Chaetozone paucispinosa, Blake, 2022

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 : 57-63

Chaetozone paucispinosa new species

Figures 29–31

Table 5

urn:lsid:zoobank.org:act:2613441D-0481-4F32-A05A-7C22A1B2EAF7

Chaetozone sp. 1 : Blake et al. 1987; Maciolek et al. 1987a: D-2 (in part); 1987b: D-2 (in part).

Material examined. (444 specimens) Off Delaware and New Jersey, U.S. Mid-Atlantic ACSAR Program, coll. R. Petrecca, Chief Scientist. Sta. 1: Cruise Mid-1, Rep. 1, 31 Mar 1984, 38°35.98′N, 72°52.89′W, 2195 m, holotype ( USNM 1661244 ) , 1 paratype ( USNM 1661245 ) ; Cruise Mid-2, Rep 1, 03 Aug 1984, 38°36.12′N, 72°53.06′W, 2209 m, 12 paratypes ( USNM 1661246 ) ; Rep. 3, 03 Aug 1984, 38°35.99′N, 72°52.87′W, 2194 m, 4 paratypes ( USNM 16612447 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°35.92′N, 72°53.03′W, 2163 m, 4 paratypes ( USNM 1661248 ) ; Rep. 2, 02 Dec 1984, 38°35.94′N, 72°53.04′W, 2175 m, 2 paratypes ( USNM 1661249 ) ; Rep. 3, 03 Dec 1984, 38°35.97′N, 72°52.01′W, 2185 m, 2 paratypes ( USNM 1661250 ) ; Cruise Mid-4, Rep. 3, 17 May 1985, 38°35.88′N, 72°53.13′W, 2195 m, 4, paratypes ( USNM 1661251 ) ; Cruise Mid-5, Rep. 2, 05 Aug 1985, 38°35.90′N, 72°53.11′W, 2185 m, 8 paratypes ( USNM 1661252 ) ; Cruise Mid-6, Rep. 2, 13 Nov 1985, 38°35.89′N, 72°53.12′W, 2199 m, (2, USNM 1661253 ) ; Rep. 3, 13 Nov 1985, 38°35.93′N, 72°53.19′W, 2194 m, 9 paratypes ( USNM 1661254 ) . Sta. 2: Cruise Mid-1, Rep. 2, 01 Apr 1984, 38°35.71′N, 72°53.69′W, 2018 m (2, USNM 1661255 ) ; Rep. 3, 01 Apr 1984, 38°35.71′N, 72°53.61′W, 2033 m (1, USNM 1661256 ) ; Cruise Mid-2, Rep. 1, 03 Aug 1984, 38°35.77′N, 72°53.58′W, 2019 m (3, USNM 1661257 ) ; Rep. 2, 03 Aug 1984, 38°35.74′N, 72°53.68′W, 2014 m (2, USNM 1661258 ) ; Rep. 3, 03 Aug 1984, 38°35.76′N, 72°53.81′W, 2004 m (1, USNM 1661259 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°35.69′N, 72°53.63′W, 2015 m (1, USNM 1661260 ) ; Rep. 3, 02 Dec 1984, 38°35.75′N, 72°53.67′W, 2010 m (1, USNM 1661261 ) ; Cruise Mid-5, Rep. 1, 05 Aug 1985, 38°35.68′N, 72°53.79′W, 2010 m (5, USNM 1661262 ) ; Rep. 3, 05 Aug 1985, 38°35.69′N, 72°53.78′W, 2005 m (4, USNM 1661263 ) ; Cruise Mid-6, Rep. 3, 13 Nov 1985, 38°35.83′N, 72°53.91′W, 1994 m (8, USNM 1661264 ) . Sta. 3: Cruise Mid-1, Rep. 1, 03 May 1984, 38°36.88′N, 72°51.41′W, 2055 m (1, USNM 1661265 ) ; Rep. 2, 03 May 1984, 38°36.88′N, 72°51.34′W, 2055 m, 1 paratype ( USNM 1661266 ) ; Rep. 3, 03 May 1984, 38°36.86′N, 72°51.29′W, 2060 m, 3 paratypes ( USNM 1661267 ) ; Cruise Mid-2, Rep. 2, 03 Aug 1984, 38°36.87′N, 72°51.45′W, 2049 m (2, USNM 1661268 ) ; Rep. 3, 03 Aug 1984, 38°36.84′N, 72°51.46′W, 2056 m (4, USNM 1661269 ) ; Cruise Mid-3, Rep. 1, 03 Dec 1984, 38°36.84′N, 72°51.50′W, 2050 m (3, USNM 1661270 ) ; Rep. 2, 03 Dec 1984, 38°36.91′N, 72°51.55′W, 2050 m (8, USNM 1661271 ) ; Rep. 3, 03 Dec 1984, 38°36.81′N, 72°51.55′W, 2050 m (1, USNM 1661272 ) ; Cruise Mid-4, Rep. 3, 16 May 1985, 38°36.75′N, 72°51.60′W, 2052 m (3, USNM 1661273 ) ; Cruise Mid-5, Rep. 2, 05 Aug 1985, 38°36.75′N, 72°51.52′W, 2058 m, 4 paratypes ( USNM 1661274 ) ; Rep. 3, 05 Aug 1985, 38°36.82′N, 72°51.54′W, 2050 m (2, USNM 1661275 ) ; Cruise Mid-6, Rep. 2, 12 Nov 1985, 38°36.75′N, 72°51.61′W, 2064 m (12, USNM 1661276 ) ; Rep. 3, 12 Nov 1985, 38°36.77′N, 72°51.64′W, 2056 m (7, USNM 1661277 ) . Sta. 4: Cruise Mid-1, Rep. 2, 08 May 1984, 38°44.45′N, 72°41.04′W, 2108 m (1, USNM 1661278 ) ; Cruise Mid-2, Rep. 1, 01 Aug 1984, 38°44.48′N, 72°41.05′W, 2124 m (7, USNM 1661279 ) ; Rep. 2, 01 Aug 1984, 38°44.53′N, 72°41.23′W, 2114 m (1, USNM 1661280 ) ; Rep. 3, 01 Aug 1984, 38°44.54′N, 72°40.95′W, 2099 m (1, USNM 1661281 ) ; Cruise Mid-3, Rep. 1, 05 Dec 1984, 38°44.36′N, 72°41.21′W, 2105 m (5, USNM 1661282 ) ; Rep. 2, 05 Dec 1984, 38°44.38′N, 72°41.00′W, 2110 m (2, USNM 1661283 ) ; Cruise Mid-4, Rep. 2, 16 May 1985, 38°44.45′N, 72°41.26′W, 2091 m, 3 paratypes ( USNM 1661284 ) ; Cruise Mid-5, Rep. 1, 03 Aug 1985, 38°44.43′N, 72°41.24′W, 2095 m (7, USNM 1661285 ) ; Rep. 2, 03 Aug 1985, 38°44.44′N, 72°41.22′W, 2095 m (2, USNM 1661286 ) ; Rep. 3, 3 Aug 1985, 38°44.41′N, 72°41.21′W, 2095 m (4, USNM 1661287 ) ; Cruise Mid-6, Rep. 1, 11 Nov 1985, 38°44.34′N, 72°41.27′W, 2112 m (2, USNM 1661288 ) ; Rep. 2, 11 Nov 1985, 38°44.40′N, 72°41.25′W, 2106 m (10, USNM 1661289 ) . Sta. 5: Cruise Mid-1, Rep. 1, 08 May 1984, 38°50.54′N, 72°33.18′W, 2055 m (2, USNM 1661290 ) ; Rep. 2, 08 May 1984, 38°50.53′N, 72°33.10′W, 2065 m (1, USNM 1661291 ) ; Rep. 3, 08 May 1984, 38°50.46′N, 72°33.14′W, 2080 m (8, USNM 1661292 ) ; Cruise Mid-2, Rep. 1, 01 Aug 1984, 38°50.42′N, 72°33.03′W, 2089 m (5, USNM 1661293 ) ; Rep. 2, 01Aug 1984, 38°50.42′N, 72°33.05′W, 2089 m, 2 paratypes ( USNM 1661294 ) ; Rep. 3, 01 Aug 1984, 38°50.52′N, 72°32.96′W, 2074 m (2, USNM 1661295 ) ; Cruise Mid-3, Rep. 3, 05 Dec 1984, 38°50.47′N, 72°33.07′W, 2070 m (2, USNM 1661296 ) ; Cruise Mid-6, Rep. 1, 11 Nov 1985, 38°50.49′N, 72°33.17′W, 2079 m (6, USNM 1661297 ) ; Rep. 2, 11 Nov 1985, 38°50.49′N, 72°33.17′W, 2084 m (10, USNM 1661298 ) ; Rep. 3, 11 Nov 1985, 38°50.44′N, 72°33.20′W, 2089 m (2, USNM 1661299 ) . Sta. 6: Cruise Mid-1, Rep. 1, 03 May 1984, 39°05.61′N, 72°02.98′W, 2090 m (5, USNM 1661300 ) ; Rep. 2, 03 May 1984, 39°05.63′N, 72°03.00′W, 2088 m (5, USNM 1661301 ) ; Rep. 3, 03 May 1984, 39°05.59′N, 72°03.00′W, 2090 m (3, USNM 1661302 ) ; Cruise Mid-2, Rep. 1, 01 Aug 1984, 39°05.65′N, 72°02.97′W, 2084 m (2, USNM 1661303 ) ; Rep. 2, 01 Aug 1984, 39°05.68′N, 72°02.99′W, 2084 m (4, USNM 1661304 ) ; Rep. 3, 01 Aug 1984, 39°05.69′N, 72°02.99′W, 2084 m (1, USNM 1661305 ) ; Cruise Mid-3, Rep. 1, 28 Nov 1984, 39°05.58′N, 72°02.81′W, 2090 m (1, USNM 1661306 ) ; Rep. 2, 28 Nov 1984, 39°05.57′N, 72°02.83′W, 2090 m (5, USNM 1661307 ) ; Rep. 3, 28 Nov 1984, 39°05.65′N, 72°02.08′W, 2085 m (3, USNM 1661308 ) ; Cruise Mid-5, Rep. 1, 02 Aug 1985, 39°05.65′N, 72°03.22′W, 2080 m (1, USNM 1661309 ) ; Rep. 2, 02 Aug 1985, 39°05.64′N, 72°03.24′W, 2080 m (6, USNM 1661310 ) ; Rep. 3, 02 Aug 1985, 39°05.65′N, 72°03.22′W, 2080 m (1, USNM 1661311 ) . Sta. 7: Cruise Mid-1, Rep. 1, 06 May 1984, 38°27.32′N, 73°03.45′W, 2110 m (2, USNM 1661312 ) ; Rep. 2, 06 May 1984, 38°27.32′N, 73°03.45′W, 2110 m (12, USNM 1661313 ) ; Cruise Mid-2, Rep. 1, 05 Aug 1984, 38°27.34′N, 73°03.41′W, 2104 m (4, USNM 1661314 ) ; Rep. 2, 05 Aug 1984, 38°27.32′N, 73°03.38′W, 2104 m (6, USNM 1661315 ) ; Rep. 3, 05 Aug 1984, 38°27.34′N, 73°03.41′W, 2104 m (11, USNM 1661316 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°27.28′N, 73°03.38′W, 2110 m (3, USNM 1661317 ) ; Cruise Mid-4, Rep. 1, 13 May 1985, 38°27.27′N, 73°03.52′W, 2106 m (8, USNM 1661318 ) ; Rep. 2, 13 May 1985, 38°27.27′N, 73°03.52′W, 2106 m (3, USNM 1661319 ) ; Cruise Mid-5, Rep. 3, 07 Aug 1985, 38°27.31′N, 73°03.54′W, 2088 m, 3 paratypes ( USNM 1661320 ) ; Cruise Mid-6, Rep. 1, 16 Nov 1985, 38°27.29′N, 73°03.58′W, 2096 m (3, USNM 1661321 ) . Sta. 8: Cruise Mid-1, Rep. 1, 06 May 1984, 38°27.36′N, 73°05.09′W, 2148 m (5, USNM 1661322 ) ; Rep. 2, 06 May 1984, 38°27.36′N, 73°04.88′W, 2150 m, 11 paratypes ( USNM 1661323 ) ; Cruise Mid-2, Rep. 2, 05 Aug 1984, 38°27.21′N, 73°04.79′W, 2159 m (3, USNM 1661324 ) ; Cruise Mid-3, Rep. 2, 01 Dec 1984, 38°27.13′N, 73°04.87′W, 2150 m (1, USNM 1661325 ) ; Rep. 3, 01 Dec 1984, 38°27.30′N, 73°04.79′W, 2155 m (7, USNM 1661326 ) .— Off New Jersey, U.S. EPA DWD-106 Site Survey, coll. R. Petrecca, Chief Scientist. Sta. F: Rep. 1, 18 Nov 1985, 38°51.10′N, 72°16.39′W, 2500 m (2, MCZ 161951 ) ; Rep. 3, 18 Nov 1985, 38°51.11′N, 72°16.39′W, 2500 m (2, MCZ 161952 ) . Sta. G: Rep. 1, 18 Nov 1985, 38°55.66′N, 72°02.53′W, 2505 m (3, MCZ 161953 ) ; Rep. 2, 18 Nov 1985, 38°55.63′N, 72°02.54′W, 2509 m (8, MCZ 161954 ) ; Rep. 3, 18 Nov 1985, 38°55.60′N, 72°02.54′W, 2505 m (3, MCZ 161955 ) .