Chaetozone castouria, 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 : 49-54

Chaetozone castouria new species

Figures 24–26

urn:lsid:zoobank.org:act:B4C0B930-5422-455A-9BE3-AF6393D053CF

Chaetozone sp. 2 . Blake et al. 1987: C-2; Maciolek et al. 1987a: D-2; Hilbig 1994: 940.

Chaetozone sp. 6 . Blake et al. 1987: C-2; Maciolek et al. 1987a: D-2; 1987b: D-2; Hilbig 1994: 940.

Material examined. (141 specimens) Off New Jersey and Delaware, U.S. Mid-Atlantic ACSAR Program , coll. R. Petrecca, Chief Scientist. Sta. 1: Cruise Mid-4, Rep. 3, 17 May 1985, 38°35.88′N, 72°53.13′W, 2194 m, holotype ( USNM 1660990 ) , 1 paratype ( USNM 1660991 ) ; Rep. 1, 17 May 1985, 38°35.88′N, 72°53.18′W, 2200 m, 2 paratypes ( USNM 1660992 ) ; Cruise Mid-1, Rep. 1, 31 Mar 1984, 38°35.98′N, 72°52.86′W, 2195 m, 2 paratypes ( USNM 1660993 ) ; Cruise Mid-2, Rep. 3, 03 Aug 1984, 38°35.99′N, 72°52.87′W, 2194 m, 2 paratypes ( USNM 1660994 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°35.92′N, 72°53.03′W, 2165 m, 1 paratype ( USNM 1660995 ) ; Cruise Mid-5, Rep. 2, 05 Aug 1985, 38°35.90′N, 72°53.11′W, 2185 m, 1 paratype ( USNM 1660996 ) ; Rep. 3, 05 Aug 1985, 38°35.91′N, 72°53.10′W, 2185 m, 1 paratype ( USNM 1660997 ) ; Cruise Mid-6, Rep. 2, 13 Nov 1985, 38°35.89′N, 72°53.12′W, 2199 m, 1 paratype ( USNM 1660998 ) . Sta. 2: Cruise Mid-1, Rep. 2, 01 Apr 1984, 38°35.71N, 72°53.69′W, 2018 (2, USNM 1660999 ) ; Cruise Mid-2, Rep. 2, 03 Aug 1984, 38°35.74′N, 72°53.687′W, 2014 m, 1 paratype ( USNM 1661000 ) ; Cruise Mid-3, Rep. 1, 02 Dec 1984, 38°35.69N, 72°53.63′W, 2015 m (1, USNM 1661001 ) ; Cruise Mid-4, Rep. 2, 17 May 1985, 38°35.66′N, 72°53.80′W, 2011 m, 1 paratype ( USNM 1661002 ) ; Cruise Mid-5, Rep. 1, 05 Aug 1985, 38°35.68′N, 72°53.79′W, 2010 m (1, USNM 1661003 ) ; Cruise Mid-6, Rep. 3, 13 Nov 1985, 38°35.83′N, 72°53.91′W, 1994 m, 1 paratype ( USNM 1661004 ) . Sta. 3: Cruise Mid-3, Rep. 2, 03 Dec 1984, 38°36.91′N, 72°51.55′W, 2050 m (1, USNM 1661005 ) ; Cruise Mid-5, Rep. 2, 05 Aug 1985, 38°36.75′N, 72°51.52′W, 2058 m (1, USNM 1661006 ) . Sta. 4: Cruise Mid-4, Rep. 1, 16 May 1985, 38°44.41′N, 72°41.24′W, 2100 m, 3 paratypes ( USNM 1661007 ) ; Rep. 2, 16 May 1985, 38°44.45′N, 72°41.26′W, 2091 m, 2 paratypes ( USNM 1661008 ) ; Cruise Mid-5, Rep. 1, 16 May 1985, 38°44.45′N, 72°41.26′W, 2091 m, 3 paratypes ( USNM 1661009 ) . Sta. 5: Cruise Mid-1, Rep. 1, 08 May 1984, 38°50.54′N, 72°33.18′W, 2055 m (2, USNM 1661011 ) ; Rep. 2, 04 May 1984, 38°50.53′N, 72°33.10′W, 2065 m, 1 paratype ( USNM 1661010 ) ; Rep. 3, 08 May 1984, 38°50.46′N, 72°33.14′W, 2080 m, (1, USNM 1661012 ) ; Cruise Mid-2, Rep. 2, 01 Aug 1984, 38°50.42′N, 72°33.05′W, 2089 m (1, USNM 1661013 ) ; Cruise Mid-3, Rep. 1, 05 Dec 1984, 38°50.42′N, 72°33.04′W, 2085 m (1, USNM 1661014 ) ; Rep. 2, 05 Dec 1984, 38°50.40′N, 72°33.12′W, 2090 m (2, USNM 1661015 ) ; Rep. 