Arrenurus europaeus, Smit, 2022

Smit, Harry, 2022, A new species of the genus Arrenurus Dugès, 1834 (Acari: Hydrachnidia: Arrenuridae) from Europe, Zootaxa 5150 (1), pp. 148-150 : 148

Arrenurus europaeus sp. nov.

( Figs. 1‒5 )

Material examined. Holotype male, turbary Meentegat , province of Overijssel, the Netherlands, 52.77423 N 5.93243 E, 20 May 2021, leg. R. Heusinkveld ( RMNH) . Paratype: One male, Lake Plavno, Berezinsky Biosphere Reserve, Belarus, 54.80920 N 28.42385 E, altitude 164 m a.s.l., 8 July 2015, leg. H. Smit ( RMNH) .

Diagnosis. Lateral margins of cauda convex, cauda with distinct posterolateral extensions, posterior margin of cauda with a pair of small rounded extensions, anterior to Dgl-4 two small humps.

Description. Male: Idiosoma yellowish, dorsally 1110 (1142) long and 599 (616) wide, ventrally 1069 (1118) long; height of idiosoma 551 (599). Anterior margin of idiosoma slightly indented. Dorsal shield incomplete, 401 (421) wide, passing onto ventral side of cauda. Cauda approximately 421 long, 263 (288) widest in the middle and 198 (211) wide posteriorly. Lateral margins of cauda convex, cauda with distinct posterolateral extensions. Anterior to Dgl-4 two small humps ( Fig. 3 ). Posterior margin of cauda with two small, rounded extensions ( Fig. 1 ). A rudimentary, drop-shaped petiole present near posterior margin of cauda. Anterior coxae not reaching anterior idiosoma margin. Coxae-III+IV well separated medially, medial margin of Cx-IV much longer than medial margin of Cx-III ( Fig. 2 ). Gonopore 54 long, genital plates broad and extending to lateral idiosoma margin. Length of P1-5: 38, 80, 50, 88, 46. P2 anteroventrally with two setae, more medially one more seta ( Fig. 4 ). Length of I-leg-4-6: 146, 160, 176. Length of IV-leg-4-6: 192, 186, 227; IV-leg-4 with a spur ( Fig. 5 ). Third and fourth legs with many swimming setae. Legs claws with clawlet and a moderately sized lamella.

Female: Unknown.

Etymology. Named for its occurrence in Europe.

Discussion. The new species is morphologically very similar to Arrenurus buccinator (Müller, 1776) . The latter species is larger (usually well above 1300), the posterolateral extensions of the cauda are indistinct and the rounded extensions of the posterior margin of the cauda are larger. Moreover, the two small setae on the posterior part of the cauda are lying closer to each other compared to the new species. Arrenurus muelleri Koenike, 1901 , A. inflexus Bader, 1955 and A. latigenitalis Lundblad, 1956 are of similar size but have the posterior part of the cauda truncated. Arrenurus geminus Piersig, 1901 lacks the posterolateral extensions of the cauda and the cauda has posteriorly a concavity. Arrenurus conicus Piersig, 1894 has the cauda without distinct posterolateral extensions, the cauda is more tapering posteriorly and is without humps. The species most close in shape is A. spatiosus Viets, 1919 . The latter species is larger (1330‒1350), the pair of small setae on the posterior part of the cauda are lying closer to each other and the posterior extensions of the cauda are less distinct (compare Fig. 3 of Smit (1996) with Fig. 1 of the new species).

Figures

FIGURES 1‒5. Arrenurus europaeus sp. nov., holotype male. 1 = dorsum; 2 = venter; 3 = lateral view; 4 = palp; 5 = IV-leg-4-6 (swimming setae not illustrated). Scale bars: 1-3 = 200 µm, 4-5 = 50 µm.