Bitentaculate Cirratulidae (Annelida: Polychaeta)

Zootaxa 3630 (1): 080–116 www.mapress.com / zootaxa / Copyright © 2013 Magnolia Press

ISSN 1175-5326 (print edition)

Article

ZOOTAXA ISSN 1175-5334 (online edition)

http://dx.doi.org/10.11646/zootaxa.3630.1.3 http://zoobank.org/urn:lsid:zoobank.org:pub:4D83BB98-9426-4138-B945-22B99034E791

Bitentaculate Cirratulidae (Annelida: Polychaeta) from the northwestern Pacific Islands with description of nine new species WAGNER F. MAGALHÃES¹,² & JULIE H. BAILEY-BROCK¹,²,3 ¹Department of Biology, University of Hawaii at Manoa, 2450 Campus Road, Dean Hall 2, Honolulu, Hawaii 96822, USA ²Water Resources Research Center, University of Hawaii at Manoa, 2540 Dole Street, Honolulu, Hawaii 96822, USA ³Corresponding author. E-mail: [email protected]

Abstract Thirteen cirratulid species from the Hawaiian, Mariana and Marshall Islands are described. Nine species are new to science: Aphelochaeta arizonae sp. nov., Aphelochaeta honouliuli sp. nov., Caulleriella cordiformia sp. nov., Chaetozone michellae sp. nov., Chaetozone ronaldi sp. nov., Monticellina anterobranchiata sp. nov., Monticellina hanaumaensis sp. nov., and Tharyx tumulosa sp. nov., from Oahu, Hawaii and Aphelochaeta saipanensis sp. nov., from Saipan in the Mariana Islands. Dodecaceria fewkesi and Monticellina nr. cryptica are newly recorded from the Hawaiian Islands. Dodecaceria laddi is widely distributed in the western Pacific and material collected from the Hawaiian, Mariana and Marshall islands is described. We provide SEM photographs for all species in addition to line drawings and methyl green staining pattern photographs for the new species. Key words: taxonomy, new species, Hawaiian Islands, Mariana Islands, Marshall Islands

Introduction The cirratulids are comprised of polychaete worms with a single pair of palps or groups of tentacles attached anteriorly. They are easily recognized by the numerous slender filiform branchiae present throughout the body. The family consists of 11 accepted genera organized by Blake (1996b) in three groups, the multitentaculate genera (i.e. Cirratulus Lamarck, 1801, Timarete Kinberg, 1866, Protocirrineris Czerniavsky, 1881, Cirriformia Hartman, 1936, and Fauvelicirratulus Çinar & Petersen, 2011), the bitentaculate soft-substrate genera (i.e. Chaetozone Malmgren, 1867, Tharyx Webster & Benedict, 1887, Caulleriella Chamberlin, 1919, Monticellina Laubier, 1961, and Aphelochaeta Blake, 1991), and the bitentaculate hard-substrate genus (Dodecaceria Örsted, 1843). Recent studies of cirratulid taxonomy have resulted in a large number of undescribed species (Blake 2006; Doner & Blake 2006; 2009; Dean & Blake 2007; 2009; Elias & Rivero 2008; 2009a,b) and a new genus (Çinar & Petersen 2011). However, cirratulids are still poorly known taxonomically since few and inconsistent diagnostic characters are used to describe their morphology (Blake 1996b). This situation is particularly true for the western Pacific islands given that most descriptions are not adequately detailed and several cirratulids have been listed as undetermined species or named after European species. Studies regarding cirratulid polychaetes from the western Pacific islands were first made by Kinberg (1866), who described Cirriformia crassicollis (formerly Audouinia crassicollis) from Honolulu reefs. A few decades later, Ehlers (1905) described Cirriformia semicincta (formerly Audouinia semicinctus) from Honolulu Harbor. Treadwell (1906) then reported Cirratulus zebuensis McIntosh, 1885 and Cirriformia capensis Schmarda, 1861 (as Cirratulus capensis) from Honolulu reefs; however, he did not describe the segmental origin of the tentacles or branchial filaments, basing his description on the shape of chaetae and hooks, which are not relevant in differentiating the multitentaculate genera. Treadwell (1943) described Audouinia branchiata from Honolulu, which was later renamed to Cirriformia hawaiensis by Hartman (1956) and transferred to the genus Timarete by Magalhães & Bailey-Brock (2010). Hartman (1954) described Dodecaceria laddi from Enewetak atoll, northern Marshall Islands, and this species is now known to be broadly distributed in the western Pacific (e.g. Woodwick 1964; Reish 1968; Gibbs 1971; Bailey-Brock et al. 1980; Bailey-Brock 1987; Devaney & Bailey-Brock 1987).

