Meiodorvillea apalpata 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 : 11-12

Meiodorvillea apalpata Jumars, 1974 [ 17]: 121–122, Fig 10

Type locality. San Diego Trough region , 32˚28.2’N 117˚29.8’W, Coronado Sea, California, United States of America, 1,224 m depth.

Type material examined. Holotype: LACM-AHF Poly 1086 , 32˚28.2’N 117˚29.8’W, 1,224 m, silty mud, 06 Dec 1972 . Paratypes: LACM-AHF Poly 1087 (1 spec) 32˚28.2’N 117˚29.8’W, 1,224 m, silty mud, 06 Dec 1972 ; LACM-AHF Poly 1088 (1 spec) 32˚28.2’N 117˚29.8’W, 1224 m, silty mud, 12 Dec 1969 and LACM-AHF Poly 1089 (1 spec) 32˚38.9’N 117˚30.1’W, 1,223 m, silty mud, 05 Jan 1972 . (m = meters depth).

Diagnosis. One pair of antennae. Palps and dorsal cirri absent. Ventral cirrus papilliform, absent in the first chaetiger. Chaetae capillary, geniculate, all three compound falcigers, and cultriform in last chaetigers in some specimens, replacing ventralmost compound. Two pairs of pygidial cirri.

Redescription of holotype. Complete specimen in poor condition, 47 chaetigers in three fragments, anterior width ca. 0.2 mm. Color in ethanol pale yellow.

Prostomium globular and pear-shaped ( Fig 7A ), as long as wide. Eyes absent. One pair of clavate antennae inserted dorsolaterally, almost at prostomium base, 2/3 the length of prostomium ( Fig 7A ). Palps absent. Anterior chaetigers slightly wider and shorter than median and posterior ones.

Jaw apparatus not dissected. Mandibles butterfly-shaped medially fused, anterior region enlarged with smooth margins without free or fused teeth, posterior region slender and curved. Pair of maxillary carrier-like structures relatively large, basal plates with dentate inner margin; maxillary plates absent [ 17].

Two peristomial rings, both as long as prostomium, clearly well-defined dorsally and ventrally; posterior wider and longer than anterior and almost as long as the following chaetigers ( Fig 7A ).

Cylindrical parapodia, shorter in anterior, longer and narrower in posterior region. Dorsal cirrus absent. Papilliform ventral cirrus inserted medially in the parapodium, absent in the first one ( Fig 7C ).

Supra-acicular chaetae: (1) one long and serrated capillary, with a small limb anteriorly, longer and slender in posterior region; (2) one geniculate with short serrated margin ( Fig 7C ). Sub-acicular chaetae: (3) three compound heterogomph falcigers, distal end of shafts serrated and blades unidentate with serrated cutting edges: dorsalmost longest and ventralmost shortest; (4) one cultriform with serrated margin replacing the ventralmost compound in last nine chaetigers. Chaetae from median and posterior regions longer and slender ( Fig 7C ).

Pygidium rounded and narrower than previous chaetigers. Two pairs of clavate pygidial cirri, dorsal pair as long as pygidium, ventral pair half as long as pygidium ( Fig 7B ).

Remarks. Although the type material was in poor condition, the following differences from the original description were observed: presence of papilliform ventral cirrus inserted in the middle of the parapodium ( Fig 7C ), similar to M. minuta ; absence of neuroacicula; presence of cultriform chaeta in some specimens, including the holotype.

Jumars [ 17] did not mention the presence of maxillary plates in the jaw apparatus, although more material is needed to better describe this structure.

Meiodorvillea apalpata resembles Meiodorvillea sp. B [ 19] in lacking palps, but the latter has dorsal cirri from chaetigers 2 to 4–5.

Geographic distribution and bathymetric range. Known only from the type locality, Northeastern Pacific Ocean , east coast of California ( USA), 1,223–1,224 m, silty mud [ 17] .

Figures

Fig 7. Meiodorvillea apalpata Jumars, 1974, LACM-AHF Poly. (A) anterior region, dorsal view; (B) pygidium, dorsal view; (C) parapodium from posterior region, anterior view; (D) mandibles; (E) basal plates and maxillary carrier-like structures. Dash lines represent broken chaeta. Abbreviations: an = antenna; capc = capillary chaeta; chc = compound heterogomph chaeta; dpc = dorsal pygidial cirrus; gc = geniculate chaeta; vc = ventral cirrus; vpc = ventral pygidial cirrus. Scale bars: (A,B) = 50 μm; (C) = 20 μm. (D,E): modified from Jumars [17] (no scale bars in the original figures). https://doi.org/10.1371/journal.pone.0264081.g007

Fig 10. Meiodorvillea penhae sp. nov. (A,B) parapodia from anterior region; (C,D) parapodia from posterior region; all anterior view. Abbreviations: fc = furcate chaeta; gc = geniculate chaeta; vc = ventral cirrus. Scale bars: (A,C) = 15.6 μm; (B,D) = 10 μm. https://doi.org/10.1371/journal.pone.0264081.g010