Parougia ougi, Ravara, Ascensão, Wiklund, Helena & Cunha, Marina R., 2021

Ravara, Ascensão, Wiklund, Helena & Cunha, Marina R., 2021, Four new species and further records of Dorvilleidae (Annelida, Polychaeta) from deep-sea organic substrata, NE Atlantic, European Journal of Taxonomy 736, pp. 44-81 : 71-73

Parougia ougi sp. nov.

urn:lsid:zoobank.org:act:C91E1B58-1DB0-49E4-B3A9-0DB4290AB587

Fig. 13

Etymology

The species is named after Dr Eivind Oug, who made a thorough revision and described several species within the genus Parougia .

Material examined

Holotype MOROCCO • incomplete spec. (ethanol, anterior region mounted in a slide preparation); GoC, Mercator MV; 35°17.916′ N, 06°38.709′ W; 354 m depth; 2 Mar. 2008; Stn 64PE284_12750W; wood substrate; NHMUK 2020.1516 (hologenophore).

Description

Incomplete specimen, with 43 chaetigers. Body cylindrical, long and slender ( Fig. 13A ). Prostomium rounded, longer than wide, without eyes ( Fig. 13 A–B). Antennae and palps missing; palp scars detected on slide mount under light microscopy ( Fig. 13E ); antennal scars not detected. Peristomium achaetous, with two rings of roughly the same length as following segments, with transversal ciliary bands. Jaws located at peristomium level, weakly sclerotized. Mandibles roughly square anteriorly, with smooth and lightly trilobed margin (median lobe much smaller than outer ones); handles short and widely divergent ( Fig. 13 C–D). Maxillae with four similar rows of denticles; both inferior and superior rows with basal plates and free denticles ( Fig. 13 F–G); basal plates formed by the fusion of 6 square denticles homogeneously toothed, left and right plates fused posteriorly ( Fig. 13G ); at least 16 free denticles, shovel-like with finely toothed margin, anterior ones very weakly sclerotized and barely visible; maxillary carriers absent. Parapodia sub-biramous, long in median chaetigers ( Fig. 13H ); dorsal cirri present from the second chaetiger, similar in length or slightly longer than acicular lobes, digitiform, indistinctly biarticulated, supported by an internal acicula in cirrophore ( Fig. 13J ); neuropodial acicular lobes conical, pre- and postchaetal lamellae poorly developed; ventral cirri shorter than dorsal cirri, inserted subdistally on the acicular lobe. Supra-acicular chaetae simple, wider and coarsely serrated basally, tapering to fine tips distally ( Fig. 13I ), ca 4 per fascicle (2 long and 2 short). Supra-acicular furcate chaetae present from third chaetiger, with coarsely serrated shaft and thin asymmetric tines ( Fig. 13K ), one per parapodium. Sub-acicular chaetae compound, with sub-distally strongly serrated shafts and bidentate, very lightly serrated blades ( Fig. 13L ), 7 per fascicle. Pygidium not examined.

