Bitentaculate Cirratulidae (Annelida: Polychaeta) from the northwestern Pacific Islands with description of nine new species Author Magalhães, Wagner F. Author Bailey-Brock, Julie H. text Zootaxa 2013 3630 1 80 116 journal article 10.11646/zootaxa.3630.1.3 1b52af07-214d-42f1-ae87-d66d081c5c3e 1175-5326 247341 4D83BB98-9426-4138-B945-22B99034E791 Monticellina anterobranchiata sp. nov. Figures 15 A–F, 16 A–F Material examined. Holotype : Mamala Bay, south shore of Oahu Island , Hawaii, underneath threadfin mariculture cages, Sta. ER2, 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m , Feb. 2003 (USNM 1195164). Paratypes : same locality as holotype (1, USNM 1195165); Sta. FWR2, 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m , Jan. 2002 (2, USNM 1195166); 21°17ʹ16ʺ N, 158°00ʹ30ʺ W, 30 m , Sta. FWR2, Sep. 2004 (1, BPBM R3649); Mamala Bay, Sand Island outfall, south shore of Oahu Island , Hawaii, Sta. C1AR2, 21°17ʹ39ʺ N, 157°55ʹ27.9ʺ W, 18.9 m , Aug. 2009 (1 on stub, USNM 1195167). Description. Holotype 6.0 mm long, 0.3 mm wide with 63 chaetigers. Paratypes 3.0– 4.5 mm long, 0.1–0.2 wide for 47–54 chaetigers. Body dorsally rounded and ventrally flattened. Thoracic chaetigers indistinct from abdominal ones; abdominal segments tapering posteriorly towards pygidium ( Figs 15 C, 16D). Color in alcohol white to pale yellow. Prostomium short, conical, rounded distally, nuchal organs postero-lateral, rounded; peristomium with three sub-equal annulations, elongate dorsal crest terminating at anterior border of chaetiger 1 ( Figs 15 A, B, 16A). First pair of branchiae antero-lateral to dorsal tentacles on posterior border of third annulation ( Fig. 16 B). Dorsal tentacles arising at level of first chaetiger, with second pair of branchiae lateral to dorsal tentacles on chaetiger 1 ( Fig. 16 B). Chaetae all capillaries of two types ; thoracic chaetigers with 8–10 simple capillaries per fascicle ( Fig. 16 C), reducing to 5–6 capillaries per fascicle in abdominal segments. Short capillaries with basally expanded blades and sawtooth edge from anterior abdominal neuropodia (chaetigers 13–16) and from far posterior abdominal notopodia (chaetigers 40–44), completely replacing simple capillaries posteriorly ( Figs 15 D, 16E, F); barbs easily seen at 400×. MGSP. The prostomium and peristomium stain intensely with the exception of an unstained ocular area; staining pattern similar to A. petersenae Blake, 1996 b ( Fig. 15 E). Transverse ventral bands present on posterior margin of thoracic segments, extending dorsally and forming complete rings ( Fig. 15 F). FIGURE 15. Monticellina anterobranchiata sp. nov. A, anterior end, dorsal view; B, anterior end, dorso-lateral view; C, posterior end with pygidium; D, abdominal capillary with barbed edge; E, MGSP of the dorsal region showing unstained ocular area; F, MGSP of the ventral region showing the transversal bands on some thoracic chaetigers. Remarks. This new species is unique among Monticellina species due to the presence of the first pair of branchial filaments anterior to the dorsal tentacles. Other species commonly have the first pair of branchiae either lateral or postero-lateral to the dorsal tentacles ( Table 4 ). The MGSP of this new species leaves an unstained ocular area on the prostomium, very similar to Aphelochaeta petersenae which is distinct from the former by the larger size ( 35 mm ), position of dorsal tentacles and first pair of branchial filaments and absence of short barbed capillaries on posterior end. The MGSP is also very similar to that of some species of Aphelochaeta with ventral bands on thoracic segments. However, this species is placed in the genus Monticellina due to the nature of the posterior capillary chaetae, with distinct lateral barbs seen at 400× in addition to the normal fibrils along the capillary edge. Table 4 summarizes relevant morphological characters for Monticellina species closely related to M. anterobranchiata sp. nov. Etymology. The Latin name of this species refers to the anterior position of the first pair of branchiae in relation to the dorsal tentacles. Biology/Ecology. Sampled from sandy bottoms adjacent to sewage outfalls at 18 m and sandy bottoms underneath threadfin mariculture cages at 30 m . Distribution. Mamala Bay, south shore of Oahu Island , Hawaii, USA . FIGURE 16. SEM of Monticellina anterobranchiata sp. nov. A, anterior end, dorso-lateral view; B, details of the insertion of the anteriormost branchiae and dorsal tentacle; C, thoracic capillaries; D, posterior end with pygidium; E, abdominal capillaries; F, detail of the barbed edge and fibrils of the short abdominal capillaries. TABLE 4. Synoptic table of morphological characteristics of five closely related species of Tharyx including the new species from Hawaii, compared to the type species Tharyx acutus Webster & Benedict, 1887 .

