Eusthenelais McIntosh, 1876

Barnich, Ruth & Haaren, Ton Van, 2021, Revision of Sthenelais Kinberg, 1856, Fimbriosthenelais Pettibone, 1971 and Eusthenelais McIntosh, 1876 (Polychaeta, Sigalionidae) in the Northeast Atlantic, European Journal of Taxonomy 740, pp. 138-171 : 161-162

Genus Eusthenelais McIntosh, 1876 (emended)

Table 1

Eusthenelais McIntosh, 1876b: 407 (type species Eusthenelais hibernica McIntosh, 1876 ). Parasthenelais Amoureux, 1972: 68 (type species Eusthenelais hibernica McIntosh, 1876 ; unjustified

name change, see remark below).

Diagnosis

BODY. Elongate, with numerous segments; mid-dorsum bordered by a few pairs of small ctenidia.

ELYTRA. Numerous, on segments 2, 4, 5, 7, continuing on alternate segments to 27, then on every segment to end of body. Dorsal tubercles on segments 3, 6, 8, continuing on alternate segments to 26.

PROSTOMIUM. Rounded, fused to first segment. Median antenna inserted terminally, with stout, cylindrical ceratophore with lateral auricles and tapering style. Lateral antennae fused to inner dorsal sides of tentaculophores, without ceratophore, length equal to that of dorsal tentacular cirri. Paired palps encircled by palpal sheath emerging ventrally to tentaculophores.

TENTACULOPHORES. With single aciculum, a pair of tentacular cirri, two bundles of capillary chaetae, L-shaped inner tentacular lobe with ciliated ridge and fused to palpal sheath, and dorsal tentacular crest.

SEGMENT 2. With first pair of elytra, biramous parapodia and buccal cirri longer than following ventral cirri. Small ctenidia on lateral lips and medial to ventral cirri in anterior segments.

SEGMENT 3. With dorsal tubercles, not fused to posterior sides of elytrophores of segment 2. Pair of dorsal cirri present.

BRANCHIAE. Cirriform, absent in anteriormost segments.

DORSAL CIRRI. Absent, except for segment 3.

VENTRAL CIRRI. Styles without basal knob or long basal papillae.

PARAPODIA. Biramous, each with up to three cup-shaped ctenidia dorsal to notopodia, noto- and neuropodial acicular lobes with accessory bracts and smooth stylodes. Notopodial acicular lobes nearly completely encircled by bract covering the basis of the notochaetae. Neuropodial acicular lobes posteriorly with large bilobed bract, anteriorly with two smaller crescent-shaped bracts.

CHAETAE. Notochaetae slender, spinous, tapering to capillary tip. Neurochaetae compound falcigers and spinigers; stems of compound chaetae usually with a few rows of spines distally. Neurochaetae arranged in three groups: upper group of neurochaetae within anterodorsal bract: all slender compound spinigers. Middle group of neurochaetae within posterior bract: compound spinigers and stout compound falcigers. Lower group of neurochaetae within anteroventral bract: all slender compound falcigers.

Remarks

Núñez et al. (2015) were the first to present an extended generic diagnosis for Eusthenelais . Their diagnosis is emended herein for the terminology used in the description of the parapodial bracts and stylodes, for characters describing the tentaculophores and the location of the different neurochaetae.

McIntosh established the genus Eusthenelais for specimens of E. hibernica differing from Sthenelais by the presence of compound spinigers in addition to bidentate falcigers ( McIntosh 1876b, 1879, 1900). In the original description ( McIntosh 1876b), he did not mention the presence of dorsal cirri on segment 3, but he refers to this character in the text and figures of his re-description of the same material ( McIntosh 1900). The presence of dorsal cirri on segment 3 is of generic relevance and puts Eusthenelais closer to Neoleanira Pettibone, 1970 and clearly differentiates it from Sthenelais and Fimbriosthenelais , which lack any dorsal cirri. Neoleanira on the other hand differs from Eusthenelais by the absence of any bidentate falcigers, all neurochaetae being compound spinigers (see Pettibone 1970).

We agree with Wehe (2007), Gil (2011) and Aungtonya & Eibye-Jacobsen (2014) that the generic name Parasthenelais Amoureux, 1972 is invalid. Amoureux (1972) redescribed the species Eusthenelais hibernica based on specimens collected in deep waters off the Galician coast and established a new generic name without valid reason.

Currently, Eusthenelais hibernica is the only valid representative of Eusthenelais . Another species assigned to the genus, Eusthenelais abyssicola McIntosh, 1879 , was described for specimens from deep waters in the Davis Strait. However, we checked the holotype (BMNH 1921.5.1.622) which is unidentifiable. The description also being insufficient, we agree with Hartman (1965) and consider this to be an indeterminable sigalionid.