A revision of the genus Arenopontia Kunz, 1937 (Copepoda, Harpacticoida, Arenopontiidae), including the description of five new species Author Sak, Serdar Department of Biology, Faculty of Science and Literature, Balıkesir University, Balıkesir, Türkiye. Author Karaytuğ, Süphan Department of Biology, Faculty of Science, Mersin University, Mersin, Türkiye. Author Huys, Rony Department of Life Sciences, Natural History Museum, Cromwell Road, London SW 7 5 BD, UK. text Zootaxa 2024 2024-04-04 5433 1 1 50 http://dx.doi.org/10.11646/zootaxa.5433.1.1 journal article 10.11646/zootaxa.5433.1.1 1175-5326 10953646 06E5A735-A276-41D7-A9EE-B09642D953B6 Arenopontia gunduzi sp. nov. https://zoobank.org/9196D0ED-D217-45E3-BD72-DB8CE1E0 ( Figs 13–16 ) Type locality. France , Pas-de-Calais , Ambleteuse ; fine sandy beach, near low-water mark . Material examined. Holotype ♀ (dissected on eight slides) ( NHMUK reg. no 2024.1036) . Paratypes are 1 ♀ dissected on nine slides ( NHMUK reg. no 2024.1037), 2 ♂♂ dissected on six and seven slides, respectively ( NHMUK reg. nos 2024.1038–1039), and 3 ♀♀ and 1 ♂ in ethanol ( NHMUK reg. nos 2024.1040–1043); all collected at type locality with Karaman-Chappuis method; leg. R . Huys & S. Conroy-Dalton , 19 May 1997 . Description of female. Total body length from tip of rostrum to posterior margin of caudal rami 340 μm (only holotype measured before dissection). Body slender and cylindrical, without clear distinction between prosome and urosome ( Fig. 13A, B ). Maximum width 25 μm measured at posterior margin of cephalothorax; width more or less uniform throughout remainder of body. Hyaline frills of thoracic somites weakly developed and crenulated, those of genital double-somite and free abdominal somites strongly developed and consisting of rectangular digitate or weakly incised lappets ( Figs 13A, B, D ; 14A ). Genital double-somite ( Figs 13A, B ; 14A ) 2.27 times longer than wide (measured in ventral aspect); without chitinous ribs marking original segmentation; with two middorsal, two lateral and two ventral pores. Anal somite ( Figs 13B, D , 14A ) with two dorsal and two lateral pores. Anal operculum pinnate; with minute spinules along free distal margin ( Fig. 13D ). Anus positioned subterminally between caudal rami. Rostrum ( Fig. 13A ) small, broadly subtriangular, tapering distally, with two delicate sensilla. Caudal rami ( Fig. 13C, D ) approximately 2.65 times longer than maximum width (measured in dorsal view), tapering posteriorly; with single pores dorsally in anterior quarter ( Fig. 13D ) and laterally in posterior half near insertion of seta III ( Fig. 13C ); outer distal corner produced into posteriorly directed, recurved spinous process, accompanied at base by outer spinular row ( Fig. 13C ); dorsal surface with spur-like process, inner margin with few spinules ( Fig. 13C ). Armature consisting of seven setae; seta I small; setae II and III long and naked; seta IV short, sparsely pinnate, located between seta V and posterior spinous process; seta V long and with fracture plane; seta VI small, naked and located at inner distal corner; seta VII foliaceous and tri-articulate at base. Antennule ( Fig. 14C ) slender, six-segmented. Segment 1 with a short seta near anterodistal margin. Segment 2 longest, about 3.7 times longer than wide. Segment 4 with long aesthetasc (L: 30 μm) fused at base with seta. Distal segment with seven naked setae (two of which spatulate) and apical acrothek consisting of short aesthetasc (L: 15 μm) and two slender setae. All setae naked except for plumose seta on dorsal surface of segment 2. Armature formula: 1-[1], 2-[7 + 