80 Accepted by P. Hutchings: 30 Jan. 2013; published: 19 Mar. 2013

The Hawaiian Islands are by far the most well-studied group of islands from the western Pacific. The first large study of the polychaetes of these islands was made by Hartman (1966), who identified 168 species including six cirratulids, all of them reported by Bailey-Brock (1987) in her treatment of the Hawaiian polychaetes, which included 243 polychaete species with seven cirratulids, adding Dodecaceria laddi to Hartman’s list. Magalhães & Bailey-Brock (2010) redescribed two poorly known endemic cirratulids, Cirriformia crassicollis and Timarete hawaiensis, but up to now the bitentaculate cirratulids have been completely neglected, even though some broadly distributed taxa have been listed in unpublished reports. Here we present an initial effort to understand the diversification of cirratulids of the Pacific Ocean, providing descriptions of 13 species from the Hawaiian, Marshall, and Mariana Islands.

Materials and methods Most of the Hawaiian cirratulids have been collected during the course of several monitoring programs in Mamala Bay, south shore of Oahu Island since 1986 (e.g. Nelson 1986; Ambrose et al. 2010). Surface sediments from the vicinities of the sewage outfalls of Sand Island, Barbers Point and Waianae were collected with a 0.1 m2 van Veen grab and fixed in a 15% buffered solution of formalin and Rose Bengal. The fixed samples were elutriated over a 0.5 mm sieve and the organisms were sorted and preserved in 70% ethanol. Other specimens from the Hawaiian Islands of Oahu, Hawaii (Big Island), Maui, northwestern Hawaiian Atoll and Johnston Atoll, Enewetak and Enewetak Lagoon in the Marshall Islands, and Guam and Saipan in the Mariana Islands were retrieved from the author’s (JHB-B) personal collection and were mostly collected in the intertidal or in shallow subtidal environments. The methyl green staining pattern (MGSP) is described for all species and photographed in the new species. Specimens were bathed in a saturated solution of methyl green and 70% ethanol for a minimum of 60 seconds and the MGSP was determined after the specimens were seated for a few seconds into clean 70% ethanol as described in Blake (1996a) and Doner & Blake (2009). Scanning Electron Microscopy (SEM) analyses were carried out for all species described herein. At least two specimens of each species were dehydrated through a series of increasing concentration of ethanol ending with two changes of absolute ethanol followed by critical point drying (in a SAMDRI-795). Subsequently, they were mounted on stubs and coated with gold/palladium. SEM observations were carried out using the Hitachi S-4800 at the Biological Electron Microscopy Facility (BEMF), University of Hawaii at Manoa. Type and voucher specimens are deposited in the Bernice Pauahi Bishop Museum, Honolulu, Hawaii, USA (BPBM) and the United States National Museum of Natural History, Smithsonian Institution, Washington, D. C., USA (USNM). The following abbreviations are used in the figures: pr, prostomium; per, peristomium; nuO, nuchal organ; br, branchia (e); dt, dorsal tentacle (s); ch, chaetiger; tf, tentacular filament (s); seg, segment; noto, notopodium; neuro, neuropodium; an, annulation.