Remarks

The genus Parougia includes, at present, nineteen nominal species ( Yen & Rouse 2020). Five of these species ( P. albomaculata ( Åkesson & Rice, 1992) , P. bermudensis ( Åkesson & Rice, 1992) , P. diapason Taboada, Bas & Avilla, 2015 , P. eliasoni ( Oug, 1978) and P. oregonensis Hilbig & Fiege, 2001 ) are represented in the phylogenetic reconstruction ( Fig. 2 ) and are found to be molecularly different from the one studied herein ( Oug 1978; Åkesson & Rice 1992; Hilbig & Fiege 2001; Taboada et al. 2015). Twelve species of Parougia are known to occur in chemosynthetic habitats: one in whale-falls in Antarctica ( P. diapason , 10 m depth), eight in methane seeps in the NE Pacific ( P. batia ( Jumars, 1974) , also in whale-falls, 587–1229 m depth; P. billiemiroae Yen & Rouse, 2020 , 587 m depth; P. ceruleibohnorum Yen & Rouse, 2020 , 588– 1433 m depth; P. indiareinhardtae Yen & Rouse, 2020 , 650 m depth; P. oregonensis , also in whale-falls, 595-850 m depth; P. sulleyi Yen & Rouse, 2020 , ~ 600–1600 m depth; P. theloniousblueski Yen & Rouse, 2020 , ~ 1000 m depth; P. zairahae Yen & Rouse, 2020 , 514– 809 m depth), and three in hydrothermal vents in the SW Pacific ( P. chutsaoi Yen & Rouse, 2020, 1991 m depth; P. jessieae Yen & Rouse, 2020, 1821 – 1845 m depth) and in the NE Pacific ( P. wolfi Blake & Hilbig, 1990, 1545 – 2200 m depth) ( Jumars 1974; Blake & Hilbig 1990; Yen & Rouse 2020). Three other species are known from shallow waters of the North Atlantic: P. caeca ( Webster & Benedict 1884) , P. macilenta ( Oug, 1978) and P. nigridentata ( Oug, 1978) and another species was described from soft sediments of the southern ocean: P. furcata (Hartman, 1953) (Hartman 1953; Oug 1978; Webster & Benedict 1884). All of these species differ from P. ougi sp. nov. at the morphological level, especially in the maxillary apparatus. In P. ougi sp. nov. all free denticles are shovel-shaped with numerous small teeth of similar size, while in the majority of the other species, at least the posterior free denticles of the superior row have a large main tooth followed by several smaller ones. The only exception is P. jessieae , for which the free denticles are very similar to those of P. ougi sp. nov. Also, the mandibles of this species have smooth anterior margins as in P. ougi sp. nov., although with a prominent median peak and slightly different shape. However, P. ougi sp. nov. differs from P. jessieae by the coarsely serrated supra-acicular chaetae and the presence of furcate chaetae (absent in P. jessieae ). Another species from a closely related genus, Ougia tenuidentis Wolf, 1986 , described from shallow sandy sediments from Florida, presents the same kind of mandibulae as P. ougi sp. nov. and is otherwise very similar ( Wolf 1986). But again, the free denticles of that species bear both small and large teeth. Ougia tenuidentis also differs from P. ougi sp. nov. in the basal plates of the maxillary superior row, which are serrated rather than composed of fused free denticles, and the presence of maxillary carriers, which are distinctive characteristics of the genus Ougia Wolf, 1986 ( Wolf 1986) . Parougia ougi sp. nov. presents what apparently are basal plates on the inferior rows of maxillary denticles. Yen & Rouse (2020) recently referred to these structures as being possible moults, although their identification as either the inferior or a replacement row was considered to be ambiguous for some species. None of these hypotheses can be confirmed in the single specimen examined in this study. Also P. wolfi was originally described as having superior basal plates with double vertical rows of teeth fused to each other and to a horny base ( Blake & Hilbig 1990). This structure may be equivalent to the presence of both inferior and superior basal plates, but further studies are needed to confirm this. Parougia wolfi clearly differs from P. ougi sp. nov. by the distinct shape of the anterior free denticles of the maxillary apparatus.

Ecology and distribution

NE Atlantic: Gulf of Cadiz (Moroccan margin). Found in experimentally deployed wood at a depth of 354 m.

Figures

Fig. 13. Parougia ougi sp. nov., holotype (NHMUK 2020.1516). Stereo (A–B) and compound (C–L) microscope images.A. Anterior fragment, dorsal view.B. Anterior end, ventral view.C. Right mandibula, dorsal view. D. Mandibulae, ventral view. E. Palp scars. F. Maxillae, dorsal view. G. Maxillae, ventral view. H. Parapodium from the second chaetiger, posterior view. I. Supra-acicular chaetae, anterior parapodium. J. Dorsal cirrus, sixth parapodium. K. Furcate chaeta, sixth parapodium. L. Sub-acicular chaetae, anterior parapodium.

Fig. 2 (next page). Majority rule consensus tree from the Bayesian analyses of a combined dataset with two genes (16S and H3). Posterior probability values near nodes result from the analyses in MrBayes. Taxon names highlighted in bold are new species or new sequences for already described species. Habitat specialization indicated by the text ‘VENT’ for hydrothermal vents, ‘SEEP’ for cold seeps, ‘BONE’ for whale/mammal-falls, ‘WOOD’ and ‘ALFALFA’ for wood- and alfalfa-falls, and ‘FISHFARM’ for the organically-enriched sediments beneath fish farms. Brown bars at the base of a clade indicate a specialization to a chemosynthesis-based ecosystem. Green and blue dots indicate depth distributions shallower and deeper than 200 m, respectively.