Neoleptastacus acanthus Sak et al. 2008

Neoleptastacus acanthus (Chappuis, 1954) (Figs 1–5) Arenopontia acantha Chappuis, 1954 Arenopontia (Neoleptastacus) acantha Chappuis, 1954: Wells (1967: 324) Arenoponthia acantha Chappuis, 1954: lapsus calami by Cottarelli (1969: 20) Arenopontia (Neoleptastacus) acantha acantha Chappuis, 1954: Kunz (1971: 356) Neoleptastacus acanthus (Chappuis, 1954) Sak et al. (2008: 412) Neoleptastacus knidosensis —nomen nudum by Sak (2004: 230) Original description. Chappuis (1954): 268–270; Figs 46–53. Additional descriptions. Masry (1970 —as A. acantha): 251–253; Fig. 13. Cottarelli (1973a —as A. acantha): Fig. 22 [mandibular palp]. Martínez Arbizu & Moura (1994 —as A. acantha): 63; Fig. 2d, g [rostrum, anal somite and caudal rami]. Alper (2009): 45–46; Fig. 3.6 [♀ lateral habitus, photograph]. Type locality. Western Mediterranean. Chappuis (1954) collected the species in various localities in Italy, Algeria and Tunisia (see below) but did not specify a locus typicus. Since P.-A. Chappuis habitually ignored type fixation, all the specimens on which he established A. acantha are syntypes and collectively constitute the name-bearing type (ICZN Art. 72.1.1). According to ICZN Art. 73.2.3 the type locality encompasses all of the places where the syntypes were collected. Material examined. One ♀ (dissected on eight slides) (reg. no NHMUK 2024.1050) and one ♂ (dissected on seven slides) (reg. no NHMUK 2024.1051); seven ♀♀ and three ♂♂ (in ethanol) (reg. nos NHMUK 2024.1052 – 1061); five ♀♀ and two ♂♂ (in ethanol) deposited in the collections of BUZM. All specimens collected from Hastanealtı Beach, Datça (Muğla Province), Türkiye on 24 November 2002; leg. A. Alper. Body length. 450 μm (♀) [Chappuis 1954]; 380–420 μm (♀), 365–390 μm (♂) [Masry 1970]; 331 μm (♀), 325 μm (♂) [present account]. Redescription of female. Total body length from tip of rostrum to posterior margin of caudal rami 350 μm (mean = 331 μm; n = 10). Maximum body width 36 μm (mean = 34 μm; n = 10), measured near posterior margin of cephalothorax. Body slender and cylindrical without clear distinction between prosome and urosome. Sensillar pattern on body as figured. 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 lappets (Figs 1A, B; 2B; 5A). Somites connected by well-developed intersomitic membranes. Genital double-somite about 1.3 times longer than wide (measured in dorsal aspect); with two middorsal, four lateral and four ventral pores (Figs 1A, B; 5A). Anal somite (Figs 2B, C; 5A) with paired, dorsally recurved, spinous processes near posterior border either side of anal opening, and two lateral pores near anterior margin; with two conspicuous pores near ventral posterior margin. Anal frill triradiate, minutely incised (giving a spinulose appearance); anal operculum slightly convex, without ornamentation. Caudal rami (Figs 2B, C; 5A) about three times longer than wide (measured in dorsal view from anterior margin to apex of spinous process), distinctly tapering posteriorly; with a pore near ventral proximal margin (Fig. 5A); outer distal corner produced into posteriorly directed, dorsally recurved spinous process; no spinular ornamentation discernible. Armature consisting of seven setae; seta I small; setae II and III (displaced to dorsal surface) long and naked; seta IV short, naked, located between seta V and posterior spinous process; seta V long, naked, with proximal fracture plane (Fig. 5A); seta VI small, naked and located at inner distal corner; seta VII distinctly foliaceous and tri-articulate at base. Rostrum (Fig. 1C) small, broadly subtriangular, tapering distally; apical part lobate and demarcated by bilateral constrictions, with two delicate sensilla. Antennule (Fig. 3A) long and slender, 6-segmented. Segment 1 with small seta near anterodistal margin. Segment 2 longest, about 3.4 times longer than wide. Segment 4 with long aesthetasc (L: 45 μm) fused at base with seta. Distal segment with eight setae (two distinctly spatulate; indicated by arrows in Fig. 3A) and apical acrothek consisting of short aesthetasc (L: 20 μm) and two setae. All setal elements 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-[8 + acrothek]. Antenna (Fig. 2D, E). Coxa small, without ornamentation (not figured). Basis and proximal endopodal segment forming incompletely fused allobasis, about 2.9 times as long as maximum width; original basis-endopod boundary marked by transverse surface suture at level of exopodal articulation; proximal part representing original basis with longitudinal row of small spinules near base of exopod. Exopod one-segmented, unornamented, and elongate, with a naked apical seta (about 1.3 times longer than exopod). Free endopodal segment with few lateral spinules proximally and transverse spinular row distally; medial armature consisting of two