Amblyosyllis enigmatica, San Martin & Hutchings, 2006

San Martin, G & Hutchings, PA, 2006, Eusyllinae (Polychaeta: Syllidae) from Australia with the Description of a New Genus and Fifteen New Species, Records of the Australian Museum 58, pp. 257-370 : 261-264

Amblyosyllis enigmatica n.sp.

Figs 1A–C, 2A–E

? Amblyosyllis granosa .— Augener, 1913: 243. Not Ehlers, 1897: 58.

Material examined. HOLOTYPE ( AM W28943) AUSTRALIA: NEW SOUTH WALES: NW corner of Bowen Is., Jervis Bay , 35°06.81'S 150°46.11'E, dense bryozoan community under rock ledge, 13 m, coll. P. Serov & G.D.F. Wilson, 8 Dec 1993.

Additional material examined. Elizabeth Reef, Tasman Sea , 29°55.8'S 159°01.3'E, algae, reef flat, near wreck “Yoshin Maru Iwaki”, 0.5 m, Elizabeth & Middleton Reefs Expedition, 1987, 14 Dec 1987, 6 + 3 on SEM stub ( AM W28923) .

Description. All specimens incomplete; holotype ( Fig. 1A) mature, epigamic specimen, with regenerating posterior end, 3.5 mm long, 0.6 mm wide, with 10 chaetigers plus regenerating segments. Body large, segments trapezoidal ( Fig. 2A), especially those of midbody, fragile; some specimens colourless, others strongly pigmented with 2–4 dorsal transverse dark bands on each segment, more marked on midbody. Prostomium oval, posteriorly notched, with 4 large red eyes in trapezoidal arrangement, covering lateral margins ( Fig. 1A). Antennae long, inserted on anterior margin of prostomium, with distinct ceratophores ( Fig. 2B). Palps free, fused basally, ventrally directed. Peristomium shorter than subsequent segments, with 2 pairs of tentacular cirri, dorsal ones twice as long as ventral; 2 ciliated, elongated nuchal lappets ( Figs 1A, 2A–C), extending to middle of chaetiger 1, with dorsal, longitudinal row of pigment ( Fig. 1A). Dorsal cirri long, as wide as body, indistinctly articulated, with numerous dark, granular inclusions, irregularly arranged in 3 longitudinal rows ( Fig. 1A). Parapodial lobes long, conical, with long, digitiform prechaetal papilla ( Fig. 2D). Ventral cirri conical, large, broad, arising ventrolaterally ( Fig. 2D), upwardly directed, with granular, dark inclusions ( Fig. 1A). Parapodia with 16–18 compound, heterogomph chaetae ( Fig. 2E), blades distinctly bidentate; within fascicle blades exhibiting dorsoventral gradation in length ( Fig. 1C), about 100 µm in length dorsally, 43 µm in length ventrally, with short spines on margin; about 6–8 aciculae per parapodium, straight, distally pointed. Pharynx slender, with several coils ( Fig. 1A); trepan composed of 6 teeth each with 5 denticles ( Fig. 1B). Proventricle extending through 1.5 segments, with 11– 13 muscle cell rows. Holotype with notoacicula and capillary notochaetae, curved, digitiform, fleshy, dark structure arising from cirrophores from chaetiger 6 onwards ( Fig. 1A, arrows); also, some ciliary bands present on lateral areas of first 4 chaetigers ( Fig. 1A). Curved structure present on holotype missing on other material examined; function unknown.

Remarks. This species is characterized by having elongated nuchal lappets and a trepan with 6 teeth, each with 5 denticles; no species of the genus has been described with such a combination of characters. The general body form is almost identical to Amblyosyllis granosa Ehlers, 1897 , from Magellan Strait and Galápagos Islands. Ehlers (1897) originally described this species with the anterior margin of the pharynx lacking teeth; subsequently, Westheide (1974) reported the same species from Galápagos, describing a trepan with 6 teeth, each formed by a long, median cusp and 2 lateral, much smaller ones. Examination of 1 specimen of the type series of Amblyosyllis granosa from Punta Arenas ( Chile) (NFMN 5318) did not reveal any teeth on anterior margin of pharynx, as originally described, so, we are describing the Australian material as a new species A. enigmatica . A previous record of A. granosa from Australia by Augener (1913) is also referred with caution to A. enigmatica n.sp. Augener’s material is not available for examination in the HZM and is presumed lost. Amblyosyllis granosa , however, could be present in Australian waters.

