Herpyllobius chambardi Suarez-Morales and Salazar-Vallejo 2025, sp. n.

Herpyllobius chambardi Suárez-Morales and Salazar-Vallejo sp. n. (Figures 1–3, 5) Material examined Holotype. (MNHN-IU 2023-500), and two paratypes (ECO-CHZ-11882), adult females, from Lepidasthenia brunnea sensu Knox, 1960 (MNHN IA 2015–1723), MADEEP Expedition, Eastern New Britain, Induna Island, RV Alis, Sta. CP 4266 (4.585°S, 152.41°E), 575–616 m, 26 April 2014, L. Corbari et al., leg. Holotype with egg sacs, paratypes lacking egg sacs. Type locality Eastern New Britain, Induna Island, Research Vessel Alis, Sta. CP4266 (04°35 ʹ 07.1988” S, 152° 25 ʹ 03.5904” E), depth range: 575– 616 m. Etymology The species name is an eponym honouring Dr Cyril Chambard (Muséum National d’Histoire Naturelle (Paris, France), who first processed the deep-living polynoids herein reported. Gender is masculine. Diagnosis Female with ectosoma globose, with longitudinal medial constriction dividing the ectosoma into two symmetrical hemispheres, except for genital area. Ectosoma with pair of prominent rounded genital swellings separated by large medial posterior protuberance lacking sclerotised dots. Ectosomal integument smooth, translucent. Ectosoma and endosoma connected by short stalk; endosoma discoid, larger than posterior part of ectosoma; endosoma thick proximally, tapering distally. Sclerotised oblong ring in proximal half of endosomal discoid section with adjacent pair of oval cement glands.Egg sacs thick,barrel-shaped, about twice as long as wide, multiseriate, with six or seven rows of eggs. Male copepodid attached by its anterior end to female genital swellings. Copepodid body comprising anterior ovoid, weakly segmented prosome carrying short, 3-segmented urosome with caudal rami and bearing 4 pairs of legs with 2-segmented exopods and 1-segmented endopods. Description of adult female Ectosoma globose, as long as wide, 954 μm long, 956 μm wide, 0.97–1.14 mm long × 0.71– 0.78 mm wide (paratypes), ectosoma with longitudinal constriction running along medial axis except for genital area, dividing most of ectosoma into two symmetrical hemispheres; constriction marked by narrow belt-like integumental cord. Ectosomal integument smooth, with thin, translucent smooth cuticle showing inner yellow egg mass; genital area undivided, whitish, soft looking, with pair of posteriorly directed genital swellings and medial protuberance (Figure 5 (A, B)). Paired genital swellings sclerotised, prominent (rounded, slightly asymmetrical, each measuring 230 μm, swellings separated medially by a 210 μm gap (gp in Figure 1 (A, B)). Genital swellings carrying egg sacs; holotype lacking egg sac; one paratype carrying one complete sac (1.14 × 0.5 mm, 78 eggs), detached egg sac slightly smaller (0.96 × 0.4 mm, 66 eggs) (es in Figure 3 (A, B)). Intergenital medial surface (= 200 μm) with large, rounded posterior protuberance (Figure 1 (A, B)). Protuberance lacking sclerotised integumental dots. Intersomital stalk short, thick, 160 μm in diameter, originating close to mid-body. Endosoma of holotype 360 μm long, discoid, 480 μm in diameter, peripheral margins simple, basally connected to thick terminal mass (Figure 3 (A, B)). Proximal discoid section with oblong sclerotised ring (sr in Figure 3 (C)) on proximal section (diameter = 260 μm). Pair of rounded cement glands adjacent to sclerotised ring (cg in Figure 3 (C)). Egg sacs barrel-shaped, paired, multiseriate, with up to 7 egg rows (Figure 3 (A, B)), eggs 75–85 μm in diameter. Description of males Holotype carrying two male individuals attached to one of the genital swellings (Figures 1 (B) and 2(A)). First male (M 1 in Figure 2 (A)) flask-shaped, attached to female genital swelling by its anterior end, with 3-segmented antennule (A 1 in Figure 2 (A)) and remains of urosome posteriorly (UR in Figure 2 (A)); otherwise limbless. Second male (M 2 in Figure 2 (A)), body length = 175 µm, male M2 lacking antennules at attachment point; body robust, subquadrate, showing dorsal indentations. Urosome (UR in Figure 2 (A)) 3-segmented, carrying pair of caudal rami armed with 3 terminal caudal setae (CR in Figure 2 (A)); male M2 likely representing cast-off exuvium of preceding male copepodid stage, with biramous legs 1–4 (P1–P 4 in Figure 2 (A)), each arising from robust protopod; legs 1–4 exopods 2-segmented, distal exopodal segments of P1–4 armed with two subequally long apical setae. Endopods of legs 1–4 1-segmented, armed with 2 apical setae. Remarks The new species H. chambardi sp. n. exhibits the main diagnostic characters of Herpyllobius according to Lützen (1964a) and Boxshall et al. (2019). The nominal species of Herpyllobius were grouped by Lützen and Jones (1976) based on taxonomically valuable characters like the presence of a medial intergenital protuberance and the number and arrangement of adjacent integumental processes (sclerotised dots) above or between the genital swellings; this grouping was updated with additional characters by López-González et al. (2000). The new Papuan–New Guinean species is assignable to Lützen and Jones’ (1976) Group I, which comprises species having the genital swellings separated by a prominent, medio-terminal bulging process, and 4 adjacent sclerotised dots. Herpyllobius chambardi lacks sclerotised dots but the presence of a large medial intergenital protuberance allows us to include it in Group I, instead of grouping it with H. haddoni Lützen, 1964, the only species lacking intergenital sclerotised dots or bulges. Group I includes ten other species: H. antepositus Stock, 1986, H. arcticus Steentrup and Lütken, 1861, H. antarcticus Vanhöffen, 1913, H. australis Lützen, 1964, H. cordiformis Lützen, 1964, H. elongata Lützen, 1967, H. rotundus Lützen and Jones, 1976, H. lobosaccus Stock, 1986, H. stocki, López-González, Bresciani and Conradi, 2000, and H. gravieri Lützen, 1964 (Lützen and Jones 1976; López-González et al. 2000; Suárez-Morales and Salazar-Vallejo 2022). The absence of sclerotised dots is a character shared only by H. hourdezi sp. n. and H. stocki among the other species of Group I. These two species can be readily distinguished by the unique medially constricted ectosoma found in H. chambardi in contrast to the unmodified ectosomal surface in H. stocki (López-González et al. 2000).