short spines (indicated by arrows in Fig. 2D, E); apical armature consisting of two naked 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 N. spinicaudatus (see Sak et al. 2008: Figs 16D, E; 17E, F). Mandibular gnathobase elongate, about as long as palp; with several curved, minute teeth and one tiny recurved seta at dorsal corner. Mandibular palp uniramous, consisting of elongate, unisetose basis and one-segmented endopod with one inner, two outer, and two apical setae. Maxillule comprising praecoxa, coxa, basis and vestigial rami; praecoxal arthrite with one anterior surface seta and five spines and two setae around distal margin; coxal endite cylindrical, with two recurved spines; basis elongate, with rami completely incorporated; basal armature consisting of three apical setae; exopod and endopod represented by one and three setae, respectively. Maxilla comprising syncoxa, allobasis and endopod; syncoxa with two cylindrical endites, proximal endite with three setae (one fused at base) and distal endite with two setae (one fused at base); allobasis drawn out into long claw with one accessory seta; endopod one-segmented, with three setae; all elements naked. Maxilliped comprising syncoxa, basis and endopod; syncoxa longer than wide, unarmed, with few spinules; basis elongate and unarmed; endopod with small accessory seta and slightly curved claw, bearing strong, subterminal spinule. P1 (Fig. 4A). Intercoxal sclerite wide and subrectangular. Praecoxa small, triangular and naked. Coxa wider than long, without ornamentation. Basis with spinular row near base of endopod; anterior surface with a small inner spine near medial margin. Exopod three-segmented; exp-1 and -2 with several spinules around outer margin, exp-3 with single spinule; exp-1 longest, with unipinnate outer spine; exp-2 without outer element; exp-3 with short unipinnate outer spine, a long curved unipinnate spine and two geniculate setae distally. Endopod two-segmented, not prehensile, longer than exopod; enp-1 about 1.25 times longer than enp-2, with a serrate seta arising from halfway down inner margin and three coarse spinules along outer margin; enp-2 without spinules, distal margin with naked outer spine and geniculate inner seta. P2–P4 (Fig. 4B–D). Intercoxal sclerites rectangular (P2) or squarish (P3–P4) with concave ventral margins. Praecoxae triangular, small and naked. Coxae squarish and without ornamentation. Bases smaller than coxae, with a spinular row near base of endopod (P3–P4) and a few spinules around outer corner in P2 and P4; anterior surface with a pore; outer basal seta absent in P2, long and plumose in P3–P4. Exopods three-segmented; segments with coarse spinular ornamentation, as illustrated; outer spine of exp-1 and -2 naked (except for P3 exp-2 sparsely unipinnate); exp-3 with an outer unipinnate spine, and two setae distally (one unipinnate and one bipinnate in P2–P3 or two bipinnate setae in P4); P4 exp-2 elongate, distinctly longer than exp-1; inner seta of P4 exp-3 serrate in distal half and originating near distal margin from posterior surface. Endopods two-segmented; P2–P4 enp-1 unarmed, about 1.1, 1.6, and 4.1 times longer than their respective distal segments, with few coarse spinules along outer margin as figured, but without ornamentation along inner margin (except for single minute spinule near inner distal corner of P4 enp-1); P2 enp-2 with long, apically serrate, backwardly directed seta near proximal margin and two unequal unipinnate setae around distal margin, with two spinules along outer margin subdistally and with one spinule at inner distal corner; P3 enp-2 with three coarse spinules on anterior surface, apical margin with long, unipinnate, inner seta and short, naked, outer spine; P4 enp-2 with a spinule halfway along outer margin, apical margin with long, distally serrate and basally fused, inner seta, and long, unipinnate, outer seta. Spine and seta formula as follows: ExopodEndopodP20.0.0210.120P30.0.0210.020P40.0.1210.020 Fifth legs (Fig. 5A) closely set together, almost touching medially. Baseoendopod and exopod fused, forming a subrectangular plate; anterior surface with two pores; inner distal corner with strong, minutely bipinnate, spinous process (homologous to inner spine); distal margin with plumose outer basal seta, one long, naked seta, and two short, equally long, bipinnate spines. Redescription of male. Total body length from tip of rostrum to posterior margin of caudal rami 336 µm (mean = 325 μm; n = 6). Maximum body width 31 μm (mean = 32 μm; n = 6), measured at posterior margin of cephalothorax. Body ornamentation (Fig. 2A) essentially as in female. Sexual dimorphism in antennule, genital segmentation, P5, and P6. Spermatophore length approximately 53 µm. Antennule (Fig. 3B) 8-segmented, haplocer; geniculation between segments 6 an