Harmothoe ruthae, Miranda & Brasil, 2014

Miranda, Vinícius Da Rocha & Brasil, Ana Claudia Dos Santos, 2014, Two new species and a new record of Scale-worms (Polychaeta) from Southwest Atlantic deep-sea coral mounds, Zootaxa 3856 (2), pp. 211-226 : 220-223

Harmothoe ruthae sp.nov.

Figures: 6 A–J; 7A–C

Material examined: 16 spms. HOLOTYPE: 1 spm., IBUFRJ-2132 , ECOPROF 5, 612 m, 40º6'10,36"W – 22º22'29,95"S, 01/09/2008, on Lophelia pertusa . PARATYPES: 1 spm., IBUFRJ-2134, CAP-BC, 605 m, 40º14'50,56"W – 22º31'13,46"S, 17/03/2006, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2146, ECOPROF 2, 622 m, 40º6'11,57"W – 22º22'32,97"S, 10/06/2008, on Lophelia pertusa ; 1 spm., IBUFRJ-2135, ECOPROF 3, 572 m, 40º6'11,45"W – 22º24'31,12"S 05/07/2008, on Enallopsammia rostrata ; 1 spm., IBUFRJ-2145, ECOPROF 5, 608 m, 40º6'16,16"W – 22º22'33,75"S, 31/08/2008, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2138, ECOPROF 5, 622 m, 40º6'42,56"W – 22º21'50,42"S, 01/09/2008, on Madrepora oculata ; 1 spm., IBUFRJ-2137 ECOPROF 5, 622 m, 40º6'16,26"W – 22º22'33,43"S, 31/08/2008, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2141, ECOPROF 7, 608 m, 40º6'20,74"W – 22º22'7,74"S, 25/10/2008, on Errina sp. ; 1 spm, IBUFRJ-2142, ECOPROF 7, 617 m, 40º6'18,81"W – 22º22'24,43"S, 25/10/2008, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2147, ECOPROF 7, 612 m, 40º6'19,30"W – 22º22'16,24"S, 25/10/2008, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2136, ECOPROF 9, 701 m, 40º5'46,88"W – 22º22'41,33"S, 22/12/2008, on Lophelia pertusa ; 1 spm., IBUFRJ-2144, ECOPROF 10, 605 m, 40º5'39,21"W – 22º22'3,21"S, 17/01/2009, on Enallopsammia rostrata ; 1 spm., IBUFRJ-2148, ECOPROF 10, 636 m, 40º5'39,21"W – 22º22'3,21"S, 17/01/2009, on Enallopsammia rostrata ; 1 spm., IBUFRJ-2143, ECOPROF 11, 617 m, 40º7'35,34"W – 22º24'13,33"S, 14/02/2009, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2133, ECOPROF 12, 599 m, 40º6'49,28"W – 22º22'53,39"S, 13/03/2009, on Solenosmilia variabilis ; 1 spm., IBUFRJ-2139, ECOPROF 14, 609 m, 40º7'46,79"W – 22º23'35,01"S, 23/05/2009, on Lophelia pertusa .

Diagnosis: Rounded to sub-reniform elytra; surface covered by conical microtubercles which become gradually bigger toward the posterior margin, all tubercles with bifid tips. Parapodia biramous; notochaetae shafts with several rows of spines and blunt tip; neurochaetae with rows of spines on the distal half, supra-acicular chaetae with pointed tip, sub-acicular chaetae falcate with bifid tips.

Description: Holotype with 42 segments (length: 21 mm; width 05 mm); paratypes with number of chaetigers varying from 30 (length: 07 mm; width 03 mm) up to 45 (length: 23 mm; width: 08 mm). Body slightly flattened dorsoventraly. Prostomium bilobed, with distinct cephalic peaks ( Fig. 6A ). Median antennae missing but ceratophore in anterior notch, lateral antennae inserted ventrally, styles of antennae with smooth surface, tapering to filiform tip. Anterior pair of eyes situated laterally at widest part of prostomium, posterior pair situated dorsally near hind margin of prostomium. Palps ventrolaterally inserted with smooth surface and pointed tips.