3, 05 Dec 1984, 38°50.47′N, 72°33.07′W, 2070 m (1, USNM 1661016 ) ; Cruise Mid-4, Rep. 1, 16 May 1985, 38°50.46′N, 72°33.23′W, 2080 m (1, USNM 1661017 ) ; Rep. 2, 16 May 1985, 38°50.48′N, 72°33.19′W, 2080 m (1, USNM 1661018 ) ; Cruise Mid-6, Rep. 2, 11 Nov 1985, 38°50.49′N, 72°33.17W, 2079 m, 3 paratypes ( USNM 1661019 ) ; Rep. 3, 11 Nov 1985, 38°50.44′N, 72°33.20W, 2089 m (3, USNM 1661020 ) . Sta. 6: Cruise Mid-1, Rep. 1, 03 May 1984, 39°05.61′N, 72°02.98′W, 2090 m, 3 paratypes ( USNM 1661021 ) ; Cruise Mid-2, Rep. 1, 01 Aug 1984, 39°05.65′N, 72°02.97′W, 2084 m (1, USNM 1661022 ) ; Cruise Mid-3, Rep. 1, 28 Nov 1984, 39°05.58′N, 72°02.81′W, 2090 m (1, USNM 1661023 ) ; Rep. 2, 28 Nov 1984, 39°05.57′N, 72°02.83′W, 2090 m (2, USNM 1661024 ) ; Rep. 3, 28 Nov 1984, 39°05.65′N, 72°02.08′W, 2085, (3, USNM 1661025 ) ; Cruise Mid-4, Rep. 3, 15 May 1985, 39°05.66′N, 72°03.22′W, 2085 m (1, USNM 1661026 ) ; Cruise Mid-5, Rep. 2, 02 Aug 1985, 39°05.64′N, 72°03.24′W, 2080 m (1, USNM 1661027 ) ; Cruise Mid-6, Rep. 1, 10 Nov 1985, 39°05.67′N, 72°03.36′W, 2089 m (2, USNM 1661028 ) ; Rep , 3, 10 Nov 1985, 39°05.51′N, 72°03.16′W, 2092 m, 2 paratypes ( USNM 1661029 ) . Sta. 7: Cruise Mid-1, Rep. 1, 06 May 1984, 38°27.32′N, 73°03.43′W, 2110 m, 4 paratypes ( USNM 1661030 ) ; Rep. 2 (4, USNM) ; 06 May 1984, 38°27.30′N, 73°03.43′W, 2100 m, 4 paratypes ( USNM 1661031 ) ; Rep. 3, 06 May 1984, 38°27.34′N, 73°03.48′W, 2100 m, 3 paratypes ( USNM 1661032 ) ; Cruise Mid-3, Rep. 2, 05 Aug 1984, 38°27.34′N, 73°03.41′W, 2104 m (2, USNM 1661033 ) ; Rep. 3, 05 Aug 1984, 38°27.39′N, 73°03.39′W, 2099 m (1, USNM 1661034 ) ; Cruise Mid-5, Rep. 1, 07 Aug 1985, 38°27.34′N, 73°03.53′W, 2085 m (1, USNM 1661035 ) ; Rep. 2, 07 Aug 1985, 38°27.32′N, 73°03.54′W, 2095 m (1, USNM 1661036 ) ; Cruise Mid-6, Rep. 3, 14 Nov1985, 38°27.28′N, 73°03.54′W, 2104 m, 2 paratypes ( USNM 1661037 ) . Sta. 8: Cruise Mid-1, Rep. 1, 06 May 1984, 38°27.36′N, 73°05.09′W, 2148 m (1, USNM 1661038 ) ; Rep. 2, 06 May 1984, 38°27.36′N, 73°05.88′W, 2150 m (4, USNM 1661039 ) ; Rep. 3, 06 May 1984, 38°27.36′N, 73°04.81′W, 2150 m (2, USNM 1661040 ) ; Sta. 9: Cruise Mid-1, Rep. 1, 06 May 1984, 38°17.24′N, 73°14.51′W, 2105 m (2, USNM 1661041 ) ; Rep. 2, 06 May 1984, 38°17.22′N, 73°14.56′W, 2108 m, 3 paratypes ( USNM 1661042 ) ; Rep. 3, 06 May 1984, 38°17.23′N, 73°14.60′W, 2108 m (3, USNM 1661043 ) ; Cruise Mid-3, Rep. 2, 30 Nov 1984, 38°17.28′N, 73°14.47′W, 2105 m (3, USNM 1661044 ) ; Cruise Mid-4, Rep. 1, 18 May 1985, 38°17.19′N, 73°14.66′W, 2100 m (1, USNM 1661045 ) ; Cruise Mid-5, Rep. 3, 09 Aug 1985, 38°17.19′N, 73°14.63′W, 2100 m (1, USNM 1661046 ) . Sta. 11: Cruise Mid-1, Rep. 2, 07 May 1984, 38°40.31′N, 72°56.31′W, 1520 m, 1 paratype ( USNM 1661047 ) ; Rep. 3, 07 May 1984, 38°40.22′N, 72°56.27′W, 1520 m, 1 paratype ( USNM 1661048 ) ; Cruise Mid-2, Rep. 2, 05 Aug 1984, 38°40.14′N, 