— Off New England, U.S. North Atlantic ACSAR Program, coll. G.W. Hampson, Chief Scientist. Sta. 2: Cruise NA-1, Rep. 1, 08 Nov 1984, 40°57.20′N, 66°13.72′W, 2112 m (1, USNM 1661327 ) ; Rep. 2, 08 Nov 1984, 40°57.18′N, 66°13.87′W, 2095 m (2, USNM 1661328 ) . Sta. 3: Cruise NA-5, Rep. 2, 27 Apr 1986, 41°01.35′N, 66°20.24′W, 1335 m (2, USNM 1661329 ) ; Cruise NA-6, Rep. 1, 25 Jul 1986, 41°01.55′N, 66°20.12W, 1345 m (2, USNM 1661330 ) ; Rep. 3, 25 Jul 1986, 41°01.51′N, 66°20.27′W, 1333 m (2, USNM 1661331 ) . Sta. 5: Cruise NA-1, Rep. 2, 05 Nov 1984, 40°05.06′N, 67°29.94′W, 2052 m (1, USNM 1661332 ) ; Cruise NA-4, Rep. 1, 25 Nov 1985, 40°05.06′N, 67°29.86′W, 2074 m (1, USNM 1661333 ) ; Rep. 2, 25 Nov 1985, 40°05.09′N, 67°29.84′W, 2071 m (1, USNM 1661334 ) . Sta. 6: Cruise NA-2, Rep. 1, 29 Apr 1985, 40°05.04′N, 67°29.99′W, 2108 m (3, USNM 1661335 ) ; Rep. 2, 29 Apr 1985, 40°05.03′N, 67°29.13′W, 2108 m (3, USNM 1661336 ) ; Rep. 3, 29 Apr 1985, 40°05.06′N, 67°29.13′W, 2107 m (4, USNM 1661337 ) ; Cruise NA-5, Rep. 2, 30 Apr 1986, 40°05.11′N, 67°29.21′W, 2110 m (4, USNM 1661338 ) . Sta. 8: Cruise NA-1, Rep. 1, 10 Nov 1984, 40°10.37′N, 67°37.43′W, 2175 m (2, USNM 1661339 ) ; Cruise NA-2, Rep. 4, 29 Apr 1985, 40°10.24′N, 67°37.25′W, 2185 m (4, USNM 1661340 ) ; Cruse NA-3, Rep. 1, 05 Jul 1985, 40°10.26′N, 67°37.22′W, 2180 m (1, USNM 1661341 ) ; Rep. 3, 05 Jul 1985, 40°10.26′N, 67°37.21′W, 2180 m (6, USNM 1661342 ) ; Cruise NA-4, Rep. 2, 22 Nov 1985, 40°10.25′N, 67°37.33′W, 2179 m (1, USNM 1661343 ) ; Cruse NA-5, Rep. 2, 29 Apr 1986, 40°10.19′N, 67°37.29′W, 2165 m (4, USNM 1661344 ) ; Rep. 3, 29 Apr 1986, 40°10.14′N, 67°37.45′W, 2130 m (2, USNM 1661345 ) ; Cruise NA-6, Rep. 2, 27 Jul 1986, 40°10.23′N, 67°37.25′W, 2193 m (3, USNM 1661346 ) ; Rep. 3, 27 Jul 1986, 40°10.21′N, 67°37.28′W, 2188 m (3, USNM 1661347 ) . Sta. 9: Cruise NA-1, Rep. 1, 12 Nov 1984, 39°50.45′N, 70°01.76′W, 1200 m (1, USNM 1661348 ) ; Rep. 3, 12 Nov 1984, 39°50.53′N, 70°01.68′W, 1225 m (1, USNM 1661349 ) ; Cruise NA-2, Rep. 1, 03 May 1985, 39°50.43′N, 70°01.58′W, 1235 m (3, USNM 1661350 ) ; Cruise NA-5, Rep. 1, 03 May 1986, 39°50.54′N, 70°01.79′W, 1214 m (1, USNM 1661351 ) ; Rep. 2, 03 May 1986, 39°50.49′N, 70°01.76′W, 1208 m (2, USNM 1661352 ) ; Cruise NA-6, Rep. 1, 28 Jul 1986, 39°50.37′N, 70°01.72′W, 1233 m (1, USNM 1661353 ) . Sta. 10: Cruise NA-1, Rep. 1, 12 Nov 1984, 39°48.22′N, 70°05.33′W, 1200 m (1, USNM 1661354 ) ; Cruise NA-6, Rep. 2, 28 Jul 1986, 39°48.07′N, 70°05.37′W, 1253 m (1, USNM 1661355 ) ; Sta. 13: Cruise NA-5, Rep. 1, 06 May 1986, 39°47.99′N, 70°55.08′W, 1270 m (4, USNM 1661356 ) ; Sta. 14: Cruise NA-1, Rep. 3, 09 Dec 1984, 39°40.89′N, 70°54.29′W, 2107 m (2, USNM 1661357 ) ; Cruise NA-2, Rep. 1, 05 May 1985, 39°40.91′N, 70°54.17′W, 2095 m (3, USNM 1661358 ) . Sta. 15: Cruise NA-1, Rep. 2, 09 Dec 1984, 39°40.10′N, 70°54.27′W, 2155 m (7, USNM 1661359 ) ; Rep. 3, 09 Dec 1984, 39°40.06′N, 70°54.30′W, 2155 m (7, USNM 1661360 ) ; Cruise NA-2, Rep. 1, 05 May 1985, 39°40.07′N, 70°54.27′W, 2145 m (7, USNM 1661361 ) ; Rep. 3, 06 May 1984, 39°40.10′N, 70°54.31′W, 2140 m (5, USNM 1661362 ) ; Cruise NA-4, Rep. 1, 28 Nov 1985, 39°40.05N, 70°54.29′W, 2124 m (1, USNM 1661363 ) ; Cruise NA-5, Rep. 2, 05 May 1986, 39°39.95′N, 70°54.19′W, 2164 m (2, USNM 1661364 ) ; Rep. 3, 06 May 1986, 39°40.00′N, 70°54.41′W, 2160 m (3, USNM 1661365 ) .— Off Cape Lookout , North Carolina, US South Atlantic ACSAR Program, coll. J.A. Blake, Chief Scientist. Sta. 5: Cruise SA-1, Rep. 3, 14 Nov 1983, 34°05.89′N, 75°18.19′W, 3040 m (1, USNM 1661366 ) ; Cruise SA-2, Rep. 2, 19 May 1984, 34°06.70′N, 75°18.60′W, 3034 m (1, USNM 1661367 ) .

