Euchone danieloi Capa & Murray, 2015, n. sp.

Euchone danieloi n. sp.

(Figs 4–5)

Material examined. Queensland, Lizard Island. Holotype: AM W.45167, MI QLD 2444; Paratypes: AM W.45486, MI QLD 2445 (3); AM W.47402 (on SEM), Watson’s Bay, 14°39′26′′S, 145°27′3′′E, sand, 6.5 m, 28 Aug 2010.

Description. Holotype 4.7 mm long (crown 1.5 mm), 0.4 mm wide, with eight thoracic and 12 abdominal chaetigers. Specimens not studied alive. Preserved specimens with 3–4 bands of pigment on radioles and pinnules, with some paired darker brown pigment spots embedded in radiolar rachis and adjacent flanges (Fig. 4 A–B). Body lacking pigmentation (Fig. 4 A–B). Two red eyespots on sides of peristomium (Fig. 4 A) and two on sides of pygidium (Fig. 4 F). Methyl blue stain reveal two transverse glandular bands on thoracic ventral shields and biannulate glandular bands on posterior abdominal segments (Fig. 4 C–E). Glandular ridge in chaetiger two very narrow. Radiolar crown with semicircular lobes, with six pairs of radioles and two pairs of ventral radiolar appendages (Fig. 4 A–B). Dorsal and ventral flanges absent. Basal membrane about 1/2 length of radioles. Radioles with narrow flanges; tapering tips distally bare of pinnules for 1/6 the length of radioles (Fig. 5 A). Two rows of vacuolated cells supporting radioles basally, not extended to radiolar flanges. Radiolar eyes absent. Dorsal lips with short radiolar appendages; pinnular appendages absent (Fig. 5 B–C). Ventral lips and parallel lamellae present; ventral sacs absent. Anterior peristomial ring lobe distally entire and digitiform, exposed beyond posterior peristomial ring collar (Fig. 5 D–E). Collar well developed with dorsal margins fused to faecal groove, anterior margin entire ventrally with a small shallow midventral depression (Fig. 5 D–E). Glandular ridge present on chaetiger 2, very narrow. Ventral shields only distinguishable after methyl blue staining (Fig. 4 C). Interramal eyespots absent. Collar chaetae narrowly-hooded arranged in oblique rows. Following thoracic notopodial prechaetal and postchaetal lobes well developed, superior notochaetae broadly-hooded, inferior shorter broadlyhooded (type B), with additional row of bayonet chaetae present (Fig. 5 G–H). Thoracic neuropodia uncini acicular with five rows of similar-sized teeth over main fang, covering half its length (Figs 4 G, 5I). Companion chaetae absent. Abdominal chaetae on short, slightly elevated neuropodia, with elongate narrowly-hooded chaetae in transverse rows (Fig. 5 J). Notopodia of anterior abdominal chaetigers with avicular uncini with five rows of similar-sized teeth over main fang, covering half its length (Figs 4 I, 5K), well developed breast and very short handle. Posterior chaetigers containing the pre-pygidial depression with uncini with 6–7 rows of teeth over main fang, covering most of its length, enlarged rounded breasts and handles absent (Figs 4 H, J, 5L). Abdomen with a broad pre-pygidial depression occupying six chaetigers, with raised membranous lateral flanges connected anteriorly by a rounded membrane (Fig. 5 M–N). Pygidium bluntly rounded, with two red pygidial eyespots (Figs 4 F, 5M–N). Pygidial cirrus absent (Fig. 5 M–N). Tube not observed.

Variation. Size range 2–5 mm in body length, crown up to 3.5 mm long; 0.3–0.8 mm wide. Eight thoracic and 12–15 abdominal chaetigers. Radiolar crown with 6–7 pairs of radioles. In paratypes pre-pygidial depression can occupy up to eight chaetigers.

TABLE 2. Known Euchone spp. with some distinguishing characters, based on Fitzhugh (2002), original and recent descriptions. States in quotation marks (“ ”) indicates terminology used in original description. (?) indicated doubtful interpretation of attributes,? unknown. Source of information other than original descriptions: Banse 1970, 1972, Hartman 1976, Fitzhugh 2002, Tovar-Hernández 2007, 2008, Tovar-Hernández & Sosa-Rodríguez 2006, Giangrande & Licciano 2006, Licciano et al. 2009. Euchone purpurea Tauber 1879, and E. laurencii McIntosh, 1916 are omitted from the table, as descriptions, drawings or morphological information about the species could not be found.

…Continued on next page …Continued on next page The size of flanges can apparently change with contraction (Hartman 1965) Remarks. This species is characterised by the presence of two pairs of ventral radiolar appendages, basal membrane joining radioles for half their length, collar with a small shallow midventral depression, inferior thoracic chaetae type B, pre-pygidial depression occupying about eight chaetigers with wide flanges joined anteriorly, and lacking a pygidial cirrus. The pigmentation pattern, maintained (at least partially) in preserved specimens, also seems a characteristic feature of the species. Other Euchone species that possess an abdominal pre-pygidial depression occupying more than seven chaetigers with lateral flanges, and with inferior thoracic notochaetae that are broadly-hooded of type B include Euchone cochranae Fitzhugh, 2002, from the Andaman Sea; Euchone heterochaeta (Rullier, 1972), from New Caledonia; Euchone pallida Ehlers, 1908, from Kerguelen Islands and Antarctica; and Euchone variabilis Hutchings & Murray, 1984, from southeastern Australia (Table 2). Euchone cochranae differs from E. danieloi n. sp. in the presence of a short pygidial cirrus (Fitzhugh 2002), absent from the new species, and in the shape of the flanges surrounding the pre-pygidial depression, deeply incised and with elongate flaps on either side, in the former species, while there is a rounded, single anterior flap in E. danieloi n. sp. Euchone heterochaeta differs from the new species by the presence of elongate flaps on either side of the incised anterior margin of the flanges surrounding the pre-pygidial depression, similar to that of E. cochranae. The radiolar crown of E. heterochaeta is unknown since it was lost in the single reported specimen to date. Euchone pallida has only a short rim surrounding the pre-pygidial depression, which is also longer, occupying over 10 chaetigers instead of eight as in the new species (Licciano et al. 2009). Euchone variabilis differs from the new species in the presence of two elongated flaps on the anterior margin of the flange, instead of a unique rounded flap as in E. danieloi n. sp., and the presence of a pygidial cirrus (Hutchings & Murray, 1984) which is absent in the new species. See also Table 2 for a summary of the diagnostic attributes reported in the literature for known all Euchone species.

Etymology. This small and attractive Euchone species is dedicated to Daniel Capa. He was part of the Lizard Island Polychaete Workshop 2013 at only two years old. Although he was not able to assist with collecting or in the laboratory, all the participants enjoyed his company and acknowledge that he tried hard.

Habitat. Sand sediments, with Halophila sea grass, coral rubble and Halimeda in shallow subtidal depths to 25 m.

Type locality. Lizard Island.

Distribution. Australia (Queensland: Lizard Island).