Amblyosyllis formosa ( Claparède, 1863) from European coasts is also similar to A. enigmatica n.sp., with regards to body form and the presence of long nuchal lappets; this species, however, has a trepan with 6 unidentate teeth (San Martín, 2003).

Little is known about reproduction within Amblyosyllis . The digitiform structures arising from cirrophores of chaetiger 6 onwards have never been described before, and their significance is unknown, but they may be used in reproduction, since they are only present on the single epigamic specimen examined. Knowing whether such structures occur in other species of the genus would be of interest.

Amblyosyllis spectabilis .— Haswell, 1920 (in part): 108, pl. 13, figs 4–10. Not Johnston, 1865: 195.

Material examined. HOLOTYPE ( AM W502 ) AUSTRALIA: NEW SOUTH WALES: Port Jackson , 33°51'S 151°16'E, Feb 1920, coll. W.A. Haswell, mounted on microscope slide . PARATYPES NW corner of Bowen Is. , Jervis Bay, 35°06.81'S 150°46.11'E, dense bryozoan community under rock ledge, 13 m, coll. P. Serov & G.D.F. Wilson, 8 Dec 1993, 3 on SEM stub ( AM W26323) ; Halfway Reef , 200 m S of Sullivan Reef, Ulladulla, 35°21.42'S 150°29.31'E, red algae on rock ledges at base of wall, 13 m, coll. A. Murray, 3 May 1997, 2 ( AM W28229) ; Port Jackson , 33°50'S 151°16'E, 1 ( AM W25245) , mounted on slide, id. W.A. Haswell as A. spectabilis .

Description. Body compact ( Fig. 4A), longest complete specimen examined 5.7 mm long, 0.6 mm wide, with 13 chaetigers and 1 posterior segment without parapodia or chaetae. Colour pattern variable; holotype collected in 1920 colourless. More recently collected paratypes with several dark, violet transverse dorsal bands of pigment on each segment; intensity of bands differs between individuals. Antennae, tentacular, dorsal and ventral cirri provided with numerous, dark, small globular glands ( Fig. 3A). Prostomium wider than long, margins rounded, with 2 pairs of eyes in open trapezoidal arrangement ( Fig. 3A), and 2 anterior, ventrally located, small eyespots. Antennae long, 3 times width of prostomium, distinctly articulated, with numerous articles, arising on anterior margin of prostomium from distinct ceratophores ( Figs 3A, 4B). Palps ventrally directed ( Fig. 4C), forming double lip over mouth, nearly invisible dorsally ( Fig. 3A). Peristomium about half of length of subsequent segments, with 2 pairs of tentacular and dorsoventral gradation in length of blades ( Fig. 3D), length in midbody segments about 102 µm, 50 µm in length ventrally on midbody. Parapodia with 5–6 aciculae, straight, distally pointed. Pharynx long extending to chaetiger 5, narrow width, with several coils visible inside pharynx ( Fig. 3A); trepan formed by 6 large teeth with 5 denticles separated by 1 unidentate, much smaller tooth ( Fig. 3B). Proventricle small, located on chaetiger 5 ( Fig. 3A), with 17–18 muscle cell rows. Pygidium small, trapezoidal, with 2 long anal cirri, half length of dorsal cirri.

Remarks. Haswell (1920) referred his Australian specimens to the European species Amblyosyllis spectabilis ( Johnston, 1865) , a poorly known species usually considered as a synonym of A. formosa , which may represent a suite of sibling species. Johnston’s description of Gattiola spectabilis states that the pharynx is short and barrel shaped without teeth and long nuchal lappets are illustrated. In contrast, Haswell (1920) reported that teeth were present in the pharynx. Re-examination of this material has shown that it belongs to a new species, Amblyosyllis multidenticulata . This new species is characterized by having small nuchal lappets and a trepan comprising 6 teeth each with 5 denticles, which are each separated by 1 small tooth ( Fig. 3B); no other described species of this genus has been described with this arrangement of teeth on the trepan. The most similar species is Amblyosyllis madeirensis Langerhans, 1879 , which occurs along European coasts; both species have small nuchal lappets, similar colour pattern, and body shape. The European species, however, has only 6 pentacuspid teeth on the trepan, and the segment that bears the proventricle is distinctly larger than other segments (San Martín, 2003). We are thus describing the Australian material as a new species. Haswell (1920) also reported some specimens 10 mm long, with 14–30 segments, these were not available for examination and because of their size we suggest that they probably represent another species.

Habitat. Occurring among bryozoans and others colonial animals, in shallow depths.

Distribution. Australia (New South Wales).

Etymology. The specific name refers to the highly denticulated trepan.