Autolytus rostripalpus Chlebovitch, 1962

Nygren, Arne, 2004, Revision of Autolytinae (Syllidae: Polychaeta)., Zootaxa 680, pp. 1-314 : 112-113

Autolytus rostripalpus Chlebovitch, 1962 (Fig. 53 A–E)

Autolytus rostripalpus Chlebovitch, 1962: 171 –173, fig. 3.

Material examined. Russia: holotype, ZIL 4572, 4 paratypes ZIL 4570, Onekotan Island, Bay of Nemo, 24 Aug 1955.

Description. Length 6–6.5 mm for 6+(27–29)+(0–10) chaetigers, width c. 0.5 mm in region a excluding parapodial lobes, width c. 0.9 mm in region b including parapodial lobes. Preserved specimens yellowish, no colour markings; eyes red. Ciliation not possible to assess.

Prostomium rounded rectangular, slightly concave anteriorly; ventrally with 2 lateral triangular processes (Fig. 53B). Eyes large, 2 pairs, with lenses; eyes situated on ventral and dorsal side of prostomium (Fig. 53A, B), ventral pair larger. Palps absent. Nuchal epaulettes as small ridges just posterior to prostomium (Fig. 53A).

Median antenna reaching chaetiger 8–9 (n=3), inserted on posterior part of prostomium (Fig. 53A). Lateral bifid antennae, inserted on anterior margin of prostomium, 2 times as long as prostomial width; basal part 1/2 of total length, outer ventral rami slightly longer than inner dorsal rami (Fig. 53A). Basal part and inner dorsal rami on lateral antennae segmented (Fig. 53A) with abundant cilia. Pair of frontal processes, inserted anterolaterally to dorsal pair of eyes, equal in length to 1/2 prostomial width (Fig. 53A, B). Tentacular cirri 2 pairs (Fig. 53B), dorsal pair equal in length to prostomial width, ventral pair 1/3 as long as dorsal. First pair of dorsal cirri, equal in length to median antenna; achaetous knobs present (Fig. 53B). Second dorsal cirri situated above first chaetigerous lobes. Cirri in region a, reciprocally equal, measuring 1/2 of body width; cirri in region b and c slightly shorter than cirri in region a, diminishing posteriorly without any alternation in length. Median ceratophore, and cirrophores on first dorsal cirri, present; cirrophores otherwise absent. Cirri in region a, and anterior part of region b fusiform (Fig. 53A), more posterior gradually more cylindrical, other appendages cylindrical.

Parapodia in region a, and c with rounded conical neuropodial lobes, of medium size; parapodia in region b flattened, with additional notopodial lobes, rectangular in outline. Notopodial lobes with single posteroventral papilla (Fig. 53C). Single neuropodial acicula in all chaetigers; 3–4 anterodorsal, and 3 thick and 3–4 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 4–8 compounds in all chaetigers. Compound chaetae with large distal tooth (Fig. 53D); serration present. Single thin bayonet chaetae (Fig. 53E), subdistally denticulated, beginning between chaetiger 14–17. Notopodial chaetal fascicle with 15–20 swimming chaetae. Anal cirri equal in length to posterior dorsal cirri.

Distribution. North West Pacific, only known from type locality.

Remarks. Autolytus rostripalpus like A. obliquatus has a combination of 6 chaetigers in region a, achaetous knobs, large distal tooth in compound chaetae, and a thin bayonet chaetae. Autolytus rostripalpus is distinct from A. obliquatus in possessing triangular processes on ventral side of prostomium, and posteroventral notopodial papillae. Like for A. obliquatus it is difficult to know generic placement, but close affinity with Proceraea is likely; it is considered as incertae sedis within Procerini . In the original description Chlebovitch states that A. rostripalpus is unique in having both 3 and 6 chaetigers in region a, and the paratypes are a mixture of 4 specimens of A. rostripalpus , and 9 specimens of another taxon with 3 chaetigers in region a. The latter type lack achaetous knobs, the triangular ventral processes, and the notopodial papilla; further, the distal tooth in compound chaetae is small.