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

Herpyllobius hourdezi Suárez-Morales and Salazar-Vallejo sp. n. (Figures 6, 7) Material examined Holotype. (MNHN-IU 2023-501)), adult ovigerous female, from Harmothoe samadiae sp. n., Papua New Guinea, Cape Croisiles, RV Alis, Sta. CP 4033 (04°52 ʹ 06.8412” S, 145° 52 ʹ 36.9228” E), 780 m, coll. 16 December 2012, S. Samadi, leg. (MNHN 2001-170), ethanol-preserved, vial. Type locality Papua New Guinea, Cape Croisiles, RV Alis, Sta. CP4033 (04°52 ʹ 06.8412” S, 145°52 ʹ 36.9228” E), depth = 780 m. Etymology The species name is an eponym honouring Dr Stéphane Hourdez (Banyuls Oceanographic Observatory in Southern France), who first processed the deep-living polynoids herein reported. Gender is masculine. Diagnosis Female Herpyllobius with pear-shaped ectosoma, tapering towards genital area. Genital area with pair of prominent, sclerotised genital swellings with attached egg sacs. Genital swellings separated by depressed margin; intergenital surface lacking sclerotised dots. Ectosomal integument smooth, translucent. Ectosoma and endosoma connected by short stalk originating on underside of ectosoma, close to mid-body. Endosoma with proximal mass extending into two digitiform processes and single, distally twisted process with simple margins. Egg sacs thick, about 4 times as long as wide, multiseriate, with 6–8 rows of eggs. Description of holotype adult female Ectosoma roughly pear-shaped, 1.2 mm at maximal width, 956 μm high in anterior section, 0.87 mm in posterior section (Figure 6 (A–D)). Ectosomal integument smooth, with thin, translucent cuticle showing inner whitish eggs mass (Figure 7 (A, B)). Genital area with pair of heavily sclerotised, ring-shaped genital swellings (diameter = 245 µm each) (gs in Figure 6 (C)); intergenital area with smooth, depressed margin narrower than genital swellings diameter (arrowhead in Figure 6 (C)). Genital swellings with attached egg sacs (gs in Figure 6 (A, B)). Paired genital swellings sclerotised, prominent, each rounded, slightly asymmetrical, about 255 μm each, swellings separated medially by smooth depression measuring almost 180 μm (arrows in Figure 6 (C, D)). Genital swellings of holotype each carrying egg sac. Egg sacs thick, cylindrical, 1 mm long, 0.45 mm wide. Intersomital stalk short, thick, 130 μm in diameter, originating on underside close to mid-body (stk in Figure 6 (B)). Endosoma 1.3 mm long, with two sections, proximal half anvil-shaped mass, 1.3 mm wide. Distal half with several intermediate lobes (L 1–4 in Figure 6 (B)), and curved subtriangular distal lobe (DL in Figure 6 (B)), 125 μm wide. Egg sacs barrel-shaped, paired, multiseriate, with up to 8 egg rows (es in Figure 6 (A–C)), eggs 65–85 μm in diameter. Remarks The new species H. hourdezi lacks a medial intergenital protuberance and sclerotised dots on the ectosoma, so it can be assigned to Group III (sensu Lützen and Jones 1976, López-González et al. 2000). This group originally contained a single species, H. haddoni Lützen 1964, which is characterised by the absence of intergenital sclerotised dots or bulging processes (Lützen 1964; López-González et al. 2000). The group was recently expanded by Suárez-Morales and Salazar-Vallejo (2022) with the addition of five more species: H. luetzeni López-González, Bresciani and Conradi, 2000, H. nipponicus Lützen, 1964, H. cluthensis Boxshall, O’Reilly, Sikorski and Summerfield, 2019, H. polarsterni López-González, Bresciani and Conradi, 2000, and H. stocki López-González, Bresciani and Conradi, 2000. With the addition of H. chambardi sp. n., Group III now comprises seven species; the new species can be distinguished from Group III congeneric species by the structure and details of the endosoma. Herpyllobius cluthensis has a distinctively long, depressed endosoma (Boxshall et al. 2019), H. luetzeni has a massive bilobate endosoma, thus diverging from that described herein for H. depressus; H. nipponicus also diverges from the new species by its possession of a disc-like multilobate endosoma; in H. polarsterni the endosoma is lump-like, with roughly wrinkled surface, clearly diverging from H. hourdezii ’s endosoma traits. We regard these differences sufficient to justify the proposal of a new species of Herpyllobius.