72°56.41′W, 1509 m (1, USNM 1661049 ) ; Cruise Mid-3, Rep. 2, 04 Dec 1984, 38°40.14′N, 72°56.31′W, 1520 m, 1 paratype ( USNM 1661050 ) ; Cruise Mid-4, Rep. 1, 17 May 1985, 38°40.10′N, 72°56.43′W, 1510 m (1, USNM 1661051 ) ; Rep. 2, 17 May 1985, 38°40.12′N, 72°56.44′W, 1510 m (1, USNM 1661052 ) . Sta. 13: Cruise Mid-1, Rep. 3, 03 Apr 1984, 37°53.36′N, 73°45.10′W, 1613 m (1, USNM 1661053 ) ; Cruise Mid-2, Rep. 2, 07 Aug 1984, 37°53.28′N, 73°45.26′W, 1619 m (1, USNM 1661054 ) ; Cruise Mid-4, Rep. 3, 19 May 1985, 37°53.27′N, 73°45.27′W, 1605 m (1, USNM 1661055 ) ; Cruise Mid-5, Rep. 1, 09 Aug 1985, 37°53.26′N, 73°45.21′W, 1607 m (2, USNM 16610556 ) ; Cruise Mid-6, Rep. 3, 15 Nov 1985, 37°53.31′N, 73°45.27′W, 1609 m, 2 paratypes ( USNM 1661057 ) . Sta. 14: Cruise Mid-4, Rep. 2, 19 May 1985, 37°53.83′N, 73°44.76′W, 1492 m (1, USNM 1661058 ) ; Cruise Mid-6, Rep. 1, 19 May 1985, 37°53.69′N, 73°44.69′W, 1515 m (1, USNM 1661059 ) .— 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 1661060 ) ; Rep. 2, 08 Nov 1984, 40°57.18′N, 66°13.87′W, 2095 m (1, USNM 1661061 ) ; Rep. 3, 09 Nov 1984, 40°57.15′N, 66°13.80′W, 2103 m (1, USNM 1661062 ) ; Cruise NA-2, Rep. 3, 26 Apr 1985, 40°57.15′N, 66°13.72′W, 2100 m (1, USNM 1661063 ) ; Cruise NA-3, Rep. 3, 03 Jul 1985, 40°57.19′N, 66°13.67′W, 2100 m (2, USNM 1661064 ) . Sta. 6: Cruise NA-5, Rep. 1, 30 Apr 1986, 40°04.94′N, 67°29.17′W, 2120 m (1, USNM 1661065 ) . Sta. 8: Cruise NA-1, Rep. 3, 11 Nov 1984, 40°10.320′N, 67°37.38′W, 2180 m (1, USNM 1661066 ) ; Cruise NA-2, Rep. 3, 20 Apr 1985, 40°10.27′N, 67°37.22′W, 2180 m (1, USNM 1661067 ) . Sta. 9: Cruise NA-6, Rep. 2, 28 Jul 1986, 39°50.41, 70°01.62′W, 1230 m, 1 paratype ( USNM 1661068 ) . Sta. 13: Cruise NA-5, Rep. 1, 06 May 1986, 39°47.99′N, 70°55.08′W, 1270 m, 1 paratype ( USNM 1661069 ) . Sta. 15: Cruise NA-5, Rep. 3, 06 May 1986, 39°40.00′N, 70°54.41′W, 2160 m (1, USNM 1661070 ) .— US South Atlantic ACSAR Program, Off Cape Lookout , North Carolina, coll. J.A. Blake, Chief Scientist. Sta. 2: Cruise SA-2, Rep. 2, 27 Mar 1984, 34°14.46′N, 75°43.85′W, 1003 m (2, USNM 1661071 ) . Sta. 3: Cruise SA-2, Rep. 2, 27 Mar 1984, 34°14.63′N, 75°40.17′W, 1513 m (4, USNM 1661072 ) ; Cruise SA-3, Rep. 3, 14 Jul 1984, 34°15.10′N, 75°40.30′W, 1489 m (1, USNM 1661074 ) ; Sta. 4: Cruise SA-2, Rep. 2, 20 May 1984, 34°11.90′N, 75°38.70′W, 2029 m (1, USNM 1661073 ) .— Off Cape Hatteras, Hatteras Canyon . Sta. 6: Cruise SA-1, Rep. 2, 19 Nov 1983, 34°48.97′N, 75°15.96′W, 1910 m (3 USNM 16611075 ) ; Cruise SA-2, Rep. 1, 25 May 1984, 34°49.90′N, 75°13.50′W, 1974 m (4, USNM 1661076 ) ; Rep. 2, 25 May 1984, 34°50.200′N, 75°13.40′W, 1979 m (1, USNM 1661077 ) ; Rep. 3, 25 May 1984, 34°49.90′N, 75°13.70′W, 1984 m (2, USNM 1661078 ) .— Off Cape Fear, North Carolina. Sta. 12: Rep. 2, 22 May 1985, 34°00.23′N, 76°07.26′W, 2010 m (2, USNM 1661079 ) .

