Arrenurus (Arrenurus) unguiculus Zheng & Guo, 2021

Zheng, Yulin, Gu, Xinyao, Guo, Jianjun & Zhang, Runzhi, 2021, Two new species and one new record species of genus Arrenurus Dugès, 1834 (Acari, Hydrachnidia, Arrenuridae) from China, Zootaxa 5072 (1), pp. 63-72 : 67-68

Arrenurus (Arrenurus) unguiculus Zheng & Guo sp. nov.

( Figs. 4–7 )

Material examined:

Holotype male, No. SD-AR-2002082901 , Weishan Lake , Jining City, Shandong Province, China (34°27’N, 117°24’E;alt 30m), 29-VIII-2002, Jianjun Guo leg . Paratypes, 5/1/0, No. SD-AR-2002082902–SD-AR-2002082907, same data as holotype .

Diagnosis. Ligulate process extending beyond posterior margin of half-length of the petiole, and nail-shaped.

Description. Male (n=6): Idiosoma L 1002 (989–1145) (including petiole), W 740 (723–752), L/W ratio 1.4 (1.3–1.5). Anterior margin of idiosoma concave, eye-capsule relatively developed, distance between the eyes 220 (215–240). Dorsal furrow incomplete, and not reaching to the middle of the pygal lobe’s dorsum ( Fig. 4B ). D 1, D 3, D 4 on humps ( Fig. 4C ). Inverted T-shaped cuticular structure between the glands of D 4 complete but undeveloped; hyaline membrane covering the proximal portion of petiole. Petiole well-developed, L 180 (167–237); ligulate process extending beyond the posterior margin for almost half-length of the petiole, and nail-shaped ( Fig. 4C ). Cx-I and Cx-II exceeding to anterior idiosoma margin, posterior margin of Cx-IV relatively developed ( Fig. 4A ); Gb–Cx-IV, 400 (395–405); Gb–Gp, 590 (571–631); Gb–Ep, 751 (738–812). Ap wide at the base and relatively narrow at the ends, extending to the sides of the body ( Fig. 4A and C ). L of palp segments: P-1, 37 (33–40); P-2, 67 (60–85); P-3, 58 (56–63); P-4, 91 (85–97); P-5, 59 (54–68); P-2 with three dorsal setae ( Fig. 4D ). L of I-L-1–6: 46 (46–52), 132 (132–139), 137 (133–140), 156 (156–162), 160 (156–171), 225 (225–231) ( Fig. 5A ). L of II-L-1–6: 55 (51–58), 140 (140–148), 145 (135–159), 177 (177–180), 170 (170–179), 241 (235–254); L of III-L-1–6: 92 (89–95), 155 (155–159), 145 (145–157), 153 (153–163), 175 (173–182), 236 (231–245); L of IV-L-1–6: 122 (122–127), 222 (219–233), 207 (205–216), 209 (209–217), 135 (124–137), 137 (127–145). Number of swimming setae: II-L-3 3 (3–5), II-L-4 8 (7–9), II-L-5 6 (6–9) ( Fig. 5B ); III-L-3 7 (6–8), III-L-4 8 (6–9), III-L-5 6 (5–8) ( Fig. 5C ); IV-L-3 10 (10–11), IV-L-4 14 (13–14) (including five short swimming setae on the spur), IV-L-5 7 (7–9) ( Fig. 5D ).

Female (n=1): Idiosoma L 1080, W 936, L/W ratio 1.2; anterior margin of idiosoma almost truncated, L 4 located on distinct posterolateral corner; distance between the eyes 228; dorsal furrow complete; D 1 on wide round humps ( Fig. 6B and 7A ). Anterior coxae not extending beyond anterior idiosoma margin; ACG medium L 190; Gb–Cx-IV, 434; Gb–Gp, 419; Gb–Ep, 814; Cx-IV mid-angle well-developed ( Fig. 6A ). Gp L 121, W 167, large and round; Ap relatively wide in the proximal half, and relatively narrow in the latter half. L of palp segments: P-1, 34; P-2, 82; P-3, 59; P-4, 104; P-5, 48 ( Fig. 7B ). L of I-L-1–6: 55, 128, 133, 171, 164, 161 ( Fig. 7C ); L of II-L-1–6: 53, 131, 155, 187, 190, 170; L of III-L-1–6: 63, 125, 150, 170, 179, 172; L of IV-L-1–6: 115, 224, 225, 224, 190, 167. Number of swimming setae: II-L-3 4, II-L-4 7, II-L-5 7; III-L-3 6, III-L-4 7, III-L-5 7; IV-L-3 12, IV-L-4 12, IV-L-5 11 ( Fig. 7D ).

Habitat. Lakes.

Etymology. Derived from the Latin word “ unguiculus ” (nail), it means that ligulate process of the petiole is nail-shaped.

Remarks. The new species is similar to Arrenurus (Arrenurus) distinctus Marshall, 1919 . However, the new species differs from A. (A.) distinctus in the following points: (1) D 4 on a continuous big hump in the new species, but D 4 on separated relatively small humps in A. (A.) distinctus . (2) Ligulate process in the new species is well developed as extending beyond the posterior margin of a half the length of the petiole, and nail-shaped; but ligulate process is enlarged and petal-shaped in A. (A.) distinctus .

Figures

FIGURE 4. Arrenurus (Arrenurus) unguiculus Zheng & Guo sp. nov., male: A = Idiosoma, ventral view; B = Idiosoma, dorsal view; C = Idiosoma, dorsolateral view; D = Palp.

FIGURE 5. Arrenurus (Arrenurus) unguiculus Zheng & Guo sp. nov., male: A = I-Leg; B = II-Leg; C = III-Leg; D = IV- Leg.

FIGURE 6. Arrenurus (Arrenurus) unguiculus Zheng & Guo sp. nov., female: A = Idiosoma, ventral view; B = Idiosoma, dorsal view.

FIGURE 7. Arrenurus (Arrenurus) unguiculus Zheng & Guo sp. nov., female: A = Idiosoma, dorsolateral view, B = Palp; C = I-Leg; D = IV-Leg.