Description. Holotype (USNM 1661244) ( Figs. 29A–C , 30A, E ) with 100 setigers, 12.1 mm long, 0.4 mm wide; largest specimen (USNM 1661295) with 151 setigers, 21 mm long, 0.5 mm wide across anterior setigers; another large specimen (USNM 1661267) with 102 setigers, 16. 5 mm long and 0.45 mm wide; a 49-setiger specimen (USNM 1661274) 5.8 mm long, 0.18 mm wide ( Fig. 30B ); a 26-setiger juvenile 2.4 mm long and 0.09 mm wide ( Fig. 30C ) and an 18-setiger juvenile 1.46 mm long and 0.08 mm wide (USNM 1661322) ( Fig. 30D ).

Body elongate, cylindrical in cross section; anterior 15–20 setigers of adults short, crowded, about 7–8 times wider than long ( Fig. 30A ), then individual segments increasing in length in middle body, becoming moniliform posteriorly ( Fig. 30B ), but with farthest posterior segments again narrowing to pygidium ( Fig. 30B–E ). Juveniles and smaller adults with middle and posterior segments moniliform ( Fig. 30C–D ). Dorsal and ventral grooves not apparent. Color in alcohol light tan; larger specimens, including holotype, with clusters of black pigment spots on lateral margins of last peristomial ring ( Figs. 29C , 30G ).

