Kirkegaardia hampsoni Blake, 2016

Freitas, Roberta, Ribeiro, Rannyele Passos & Ruta, Christine, 2022, Kirkegaardia Blake, 2016 (Annelida: Cirratulidae) from Southeastern Brazil with description of nine new species, PLoS ONE (e 0265336) 2016 (5), pp. 1-27 : 5

Kirkegaardia hampsoni Blake, 2016

Fig 2

Tharyx dorsobranchialis : Maciolek-Blake et al., 1985 [ 35]: 75, 142, Appendix B-3, Appendix D-8

Monticellina dorsobranchialis : Blake 1991 [ 27] (In part); Hilbig & Blake 2000 [ 36]: 162. Not Kirkegaard 1959.

Kirkegaardia hampsoni : Blake 2016 [ 22]: p. 28, figs. 12–13.

Material examined. BRAZIL: Campos Basin–-19.62828611˚S -39.59208889˚W, 35 m, 15/07/ 11, one ind., (MNRJP-002966); -19.58677500˚S -39.64254444˚W, 29 m, 12/12/10, two ind., (MNRJP-002967); -19.87490556˚S -39.81891667˚W, 42 m, 16/07/11, one ind., (MNRJP-002968).

Description. Largest individual with 58 setigers, 2.3 mm long, thoracic region 0.09 mm wide and 0.2 mm high, abdominal region 0.11 mm wide. All specimens incomplete. Prostomium triangular ( Fig 2A ). Eyes absent, nuchal organs not observed. Peristomium smooth, elongated with 1–2 rings. Peristomium with dorsal crest extending from peristomium to first thoracic setiger ( Fig 2A ). Dorsal tentacles inserted in posterior margin of peristomium; first pair of branchiae postero-lateral to the tentacles, second pair located in first setiger; branchiae visible up to abdominal region ( Fig 2A ). Thoracic region narrow with 9–12 setigers ( Fig 2A ); dorsal parapodia expanded in thoracic region, forming a mid-dorsal groove, dorsal thoracic groove with elevated narrow mid-dorsal ridge. Abdominal region narrow with anterior segments longer than medial abdominal segments ( Fig 2B and 2C ). Parapodia reduced with poorly developed lobes, barely visible with light microscopy. Thoracic parapodia with 4–5 noto- and neuropodial smooth capillary setae per segment. Abdominal segments with 4–5 noto- and neuropodial smooth capillaries and denticulate setae per segment ( Fig 2D and 2E ). Denticulate neurosetae present from the setiger 17. Noto- and neurosetae with well-developed denticles along one edge.

Remarks. The specimens from the Campos Basin are similar to the type specimens of Kirkegaardia hampsoni Blake, 2016 [ 22], described for Massachusetts ( USA), by having an elongated, smooth peristomium, a dorsal peristomial crest that extends from the final portion prostomium to the first thoracic setiger, and a mid-dorsal channel or thoracic groove; the region closer to the prostomium that has one or two rings. Specimens from the Campos Basin are similar to K. hampsoni in having the dorsal tentacles inserted in the posterior portion of the peristomium and by having the first pair of branchiae inserted lateral to the dorsal tentacles on the peristomium, and with the second pair of branchiae arising from the first setiger. K. hampsoni from the Campos Basin also has a narrow ridge in the middle of the dorsal thoracic groove, and the medial abdominal segments are increasingly shorter and wider as in K. hampsoni . K. hampsoni specimens from the Campos Basin differ in having between 9–12 thoracic setigers, instead of 10–15 thoracic setigers as described by Blake [ 27]. The presence of a peristomial ridge K. hampsoni places the species in the Kirkegaardia dorsobranchialis-heterochaeta group as defined by Blake [ 22], which includes: K. annulosa , K. cristata , K. kladara and K. hampsoni . The present work represents the record of K. hampsoni for the South Atlantic Ocean. K. hampsoni , was found between 19 to 121 m in the Campos Basin whereas Blake [ 27] records K. hampsoni from between 30 to 150 m. According to Blake [ 22] K. hampsoni was registered locally as Tharyx and/or Monticellina dorsobranchialis at various locations on the continental shelf of the US Atlantic, from the Gulf of Maine to the mid-Atlantic, the Campos Basin record points out that K. hampsoni is a species with extensive distribution, but more in-depth studies on the distribution of Kirkegaardia species including K. hampsoni are needed. The samples from the Campos Basin are not complete, and it is not possible to observe the pre-pygidial region and the pygidium.

Figures

Fig 2. Kirkegaardia hampsoni. (A) anterior end, dorsal view; (B) segments of the anterior abdominal region; (C) segments of the posterior abdominal region; (D) notopodial setae in posterior region; (E) neuropodial capillary denticulated. A–C (MNRJP-002966). Scale bars: 100 μm (A–C). Type locality. Atlantic Ocean: Massachusetts (USA) [27]. Habitat. Fine sediments, 30–150 m depth [27]. In the present study, fine sediments, mainly silt/clay, 19–683 m depth. Distribution. Atlantic Ocean: Massachusetts (USA) [27]; Campos Basin (Brazil). https://doi.org/10.1371/journal.pone.0265336.g002