Eunice decolorhami Díaz-Díaz & Rozbaczylo & Sellanes & Tapia-Guerra 2020, sp. n.
Creators: name: Díaz-Díaz, Oscar Felipe
name: Rozbaczylo, Nicolás
name: Sellanes, Javier
name: Tapia-Guerra, Jan M.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Eunicida
Eunicidae
Eunice
Eunice decolorhami

description: Eunice decolorhami sp. n. Díaz-Díaz & Rozbaczylo
Figs. 2–4
LSID urn:lsid:zoobank.org:act: A8C80D3F-A411-4238-9E59-D8661473EDB6
Diagnosis. Prostomium with five cephalic appendages with articulations inconspicuous. Peristomium biannulated, with peristomial cirri with up to six articulations, exceeding anterior end of peristomium. Maxillary apparatus with MF =: 1+1; 6+7; 9+0; 9+12; 3+1; 1+1. (Figs 3b; 4o). Postchaetal lobe oval on chaetigers 1 and 2; subtriangular on subsequent parapodia. Dorsal cirri cirriform, weakly articulated. Branchiae pectinate from chaetigers 7–8 to posterior end of body, with up to 16 filaments. Pectinate chaetae in anterior chaetigers with 12–14 teeth with filiform tips; in middle and posterior chaetigers with up to 16 teeth. Neuropodia with 2–3 blunt-tipped black aciculae. Subacicular bidentate hooks from chaetiger 25, with black color concentrated on most length of hook; in mid-posterior chaetigers, black color concentrated toward subdistal end, and in last chaetigers, color fades. Tube white bone colored, parchment-like, branched with alternating openings.
Material examined. Holotype MNHNCL ANN-15035, station C22.S22, 015 (26°19’40”S, 79°59’52”W), slope of San Ambrosio and San Félix islands (Desventuradas islands), trawled at 340 m depth, October 23, 2016. Paratype 1 SCBUCN 6854, 1 specimen, same as holotype. Paratype 2 MNHNCL ANN-15036, 1 specimen, Seamount SF 5, northwest of San Ambrosio and San Félix islands, station C22. SF5 047.045 (25°25’40”S, 81°53’6”W), November 01, 2016, trawled at 180 m depth. Paratype 3 SCBUCN 8674, Seamount SF 9, northwest of San Ambrosio and San Félix islands, station C22.SF9.077.011 (25°46’37”S, 83°18’57”W), October 27, 2016, trawled at 200 m depth. Paratype 4 SCBUCN 6856, Seamount SFX, northwest of San Ambrosio and San Félix islands, station C22. SFX.027 (25°5’6”S, 82°0’54”W), October 31, 2016, trawled at 230 m depth.
Additional material: SCBUCN 6937, 1 specimen, same as paratype 2; SCBUCN 7248, 3 specimens, same as paratype 2; SCBUCN 7150, 2 specimens, same as paratype 2; SCBUCN 8068, 2 specimens, same as paratype 2; SCBUCN 6966, 1 specimen, same as paratype 3; SCBUCN 7271, 1 specimen, same as paratype 3; SCBUCN 8040, 1 specimen, same as paratype 4.
Description. Holotype (Fig. 2c) complete, in two fragments, with 105 chaetigers, total length 55.5 mm; first 10 chaetigers measure 10 mm in length, widest part measures 4.5 mm without parapodia (6.5 mm with parapodia). Preserved color pale with dorsal light brown color stripes on all chaetigers and pygidium. Distal end of prostomium clearly notched (i.e., a very deep sulcus present). Prostomium shorter and narrower than peristomium, almost 2/3 length of peristomium (Figs 2 a-c; 4a). A pair of large rounded black eyes situated outside lateral antennae behind the palps (Figs 2 a–c; 4a; 5a, b). Palps and antennae evenly spaced. Palps slightly thinner than antennae. Antennae and palps articled distally, medial antennae with ten subequal cylindrical articulations, first three basal articulations inconspicuous, reaching chaetiger 12 (Fig. 4a); lateral antennae with six subequal drop-shaped articulations, reaching posterior margin of chaetiger 3. Palps with three subdistal subequal drop-shaped articulations, slightly exceeding anterior peristomial margin (Figs 2c; 4a). Peristomium biannulated, anterior ring about ¾ of total length (Figs. 2 a-c, 4a), separation between rings clear dorsally and ventrally (Fig. 2a, c). Peristomial cirri with up to six articulations, exceeding anterior end of peristomium. Mandibles dark, calcareous cutting plates subsquare-shape (Fig. 3a), with eight growth rings. Maxillary apparatus with MF = 1+1; 6+7; 9+0; 9+12; 3+1; 1+1 (Figs 3b; 4o). MxI and MxII with distinct thickened outer ridge; MxIII short; part of distal arc with left MxIV and V; MxVI ridge-shaped.
Prechaetal lobe low, lightly oval on anterior parapodia, median and median to posterior parapodia subtriangular with apex shifted slightly upwards (Figs. 2 e–g; 4c–e) and becoming straight and as long as postchaetal lobe on most posterior parapodia (Fig. 4f). Postchaetal lobe oval on chaetigers 1 and 2; subtriangular on subsequent parapodia (Fig. 3 b–e), longer than prechaetal lobe. Dorsal cirri cirriform, weakly articulated, two times longer than ventral cirri on four anterior chaetigers (Fig. 1b); 2.5 times longer than ventral cirri on chaetigers 8–30 (Figs. 2e; 4c); two times longer than ventral cirri on middle (Figs 2f; 4d, e) and posterior (Fig. 2g) chaetigers; on most posterior chaetigers both with almost same length (Fig. 4f). First four ventral cirri slender, digitiform (Figs. 4b; 5a, b); subsequent ones, with suboval inflated base from chaetiger 5 through chaetiger 33 with a short tapering tip (Fig. 2d,e, 4c). Subsequent ventral cirri digitiform, three times shorter than dorsal cirri on posterior chaetigers (Fig. 2f, g, 4d, e).
