Kirkegaardia helenae, 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 : 12

Kirkegaardia helenae sp. nov.

urn:lsid:zoobank.org:act:A8469F0C-EC3F-4C39-BCE7-9F7252F9B84E .

Fig 6

Material examined. BRAZIL: Campos Basin – Holotype – -19.60138889˚S -39.17581389˚W, 145 m, 21/04/12, ( MNRJP-002992 ); Paratypes – -19.60138889˚S -39.17581389˚W, 145 m, one ind. , 21/04/12, ( MNRJP-002993 ); -20.57621389˚S -40.34743611˚W, 21 m, one ind., 12/07/13, ( MNRJP-002994 ); -19.60850000˚S -39.17205278˚W, 349 m, two ind., 26/06/12, ( MNRJP-002995 ); -19.78693056˚S -39.92095000˚W, 14 m, one ind., 16/07/11, ( MNRJP-002996 ).

Diagnosis. Peristomium large, with 3–4 rings, first pair of branchiae postero-lateral to the tentacles in setiger 1. Noto and neurosetae denticulate in abdominal region. Pre-pygidial abdominal region prominently expanded.

Description. Complete holotype with 80 setigers, body 2.2 mm long, 0.11 mm wide in across thoracic region, and 0.13 mm wide in abdominal region. Prostomium conical, narrow ( Fig 6A ); eyes absent. Peristomium large, with 3–4 rings visible under the light microscope ( Fig 6A ). Dorsal tentacles on mid-posterior margin of peristomium ( Fig 6A ); first pair of branchiae arises postero-lateral to the tentacles on setiger 1 medial to notosetae; subsequent branchiae in same location on following segments ( Fig 6A ); branchiae present up to the pre-pygidial abdominal region. Thoracic region expanded with 12–18 setigers, dorsal groove absent. Parapodia with poorly developed lobes, difficult to see with optical microscopy. Thoracic parapodia with 5–7 neuro- and notosetae capillary with fringe of stiff, sparsely occurring fibrils along shaft ( Fig 6D ). Abdominal segments short, wider than long ( Fig 6E ). Posterior abdominal parapodia with 4–8 denticulated notosetae and 7–10 denticulated neurosetae per segment ( Fig 6B and 6C ). Denticulated neurosetae appear between the abdominal setigers 27 and 31. Pre-pygidial segments greatly expanded, rounded dorsally, and flattened ventrally, with lateral parapodia ( Fig 6F ). Pygidium formed by a ventral conical lobe ( Fig 6F ).

Remarks. Kirkegaardia helenae sp. nov. belongs to the Kirkegaardia baptisteae -tesselata group, due to their similar morphology, species in this group have elevated thoracic parapodia, and a mid-dorsal channel is not produced, although a dorsal crest sometimes develops. Kirkegaardia helenae sp. nov. is similar to K. zafirae sp. nov. and K. baptisteae in that it presents denticulated noto and neurosetae, although it differs from both species in that its first pair of branchiae appear in the first setigerous and not in the posterior region of the peristomium. Kirkegaardia helenae sp. nov. also differs from K. zafirae sp. nov. in that it does not have a ventral sulcus in the pre-pygidial region. The shape of the pre-pygidial region of K. helenae sp. nov. is similar to that of K. lueldredgei , but it has abdominal segments that are wider than long, unlike K. lueldredgei , which has abdominal segments that are longer than wide. These species also differ in the number of neurosetae in the posterior abdominal region, two or three setae in K. lueldredgei , and 7–10 in K. helenae sp. nov. The disposition of the tentacles and first pair of branchiae of K. helenae sp. nov. is similar to K. setosa (Dean & Blake, 2009) [ 38] but this species has only denticulate neurosetae and K. helenae sp. nov. has noto and neurosetae denticulate in its abdominal region. For these characteristics, the species was considered as new to science.

Etymology. This species is named in honor of Dr. Helena Passeri Lavrado, for her important contribution to Brazilian marine biology.

Figures

Fig 6. Kirkegaardia helenae sp. nov. (A) anterior end, dorsal view; (B) neuropodial capillary denticulated; (C) notopodial capillary denticulated; (D) capillaries in thoracic setigers with fibrils; (E) abdominal segments, dorsal view; (F) posterior end, lateral view. A–C (MNRJP-002992). Scale bars: 100 μm (A) 200 μm (B and C). Type locality.Atlantic Ocean: Campos Basin (Brazil). Habitat. Thin silt and clay sediments, 14 to 349 m depth. Distribution. Presently known only from Atlantic Ocean: Campos Basin (Brazil). Methyl Green. Parapodia with stain concentrated on posterior borders of noto- and neuropodia along entire body. https://doi.org/10.1371/journal.pone.0265336.g006