New species of subgenus Megaluracarus (Acari: Hydrachnidiae: Arrenuridae: Arrenurus) from Mexico Author Ramírez-Sánchez, Marcia M. Author Rivas, Gerardo text Zootaxa 2013 3718 4 317 330 journal article 42984 10.11646/zootaxa.3718.4.2 e1faacdd-41f0-4693-a17a-d90cc7a6c330 1175-5326 218297 C7C06AE3-FBAB-4640-9935-CB81059BDB05 Arrenurus (Megaluracarus) urbanus sp. nov. ( FIGURES 1 D, 2D, 3D, 4G–H, 26–32) Type material. Holotype male from Cuemanco canal, Xochimilco ecological park, Mexico City, 2242 masl, 19º17’20” N 99º06’06” W , 27 October 2001 , coll. J. Cime and G. Rivas. Paratypes : Two females (one of them same data as holotype ) and two males (CNAC007183), same locality as holotype , 16 December 2001 , coll. J. Cime and M. Ramírez-Sánchez. Diagnosis. Idiosoma margins smooth, cauda moderately long, slightly constricted at its base and proportioned with the anterior idiosoma ( Fig. 1 D). Idiosoma and cauda bulky in lateral view (Fig. 2D). P-II medially with a characteristic patch of two types of setae: Needle and snake-shaped ( Fig. 28 ). The idiosoma and appendages intense greenish blue, without pale areas in the integument. Description. MALE: Idiosoma 693 (729–735) long and 467 (441–473) wide; anterior idiosoma margin rounded ( Fig. 1 D). Greatest width of dorsal shield 368 (357–378); dorsal shield length including cauda 609 (620– 646); non-caudal portion bearing the postocularia and three pairs of glandularia, D2 setae well separated from its corresponding glands; D3 setae and glands close to each another and located rostral to its widest portion ( Fig. 26 ). Cauda moderately long in proportion with anterior idiosoma ( Fig. 1 D), 189 (210–220) long, slightly constricted at its base, proximal width of cauda 247 (257), distal width of cauda 278 (284); posterior margin rounded and smooth when viewed dorsally; in lateral view, cauda thicker at its base than the anterior idiosoma (Fig. 2D, 27). First coxae with sharp but not projecting anterior corners ( Fig. 3 D); second coxae with blunt corners; second and third coxae separated by two rows of body pores; medial margin of third and fourth coxae parallel, with FIGURES 26–32. Arrenurus (Megaluracarus) urbanus sp. nov. ; 2630 : Holotype male, 31–32 : Paratype female. 26. Idiosoma, dorsal view; 27. Idiosoma, lateral view; 28. Palp, medial view; 29. I-Leg-5–6; 30. IV-Leg-4–6; 31. Idiosoma, dorsal view; 32. Idiosoma, ventral view. Scale bars 100 mm. posterior corner squared; posterior margin of fourth coxae straight. Acetabular plates of moderate size extending straight out from genital opening and reaching posterior angles of fourth coxae; a few hairs on the posterior margin of fourth coxae but they are not visible in dorsal view. Dorsal lengths of palpal segments ( Fig. 28 ): P-I 25 (28–30); P-II 65 (65–69); P-III 43 (33–38); P-IV 68 (65–68); P-V 38 (30–32). P-II medial bears a patch of numerous long needle-shaped setae and four snake-shaped setae; P-IV distoventral portion angular, with a relatively large antagonistic seta, 28 in length. Dorsal lengths of distal segments of first leg ( Fig. 29 ): I-Leg-4 94 (90–93); I-Leg-5 90 (93–95); I-Leg-6 120 (125–138). Dorsal lengths of distal segments of fourth leg ( Fig. 30 ): IV-Leg-4 120 (125), 170 (178) to tip of distal extension; IV-Leg-5 133 (125); IV-Leg-6 165 (185–188); III-Leg-3 and 4 with long, stiff swimming setae; the IV-Leg-4 distal process bears four thick, somewhat wavy swimming setae; IV-Leg-3 and 5 bear long stiff, swimming setae; dorsal surface of IV-Leg-5 bears three short, spine-like setae placed in a straight line. FEMALE: Idiosoma 788–809 long, 651–662 wide; both anterior and posterior margins rounded ( Fig. 4 G). Dorsal shield 663–683 long and 515–536 wide, bearing the postocularia and three pairs of glandularia ( Fig. 31 ). Acetabular plate region 420–425 wide; acetabular plates laterally directed, short, bowed and narrow in relation to gonopore length; gonopore 189 long and 179 wide; one and a half rows of idiosoma pores between second and third coxae, three rows between left and right posterior coxae ( Fig. 4 H, 32). Dorsal lengths of palpal segments: P-I 29–30; P-II 68–71; P-III 41–43; P-IV 69–70; P-V 30–34. Palp structure and chaetotaxy as in the male. Dorsal lengths of distal segments of first leg: I-Leg-4 (91–95); I-Leg-5 (88–94); I-Leg-6 (115–125). Dorsal lengths of distal segments of fourth leg: IV-Leg-4 (140–150); IV-Leg-5 (163–168); IV-Leg-6 (175–195); IV-Leg-3 and 4 bear considerably long, stiff swimming setae; IV-Leg-5 and 6 bear numerous short swimming setae; dorsal surface of IV-Leg-5 bears three short, spine-like setae placed in a line. Etymology. The name refers to the urban conditions surrounding the Xochimilco natural reserve, where the specimens were collected. Discussion. The P-II chaetotaxy of Arrenurus urbanus sp. nov. is complicated, as it consists of a mixture of two types of setae, i.e., many long needle-shaped setae and four snake-shaped setae. Arrenurus spathulifer Lundblad from Argentina , Brazil , Paraguay and Uruguay (Lundblad, 1944) presents very similar palp chaetotaxy and idiosoma shape to A. urbanus , except that in A. spathulifer the cauda is not constricted at its base. Arrenurus willinki Rosso de Ferradás 2000 from Argentina and Uruguay , and Arrenurus brevicaudatus Viets 1936 known from Argentina , Bolivia , Brazil , Colombia , Guyana , Peru , Uruguay and Venezuela , also exhibit a mixture of two types of setae in the palp, but considerably fewer than A. urbanus ; in those species, the dorsoglandularia position and the general shape of idiosoma are also similar to A. urbanus , but the proportions of the cauda are different among the three species.