Pre-setiger region elongate, narrow, as long as first ten setigers in larger specimens ( Figs. 29A–C , 30A ). Prostomium conical, tapering to narrow rounded tip; entire prostomium turned upward in some specimens ( Figs. 29A , 30A–B ); eyespots absent; nuchal organs curved notches on posterior lateral margin, appearing as pigmented spots in some juveniles. Peristomium long, divided into three distinct rings with grooves apparent laterally ( Fig. 29A–B ); rings not complete dorsally; first ring merged dorsally with posterior margin of prostomium and ventrally surrounding oral opening from which bulbous pharynx or proboscis emerges ( Figs. 29B–C , 30F–G ). Some specimens with first peristomial ring dorsally elevated producing rounded crest, but consistent dorsal crest not present in this species. Ventrally, first peristomial ring separated from merged second and third ring by deep groove ( Fig. 29B ); second and third rings only separated laterally, but distinctly separated from setiger 1 by a deep groove ( Fig. 29C ). Dorsal tentacles arising from posterior margin of peristomium with first pair of branchiae lateral to tentacles ( Fig. 29A ). Second pair of branchiae on setiger 1 dorsal to notosetae; branchiae in similar location on following segments. Branchiae mostly missing, but when present each long and thin, occurring along most of body ( Figs. 29A–B , 30A, D ).

