Arrenurus (Megaluracarus) olmeca Ramírez-Sánchez & Rivas, 2013, sp. nov.
Creators: name: Ramírez-Sánchez, Marcia M.
name: Rivas, Gerardo
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Arrenuridae
Arrenurus
Arrenurus olmeca

description: Arrenurus (Megaluracarus) olmeca sp. nov.
(FIGURES 1 B, 2B, 3B, 4C–D, 12–18)
Type material. Holotype male from Loma del Caballo lake, route 180 km 7.5, Centro, Tabasco, 9 masl 17º59’01”N 93º00’04” W, 21 November 2004, coll. C. Cramer. Paratypes: One female and three males (CNAC007181) same data as holotype. Other material: 40 males, same locality as holotype, 17 August 2003, coll. G. Rivas and M. Ramírez-Sánchez. 32 males and 22 females, Del Negro lake, Villahermosa, Tabasco, 3 masl 18º00’31” N 92º55’08” W, 24 September 2000, coll. G. Rivas et al. Two males, small lake on route Villahermosa— Nacajuca at km marker 12, Nacajuca, Tabasco, 8 masl 18º06’26” N 92º57’50” W, 20 April 2001, coll. C. Cramer. Seven males, Del Pueblo lake, Luis Pérez Gil, Centro, Tabasco, 11 masl 17º52’39” N 93º04’28” W, 7 July 2001, coll. C. Cramer. 13 males, roadside pond on route 186 at km 6, Villahermosa, Tabasco, 5 masl 18º00’08” N 92º52’25” W, 4–5 February 2003, coll. G. Rivas et al. Seven males, Polo canal, Centla, Tabasco, 1 masl 18º30’41” N 92º39’00” W, 23 September 2001, coll. G. Rivas et al. Nine males, lake on route Villahermosa—Nacajuca at km 1, Centro, Tabasco, 11 masl 18º02’13” N 92º55’59” W, 17 August 2003, coll. G. Rivas and M. Ramírez-Sánchez.
Diagnosis. Anterior idiosoma almost round in dorsal view except by a slight concavity between the eyes, considerably bigger than the cauda which is short and wider at its base than at its tip; cauda with subtle lateral notches (Fig. 1 B, 12); conversely in lateral view, the difference in thickness between the anterior idiosoma and the cauda is less evident (Fig. 2B, 13). P-II medial side bears eight large scimitar-shaped setae (Fig. 14). Both males and females present a characteristic color pattern: Idiosoma is intense blue with colorless zones over dorsoglandularia, palps, legs and cauda.
Description. MALE: Idiosoma 777 (746–798) long and 646 (609–625) wide; anterior idiosoma margin smooth, slightly concave between the eyes. Greatest width of dorsal shield 494 (483–494), dorsal shield (including cauda) 672 (641–683) long; non-caudal portion bears the postocularia, which are situated posterior to the D2 setae; these setae are remarkably far from their corresponding glands. D2 and D3 are close to each other, and both pairs are located just above the widest portion of the dorsal shield; D3 and setae relatively close to each other (Fig. 1 B, 12). Anterior part of idiosoma considerably bigger than the cauda which is short and narrow, wider at its base than at its tip, 198 (179–200) long; proximal width of cauda 347 (284–357), distal width of the cauda 238 (189–213) (Fig. 1 B, 12); posterior margin of the cauda convex with subtle lateral indentations (Fig. 1 B, 12). Viewed laterally, the cauda has a moderate bump at its base, where D4 are positioned (Fig. 2B, 13); in this view, the difference in thickness between the anterior idiosoma and the cauda is less evident (Fig. 2B, 13). Second and third pairs of coxae separated by only two rows of tightly arranged body pores; anterior coxae with sharply projecting anterior corners extending beyond the anterior margin of idiosoma; medial margin of third and fourth pairs of coxae parallel, with convex corners; posterior inner margin of fourth coxae slightly concave (Fig. 3 B); acetabular plates long and narrow, extending laterally from the genital opening, reaching beyond the lateral margins of fourth coxae and curving along with the ventral plate posterior margin, not visible in dorsal view. Dorsal lengths of palpal segments (Fig. 14): P-I 30 (25–30); P-II 65 (63–67); P-III 38 (37–38); P-IV 63 (53–56); P-V 23 (28–30). P-II medial side bears two rows of four large scimitar-shaped setae; P-IV distoventral portion rounded with a large antagonistic seta, 25 in length. Dorsal lengths of distal segments of first leg (Fig. 15): I-Leg-4 100 (97–122); I-Leg-5 125 (112); I- Leg-6 137 (137–147). Dorsal lengths of distal segments of fourth leg (Fig. 16): IV-Leg-4 125 (125–130), 212 (200– 210) to tip of distal extension; IV-Leg-5 155 (138–155); IV-Leg-6 168 (160–178); the distal process bears five flexible swimming setae; III-Leg-4 bears long and stiff swimming setae; IV-Leg-3–5 bear long and stiff setae; dorsal surface of IV-Leg-5 bears three spine-like setae, inserted in a line. Both males and females present a characteristic color pattern: Idiosoma intense blue with colorless zones over dorso-glandularia, palps, legs and cauda.
FEMALE: Idiosoma 824 long, 158 wide; both anterior and posterior margins rounded (Fig. 4 C); dorsal shield 698 long, 599 wide, bearing the postocularia and three pairs of glandularia (Fig. 17). Acetabular plate region 462 wide (Fig. 4 D, 18); gonopore 125 long, 113 wide; acetabular plates slightly curved and postero-laterally directed; two rows of tightly arranged idiosoma pores between second and third coxae, three rows between left and right posterior coxae. Dorsal lengths of palpal segments: P-I 30; P-II 65; P-III 34; P-IV 55; P-V 22; structure and chaetotaxy of the palp as given for the male. Dorsal lengths of distal segments of first leg: I-Leg-4 122; I-Leg-5 105; I-Leg-6 107. Dorsal lengths of distal segments of fourth leg: IV-Leg-4 142; IV-Leg-5 155; IV-Leg-6 170; III- Leg-3–5 bear long stiff swimming hairs; IV-Leg-3–4 bear long stiff swimming hairs; dorsal surface of IV-Leg-5 bears three spine-like setae in a straight line.
Etymology. The specific epithet olmeca is derived from the Olmeca civilization, the first major society in Mexico that flourished in the southeast region from 1400 to 400 BC.
Discussion. The shape of the idiosoma of Arrenurus olmeca sp. nov. is similar to that of A. amazonicus Viets 1954 from Bolivia, Brazil, Colombia, Guyana, Peru, and Venezuela. The pattern of setae (number and shape) of the medial surface of P-II, is also very similar in both species. The major differences is related to size, A. amazonicus being smaller than A. olmeca, both in the proportions of the anterior idiosoma and of the cauda. A. gladiiferus Lundblad from Paraguay (Lundblad, 1944) presents exactly the same type of P-II chaetotaxy that A. amazonicus and A. olmeca, but in A. gladiiferus the anterior idiosoma is not rounded and the cauda is longer.
description: Published as part of Ramírez-Sánchez, Marcia M. & Rivas, Gerardo, 2013, New species of subgenus Megaluracarus (Acari: Hydrachnidiae: Arrenuridae: Arrenurus) from Mexico, pp. 317-330 in Zootaxa 3718 (4) on pages 321-326, DOI: 10.11646/zootaxa.3718.4.2, http://zenodo.org/record/218297