Meiodorvillea hartmanae sp. nov.

(Figs 13–17, Table 1)

urn:lsid:zoobank.org:act: 9DC54BE0-27ED-44E2-AD4D-2CB22E05D830

Type locality. Southwest Atlantic Ocean, 23˚15’11,480"S, 40˚53’53,304"W, off Rio de Janeiro State, Brazil, 1,228.5 m depth.

Type material examined. Holotype: State of Rio de Janeiro – ZUEC-POL 21406 23˚ 15’11.480"S 40˚53’53.304"W, 1,228.5 m, 14 Jan 2009 . Paratypes: State of Rio de Janeiro – ZUEC-POL 21407 (2 spec) 23˚15’10.577"S 40˚53’54.586"W, 1,300.7 m, 15 Jan 2009; ZUEC-POL 21408 (1 spec) 23˚13’46.474"S 40˚55’56.178"W, 986.4 m, 08 May 2008; ZUEC-POL 21409 (1 spec) 23˚13’48.724"S 40˚55’53.562"W, 1,001.4 m, 16 Jan 2009; ZUEC-POL 21410 (1 spec) 23˚13’47.452"S 40˚55’56.256"W, 986.4 m, 08 May 2008; ZUEC-POL 21411 (2 spec) 23˚ 13’48.742"S 40˚55’55.134"W, 986.4 m, 08 May 2008; ZUEC-POL 21412 (1 spec) 23˚41’9.142"S 41˚16’7.032"W, 1,001.5 m, 13 Jan 2009 . (m = meters depth).

Other material examined. State of Rio de Janeiro – ZUEC-POL 21413 (1 spec) 21˚ 45’54.702"S 39˚59’27.418"W, 1,030 m, 06 Feb 2009; ZUEC-POL 21414 (1 spec) 23˚13’48.868"S 40˚55’54.397"W, 1,010.8 m, 16 Jan 2009; ZUEC-POL 21415 (1 spec) 23˚15’11.480"S 40˚ 53’53.304"W, 1,228.5 m, 14 Jan 2009; ZUEC-POL 21416 (1 spec) 21˚55’7.018"S 39˚ 54’31.298"W, 996.9 m, 07 Feb 2009. State of Espírito Santo – ZUEC-POL 21417 (1 spec) 21˚ 4’37.64"S 40˚8’32.68"W, 1,015 m, mud, 08 Jun 2013; ZUEC-POL 21418 (1 spec) 20˚15’36.86"S 39˚46’15.05"W, 1,040 m, sandy mud, 09 Jan 2012. (m = meters depth).

SEM material. State of Rio de Janeiro – ZUEC-POL 21419 (3 spec): 23˚1’30.862"S 40˚ 45’22.948"W, 964.8 m, 16 Jan 2009; 21˚55’6.677"S 39˚54’32.810"W, 997 m, 28 May 2008; 23˚ 13’48.868"S 40˚55’54.397"W, 1,010.8, 16 Jan 2009 (m = meters depth).

Diagnosis. One pair of antennae and one pair of palps. Dorsal cirri absent. Ventral cirrus papilliform, absent in the first chaetiger. Chaetae capillary, furcate asymmetrical, dorsalmost compound spiniger or falciger, median and ventralmost falcigers, and cultriform in last chaetigers in some specimens, replacing the ventralmost compound. Two pairs of pygidial cirri.

Description of the holotype. Complete specimen, 37 chaetigers, 1.9 mm long, anterior region 0.17 mm wide, excluding parapodia; body width uniform (Fig 13A), anterior region slightly wider. Color in ethanol pale yellow.

Prostomium pear-shaped, as long as wide, anterior half depressed and rounded, posterior half wider and globular (Figs 13A, 13B and 14A–14C). Eyes absent. One pair of clavate antennae inserted dorsolaterally on middle posterior half of prostomium, 1/3 of prostomium length (Figs 13B, 13C and 14A–14C). One pair of very small and clavate palps inserted laterally at prostomium base, difficult to see in dorsal view (Figs 13C and 14C).

Two peristomial rings, half as long as prostomium, posterior wider than anterior (Figs 13B and 14 A-14C).

Cylindrical, long and stout parapodia, gradually tapering posteriorly (Fig 15). Dorsal cirrus absent. Small and papilliform ventral cirrus, inserted medially in the parapodium (Fig 15), absent in the first one.

Supra-acicular chaetae: (1) one long and serrated capillary; (2) one elongated and thin furcate, asymmetrical prongs in shape and size and serrated base (Fig 16A–16D). Sub-acicular chaetae: (3) three compound heterogomphs, dorsalmost longest with falcigerous or spinigerous blade, median falcigerous, ventralmost falcigerous and shortest; blades unidentate with serrated cutting edge (Fig 16E–16G); (4) one cultriform with serrated margin replacing the ventralmost compound in last chaetigers (Fig 16H). Chaetae gradually slender and longer along body. One internal thick acicula (Fig 15B and 15D).

Pygidium rounded and narrower than previous chaetigers. Two pairs of clavate pygidial cirri, dorsal pair twice as long as ventral pair (Figs 13E, 14D and 14E).

Jaw apparatus from additional non-type material with ventral and medially fused mandibles, anterior region enlarged with smooth margins without free or fused teeth, posterior region slender and curved (Fig 17A). Basal plates of maxillae with smooth inner margin, two subsymmetrical rows with 10–12 pairs of free rectangular and denticulate maxillary plates, each one with one posterior main fang and usually four anterior teeth last and anteriormost plates larger and rounded, with small and more numerous teeth. (Fig 17A–17C).

Variation. Complete specimens 1.5–2.9 mm long, maximum width 0.28 mm, 28–48 chaetigers; some with posterior moniliform segments (width equal to length). Palps visible only ventrally in some specimens. Most specimens with cultriform chaetae, with serrated cutting edge, in last 9–13 chaetigers, or randomly (Fig 16H). Maxillary plates varying from 10 to 13 pairs.

Remarks. Meiodorvillea hartmanae sp. nov. resembles M. apalpata and M. penhae in having papilliform ventral cirrus in all parapodia (except the 1 st), but differs having furcate and lacking geniculate chaetae. On the other hand, M. minuta differs in having dorsal cirri on anterior chaetigers and a different shape of furcate.

Meiodorvillea hartmanae sp. nov. has smaller palps than all other species of the genus. In some specimens the palps are very difficult to see in dorsal view; in others, only ventrally. The species also has remnants of ciliary bands in the prostomium, peristomium, and chaetigers, as M. penhae and M. minuta . This character may possibly be shared by all species of Meiodorvillea .

Geographic distribution and bathymetric range. Southwestern Atlantic Ocean, States of Espírito Santo and Rio de Janeiro (Brazil), 964.8 to 1,300.7 m; mud, muddy sand, sandy mud. Etymology. The specific epithet “ hartmanae ” honors Olga Hartman for her insight contributions to the taxonomy of Polychaeta and for describing the type species of Meiodorvillea .