Streptosyllis arenae Webster & Benedict 1884

Faulwetter, Sarah, Vasileiadou, Aikaterini, Papageorgiou, Nafsika & Arvanitidis, Christos, 2008, Description of a new species of Streptosyllis (Polychaeta: Syllidae) from the Mediterranean and Canary Islands with a re-description of Streptosyllis arenae and comments on the taxonomy of Streptosyllis and some morphologically similar genera, Zootaxa 1847, pp. 1-18 : 3-4

Streptosyllis arenae Webster & Benedict 1884

Figures 1–3

Streptosyllis arenae Webster & Benedict, 1884: 711–713 , Figures 17–23.

Streptosyllis arenae - Pettibone, 1963: 127, Figures 31 l–m; - Hartmann-Schröder, 1996: 163.

Material examined: 3 out of 5 paratypes USNM 417 labelled as S. arenae (holotype unavailable) .

Type locality: Provincetown , Cape Cod, Massachusetts, USA .

Habitat: Sandy bottoms, shallow water.

Description: (based on the paratype labelled 119/1717, fixed on slide): Body ca. 2.8 mm long, for 40 chaetigers; maximal width 300 µm without parapodial lobes, 440 µm with parapodial lobes and 570 µm including chaetae (5 th segment) ( Figure 1). Head semi-circular, wider than long, anterior margin regularly rounded. Two pairs of eyes, one pair of eyespots, latter located near anterior margin (near eye spots). Three antennae present, each irregularly wrinkled, median antenna inserted between two pairs of lateral eyes in middle of prostomium, lateral antennae located near anterior margin of prostomium. Median antenna ca. 370 µm long, lateral ones ca. 120 µm. Palps form two rounded lobes, fused basally, outer margins prolonged into vestigial cirrus ( Figure 2g). Palps directed ventrally, not visible dorsally. Peristomium indistinct, bearing two pairs of tentacular cirri, each about as long as lateral antennae. Dorsal cirri about same length as lateral antennae, some longer, generally shorter near posterior end. Shape and structure of dorsal cirri varies within same animal: either smooth, wrinkled, pseudo-articulated with granular rounded inclusions, articulated with each article divided longitudinally or articulated without divided articles ( Figures 1, 2d–f). Ventral cirri slightly wrinkled, digitiform, wide at base, about length of parapodial lobe of first segments, then becoming longer, about twice length of parapodial lobe in posterior part and longer than dorsal cirri ( Figures 2a–c). Pygidium with tiny median anal cirrus, lateral anal cirri not observed ( Figure 1). Dorsal simple chaeta present from chaetiger 1, slightly curved, ca. 55 µm anteriorly, 90 µm posteriorly, tip bluntly rounded and covered by hyaline hood ( Figures 3j–o). Up to ten hemigomph compound chaetae in each parapodium, length ca. 45 µm anteriorly, 85 µm posteriorly ( Figures 2a–c). Shaft of compound chaetae ending in up to three rounded teeth (Webster and Benedict report four teeth, not observed in material examined), sometimes with notched tips. Blades of two kinds, longer ones (ca. 19 µm) in dorsal chaetae, shorter ones (ca. 12 µm) in ventral chaetae, becoming longer towards posterior end. In first five chaetigers only chaetae with short blades present ( Figures 3p–s); from chaetiger 6 onwards, two long-bladed and 8–9 short-bladed chaetae per bundle present. Longer blades unidentate with rounded tip covered by halo-shaped hyaline hood, and small tooth near distal part ( Figures 3t –v). Shorter blades with more acute tip and hood covering not only tip of blade but prolonged down to distal end of shaft. ( Figure 3s). Aciculae distinctively enlarged on chaetigers 2–5, one per parapodium, each distally knobbed, terminating at tip of parapodial lobe ( Figure 3a–i). Length of aciculae ca. 130 µm in anterior chaetigers, 190 µm in posterior chaetigers. Pharynx unarmed, extending from anterior end to chaetiger 3. Proventriculus extending through 6–7 segments, with about 56 muscle cell rows ( Figure 1).

Character variation: Length of median anal cirrus varies among paratypes: from very short to about as long as dorsal cirri.

Remarks: Of the five individuals labelled as paratypes of Streptosyllis arenae (USNM 417), one is preserved in alcohol, the four others are fixed on three slides. The fixative is unknown; it is assumed that euparal had been used. Two of the five paratypes can be identified as belonging to other species: a) The individual preserved in alcohol was identified by Pettibone as S. varians , which is confirmed here; b) The red coloured worm on the slide labelled 118/1717 can only be tentatively identified as S. cf. latipalpa because the quality of the individual does not allow its exact identification.

Distribution: Northwestern Atlantic (Cape Cod, Massachusetts).