Description. A moderately sized species, with a long, narrow, threadlike body. Largest specimens available include a paratype (USNM 1661000) from Mid-Atlantic slope with 72 setigers, 16 mm long, and 0.20 mm wide and a paratype (USNM 1661068) from North Atlantic slope (USNM 1661068), broken in two parts, sexually mature, with 88 setigers, 17.6 mm long and 0.25 mm wide across anterior segments ( Figs. 24A–B , 25D–F ). Holotype (USNM 1660990) from the Mid-Atlantic slope, with 50 setigers, 7.3 mm long and 0.15 mm wide across anterior setigers ( Fig. 25A–C ); most paratypes of a similar size.

Body of a more-or-less consistent width, slightly wider in pre-setiger region and first few setigers ( Figs. 25A–B , 26A ); posterior end distinctly inflated, rounded dorsally, and flattened ventrally ( Figs. 25A, C, F , 26A ). First 10–15 setigers narrow, crowded; subsequent setigers becoming moniliform, about as wide as long with those in posterior half of body more elongate, about 1½ to 2 times as long as wide ( Fig. 26A ); posterior inflated segments again crowded ( Figs. 25A,C, F , 26A ). Some specimens with an expanded “stomach” area consisting of 4–5 swollen segments filled with fine-grained sediment ( Fig. 25A ). Dorsal and ventral grooves absent. Color in alcohol opaque white to light tan, with no pigmentation.

Pre-setiger region elongate, about as long as first seven setigers ( Fig. 24A–B ). Prostomium short, pear-shaped, as long as wide, tapering to pointed tip when viewed dorsally ( Fig. 24A ), more pointed when viewed laterally and often directed dorsally ( Figs. 24B , 25D, G ); eyespots absent; nuchal organs narrow slits on posterior lateral margin. Peristomium divided by lateral grooves into three weakly developed rings, each about equal in size ( Fig. 24A–B ); dorsal and ventral surfaces smooth, not interrupted by groove, with parapodia forming dorsolateral shoulders ( Fig. 24A–B ). Dorsal tentacles arise from medial location on posterior margin of peristomium ( Fig. 24A–B ); first pair of branchiae on setiger 1 dorsal to notosetae; subsequent branchiae in a similar location ( Fig. 24A ), mostly in anterior setigers with only a few on middle and posterior segments.

Parapodia of anterior segments weakly swollen, with noto- and neurosetae arising directly from body wall. Parapodia of moniliform segments inconspicuous, no distinct podia evident where setae emerge. Setae include long, smooth capillaries and acicular spines in both noto- and neuropodia. Capillaries numbering 10–12 per noto- and neuropodium in anterior setigers, reduced to 6–7 in middle segments, and 0–2 in posterior setigers. Some capillaries with thicker shafts transitioning to short acicular spines in posterior quarter of body, at about setiger 40 in 50-setiger holotype and setiger 70 in 88-setiger paratype (USNM 1661068). Spines in posterior setigers numbering 1–3; with no more than two per neuropodium and one per notopodium, accompanied by 0–3 capillaries. Spines short, narrow, tapering to pointed tip covered with dense cloak of fibrils ( Fig. 24C–E ) producing dark bristled tip in light microscope ( Fig. 26B–D ). Sexually mature specimen (USNM 1661068) with long natatory capillaries in anterior and middle setigers.