Results Family Cirratulidae Ryckholt, 1851 Genus Aphelochaeta Blake, 1991 Type Species: Tharyx monilaris Hartman, 1960 designated by Blake, 1991

Diagnosis (modified after Doner & Blake 2009). Prostomium conical; peristomium elongate with 1–4 achaetigerous annulations, with pair of grooved dorsal tentacles arising either on or anterior to chaetiger 1; first pair of branchiae arising either on or anterior to chaetiger 1; thoracic region frequently expanded, with crowded segments; abdominal segments variable, sometimes moniliform; chaetae simple capillaries, with distinct serrations or sawtooth edge not visible in light microscopy, but fibril endings sometimes seen with SEM; far posterior segments may be expanded or not, with or without dorsal and/or ventral grooves, tapering to simple pygidial lobe. BITENTACULATE CIRRATULIDAE FROM THE PACIFIC ISLANDS

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Aphelochaeta arizonae sp. nov. Figures 1 A–D, 2 A–F Material examined. Pearl Harbor, south shore of Oahu, Hawaii. Holotype: Sta. F1R2, fuel pier, 21°21′55.5″ N, 157°58′0.21″ W, 20 Dec. 1994, coll. R. Brock (USNM 1195144). Paratypes: same locality, date and collector as holotype (2, USNM 1195145; 2 on stub USNM 1195146; 2, BPBM R3639). Description. Holotype 10.5 mm long, 0.4 mm wide for 82 chaetigers. Paratypes 8–10 mm long, 0.3–0.4 mm wide for 79–88 chaetigers. Body elongate, thin, with slightly expanded anterior end and narrow posterior end; rounded dorsally and ventrally flat; last segments with ventral groove. Body with two distinct regions: thoracic region with 8–10 crowded chaetigers, wider than long, and abdominal region with round to sub-moniliform segments, as long as wide (Fig. 2D). Pygidium with a ventral lip, anal aperture placed dorsally (Fig. 1C). Prostomium triangular, as long as 3–4 anterior chaetigers, without eyes; nuchal organs present, postero-lateral as vertical slits (Figs 1A, B, 2A–C). Peristomium with three sub-equal annulations; dorsal tentacles arising from anterior margin of chaetiger 1 (Figs 1A, B, 2A–C). First pair of branchiae postero-lateral to dorsal tentacles; branchiae more abundant anteriorly but present throughout (Fig. 1A, B). Chaetae all capillaries, fibrils not visible in light microscopy; thoracic chaetae numerous, about 10–12 per fascicle, abdominal chaetae longer than thoracic ones, about 4–6 per fascicle; last chaetigers with short neurochaetae (Fig. 2E, F).

FIGURE 1. Aphelochaeta arizonae sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior end with pygidium; D, MGSP of anterior end in ventral view.

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MAGALHÃES & BAILEY-BROCK

FIGURE 2. SEM of Aphelochaeta arizonae sp. nov. A, complete individual; B, anterior end, dorso-lateral view; C, specimen regenerating posterior end; D, mid-body segments; E, thoracic capillary chaetae; F, abdominal capillary chaeta.

MGSP. The body stains uniformly. Thoracic ventral bands present on anterior end of segments, extending to parapodial ridges from chaetigers 4–10 (Fig. 1D). Remarks. The nature of posterior segments and methyl green staining patterns seem to be resourceful characteristics to distinguish the four new Aphelochaeta species reported here (Table 2). For instance, Aphelochaeta arizonae sp. nov., does not have an inflated posterior end as in A. honouliuli sp. nov., and A

