1................. 8

7B. Without distinct achaetous segment between peristomium and setiger 1.......................................... 15

8A. Achaetous segment bearing both first pair of branchiae and dorsal tentacles........................................ 9

8B. Achaetous segment bearing only first pair of branchiae; dorsal tentacles arising from peristomium or notch at posterior margin................................................................................................... 10

9A. Body with distinct enlargement (stomach) between esophagus of thoracic segments and intestine of abdominal segments, this imparting characteristic shape to body; with brown pigment over most of body, concentrated in anterior segments; posterior cinctures well developed, with 16‒18 spines on a side; no MG pattern evident............................ C. brunnea 2

9B. Body without distinct morphological enlargement except for segments sometimes swollen with gametes; pigment absent; posterior cinctures well developed, with 15-17 spines on a side; MG pattern on prostomium, peristomium, and anterior parapodia; peristomium with two prominent annulations anterior to achaetous segment separated by deep grooves, first annulation inflated, twice size of second............................................................ C. malmgreni n. sp. 3

10A. Neuropodial spines from setiger 50–70 or greater in middle body segments, in middle body segments; spines arranged in partial or complete cinctures; MG staining pattern present or absent............................................... 11

10B Neuropodial spines from setiger 5‒40 in anterior third of body; spines arranged in partial or complete cinctures; MG staining pattern present or absent............................................................................... 12

11A. Neuropodial spines from setiger 70 or greater; posterior cinctures partial, with up to 14 spines on a side; peristomium not overlain with dorsal crest; MG stains prostomium and peristomium intensely, except for tip of prostomium and dorsal surface of peristomial annulations; parapodia with weak stripes across dorsum and venter........................... C. hedgpethi 1

11B. Neuropodial spines from setiger 50‒53; cinctures with 17‒19 spines on a side; peristomium overlain with prominent crest; no MG pattern......................................................................... C. pugettensis, n. sp. 3

12A. Posterior cinctures with 20‒22 unusually long, broad, flattened, pointed noto- and neuropodial spines on a side, without accompanying capillaries; with MG pattern.......................................................... C. palaea 2

12B. Posterior cinctures with thick, rounded noto- and neuropodial spines, pointed or blunt-tipped, with accompanying and alternating capillaries....................................................................................... 13

13A. Some anterior capillaries sometimes with splayed fibrils; other capillaries from setiger 40‒45 short, an oblique edge with fibrils, tapering to pointed tip; with posterior cinctures greatly reduced to only 8 spines on a side, each with thin fringe along convex side; neuropodial spines from setiger 18‒40; no MG pattern........................................ C. acuta 1

13B. Fibrils not conspicuous on capillaries; posterior cinctures reduced or complete, but with 13 or more spines on a side...... 14

14A. Body heavily pigmented with numerous brown to black pigment speckles over entire body; with a prominent mid-ventral ridge line along entire length of body formed of ventromedial bulges arising from each segment; with weak mid-dorsal groove in middle body segments; neuropodial spines from setigers 5–26; posterior cinctures reduced, with 13‒19 spines on a side; no MG pattern.......................................................................... C. pigmentata n.sp. 3

14B. Body with anterior segments with diffuse black pigment, not discrete speckles, limited to certain areas of the body, not all over; ventral ridge low, not conspicuous; posterior cinctures well developed, with elevated membranes with 20‒22 spines on a side; with distinct MG staining pattern, with all of prostomium except tip staining, with most of peristomium staining forming “mask” over the head region............................................................... C. bathyala n.sp. 3

15A. Neuropodial spines from setiger 1................................................................ C. corona 1

15B. Neuropodial spines from setiger 20 or later................................................................ 16

16A. Neuropodial spines from setiger 21‒40................................................................... 17

16B. Neuropodial spines from setiger 65 or later................................................................ 19

17A. Posterior notopodial spines typically longer, narrower and pointed than heavier, blunt-tipped neuropodial spines, forming partial cinctures........................................................................................ 18

17B Posterior notopodial and neuropodial spines both similar, curved with smooth shafts and pointed tips; fully developed cinctures with 17‒19 spines on a side; with MG....................................................... C. hobsonae n.sp. 3

18A. Posterior spines in partial cinctures, 8‒10 spines on a side; with 4‒5 long, narrow, straight, blunt-tipped notopodial spines and 4‒5 short, thick, curved, neuropodial spines having short serrations on convex side of curved tip; with MG staining.................................................................................................. C. hartmanae 1

18B. Posterior spines in partial cinctures, 16‒18 spines on a side; posterior notosetae spinous with sharp tips; posterior neurosetae becoming shorter, forming blunt-tipped spines; no MG staining pattern.................................. C. spinosa 1,2

19A Neuropodial spines from mid-body segments, setigers 58‒65; MG staining present or absent......................... 20

19B. Neuropodial spines from posterior third of body, setigers 105‒120; posterior cinctures partially developed, with 11‒12 spines on a side; MG stains with distinctive pattern..................................................... C. columbiana 1

20A. Neuropodial spines from setiger 65‒80; posterior cinctures weakly developed, with 8‒9 spines on a side; with weak MG reaction........................................................................................ C. senticosa 1

20B Neuropodial spines from setiger 58‒65; posterior cinctures fully developed with up to 22 spines on a side; without MG staining pattern................................................................................ C. ruffi n. sp. 3