Tentaculophores inserted laterally to prostomium, presenting two notochaetae and a pair of dorsal and ventral tentacular cirri, styles of cirri smooth, tapering gradually to filliform tip. Second segment with the first pair of elytra ( Fig. 6B ), parapodia biramous with a ventral buccal cirri, which is as long as all tentacular cirrus. Following segments present only tapering ventral cirri in the parapodia.

Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 6, 7, on alternating segments until segment 23, then on segments 26, 29 and 32, last ten segments cirrigerous. First pair of elytra nearly circular ( Fig 6B ), subsequent ones larger and more or less reniform ( Fig. 6C ). First pair of elytra with margin smooth and surface tubercles from first elytra shows bifid tips ( Fig. 6D ). Remaining elytra with cirriform papillae on the posterior margin; surface covered by microtubercles which become slightly bigger toward the posterior margin ( Fig. 6C ). Microtubercles conical shape with bifurcate tips, some of the tubercles, present single tips. Segments without elytra with distinct dorsal tubercle and filliform dorsal cirri with sparsely papillate surface and abruptly tapering tip.

Parapodia biramous ( Fig. 6E ); notopodia with elongate acicular lobe and neuropodia with elongate prechaetal acicular lobe, bigger than postchaetal, presenting a digitiform supra-acicular process. Tips of notoacicula and neuroacicula penetrating epidermis. Notochaetae stouter than neurochaetae, both with distinct rows of spines; notochaetae with blunt tips ( Figs. 6F–G ; 7A ); neurochaetae mainly with bidentate tips and a distinct secondary tooth ( Figs. 6H–I ; 7B ), a minority, located above, with single tip ( Figs. 6J ; 7C ).

Remarks: Some characters present on the elytra of H. ruthae sp.nov. make it distinct from all other species of Harmothoe previously reported to Brazil. By possessing only microtubercles and no macrotubercles, H. ruthae sp.nov. is distinct from H. aculeata Andrews, 1891 and H. ernesti Augener, 1931 . When H. ruthae sp.nov. is compared with H. lepida ( Amaral & Nonato, 1982) , also reported for Brazil, they differ from each other because H. ruthae sp.nov. possess microtubercles with bifid tips while H. lepida presents conical and single microtubercles.

Harmothoe ruthae sp.nov. can be differentiated from other species that present microtubercle with bifid tips, such as H. macginitiei Pettibone, 1955 , H. propinqua ( Malmgren, 1867) and H. antilopes McIntosh, 1876 , because those species also present tubercles with other kinds of tips: H. macginitiei presents single and quadrifid tips; H. propinqua presents quadrifid tips but lacks the single ones; in H. antilopes the bifid tips are present, but also are the crown-like and some scattered ones. Harmothoe discoveryae Pettibone, 1993 also has microtubercles with bifid tips with different size, but according to the description provided by the author the species presents tubercles with two to five tips; another discriminating characteristic between H. discoveryae and H. ruthae sp. nov. is the fact that the former possess mottled areas over the elytra and the latter has translucid elytra. Lastly, some elytra may present microtubercles with single tips, possibly these are the oldest ones and one of the tips suffered abrasion.

Etymology: The species epithet is homage to Dr. Ruth Barnich, for her important contributions to the study of the Polynoidae and other scale-worms.

Habitats: Individuals of Harmothoe ruthae sp.nov. were collected associated with the coral species L. pertusa , S. variabilis , E. rostrata and the hydrocoral Errina sp. , at a depth range from 570m to 647m.

Distribution: Southwest Atlantic, currently known only from the type locality, Campos Basin off Rio de Janeiro, Brazil.

Figures

FIGURE 6. Harmothoe ruthae sp. nov. (Holotype, IBUFRJ-2132). (A) Dorsal view of the anterior end; (B) first elytron, left side; (C) Middle elytron right side; (D) Right middle parapodium; (E) Detail of microtubercles and posterior margin of elytra; (F) Notochaeta; (G) tip of same chaeta; (H) Bidentate neurochaeta (I) Tip of same chaeta; (J) Tip of unidentate neurochaeta (Scales bars: A= 2 mm; B, C= 200 µm; D= 500 µm; E= 15 µm; F, H= 250 µm; G, I, J= 40 µm).

FIGURE 7. Harmothoe ruthae sp. nov. chaeta SEM. (A) Notochaeta; (B) tip of lower neurochaeta; (C) tip of upper neurochaeta (Scales bars: A= 100 µm; B, C= 20 µm).