1 plumose], 3-[4], 4-[(1 + ae)], 5-[1], 6-[7 + acrothek]. Antenna ( Fig. 16B, C ). Coxa small (not figured), without ornamentation. Basis and proximal endopodal segment fused, forming elongate allobasis; with fine spinules along exopodal margin as figured; original basis-endopod boundary marked by incomplete transverse spinule row. Exopod one-segmented, elongate, with a naked apical seta (about 1.35 times longer than exopod). Distal endopodal segment with spinules on medial surface and at outer distal corner; medial armature consisting of two short spines; apical armature consisting of two spines and three geniculate setae, longest of which with spinules around geniculation and fused basally to naked accessory seta. Mandible, maxillule, maxilla and maxilliped as in A. anatolica sp. nov. P1 ( Fig. 15A ). Intercoxal sclerite wide and subrectangular. Praecoxa represented by triangular naked sclerite. Coxa without ornamentation. Basis with few coarse spinules near base of endopod and fine spinules around outer margin; anterior surface with a pore and a small, setiform, naked spine near medial margin. Exopod three-segmented; exp-1 and -2 with spinules around outer margin; exp-1 1.55 times longer than exp-2, with unipinnate outer spine; exp-2 without outer element; exp-3 with short unipinnate outer spine, a longer curved unipinnate spine and one geniculate seta distally, and one inner, apically penicillate seta subdistally. Endopod two-segmented, prehensile; enp-1 about eight times longer than wide, and 1.73 times longer than exopod; with a serrate inner seta in proximal third, and one spinule near outer distal corner; enp-2 about as long as wide, with a short unipinnate outer spine and a slightly longer geniculate inner claw, in addition to one large spinule. P2–P4 ( Fig. 15B–D ) intercoxal sclerites naked, with concave distal margin. Praecoxae triangular, small and naked. Coxae wider than long and without ornamentation. Bases smaller than coxae, with a spinular row near base of endopod and at outer distal corner; anterior surface with a pore near coxa-basis boundary; outer basal seta absent (P2), plumose (P3) or naked (P4). Exopods three-segmented; segments with spinular ornamentation as figured; inner distal spine of exp-3 bipinnate, all other exopodal elements unipinnate; hyaline frills of exp-1 and -2 well developed; exp-2 with lateral pore halfway down inner margin length; P3–P4 exp-3 with anterior surface pore. Endopods two-segmented, with enp-1 distinctly longer than enp- 2 in P3–P4; P2–P4 enp-1 about 1.8, 2.4 and 3.8 times longer than their respective distal segments, with few coarse spinules along outer margin as figured. P2 enp-2 with a long, apically serrate, posteriorly directed seta near proximal inner margin. P2–P3 enp-2 with a long bipinnate seta terminally. P4 enp-2 small, with a basally fused, apically serrate seta, and a long bipinnate seta at outer distal corner. Spine and seta formula as follows: FIGURE 13. Arenopontia gunduzi sp. nov. (♀): (A) habitus, dorsal; (B) habitus, lateral; (C) anal somite and left caudal ramus, lateral; (D) anal somite and caudal rami, dorsal. FIGURE 14. Arenopontia gunduzi sp. nov. : (A) urosome ♀, ventral; (B) urosome ♂, ventral; (C) antennule ♀, ventral. FIGURE 15. Arenopontia gunduzi sp. nov. (♀): (A) P1, anterior; (B) P2, anterior; (C) P3, anterior; (D) P4, anterior. FIGURE 16. Arenopontia gunduzi sp. nov. : (A) habitus ♂, dorsal; (B) antenna ♀, lateral; (C) antenna ♀, medial; (D) antennule ♂, ventral [armature of segments 3–6 partly omitted; see (E)]; (E) antennulary segments 3–6, anterior ♂ [modified elements on segments 7–8 omitted].

