Arenopontia basibuyuki, Sak & Karaytuğ & Huys, 2024

Sak, Serdar, Karaytuğ, Süphan & Huys, Rony, 2024, A revision of the genus Arenopontia Kunz, 1937 (Copepoda, Harpacticoida, Arenopontiidae), including the description of five new species, Zootaxa 5433 (1), pp. 1-50 : 17-23

Arenopontia basibuyuki sp. nov.

https://zoobank.org/ 18347A20-27B8-4BD9-9782-0C84486E04E2

( Figs 7–10 )

Type locality. Türkiye, Sinop Province, Sarıkum (42°01.129’ N, 34°54.032’ E); sandy beach .

Material examined. Holotype ♀ (dissected on eight slides) ( NHMUK reg. no 2024.1009) . Paratypes are 2 ♂♂ dissected on seven slides each ( NHMUK reg. nos 2024.1010–1011), 1 ♀ and 1 ♂ dissected on eight and three slides, respectively ( BUZM), 10 ♀♀ and 10 ♂♂ in ethanol ( NHMUK reg. nos 2024.1012–1031), 23 ♀♀ and 20 ♂♂ in ethanol ( BUZM); all collected at type locality with Karaman-Chappuis method; leg. S. Karaytuğ and S. Sak, 13 September 2002 .

Description of female. Total body length from tip of rostrum to posterior margin of caudal rami 254–334 μm (mean = 310 μm; n = 28; holotype = 304 μm). Maximum width 45 μm measured at posterior margin of P4-bearing somite. Body slender and cylindrical, without clear distinction between prosome and urosome ( Fig. 7A, B ). 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 7A, B ; 8A, C ). Genital double-somite ( Figs 7A, B ; 8A ) 1.15 times longer than wide (measured in dorsal aspect); without chitinous ribs marking original segmentation; with two middorsal, two lateral and two ventral pores. Anal somite ( Fig. 8A, C, D ) with two dorsal, two lateral and two ventral pores. Anal operculum pinnate; with minute spinules along free distal margin ( Fig. 8D ). Anus positioned subterminally between caudal rami. Rostrum ( Fig. 7B ) small, broadly subtriangular, tapering distally, with two delicate sensilla.

Caudal rami approximately 2.9 times longer than maximum width (measured in dorsal view), tapering posteriorly; with single pores dorsally and ventrally near anterior border ( Fig. 8A, D ) and laterally near insertion site of seta III ( Fig. 8C ); outer distal corner produced into posteriorly directed, recurved spinous process, accompanied at base by outer spinular row ( Fig. 8C ); dorsal surface without spur-like process but with spinules near inner margin ( Fig. 8D ). 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. 9C ) slender, six-segmented. Segment 1 with a short seta near anterodistal margin. Segment 2 longest, about 2.6 times longer than wide. Segment 4 with long aesthetasc (L: 35 μm) fused at base with seta. Distal segment with seven naked setae (one of which spatulate) and apical acrothek consisting of short aesthetasc (L: 21 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. 9D ). Coxa small (not figured), without ornamentation. Basis and proximal endopodal segment discrete and without ornamentation. Exopod one-segmented, elongate, with a naked apical seta (about 1.9 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. 10A ). Intercoxal sclerite wide and subrectangular. Praecoxa represented by triangular naked sclerite. Coxa without ornamentation. Basis with spinular row near base of endopod and around outer margin; anterior surface with a pore and a small spine near medial margin. Exopod three-segmented; exp-1 and -2 with spinules around outer margin; exp-1 slightly 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 10 times longer than wide, and 2.2 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. 10B–D ) intercoxal sclerites naked, with concave distal margin. Praecoxae small and naked. Coxae wider than long and without ornamentation. Bases smaller than coxae, with a spinular row near base of endopod (P3–P4) and at outer distal corner (P2–P4); 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 (except P4), 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 1.1, 2.1 and 5.2 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 minute, with a basally fused, apically serrate seta, and a long bipinnate seta at outer distal corner. Spine and seta formula as follows:

Fifth legs ( Fig. 8A ) closely set together but not touching medially. Baseoendopod and exopod fused forming a rectangular plate with anterior surface pore; distal margin with four pinnate setae, middle two less than half the length of inner and outer ones; outer basal seta long and plumose.

Genital field positioned near anterior margin of genital double-somite ( Fig. 8A ). Genital apertures ( Fig. 8A ) fused forming median common slit; closed off by fused P6 forming operculum with one minute dentiform processes on either side; copulatory pore 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 250–317 μm (mean = 285 μm; n = 22). Body ornamentation ( Figs 7C , 8B ) essentially as in female. Sexual dimorphism in antennule, urosomal segmentation, P5 and P6. Spermatophore length approximately 55 μm.

Antennule ( Fig. 9A, B ) nine-segmented, haplocer; geniculation between segments 7 and 8. Segment 2 longest and about 2.6 times longer than wide; segment 4 an incomplete sclerite with two small elements (one spiniform, one setiform) ( Fig. 9B ); segment 5 with three setae plus long aesthetasc (L: 42 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-[4 + 2 unipinnate spines], 4-[2], 5-[3 + (1 + ae)], 6-[2], 7-[2 modified], 8-[1 modified], 9-[7 + acrothek]. Acrothek consisting of short aesthetasc (L: 18 μm) fused basally to two slender setae.

P5 ( Fig. 8B ) with anterior surface pore and with armature as in female but all elements on distal margin comparatively shorter; inner and outer marginal elements spiniform (instead of setiform as in the ♀), middle elements minute and naked (instead of bipinnate as in the ♀). Outer basal seta plumose.

Sixth legs ( Fig. 8B ) 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. Hasan Hüseyin Başıbüyük (Akdeniz University, Antalya), in recognition of his contributions to zoology in Türkiye.

Remarks. Arenopontia basibuyuki sp. nov., A. gunduzi sp. nov. and A. nesaie belong to the same species group, characterized by the presence of a single coarse spinule near the outer distal corner of P1 enp-1 and male sixth legs displaying a reduced armature represented by an outer plumose seta. The latter two species differ from A. basibuyuki sp. nov. in the presence of a dorsal spur (instead of a raised spinular row; Fig. 8D ) on the caudal ramus and only four elements (instead of five; Fig. 8A, B ) on the fifth leg in both sexes. The relatively longer P1 enp-1 (2.2 times as long as exopod) also serves to distinguish A. basibuyuki sp. nov. from A. nesaie (2.0) and A. gunduzi sp. nov. (1.7).

The known records from the type locality, Karasu (Sakarya Province) and Yoroz Feneri (Trabzon Province) ( Sak 2004) suggest that the species is distributed along the entire Turkish Black Sea coast and may overlap in distribution with A. anatolica sp. nov .

Figures

FIGURE 7. Arenopontia basibuyuki sp. nov.: (A) habitus ♀, lateral; (B) habitus ♀, dorsal; (C) habitus ♂, dorsal.

FIGURE 8. Arenopontia basibuyuki sp. nov.: (A) urosome ♀, ventral; (B) urosome ♂, ventral; (C) anal somite and right caudal ramus ♀, lateral; (D) anal somite and caudal rami ♀, dorsal.

FIGURE 9. Arenopontia basibuyuki sp. nov.: (A) antennule ♂, anterior [armature of segments 3–6 partly omitted; see (B)]; (B) antennulary segments 3–6 ♂, anterior; (C) antennule ♀, anterior; (D) antenna ♀, lateral.

FIGURE 10. Arenopontia basibuyuki sp. nov. (♀): (A) P1, anterior; (B) P2, anterior; (C) P3, anterior; (D) P4, anterior.