Species	Prostomium	Number of peristomial annulations	Position of first pair of branchiae	Abdominal segments
T. acutus Webster & Benedict, 1887	Elongate, pointed	2–3	Posterior to dorsal tentacles; on peristomium	Narrow?
T. kirkegaardi Blake, 1991	Acutely pointed	1–2	Postero-lateral to dorsal tentacles; on peristomium	Longer than thoracic, beadlike in juveniles
T. longisetosa (Hutchings & Murray, 1984)	Short, conical	3	Postero-lateral to dorsal tentacles; on peristomium	Dorso-ventrally flattened
T. retusiseta (Hutchings & Murray, 1984)	Short, conical	3	Postero-lateral to dorsal tentacles; on peristomium	Dorso-ventrally flattened
T. parvus Berkeley, 1929	Short, pointed	1	Postero-lateral to dorsal tentacles; on chaetiger 1	Longer than thoracic, never moniliform
T. tumulosa sp. nov.	Elongate, pointed	3	Postero-lateral to dorsal tentacles; on chaetiger 1	Rounded to moniliform
continued.

Species First appearance of spines Nature of spines Posterior end (max. number of spines) T. acutus Webster & Absent on notopodia Short or long, irregular knob-tipped, Expanded laterally, simple Benedict, 1887 100 neuropodia (1–3) thickened on convex side conical pygidium Material examined. Hanauma Bay, southeast shore of Oahu Island , Hawaii. Holotype : Olive Beach, 21°16ʹ6.52ʺ N, 157°41ʹ47.35ʺ W, 18 Apr. 2000 , coll. R. Brock (USNM 1195168). Paratypes : same locality, date and collector as holotype (4, USNM 1195169; 2 on stub, USNM 1195170; 3, BPBM R3650). Additional material: Sand Island outfall, south shore of Oahu Island , Hawaii: Sta. E3R3, 21°16ʹ43.4ʺ N, 157°54ʹ39.1ʺ W, 101.2 m , Aug. 2011 (16).

