Kirkegaardia medusa, Freitas & Ribeiro & Ruta, 2022

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 : 15-17

Kirkegaardia medusa sp. nov.

urn:lsid:zoobank.org:act:4A38559A-3F95-419F-B99A-64E893478AB5 .

Fig 8

Material examined. BRAZIL: Campos Basin – Holotype – -20.69275833˚S -39.58946111˚W, 41 m, 17/07/13, (MNRJP-003000); Paratypes – -19.60138889˚S -39.17555556˚W, 148 m, four ind., 24/01/12, ( MNRJP-003001 ); -19.60728889˚S -39.17148611˚W, 352 m, one ind., 14/12/11, ( MNRJP-003002 ) .

Diagnosis. Peristomium with one ring. First pair of branchiae on setiger one. Notosetae with fibrils in abdominal region. Only neurosetae denticulated, present from abdominal setigers 15 or 16.

Description. All specimens incomplete, holotype with 43 setigers, 9.0 mm long, 0.12 mm wide in the thoracic region, and 0.10 mm wide in abdominal region. Prostomium long, conical ( Fig 8A ). Eyes absent. Peristomium with one ring, without dorsal crest ( Fig 8A ). Dorsal tentacles on posterior margin of peristomium ( Fig 8A ). First pair of branchiae postero-lateral to the tentacles in setiger 1, second pair of branchiae in setiger 2; branchiae present only in thoracic region. Thoracic region narrow, with 7–10 setigers, without dorsal groove ( Fig 8A ). Abdominal segments longer than wide ( Fig 8B and 8C ); first abdominal segments shorter than median abdominal segments ( Fig 8B ). Parapodia with poorly developed lobes. Thoracic parapodia with four or five capillary noto- and neurosetae per segment. Posterior abdominal parapodia with four or five capillary notosetae simple with numerous thin fibrils ( Fig 8D ), and 4–8 denticulate neurosetae per fascicle ( Fig 8E ). Denticulate neurosetae from abdominal setigers 15 or 16. Pre-pygidial segments and pygidium not observed.

Remarks. Kirkegaardia medusa sp. nov. is similar to K. baptisteae (Blake, 1991) [ 27], K. dutchae Blake, 2016 [ 22], K. neotesselata Blake, 2016 [ 22] and K. serratiseta (Banse & Hobson, 1968) [ 25] in only having denticulate neurosetae. Kirkegaardia baptisteae has a nuchal organ lateral to the prostomium and first pair of branchiae anterior to the tentacles. In contrast, the first pair of branchiae from K. medusa sp. nov. is postero-lateral to the tentacles. They also differ in that, K. baptisteae has abdominal segments that are wider than long, while K. medusa sp. nov. has abdominal segments that are longer than wide, up to the median abdominal region. Kirkegaardia dutchae differs from K. medusa sp. nov. by the presence of a peristomial crest and the lateral position of the 1st pair of branchiae to the tentacles. Kirkegaardia neotesselata differs has an elevated peristomial crest that merges with the thoracic crest, while K. medusa sp. nov. has no crest. K. serratisseta has a thoracic region with about 40 segments, while K. medusa sp. nov. only has 7 to 10 abdominal segments. For all these characteristics, the species was considered as new to science.

Etymology. This species name refers to the Greek myth of Medusa. Medusa is often seen as evil but was convicted of a crime committed by the God Poseidon, who is more powerful and less vulnerable. This species name represents the fight against misogyny, which is suitable for a study performed by female researchers.

Figures

Fig 8. Kirkegaardia medusa sp. nov. (A) anterior end, dorsal view; (B) abdominal segments, lateral view; (C) posterior abdominal segments, lateral view; (D) notopodial capillary with fibrils in abdominal region (E) neuropodial capillary denticulated. B–C (MNRJP-003000).Scale bars: 2 mm (B and C). Type locality. Atlantic Ocean: Campos Basin (Brazil). Habitat. Fine sediments composed of silt and clay, between 41 to 352 m deep. Distribution. Presently known only from Atlantic Ocean: Campos Basin (Brazil). Methyl Green. No pattern, but prominent staining on the thoracic region. https://doi.org/10.1371/journal.pone.0265336.g008