Amblyosyllis Grube, 1857

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 : 260-261

Genus Amblyosyllis Grube, 1857

Amblyosyllis Grube, 1857: 186 .

Gattiola Johnston, 1865: 195 .

Nicotia Costa, 1864: 160 .

Pterosyllis Claparède, 1863: 46 .

Thylaciphorus Quatrefages, 1865: 55 .

Pseudosyllides Czerniavsky, 1882: 173 .

Type species. Amblyosyllis rhombeata Grube, 1857 by monotypy.

Diagnosis. Body less than 5 mm in length, dorsoventrally flattened, extremely fragile, with few segments; peristomium and last segment without parapodia and chaetae, each with 2 pairs of cirri. Intersegmental constrictions strongly marked, midbody segments typically trapezoidal in shape. Prostomium with 3 antennae, 4 eyes, and usually 2 anterior eyespots, sometimes ventrally located. Palps short, less than length of prostomium, basally fused, divergent, usually ventrally folded, and difficult to see dorsally. Peristomium shorter than following segments, with 2 pairs of tentacular cirri, and 2 nuchal organs, forming nuchal lappets, usually ciliated. Antennae, tentacular and dorsal cirri long, greater than body width, usually strongly coiled, sometimes forming skeins, smooth to indistinctly articulated, fragile. Pigmentary glands on dorsal and ventral cirri, sometimes forming distinct vesicles. Pharynx long, slender, highly convoluted, with trepan formed by several teeth, lacking median tooth. Proventricle proportionally small to body width. Ventral cirri large, located lateroposteriorly to parapodial lobes, similar in length. Compound chaetae, heterogomph, bidentate falcigers, numerous, present on all chaetigers, other types of chaetae rarely present; chaetae similar in all species. Pygidium with 2 long anal cirri, third length of dorsal cirri.

Remarks. Species belonging to this genus appear to be uncommon and are typically known from damaged incomplete specimens. Distinguishing species is therefore difficult. The structure of the nuchal organs and trepan are useful characters. The method of reproduction not well known, although a mature male has been observed with natatory chaetae and one species is known to brood eggs in a gelatinous mass, suggesting that the species of this genus are epigamic ( Pernet, 1998).

Key to Australian species of Amblyosyllis 1 Nuchal lappets elongated, reaching middle of chaetiger 1 .............................. A. enigmatica n.sp.

—— Nuchal lappets rounded, small, not extending beyond peristomium ................................................. 2

2 Dorsal cirri with few, large, distinct vesicles ( Fig. 5A). Compound chaetae with blades all similar, with small dorsoventral gradation in length ( Fig. 5C). Trepan with monocuspid teeth ................................................... A. vesiculosa

—— Dorsal cirri with small, numerous granules ( Fig. 3A). Compound chaetae with blades elongated (50–102 µm in length) ( Fig. 3D),

with distinct dorsoventral gradation in length. Trepan with 6 penta cuspid teeth, 2 of them separated by single monocuspid tooth ............... A. multidenticulata n.sp.