Arrenurus (Megaluracarus) concavus longifissus, Smit, 2012

Smit, H., 2012, New records of the water mite family Arrenuridae from the Afrotropical region, with the description of 11 new species and two new subspecies (Acari: Hydrachnidia), Zootaxa 3187, pp. 1-31: 13

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Arrenurus (Megaluracarus) concavus longifissus

n. subsp.

Arrenurus (Megaluracarus) concavus longifissus   n. subsp.

( Figs. 30–34)

Material examined. Holotype male, ditch along Okavango Swamp at Drotsky’s Camp, S of Shakawe, Botswana, 18° 25’ 24,20 S 21° 53’ 28.17 E, 23-vii-1996 ( RMNH) GoogleMaps   . Paratypes: one male, same data as holotype ( RMNH) GoogleMaps   ; one male, tributary of Okavango River , near Drotsky’s Camp, S of Shakawe, Botswana, 23-vii-1996 ( RMNH)   ; six males, one female, marsh near Lake Awasa , Awasa, 7° 02.964 N 38° 27.621 E, alt. 1684 m a.s.l., 3-xi-2006 GoogleMaps   .

Other material. GHANA. 1/0/0/, Inlet Volta River at Kpong , 6° 09.183N 0° 03.709 W, alt 25 m asl, 10-iii- 2011 GoogleMaps   .

Diagnosis. Posterior median cleft long and closed.

Description. Male: Idiosoma brownish, 883 (923–1045) long and 551 (573–575) wide. Dorsal shield 401 (421–437) wide; dorsal furrow incomplete, passing onto cauda. Anterior idiosoma margin straight to slightly concave. D4 lying anterior of median cleft in an area with irregular lineation. Cauda long, with distinct posterolateral corners giving the lateral margin an angular appearance; posterior margin of cauda sloping. Cauda posteriorly with a long median cleft, which is closed but anteriorly widened; a pair of small setae near anterior margin of cleft. The so-called rudimentary petiole absent. Cleft ventrally with a concavity, but in specimens from Ethiopia cleft hardly widened anteriorly. Anterior coxal plates reaching to anterior idiosoma margin. Genital plates long and narrow, passing onto dorsum. Lengths of PI-PV: 30, 60, 44, 70, 38; PII with three setae in anteroventral corner. Lengths of I-leg-4-6: 134, 130, 132. Lengths of IV-leg-4-6: 180, 178, 164; IV-leg-4 with a spur.

Female (from marsh near Lake Awasa): Idiosoma brownish, 1118 long and 834 wide, anterior idiosoma margin straight, posteriorly without lateral corners. Dorsal shield complete, 903 long and 640 wide. Anterior coxal plates not extending to anterior idiosoma margin. Medial margin of fourth coxal plates slightly longer than medial margin of third coxal plates. Medial distance of fourth coxal plates shorter than width of one genital valve. Posteromedial corner of fourth coxal plates rounded. Gonopore 124 long and 164 wide; genital valves medially with a sclerotized area, enlarged anteriorly and posteriorly. Genital plates narrow, slightly enlarged laterally, about four times as long as width. Lengths of PI-PV: 32, 70, 52, 78, 42: PII medially with three setae, two of these in anteroventral corner. Lengths of I-leg-4-6: 130, 134, 110. Lengths of IV-leg-4-6: 174, 192, 174.

Etymology. Named after the long median cleft of the cauda.

Remarks. The new subspecies is close to A. concavus concavus   but differs in the long posterior cleft, which is closed. Although there is some variation in the shape of the cauda and cleft of A. concavus concavus   , it is open and not as long as in the new subspecies. Moreover, the genital plates are narrower than in the nominate taxon. In a number of other characters the new subspecies is close to the nominate taxon, e.g. the presence of an area with irregular lineation around D4 and the shape of the palp. The cleft of the specimen from Ghana differs from the specimens from Botswana in not being widened anteriorly, but this specimen is otherwise similar. The cauda of the specimens from Ethiopia lack the posterolateral corners. Lundblad (1949) illustrated a specimen from Congo similar to the one from Ghana, but identified it as A. insecutus K. Viets, 1916   . This specimen has a long, narrow cleft but lacks posterolateral corners of the cauda. It might also belong to the new subspecies, but as important details are lacking (e.g. the lineated area near D4), a decision cannot yet be made. It must be noted that A. concavus concavus   and A. insecutus   are very similar, but according to K. Viets (1916) differ in the longer cauda of A. insecutus   , while the latter species has no undulating lateral idiosoma margin. The female differs from the female of A. concavus concavus   (characters of the latter in brackets) in the egg-shaped shape idiosoma (pear-shaped), long and narrow genital plates (more wider and shorter genital plates) and the rounded posteromedial corners of the fourth coxal plates (corners absent).


National Museum of Natural History, Naturalis