Posterior expanded section with nine segments in holotype and up to 14 segments in larger specimens Fig. 25 A, C, F ). These expanded sections rounded dorsally, flattened ventrally, tapering to pygidium consisting of a short, rounded lobe ventral to anal opening.

Methyl green staining. The tip of the prostomium stains intensely with MG as well as several segments on venter of 5–7 anterior setigers ( Fig. 25G ). The dorsal tentacles when present may retain stain lightly; the rest of the body does not retain any stain externally.

Remarks. Chaetozone castouria n. sp. is a small deep-water threadlike species with a long, moniliform abdominal section terminating in an expanded posterior region with crowded segments that is rounded dorsally and flattened ventrally. The acicular spines of C. castouria n. sp. are limited to the posterior quarter of the body or in the largest specimens, a few far posterior setigers. The spines occur in both noto- and neuropodia and are short and taper to a pointed tip that is covered with fine bristles ( Fig. 24C–E ); in phase contrast, these bristles produce a darkened apex to the spines ( Fig. 26B–D ). The spines number no more than two per neuropodium and one per notopodium and are usually accompanied by 2–3 capillaries.

The moniliform segments, the expanded posterior section of the body, and MG bands on the venter of some anterior setigers of Chaetozone castouria n. sp. are reminiscent of similar morphology among species of the genus Aphelochaeta , including the type-species, Aphelochaeta monilaris Hartman, 1961 from offshore California. However, by definition, species of Aphelochaeta do not have acicular spines anywhere along the body. As such, C. castouria n. sp. is unique among species of Chaetozone by having an expanded posterior end to the body and acicular spines with a bristled apex.

Biology. One paratype (USNM 1661068) was observed with three large blister-like egg-bearing pouches on the dorsal surface of anterior setigers. Each pouch contains at least 5– 6 eggs having diameters of ca. 160–200 µm. Each egg has a smooth cytoplasm and distinct nucleolus. The specimen also has long natatory capillaries along much of the body. With relatively few large eggs relative to the size of the worms, it is likely that development is direct, perhaps with a type of brooding. Gametes were not observed in other specimens.

Most of the long, moniliform segments of the middle and posterior sections of the body have the gut filled with sediment giving these segments the appearance of strings of fecal pellets ( Fig. 26A ). The sediments in the gut consist of numerous tightly packed fine sand and silt-sized particles. Sediment particle size in sediments where C. castouria n. sp. occurred consisted of 70% or more silt + clay ( Blake & Grassle 1994; Maciolek et al. 1987a –b). The species occurs in middle and lower slope depths from about 1200–2200 m. Another widespread cirratulid in similar depths along the U.S. Atlantic slope with an elongate threadlike body and fecal pellets in elongate moniliform segments is the recently described Caulleriella rodmani Blake, 2021b .

Etymology. The epithet, castouria , is from the Greek castor, for beaver and oura, Greek for tail in reference to the expanded and flattened posterior segments of this species that when best developed, resembles the tail of a beaver.

Distribution. Widespread along the entire U.S. Atlantic slope from off New England to the Carolinas: New England slope, 1230–2180 m; Mid-Atlantic slope, 1492–2200 m; South Atlantic slope, 1003–2029 m.

Figures

FIGURE 24. Chaetozone castouria n. sp. Paratype (USNM 1660996): A, anterior end, dorsal view; B, anterior end, ventral view; C–E, neuropodial acicular spines.

FIGURE 25. Chaetozone castouria n. sp. A, entire worm; B, anterior end, left lateral view; C, posterior end, dorsal view; D, anterior end of ovigerous specimen (arrows denote egg masses); E, detail of egg mass (not to scale); F, posterior end, dorsal view; G, anterior end of specimen (arrows denote MG concentrations). A–F stained with Shirlastain A; G, stained with MG. A–C, Holotype (USNM 1660990); D–F, Paratype (USNM 1661068); G, Paratype (USNM 1661069).

FIGURE 26. Chaetozone castouria n. sp. Paratype (USNM 1660991);A, entire worm, right lateral view. B–D, paratype (USNM 1660997): acicular spines and capillaries. A, Stained with Shirlastain A.