Arrenurus mocovi, Ferradás, Rosso & Beatriz, 2006

Ferradás, Rosso & Beatriz, 2006, New species and records of Arrenurus from the Paraná river, Argentina (Acari: Parasitengona: Arrenuridae), Zootaxa 1208, pp. 25-35 : 26-29

Arrenurus mocovi n.sp.

Description

Female: Suboval body with three pairs of humps ( Fig. 1 ); dark green coloration; length 1937 (1979–2145); distance between the ends of the most anterior and the posterior humps 2021; width 1687 (1560–1666); maximum width between humps 1723; the front of the idiosoma is concave in the center, the eyes on an elevation; dorsal­glandularium 1 located at the base of a pair of rounded, separate humps; the posterior border of the body terminates in a slightly higher pair of humps and another pair toward the ventral area, equally wide and blunt; complete dorsal furrow; length of the dorsal shield 1333 (1125–1334); width 1083 (1000–1083), with three pairs of glands; anterior borders of Cx­ I and II are sharply pointed, but do not surpass the anterior border of the body; coxae, length between the anterior end Cx­I and the posterior border Cx­IV 999 (1016–1083); width between the articulating apophysis IV­Leg 1625 (1586–1693); numerous hairs are inserted in the coxae ( Fig. 2 ); genital field is relatively distant from the coxae, extending laterally with respect to the valves of the gonopore, without reaching the border of the body; genital field, length 289 (306–372); width 1156 (1024–1156); genital valves, length 210 (210–227); width 239 (214–240); capitulum, ventral length 275 (279); palp stocky with several bipectinate hairs ( Fig. 3 ); length of the dorsal border of the palpal segments: P­I, 66 (56–58); P­II, 148 (132–161); P­III, 90 (94–113); P­IV, 185 (181–201); P­V, 103 (93–99); dorsal lengths of the distal segments of the first leg: I­Leg­4, 337 (330–396); I­ Leg­5, 308 (289–341); I­Leg­6, 314, plus 62 of the very lengthened proximal end (380–429, with the proximal end) ( Figs. 4 and 5 ); dorsal lengths of the distal segments of the fourth leg: IV­Leg­4, 473 (363–454); IV­Leg­5, 411 (382–413); IV­Leg­6, 390 (339–460); IV­Leg­3, distal end with 13 swimming hairs (s.h.); IV­Leg­4 with 9 proximal s.h. and 14 distal s.h.; IV­Leg­5: 13 s.h.; IV­Leg­6 with abundant feathery hairs on the proximal surface and simple hairs on the rest of the segment ( Fig. 6 ); female with numerous eggs, approximately 200, whose diameters ranged between 129 and 206. Type location: Caengua Stream (28º S and 58º W, approximate).

Material studied

Type: Ψ. ARGENTINA, province of Corrientes, Iberá marshland, Caengua stream, Aug./4/1981, leg. J. J. Neiff, CECOAL, deposited in C.C.D.A.I; 3 paratypes Ψ, same references, deposited in C.C.D.A.I.

Etymology

This species is dedicated to the Mocoví ethnic group, who inhabited those areas.

Differential diagnosis

This species may be clearly separated from other similar species based on the following: the conformation of the dorsal humps; the morphology and chaetotaxy of the palps and the shape of the genital field. Below I point out specifically how A. mocovi n. sp. differs from the close Neotropical species and subspecies, considering only their females. These species are: Arrenurus (Brevicaudaturus) imperator imperator Lundblad, 1944 ; Arrenurus (Brevicaudaturus) imperator goliath Lundblad, 1953 and A. (Megaluracarus) bilaciniatus Viets, 1954 . The descriptions of the first two taxa were based on females alone, whereas for the third, both females and males are known.

The new species can be separated from females of A. i. imperator considering the conformation of the humps of the 1º dorso­glandularia, which are united in the center of imperator , forming a kind of flange (compare Figs. 1 and 7 ), and of possessing a pair of humps in the posterior part of the dorsal shield; the genital field of imperator extends posterolaterally to the valves and its shape is curved, leaving the pair of genital valves located in a very anterior position (see Figs. 2 and 8 ); P­II of imperator has a group of 6 simple, short setae on its internal face; the remaining are simple hairs, smaller in number than in mocovi (see Figs. 3 and 11 ).

Arrenurus mocovi n. sp. differs from A. i. goliath in the number and disposition of the humps and the shape of the genital field, which is similar to subspecies A. i. imperator , and fundamentally on account of the palpal chaetotaxy, which is composed in A. i. goliath of simple hairs, one or two per segment and only one in internal surface of P­II. These two subspecies, as well as mocovi , are very large, around 2000 microns in body length.

Arrenurus mocovi n. sp. has a very similar ventral shield to that of females of A. bilaciniatus , but can be differentiated from this species because the humps on the back are very different and P­II carries 2 proximal spurs in bilaciniatus (compare with Fig. 3 ). As well, A. bilaciniatus only reaches 40% of size of the n. sp.

Discussion

Numerous species of Arrenurus in South America are known only through the females but as males are those that carry the diagnostic defining characteristics for the subgenera, these remain provisionally assigned to the typical subgenus as "incertae sedis". For this reason, I have not placed A. mocovi into a subgenus.

The known distribution of the species mentioned above is the following: A. i. imperator has been recorded in the swamps of Tuyutí, Departamento Villarrica, Paraguay; A. i. goliath , comes from a pond in the Colombian Andes, in the town of El Tambo, Departamento Cauca, at 1700 m above sea level; A. bilaciniatus was collected in aquatic vegetion in shallow water of Iruçanga lake, in the State of Roraima, Brazil.

In the same lotic environment of the Iberá marshland, in addition to A. mocovi n. sp., I collected specimens of Arrenurus (Arrenurus) oxyurus Ribaga (other distribution records of this genus in Argentina are in Rosso de Ferradás, 1987) as well as species of Hydrodroma (Hydrodromidae) Limnesia (Limnesiidae) and Koenikea (Unionicolidae) .

Figures

FIGURES 1 – 6. Arrenurus mocovi sp. nov., female, 1, dorsal view (scale line = 130 µm); 2, ventral view (scale line = 130 µm); 3, lateral view of palp (scale line = 40 µm); 4, I­leg­ 4 ­ 6 (scale line = 56 µm); 5, distal segment of I­leg­ 6 (scale line = 25 µm); 6, IV­leg­ 3 ­ 6 (scale line = 56 µm).

FIGURES 7 – 11. Arrenurus i. imperator Lundblad, female, 7, dorsal view (scale line = 114 µm); 8, ventral view (scale line = 114 µm); 9, I­leg­ 4 ­ 6 (scale line = 60 µm); 10, IV­leg­ 5 ­ 6; 11, lateral view of palp (scale line = 60 µm).