Branchiae pectinate, appearing from chaetiger 8 in holotype (chaetigers 7–8 in paratypes) to posterior end of body (Fig. 2c). Last two chaetigers not branchiated. Branchiae best developed around chaetiger 40 with up to 16 filaments (Fig. 4e); some specimens with dichotomous filaments (Figs 2f; 4d, e); first pair of branchiae with four filaments (Fig. 4c), last pair with 1–3 short filaments (Fig. 4f). On posterior segments, branchial filaments similar in length to notopodial cirri (Fig. 4f).
Limbate chaetae (Fig. 4g) marginally striated, giving appearance of being serrated. Pectinate chaetae in all chaetigers, inserted between dorsal bundle of limbates and neuroaciculae, with similar position all along body; pectinate chaetae in anterior chaetigers 8–10 thin, all pectinate chaetae scoop-shaped, serrated, isodont with external teeth differing in length, asymmetrical, with 12–14 teeth with filiform tips (Figs 2i; 4i); in middle and posterior chaetigers with 4–6 thick, flat to slightly curved, isodont, asymmetrical, with up to 16 teeth, with blade slightly wider than that of anterior chaetigers, both with the outer tooth almost two times longer than median teeth. Compound falcigers bidentate (Figs. 2h; 4h); distal tooth strongly curved and pointing in same direction as proximal tooth. Proximal tooth larger and thicker than distal one. Guards distally asymmetrical, bluntly pointed and basally serrated. Shafts of compound falcigers marginally serrated with a distinct core (Fig. 2h). Neuropodia with two black aciculae usually, sometimes up to three; blunt-tipped (Figs 2f; 4j) from about chaetiger 30 to posterior ones, becoming pointed and distally falcate in last few chaetigers. Subacicular hooded hooks (Figs 2j, j´; 4k–n) present from chaetiger 25 (paratypes: 28–30); usually a single bidentate hook with a distinct hood, with black color concentrated on most of its length (Figs 2j, j´; 4k, l), but in mid-posterior chaetigers (from chaetigers 85 to 98), black color concentrated toward subdistal end (Fig. 4m) and color fades in last chaetigers (Fig. 4n). Few parapodia with two subacicular hooded hooks (Fig. 2g). Pygidium with two ventral pairs of anal cirri; ventral-most pair shortest, finger-shaped, dorsal one longest, with 4–5 subequal cylindrical articulations; cirri as long as last nine chaetigers (Fig. 2k).
Tube white bone colored, parchment-like, branched with alternating openings (Fig. 5c). Tubes forming complexes on the sandy bottom at depths between 180 to 340 m. Usually a single specimen found per tube.
Variation. Paratypes and non-type material with 73–104 chaetigers, total length 32.0–54.5mm; widest part measuring 2.2–4.5 mm without parapodia (up to 6.5 mm with parapodia). In some specimens, separation between peristomial rings is not clear. Peristomial cirrus in some paratypes reaching anterior end of peristomium (Figs 4a; 5b). Maxillary apparatus with MF =1+1; 6–7+6–7; 8–9+0; 7–8+11; 1–2+1; 1+1.
In all specimens examined, branchiae begin on chaetigers 7–8, ending on two or three chaetigers before pygidium. Branchiae with up to 18 filaments and in some specimens, most dorsal filaments are dichotomous; shortest specimens with 2–3 filaments in posterior branchiferous segments. Subacicular hooded hooks (Figs 2j, j´; 4k–n) usually present from chaetiger 25 (paratypes: 28–30), at widest segment including parapodia.
Etymology. The name of the species derives from Latin: decolorata = decolorated and hami = hooks and refers to the gradual discoloration of the subacicular hooks from black-brown to clear sheaths-translucent that occur from the mid-posterior region of the body until the last chaetigers.
Type locality. Upper slope northwest of San Ambrosio and San Félix islands (Desventuradas Islands), 26°19’40”S, 79°59’52”W, 340 m depth.
Distribution and habitat. Specimens come from samples obtained from the slope of Desventuradas Islands, station S22 (26°19’40”S, 79°59’52”W, 340 m depth) and the summit of three nearby seamounts: SF5 (25°25’40”S, 81°53’6”W, 180 m depth), SF9 (25°46’37”S, 83°18’57”W, 200 m depth) and SFX (25°5’6”S, 82°0’54”W, 230 m depth). The habitat of three stations (S22, SF9 and SFX), of the four in which the specimens of the new species were collected, was explored using a ROV. The bottom at SF9 and SFX was dominated by coarse calcareous sediments produced by foraminiferous tests, debris of deep-sea corals, holopelagic gastropod shells (Cavolinia sp. and Cuvierina sp.) and rhodoliths, with scattered rocky outcrops (Fig. 6 b–c). Habitat at S22 differed by the predominance of fine sand (Fig. 6a).
description: Published as part of Díaz-Díaz, Oscar Felipe, Rozbaczylo, Nicolás, Sellanes, Javier & Tapia-Guerra, Jan M., 2020, A new species of Eunice Cuvier, 1817 (Polychaeta: Eunicidae) from the slope of the Desventuradas Islands and seamounts of the Nazca Ridge, southeastern Pacific Ocean, pp. 211-226 in Zootaxa 4860 (2) on pages 213-218, DOI: 10.11646/zootaxa.4860.2.4, http://zenodo.org/record/4413701