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saipanensis sp. nov., and it also only has a ventral groove in posterior segments. Aphelochaeta elongata Blake, 1996 also has a narrow posterior end, but differs from A. arizonae sp. nov., by the elongated peristomium without annulations. The ventral bands formed by the MGSP in the thoracic segments seem to be common among several Aphelochaeta species (and also present in Monticellina anterobranchiata sp. nov.) but differs in relation to location of these bands, extent on chaetigers, extension to parapodial ridges and margin of the segments stained (i.e. anterior half, posterior half, whole segment, inter-segmental region). Aphelochaeta arizonae sp. nov., has ventral bands stained throughout the thoracic chaetigers but only present on the anterior margin of the segments and extending to the parapodial ridges. This staining pattern is distinct from Aphelochaeta honouliuli sp. nov., which has a very unique pattern with the thoracic region divided in three, including an unstained ‘glandular’ region. Aphelochaeta saipanensis sp. nov., has ventral bands in the posterior margin of the thoracic segments and A. arizonae sp. nov., has ventral bands in the inter-segmental areas only. Etymology. This species is named in honor of the ship USS Arizona that served during World War I. The USS Arizona sank during the Japanese attack on Pearl Harbor (type locality of this species) on 7 December 1941, taking 1,177 lives. Biology/Ecology. One specimen with regenerating posterior end (Fig. 2C) observed. Specimens collected in shallow subtidal sandy habitats. Distribution. Pearl Harbor, south coast of Oahu Island, Hawaii, USA. TABLE 1. Synoptic table of morphological characteristics of the three new Aphelochaeta species from the western Pacific Ocean compared to the type species A. monilaris (modified from Doner & Blake, 2009). Species

Number peristomial Position of first pair annulations branchiae

Thoracic profile

Abdominal segments

A. monilaris (Hartman, 1960)

2–3

Peristomium

Dorsoventrally round

Moniliform

A. arizonae sp. nov.

3

Chaetiger 1, postero-lateral Dorsally round, ventrally to dorsal tentacles flattened

Rounded to submoniliform

A. honouliuli sp. nov.

3

Chaetiger 1, postero-lateral Dorsoventrally round to dorsal tentacles

Rounded, never moniliform

Chaetiger 1, postero-lateral Dorsally round, ventrally to dorsal tentacles flattened

Narrow, never moniliform

A. saipanensis sp. nov. 3–4

continued. MGSP

Species

Ventral groove

Nature of posterior segments

A. monilaris (Hartman, 1960)

Absent

Inflated, without dorsal or Thoracic ventral bands ventral grooves

A. arizonae sp. nov.

Present in posterior abdominal segments

Not inflated with ventral groove

Thoracic ventral bands present on anterior margin of segments

A. honouliuli sp. nov.

Present in abdominal segments

Inflated with dorsal and ventral grooves

Prostomium, anterior end or 1st and posterior end of 3rd peristomial annulation stained; Thoracic bands present alternating with an unstained glandular area.

A. saipanensis sp. nov.

Shallow groove present Inflated with shallow from posterior thoracic ventral groove segments


