Occurrence of the mite Acanthonyssus proechimys (Mesostigmata: Macronyssidae) on a spiny rat in Brazil

Macronyssid mites are ectoparasites of terrestrial vertebrates. We slide-mounted and re-examined mite material collected in a 1987-1989 expedition to Maracá Ecological Station, Roraima State, Brazil. The specimens were identified as Acanthonyssus proechimys Yunker and Saunders (Mesostigmata: Macronyssidae), which were collected parasitizing a South American spiny rat, Proechimys sp. This represents the first record of Acanthonyssus in Brazil.

The material examined in the present study originated from an expedition to Maracá Ecological Station (3°24'04"N, 61°39'19"W), a fluvial island in Roraima state, northern Brazil, organized and sponsored by the Royal Geographical Society (UK) and Instituto Nacional de Pesquisas da Amazônia (INPA), Manaus, Amazonas State, Brazil, between 1987 and1989.Ectoparasites including mites were collected from small mammals during this expedition and stored in 70% ethanol at the Ectoparasite Sector of the Department of Parasitology of Universidade Federal de Minas Gerais (UFMG) (Linardi et al. 1991).

ACTA AMAZONICA
Recently, the Acari Collection of Instituto Butantan (IBSP), São Paulo, Brazil, received the expedition material identified as a novel species of the genus Echinonyssus, by Linardi et al. (1991).In order to confirm the identification, we remounted the slides according to the techniques described by Jacinavicius (2013).The specimens were deposited in the IBSP collection.More detailed information on the collection, locality description, and diversity of the hosts have been reported by Linardi et al. (1991) for this material.
These mites were identified using the keys to genera by Radovsky (2010).Unlike what was stated by Linardi et al. (1991), our examination revealed that the material did not represent a new species of Echinonyssus, and was in fact A. proechimys.In addition, we compared the specimens with the original description of A. proechimys (Yunker and Saunders 1973).Images were obtained using an Olympus DP73 digital camera coupled with an Olympus BX43 microscope.

Order Mesostigmata Canestrini, 1891 Family Macronyssidae Oudemans, 1936 Genus Acanthonyssus Yunker and Radovsky, 1966
Diagnosis.Acanthonyssus can be separated from the other genera in Macronyssidae by the following sets of characters: peritremes elongated (Figure 1a); sternal shield wider than long (Figure 1c); presence of a recurved ventral spur in the proximal region of the leg segments Tfe IV, Ge II-IV and Ti IV (Figure 1b); all coxae with ventral spurs, sometimes bifid (Figure 1d).

Differential diagnosis. Compared to A. dentipes, A.
proechimys has the peritreme starting from the middle of Cx I (Figure 1a), and the st1 not reaching the posterior margin of the sternal shield (Figure 1c).
Remarks on distribution.This is the first record for the genus Acanthonyssus, and A. proechimys in particular, in Brazil.Apart from this record from Maracá, no other specific locality record exists for A. proechimys, as the type locality in the original description was broadly defined only as Zulia state, in Venezuela.Yunker and Saunders (1973) state that they collected this species throughout the Venezuelan territory on several rodent hosts, mainly echimyid rodents, but do not mention specific localities.Therefore, the known distribution range of A. proechimys is based on two known locality records (Figure 2).The record described herein from Maracá Island is at a minimum distance of approximately 1400 km from the type locality in Zulia state.

Figure 1 .
Figure 1.Morphological details of the females of Acanthonyssus proechimys Yunker and Saunders, 1973 (Mesostigmata: Macronyssidae) collected in Maracá Island, Roraima State.A -Dorsal region of the opisthosoma with the peritremes elongated, sinuous.Arrows highlight the peritremes; B -Legs I and II showing the ventral recurved spur in the proximal region of the segments Tfe III, Ge III-IV and Ti IV; C -sternal shield; D -Coxa I and II with ventral spurs.The arrow indicates the ventral spurs of coxae of the legs I and II.Abbreviations: st1 = sternal setae 1; st2 = sternal setae 2; st3 = sternal setae 3. Scale bars: A-B = 20 µm; C-D = 10 µm.This figure is in color in the electronic version.

Figure 2 .
Figure 2. Known geographical distribution of Acanthonyssus proechimys Yunker and Saunders, 1973 (Mesostigmata: Macronyssidae).The yellow square represents the type locality, and the red dot is the new record.This figure is in color in the electronic version.