Meiodorvillea Jumars, 1974

Bonaldo, Rafael de Oliveira, Steiner, Tatiana Menchini & Amaral, Antônia Cecília Zacagnini, 2022, Revision of Meiodorvillea Jumars, 1974 (Annelida: Dorvilleidae) including descriptions of three new species from the Southwestern Atlantic Ocean, PLoS ONE (e 0264081) 1974 (3), pp. 1-27 : 3-4

publication ID	https://doi.org/ 10.1371/journal.pone.0264081
DOI	https://doi.org/10.5281/zenodo.12630843
persistent identifier	https://treatment.plazi.org/id/039F6D46-2C6D-FFF8-4131-7676FDE026CF
treatment provided by	Felipe
scientific name	Meiodorvillea Jumars, 1974
status

Treatment

Genus Meiodorvillea Jumars, 1974 View in CoL

Type-species. Protodorvillea minuta Hartman, 1965 [ 13]

Type locality. Block Canyon , off New England ( USA), 39˚58’24"N, 70˚40’18"W

Amended diagnosis. Prostomium pear-shaped. One pair of simple and clavate dorsal antennae ( Fig 3A and 3B View Fig 3 ). One pair of simple and clavate lateral palps, sometimes absent, shorter than antennae ( Fig 19A and 19B View Fig 19 ). Jaw apparatus ( Fig 12 View Fig 12 ) with paired and medially fused butterfly-shaped mandibles. Maxillae with one pair of V-shaped dorsal carrier-like structures and one pair of ventral basal plates, each one fused posteriorly, and free from each other. Inner margin of basal plates smooth, rarely dentate. Ten to 15 pairs of maxillary plates in two rows, anteriorly to the basal plates, denticulate on its margin, absent in M. apalpata . Two peristomial rings. Small dorsal cirri sometimes present, without acicula ( Fig 4A and 4B View Fig 4 ). Small ventral cirri present ( Fig 10 View Fig 10 ). Supra-acicular chaetae: (1) capillaries ( Fig 11A View Fig 11 ), (2) geniculates ( Figs 11C View Fig 11 and 21A View Fig 21 ) and (3) furcates ( Figs 11B, 11H View Fig 11 and 16 View Fig 16 A-16D). Sub-acicular chaetae: (4) compound falcigers and/or spinigers ( Figs 11E–11G View Fig 11 and 21C View Fig 21 ) and (5) cultriforms ( Figs 16H View Fig 16 and 21D View Fig 21 ). Pygidium with two pairs of cirri ( Fig 9E and 9F View Fig 9 ).

Remarks. Jumars [ 17] erected Meiodorvillea naming M. minuta as type species, describing M. apalpata , and raising M. chilensis (previously Protodorvillea gaspeensis chilensis Hartmann-Schröder, 1965 [ 18]) to species. Meiodorvillea chilensis and P. gaspeensis Pettibone, 1961 [ 22] have short biarticulated palps, so that the latter was considered to belong to a new genus [ 23] and assigned as type species of Marycarmenia Núñez, 1998 [ 24]. The jaw apparatus of this genus is markedly different from Meiodorvillea in the absence of maxillary carrier-like structures and the presence of denticles on the anterior margin of mandibles [ 24]. Meiodorvillea chilensis was described based on one specimen, and although it was well described and illustrated, the jaw apparatus was not examined, which makes its determination questionable [ 19]. Given the lack of information about its jaw apparatus, M. chilensis must remain as species inquirenda possibly also belonging to Marycarmenia . The character “biarticulated palps”, proposed by Jumars [ 17], has been removed from the diagnosis, as it only occurred in M. chilensis .

Eibye-Jacobsen & Kristensen [ 23] proposed the erection of a new genus to M. apalpata , suggesting that it could be a sister group of Meiodorvillea sensu stricto. However, Jumars [ 17] stated that no ‘free denticles’ (maxillary plates) remained in the specimens, which did not allow distinguishing a real absence from a handling artifact. Therefore, maxillary plates could be present, but this could not be assessed in handled specimens. Although M. apalpata is the only one with lacking palps, it shares characters, such as absence of dorsal cirri, shape of mandibles, absence of denticles on its anterior margin, and presence of maxillary carrier-like structures. Furthermore, the absence of furcate chaeta is also verified in other species, either in the anterior or posterior region. As proposed by Wolf [ 19], our analysis found no significant morphological differences to support the erection of the new genus proposed by Eibye-Jacobsen & Kristensen [ 23]. Therefore, M. apalpata should remain within Meiodorvillea until more specimens will be carefully examined, especially regarding the jaw apparatus.

The present revision allowed including new morphological character states in the generic diagnosis, such as presence and shape of geniculate, furcate and cultriform chaetae and details of jaw apparatus.

The posterior peristomial ring frequently covers the anterior ring in specimens where the contraction of the anterior region is markedly visible ( Fig 14A and 14B View Fig 14 ), which apparently demonstrates the presence of one ring ( Figs 1C View Fig 1 and 3B View Fig 3 ) [ 13, 17]. Although this is not a diagnostic character, this variation is mentioned in the descriptions as being rather variable and dependent on the state of contraction caused by fixation of the specimens.

The free denticles, terminology adopted by Jumars [ 17], Oug [ 25], and Eibye-Jacobsen & Kristensen [ 23], are here referred as the paired maxillary plates (placed anteriorly to basal plates), following Wolf [ 26] and Purschke [ 27]. Each maxillary plate contains denticles on its margin.