Parapodia of anterior and middle segments reduced to low ridges or mounds from which setae arise; segments moniliform in posterior and more anteriorly in smaller specimens with parapodia dorsolateral with noto- and notopodia close to one another ( Fig. 31A ). Parapodial cinctures not present.Anterior setae all long capillaries numbering about 12–15 per fascicle in largest specimens and usually including long natatory-like setae in notopodia of anterior and middle segments; these not associated with sexual maturity. Neuropodial spines from middle body segments in juveniles and specimens with fewer than 75 setigers; holotype and larger specimens with neuropodial spines from posterior quarter of body, setiger 73 of 100 in holotype. Neuropodial spines numbering 1–3 in juveniles, increasing to 7–8 per fascicle in largest specimens. Neuropodial spines narrow, with rounded tip, distinctly curved sigmoidally in ventral-most spines, becoming straighter and more elongate in dorsal part of fascicle ( Figs. 29D–F , 31C ). Notosetae of posterior setigers mostly capillaries ( Fig. 31B ), with spines only present in a few pre-pygidial setigers in largest specimens, these numbering no more that 1–2 per fascicle; each straight, with sharply pointed tip. Maximal number of spines observed in largest specimens 8–10 on a side; most specimens with no more than 4–7 spines on a side.

Body terminating in short pygidium bearing a semicircular disk ventral to the anal opening ( Fig. 30E ).