T. kirkegaardi Blake , 125 notopodia (4) 1991 95 neuropodia (4)	Short or long, slightly expanded knoblike tip with subapical serrations	Tapers posteriorly toward pygidium; pygidium simple blunt lobe
T. longisetosa 70 notopodia (3) (Hutchings & 58 neuropodia (4) Murray, 1984)	Long, faintly striated shafts, shallowly notched	Tapers posteriorly toward pygidium; pygidium with a flattened ventral flange
T. retusiseta 70 notopodia (3) (Hutchings & 45 neuropodia (4) Murray, 1984)	Short, slightly knobbed with distal end minutely concave	Tapers posteriorly toward pygidium; pygidium with a round flattened ventral flange
T. parvus Berkeley, Far posterior noto- and 1929 neuropodia with 2–3 spines in each	Short, curved, narrowing to blunt tip, notched with 2 poorly developed teeth	Expanded laterally, pygidium with a terminal lobe
T. tumulosa sp. nov. Far posterior noto- and neuropodia with 3–4 spines in each	Short or long with sub-equal blunt teeth and denticulate edge	Tapers posteriorly toward pygidium; pygidium simple rounded lobe
Monticellina hanaumaensis sp. nov. Figures 17 A–E, 18 A–D

Description. Holotype 11 mm long, 0.4 mm wide in thoracic segments, 0.3 mm wide in abdominal segments for about 97 chaetigers. Paratypes 4–10 mm long, 0.2–0.5 mm wide, for about 60–88 chaetigers. Body divided into three parts ( Fig. 17 E): thoracic chaetigers distinct but not crowded, not expanded, rounded dorsally and slightly flattened ventrally ( Fig. 17 A); abdominal segments apparently longer than wide, never moniliform ( Fig. 17 E); posterior end slightly expanded, chaetigers distinct, rounded dorsally, flattened ventrally, without ventral and dorsal grooves ( Fig. 17 C). Body color in preserved specimens light to dark brown; anterior and posterior ends darker than mid-body chaetigers ( Fig. 17 E). Pygidium with simple dorsal lobe above anal aperture ( Fig. 17 C). Prostomium conical, rounded anteriorly, without eyes and with a pair of postero-lateral nuchal organs ( Figs 17 A, B, 18A, B). Peristomium elongate, as long as 5–6 anterior chaetigers, without distinct annulations ( Figs 17 A, B, 18A, B). Dorsal tentacles arising between peristomium and chaetiger 1 ( Fig. 18 B); first branchiae postero-lateral to dorsal tentacles on chaetiger 1 and present throughout; branchiae from abdominal chaetigers 2–3 times thicker than thoracic branchiae and directed anteriorly ( Fig. 17 A, D). Chaetae all capillaries of two types ; thoracic chaetigers with 8–10 simple capillaries per fascicle ( Fig. 18 D); short capillaries slightly expanded basally with very fine dentition not seen under light microscopes, beginning after chaetiger 30–35 in neuropodia and from far posterior abdominal notopodia, 2–4 capillary chaetae per fascicle ( Fig. 18 C). MGSP. Body stains light green throughout, thoracic ventral bands present in inter-segmental areas only from about chaetigers 4–12 ( Fig. 17 D). FIGURE 17. Monticellina hanaumaensis sp. nov. A, anterior end, dorsal view; B, anterior end, dorso-lateral view; C, posterior end with pygidium; D, MGSP of anterior end in ventral view; E, holotype preserved in U-shape with anterior and posterior end darker than mid-body segments. Remarks. Monticellina hanaumaensis sp. nov. , appears to be a unique species because specimens were removed from coral rubbles by dissolution of the coral skeletons with a solution of nitric acid as described in Brock & Brock (1977). The dark coloration of preserved specimens is uncommon among Monticellina . It shows similarities with Monticellina tesselata (Hartman, 1960) in the nature of the modified chaetae with very fine denticles, peristomium with indistinct annulations and posterior end with expanded segments but differs most notably by the presence of a mid-dorsal thoracic ridge and presence of conspicuous lateral processes formed from adhering mucus in the tubes of M. tesselata . This new species may easily be misidentified as belonging to Aphelochaeta due to the presence of very fine dentition in the modified chaetae. For instance, it shows some similarities with Aphelochaeta elongata Blake, 1996 and Aphelochaeta multifilis (Moore, 1909) in which the prostomium is merged with the peristomium forming a head with indistinct annulations. However, A. elongata has a narrow posterior end, while M. hanaumaensis sp. nov. , and A. multifilis have an expanded posterior end and the latter differs from M. hanaumaensis sp. nov. , by having a ventral groove. Etymology. This species is named after its type locality Hanauma Bay in Oahu Island , Hawaii. Biology/Ecology. Specimens were recovered from acid dissolved samples and may be residents of burrows made by other organisms as observed in Cirratulus balaenophilus which live in fresh whale bones but do not appear to bore into them (Taboada et al. 2012). Distribution. Hanauma and Mamala bays, south shore of Oahu Island , Hawaii, USA .