Exopod	Endopod
P2	0.0.021	0.110
P3	0.0.021	0.010
P4	0.0.021	0.020

Fifth legs ( Fig. 14A ) closely set together but not touching medially. Baseoendopod and exopod fused forming a trapezoid plate with anterior surface pore near outer margin; distal margin with three pinnate setae, outer one longest, middle one shortest an inner one spiniform and swollen in proximal half; outer basal seta long and plumose. Genital field positioned near anterior margin of genital double-somite ( Fig. 14A ). Genital apertures ( Fig. 14A ) fused, forming median common slit; closed off by fused P6 forming operculum, rudimentary armature elements not discernible; copulatory pore small, located midventrally, close to genital slit; seminal receptacles difficult to discern. Description of male. Total body length from tip of rostrum to posterior margin of caudal rami 336 μm. Body ornamentation ( Figs 14B , 16B ) essentially as in female. Sexual dimorphism in antennule, urosomal segmentation, P5 and P6. Spermatophore length approximately 68 μm. Antennule ( Fig. 16D, E ) nine-segmented, haplocer; geniculation between segments 7 and 8. Segment 2 longest and about 2.7 times longer than wide; segment 4 an incomplete sclerite with two small spiniform elements (one pinnate) ( Fig. 16E ); segment 5 with three naked setae and one spinulose element plus long aesthetasc (L: 57 μm) fused basally to a small slender seta; segment 6 with two setae; segment 7 with two modified spines and a seta; segment 8 with a short unipinnate spine; distal segment with seven naked setae (two of which spatulate) and apical acrothek. Setal formula: 1-[1], 2-[7 + 1 plumose], 3-[6], 4-[1 + 1 pinnate], 5-[3 + 1 spinulose + (1 + ae)], 6-[2], 7-[1 + 2 modified], 8-[1 modified], 9-[7 + acrothek]. Acrothek consisting of short aesthetasc (L: 28 μm) fused basally to two slender setae. P5 ( Fig. 14B ) with anterior surface pore and with armature as in female but all elements on distal margin comparatively shorter and more spiniform; outer element longest and bipinnate, middle one minute and naked, inner one bipinnate but without flagellate distal part observed in ♀ . Outer basal seta plumose. Sixth legs ( Fig. 14B ) asymmetrical, with smallest P6 closing off functional gonopore; each with a long sparsely plumose seta. Etymology. The species name (a noun in the genitive case) is named after Prof. İslam Gündüz (Ondokuz Mayıs University, Samsun ), in recognition of his contributions to zoology in Türkiye . Remarks. Arenopontia gunduzi sp. nov. shares the presence of a dorsal spur on the caudal ramus with A. riedli and A. nesaie . While A. riedli can readily be distinguished by the much shorter P1 endopod, the presence of two distal elements on P2–P3 enp-2, five elements on the female P5 and two elements on the male P6, A. gunduzi sp. nov. and A. nesaie are morphologically very similar. Differences between both species include (1) relative length of P1 enp-1 (1.7 times length of exopod vs 2.0); (2) proportional lengths of endopodal segments of P2 (enp-1:enp-2 1.75 vs 1.5); (3) P4 endopod (distinctly longer than exp-1 and setae of enp-2 extending beyond exp-3 vs about as long as exp-1 and setae of enp-2 not extending beyond exp-3); (4) length of ♀ P5 middle marginal element (0.3 times length of outer marginal seta vs 0.45–0.50); (5) length of outer and inner marginal elements of ♀ P5 distinctly different (inner one shorter) vs equally long); (6) ♂ P5 inner marginal element shorter in A. gunduzi sp. nov. (0.5 vs 0.75 times length of outer marginal seta); (7) ♂ P5 middle marginal element naked and reduced (15% length of outer marginal element) vs bipinnate and longer (one-third length of outer marginal element); and (8) female genital operculum (fused sixth legs) without armature vs with three minute processes (vestigial setae). The only confirmed record of A. gunduzi sp. nov. is from the type locality. Bonne’s (2003) record of A. nesaie from the Kwinte Bank, a sand bank off the Belgian coast, may in reality refer to A. gunduzi sp. nov. The same conspecificity may apply to the records of A. subterranea from southern England ( Harris 1972 ; Gee 1987 ; Joint et al. 1982; Wells 1961 , 1963 , 1970 ) and northern France ( Bodin 1988 ; Le Guellec 1988 ; Renaud-Debyser & Salvat 1963 ).