Methyl green staining. A distinctive MG staining pattern is evident on the pre-setiger region ( Figs. 30 F–G ) where the prostomium and peristomium stain prominently with dorsolateral unstained patches; the second and third peristomial rings typically stain dark blue; the proboscis when extended and posterior lips of the mouth do not stain ( Fig. 30F–G ). In larger specimens, the parapodia of 3–4 anterior setigers also stain to varying degrees. The rest of the body de-stains rapidly with no pattern.

Remarks. Chaetozone paucispinosa n. sp. is a widespread lower continental slope species along the US Atlantic coast, with numerous specimens available for study including juveniles and sexually mature adults. Due to the large number of specimens that were collected, it was possible to document the considerable variation in their overall appearance with growth. Juveniles initially have moniliform segments along most of their length; after about 50 setigers are developed, the first third of the body has crowded segments, with moniliform segments retained in the posterior two-thirds. The largest specimens only have moniliform segments in the last 15 or so segments. Most specimens, large or small, have an expanded oral opening from which a partially protruding pharynx is typically observed ( Figs. 29A–C , 30B–D, F–G ). In lateral view the everted pharynx is easily visible and provides a superficial clue relative to the identification of this species. In many of the larger specimens, the prostomium is turned up, or somewhat directed dorsally, best seen in lateral view ( Figs. 29C , 30B ). The acicular spines are generally narrow with the smaller spines being curved and the longer ones having straighter shafts. The largest specimens also have black pigment spots located ventrolateral on the last peristomial ring ( Figs. 29C , 30G ). A summary of size and acicular spine data for this species is presented in Table 5 .

Relative to the nature and number of acicular spines, C. paucispinosa n. sp. is most similar to Chaetozone homosetosa from Antarctica ( Blake 2018). Both species have the peristomium divided into three rings and the dorsal tentacles and first branchiae arising from the posterior margin of the peristomium. In addition, both species are recorded as having black pigment spots on the lateral margins of the last peristomial ring and similar methyl green staining patterns. However, C. homosetosa has a prominent dorsal peristomial crest that is entirely lacking in C. paucispinosa n. sp. In addition, the acicular spines of C. homosetosa while similarly narrow are more sigmoidally curved than in C. paucispinosa n. sp.

Biology. Although widespread along the entire U.S. Atlantic continental slope, C. paucispinosa n. sp. (as C. sp. 1) was never reported as a dominant taxon at any station in any of the three ACSAR program areas. Sperm packets were observed in several specimens (e.g., USNM 1661350).

Etymology. The epithet paucispinosa is from paucis, Latin for few and spina, Latin for thorn, in reference to the reduced number of spines in the posterior setigers of this species.

Distribution. Widespread along the U.S. Atlantic continental slope in depths of 1200–3040 m.

Abbreviation: set, setiger(s).

The Chaetozone setosa group

Remarks. Chaetozone setosa , the type-species of the genus, has noto- and neuropodia with spreading fascicles of numerous and enlarged sigmoid-shaped acicular spines with rounded or pointed tips that are not curved or recurved, and that usually alternate with capillaries. This type of armature is represented by six species in the present study, three of which are new to science.

Figures

FIGURE 29. Chaetozone paucispinosa n. sp. Holotype (USNM 1661244):A, anterior end, dorsal view; B, anterior end, ventral view; C, anterior end, right lateral view. Paratype (USNM 1661266): D–G, neuropodial acicular spines.

FIGURE 30. Chaetozone paucispinosa n. sp. A, anterior end, dorsal view; B, entire 49-setiger specimen, left lateral view; C. entire 26-setiger specimen, left lateral view; D, entire 18-setiger juvenile, right lateral view; E, posterior end, dorsal view; F, anterior end, left lateral view; G, anterior end, right lateral view. A, E, G holotype (USNM 1661244); B USNM 1661274; C, USNM 1661296; D, USNM 1661322; F, MCZ 161954. A–E stained with Shirlastain A; F–G, stained with MG.

FIGURE 31. Chaetozone paucispinosa n. sp. (USNM 1661276); A, posterior setiger, right side, anterior view; B, notosetae from (A); C, neurosetae from (A).