Thoracic ventral bands present on posterior margin of segments


Aphelochaeta honouliuli sp. nov. Figures 3 A–E, 4 A–F Material examined. Mamala Bay, Sand Island outfall, south shore of Oahu Island, Hawaii. Holotype: Sta. E6R3, 21°15′50.8″ N, 157°50′57.8″ W, 105 m, Aug. 2008 (USNM 1195147). Paratypes: Sta. E6R3, 21°15′50.8″ N, 157°50′57.8″ W, 105 m, Aug. 2008 (1, BPBM R3640); Sta. E5R2, 21°16′22.7″ N, 157°51′41.2″ W, 101.8 m, Aug. 2008 (2, USNM 1195148); Sta. E1R3, 21°17′10.6″ N, 157°55′33.5″ W, 102.1 m, Aug. 2008 (2, BPBM R3641), Sta. D3R3, 21°16′55.7″ N, 157°53′48.3″ W, 50.9 m, Aug. 2008 (2, on stub, USNM 1195149). Description. Holotype 11 mm long, 0.7 mm wide in thoracic segments, 0.5 mm wide in abdominal segments, for 107 chaetigers. Paratypes 3–10 mm long, 0.2–0.5 mm wide, for about 65–120 chaetigers. Body slender and elongate, divided into three regions: expanded thoracic region with short and crowded chaetigers (10–15 chaetigers), cylindrical in cross section; abdominal region with chaetigers as long as wide, rounded, with a shallow ventral groove (Fig. 4C); and a posterior expanded region of 15–20 crowded chaetigers with dorsal and ventral grooves (Figs 3C, 4D). Pygidium a simple lobe with anal opening placed dorsally (Fig. 4D). Prostomium conical, as long as 2–3 anterior chaetigers, without eyes and with a pair of postero-lateral nuchal organs, rounded (Figs 3A, B, 4A, B). Peristomium with three annulations, third annuli slightly longer than first and second one; dorsal crest present on second and third annuli (Figs 3A, B, 4A, B). Dorsal tentacles inserted above posterior end of third peristomial annulation (Fig. 4A). Branchiae from chaetiger 1, postero-lateral to dorsal tentacles; present until posterior abdominal chaetigers (Fig. 4A). Chaetae all capillaries, fibrils not visible in light microscopy. Thoracic chaetigers with 10–12 capillary chaetae per fascicle, reduced to 8–10 in abdominal chaetigers (Fig. 4E). Abdominal notochaetae 3–4 times longer than abdominal neurochaetae (Fig. 4F).

FIGURE 3. Aphelochaeta honouliuli sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior end with pygidium in dorsal view; D, MGSP of anterior end in lateral view; E, MGSP of anterior end in ventral view.

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FIGURE 4.SEM of Aphelochaeta honouliuli sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, mid-body segments; D, posterior end with pygidium in ventral view, ventral view; E, thoracic capillary chaetae; F, abdominal capillary chaeta.

MGSP. Anterior end of prostomium and first peristomial annulation stained densely; second peristomial annulation with irregular speckles and third annulation densely stained (Fig. 3D). Transverse ventral bands present on thoracic segments (Fig. 3E); anterior third of thoracic segments with bands only on the anterior margin of segments, extending laterally to parapodial ridges, middle third with a lightly speckled ‘glandular’ area of 4–5 segments, and posterior third with the whole segmental area stained intensely, not extending laterally to parapodial ridges (Fig. 3E). Remarks. Aphelochaeta honouliuli sp. nov., seems to be closely related to Aphelochaeta glandaria Blake, 1996 and a group of undescribed species with an expanded thoracic region with several crowded chaetigers, posterior end expanded with dorsal and ventral grooves, and MGSP distinct with an unstained ‘glandular’ area on



the ventrum of the thorax (Blake 1996b). Apparently, the Hawaiian species A. honouliuli sp. nov., differs from A. glandaria mainly by the MGSP. The prostomium is stained in A. honouliuli sp. nov., while the tip is not stained in A. glandaria; peristomium with an anterior and posterior bands stained intensely in A. honouliuli sp. nov., and not reported to be intensely stained in A. glandaria. The unstained region on mid-thoracic segments is followed by complete bands in A. honouliuli sp. nov., while in A. glandaria the glandular region extends throughout the thoracic region. See Remarks for Aphelochaeta arizonae sp. nov., for further information. Etymology. Honouliuli in Hawaiian language means ‘dark harbor’ and it is the name of the sewage plant outfall in which this species thrives, being the most abundant cirratulid species found. Biology/Ecology. Two specimens were found regenerating the posterior end. Found on sandy bottoms at 50–105 m in depth. Distribution. Mamala Bay, south shore of Oahu Island, Hawaii, USA. TABLE 2. Synoptic table of morphological characteristics of the two new species from Hawaii compared to the type species Chaetozone setosa Malmgren, 1867 and two other closely related species (modified from Blake, 2006 and Dean & Blake, 2007). Species

