Syllidia inermis ( Ehlers, 1912 ), 2006

Ruta, Christine & Pleijel, Fredrik, 2006, A revision of Syllidia (Psamathini, Hesionidae, Polychaeta), Journal of Natural History 40 (9 - 10), pp. 503-521 : 517

Syllidia inermis ( Ehlers, 1912) , incertae sedis

Magalia inermis Ehlers 1912, p 15 –17, Plate 2, Figures 1–5 ; McIntosh 1924, p 16; McIntosh 1925, p 42; Hartman 1959, p 188.

Syllidia inermis Horst 1921, p 77 ; Hartman 1959, p 193; 1964, p 75, Plate 23, Figures 5 , 6 ; Averincev 1972, p 147, Plate 20, Figure 5 ; Knox and Cameron 1998, p 46; Pleijel 1998, p 126, 163.

Syllidia cf inermis Hartmann-Schröder and Rosenfeldt 1988, p 37 .

Material examined

Antarctic: Three (or more?) syntypes ( BMNH 1911.11.1.128), McMurdo Sound , Ross Island , Hut Point, Winter Quarter, 18 m, dredge net, 2 October 1903 .

Remarks

Ehler’s types have not previously been recognized as such, but comparison of his description with specimens and labels leaves no doubt that they constitute his original ones. They were collected during the British National Antarctic Expedition 1901–1904 (when the R/V Discoυery was blocked for several years in the ice in McMurdo Sound at Ross Island), probably by the marine biologist Thomas Vere Hodgson, specialist of hydroids and jellyfishes. They include one entire specimen, one specimen with the posteriormost part missing, and four median pieces, all in excellent condition. However, examination of these specimens indicates that they do belong within Psamathini but are not members of Syllidia ; among other features, they lack the jaws of Syllidia , and the neuropodia and neurochaetae start on segment 5, not on segment 3 or 4. Instead they likely belong to Psamathe Johnston, 1836 ; the issue will be further detailed in a forthcoming revision of Psamathe (F. Pleijel, in preparation).

As for the other records of S. inermis . Averincev (1972) reported it from Ross Sea and Davis Sea in the Antarctic, but we have not had the possibility to examine his specimens. The descriptions in Hartman (1964) and Knox and Cameron (1998) are based on Ehler’s original description and include no new specimens or observations, whereas Hartmann- Schröder and Rosenfeldt (1988) reported one specimen of this species (as S. cf inermis ) from the Antarctic Peninsula. This specimen is unfortunately in very poor condition, and the only statements we can make is that it is likely a member of Psamathini but not of Syllidia .

Figures

Figure 1. Relationships between number of segments and length in Syllidia armata (n) from Sweden and southern France and S. hongkongensi, new species (©) from the type locality.

Figure 2. Micrograph of mature female of Syllidia armata from the Koster area, Sweden, dorsal view. Exact scale unknown but whole animal, excluding cirri, is about 9 mm long.

Figure 3. Anterior end of Syllidia armata (after Marion and Bobretzky 1875).

Figure 4. SEM micrographs of Syllidia armata from Sweden. (A) Anterior end, dorsal view; (B) anterior end, ventral view of subadult specimen (22 segments) with neuropodial lobes and chaetae on segment 3; (C) distal part of everted proboscis, ventral view, with papillae embedded in cilia. The two visible folds (arrows) will extend to form the ventral incision in the fully everted proboscis; (D) anterior end, ventro-lateral view of same specimen as in (B). Scale bars: 100 mm (A); 150 mm (B, C); 120 mm (D).

Figure 5. SEM micrographs of Syllidia armata from Sweden. (A) Chaetae from median parapodium; (B) close-up of chaetae with prolonged teeth; (C) posterior end, ventral view. Scale bars: 60 mm (A); 15 mm (B); 120 mm (C).

Figure 6. LM micrographs of Syllidia armata from Sweden. (A) Median parapodium; (B) jaws. The inset shows the median stylet (not to scale). Scale bars: 250 mm.