Number of peristomial Nature of segment 1 annulations

Position of first pair of branchiae

Nature of posterior cinctures

C. setosa Malmgren, 1867

3

Chaetigerous, complete

Dorsal to notochaetae on segment 1

Complete

C. brunnea Blake, 2006

1

Achaetous, reduced

Posterior to dorsal tentacles; Complete on achaetous segment 1

C. columbiana Blake, 3 1996b

Chaetigerous, partially reduced dorsally

Lateral to dorsal tentacles; posterior end of peristomium*

Complete, large dorsal and ventral gaps

C. michellae sp. nov. 3

Chaetigerous, complete

Lateral to dorsal tentacles; on chaetiger 1

Complete

Achaetous, complete

Postero–lateral to dorsal tentacles; on achaetous segment 1

Complete; spines overlap ventrally

C. ronaldi sp. nov.

1

continued. Species

First appearance of spines (max. number of spines)

Companion chaetae

Pygidium

C. setosa Malmgren, 1867

50 notopodia (10–12) 40 neuropodia (10–12)

Long, thin capillaries

Simple ventral lobe

C. brunnea Blake, 2006

35 notopodia (7–8) 30 neuropodia (9–10)


Simple ventral disk

C. columbiana Blake, 1996b

120–135 notopodia (5–6) 105–120 neuropodia (5–6)

Long, thickened capillaries

Short blunt lobe with thin terminal filament

C. michellae sp. nov.

50–60 notopodia (6–7) 40 neuropodia (6–7)


Simple ventral lobe

C. ronaldi sp. nov.

26–27 notopodia (9–10) 22–24 neuropodia (9–10)


Simple ventral disk

* The original description of this species states that the branchiae arise from above the peristomium, lateral to dorsal tentacles. The key to species in the same paper describes the position as being from chaetiger 1. The drawings indicate that the first pair of branchiae are peristomial but chaetiger 1 seems to be reduced.

Aphelochaeta saipanensis sp. nov. Figures 5 A–E, 6 A–F Material examined. Saipan, Mariana Islands. Holotype: Tanapag reef flats, 15°14′12.40″ N, 145°44′36.33″ E, Dec. 2006, coll. D. Bybee (USNM 1195150). Paratypes: same locality, date and collector as holotype (4, USNM BITENTACULATE CIRRATULIDAE FROM THE PACIFIC ISLANDS


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1195151; 2 on stub, USNM 1195152; 5, BPBM R3642; 20 incomplete specimens, BPBM R3643). Additional material: same locality, date and collector as type series (21). Description. Holotype 4.2 mm long, 0.2 mm wide in thoracic and abdominal segments for 67 chaetigers. Paratypes 3–6.0 mm long, 0.1–0.2 mm wide, for about 60–84 chaetigers. Body divided into three regions: thoracic region slightly expanded, rounded dorsally and flattened ventrally (sometimes with a shallow ventral groove), with 8–10 more or less crowded chaetigers; abdominal region with narrow segments, wider than long, never moniliform (Fig. 6C); posterior end with 15 expanded crowded chaetigers with a shallow ventral groove only (Fig. 6D). Pygidium with a ventral lip and anal aperture placed dorsally (Figs 5C, 6D). Prostomium conical, rounded anteriorly, without eyes and with a pair of postero-lateral nuchal organs, as vertical slits (Figs 5A, B, 6A, B); peristomium elongate, with 3–4 annulations, first and second sub-equal and third elongate, almost as long as the two first combined; second annulation sometimes seen as two (Figs 5A, B, 6A, B). Dorsal tentacles arising anterior to chaetiger 1 (Fig. 6A); first pair of branchia postero-lateral to dorsal tentacles on chaetiger 1 (Fig. 6A), continuing until posterior end. Chaetae all capillaries with thick, dark gold base of about 1/4 of the capillary length (Figs 5E; 6E); fibrils not visible in light microscopy. Thoracic chaetigers with 10–12 capillary chaetae per fascicle (Fig. 6E, F) reducing to 4–6 posteriorly in abdomen.

FIGURE 5. Aphelochaeta saipanensis sp. nov. A, anterior end, dorsal view; B, anterior end, dorso-lateral view; C, posterior end with pygidium; D, MGSP of anterior end in lateral view; E, abdominal capillary chaetae showing brown coloration.



FIGURE 6. SEM of Aphelochaeta saipanensis sp. nov. A, anterior end, dorsal view; B, anterior end, lateral view; C, mid-body segments; D, posterior end with pygidium, ventral view; E, base of thoracic capillary chaetae; F, distal portion of thoracic capillary chaeta.

MGSP. Third peristomial annulation densely stained, transverse ventral bands present on posterior margin of thoracic segments. Remarks. See Remarks for Aphelochaeta arizonae sp. nov., and Table 2. This new species has distinct capillary chaetae that are basally thick and brown in color, readily seen under light microscope (Fig. 5E). BITENTACULATE CIRRATULIDAE FROM THE PACIFIC ISLANDS


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Etymology. This species is named after the type locality Saipan in the Mariana Islands. Biology/Ecology. Several specimens found regenerating anterior and posterior ends. Distribution. Only known from Saipan, Mariana Islands, northwestern Pacific Ocean.

Genus Caulleriella Chamberlin, 1919 Type Species: Cirratulus viridis Langerhans, 1880, original designation by Chamberlin, 1919.

Diagnosis (after Dean & Blake 2007). Prostomium elongate; peristomium elongate to short, with achaetigerous annulations; dorsal tentacles usually beginning anterior to setiger 1; middle body segments not moniliform; parapodia with widely separated noto- and neuropodia; modified chaetae include bidentate crotchet-like hooks, not arranged in cinctures.

Caulleriella bioculata (Keferstein, 1862) Figure 7 A–F Cirratulus bioculatus Keferstein, 1862: 121–122, figs. 23–27. Caulleriella bioculatus: Day 1967: 509, fig. 20.2. q. Caulleriella bioculata: Hartman 1961: 107. Hartman 1965: 324. Hartman 1969: 227–228. Hutchings & Murray 1984: 65.

Material examined. Mamala Bay, Barbers Point outfall, south shore of Oahu Island, Hawaii: Sta. HB4R2, 21°16′48.0″ N, 158°01′38.3″ W, 61 m, Mar. 2000 (2, USNM 1195153); Sta. HB4R3, 21°16′47.9″ N, 158°01′38.3″ W, 61.3 m, Mar. 2000 (4); Sta. HB4R4, 21°16′47.7″ N, 158°01′38.3″ W, 61.3 m, Feb. 2001 (5 on stub, USNM 1195154); Sta. HB4R5, 21°16′48.0″ N, 158°01′38.3″ W, 61 m, Feb. 2001 (3, BPBM R3644). Sand Island outfall, south shore of Oahu Island, Hawaii: Sta. E2R2, 21°16′43.4″ N, 157°54′39.1″ W, 101.2 m, Mar. 2002 (2); Sta. D1R2, 21°17′23.2″ N, 157°55′29.5″ W, 48.8 m, Mar. 2002 (1); Sta. E6R2, 21°15′50.8″ N, 157°50′57.9″ W, 102.1 m, Aug. 2008 (2). Waianae outfall, southwest shore of Oahu Island, Hawaii: Sta. W9R1, 33 m, May 1998 (3); Sta. ZER5, 27 m, Mar. 1992 (2); Sta. ZR3, 35 m, Mar. 1992 (1). Hanauma Bay, Keyhole Point, southwestern shore of Oahu Island: Sta. R2, 08 Jul. 1999 (4). Kahekili Beach Park, Maui Island, collected on Halimeda kanaloana meadows, 30 m, 15 Jun. 2005, coll. A. Fukunaga (1). Guam, Mariana Island, Sta. 0063, Jul. 2006 (8). Description. Specimens 1.8–7 mm long, 0.1–0.5 mm wide for about 27–78 chaetigers. Body elongate and cylindrical in cross section, mid-body segments wider than anterior and posterior ones. Juveniles (