Acariform mites (Acariformes) - permanent symbionts of Hapalomys delacouri Thomas (Rodentia, Muridae) in Vietnam

Abstract Two new species of parasitic acariform mites (Acariformes) are described from the Delacour’s marmoset rat Hapalomys delacouri Thomas (Rodentia: Muridae) in Vietnam: Afrolistrophorus (Afrolistrophorus) hapalomys sp. n. (Listrophoridae) and Radfordia (Radfordia) mirabilis sp. n. (Myobiidae). Based on morphological evidences, we show that species of both mite genera associated with Hapalomys Blyth do not demonstrate clear phylogenetic links with respective congeners from rodents of the closest genus Chiropodomys Peters (Rodentia: Muridae).


Introduction
Marmoset rats of the genus Hapalomys Blyth (Rodentia: Muridae: Murinae) are medium-sized arboreal from Southeast Asia, with highly patchy distributions throughout their range from southern China to the Malay Peninsula. The genus consists of two species, Hapalomys delacouri Thomas and H. longicaudatus Blyth (Musser 1972, Musser andCarleton 2005). Little is known about the life history of marmoset rats because of paucity of museum materials available for study. Parasitic mites of marmoset rats have never been reported.
Several specimens of the Delacour's marmoset rat Hapalomys delacouri were collected in southern Vietnam during the mammalogical surveys carried out by the Joint Vietnamese-Russian Tropical Research and Technological Centre (Abramov et al. 2012). In this paper, we describe two new mite species belonging to the families Listrophoridae and Myobiidae (Acariformes) collected from this host. Mites of both families are represented by permanent and highly specialized mono-or stenoxenous ectoparasites inhabiting the fur (Listrophoridae) and skin (Myobiidae) of mammals (Bochkov 2009(Bochkov , 2010.

Material and methods
In the field, the trapped hosts were individually wrapped in cheesecloth to prevent falling-out of ectoparasites and preserved in 70% ethanol. In the laboratory conditions, mites were collected from ethanol preserved hosts with fine forceps under dissection microscope and mounted in Hoyer's medium. Specimens were studied using a Leica microscope under phase contrast and Nomarsky (DIC) optics. Drawings were made with a camera lucida, and measurements were taken using a calibrated ocular micrometer. In the descriptions below, the idiosomal setation of listrophorid mites follows Griffiths et al. (1990) with modifications by Norton (1998) concerning coxal setae; the leg setation follows Grandjean (1939a). The idiosomal setation of myobiid mites follows Grandjean (1939b) as interpreted by Bochkov et al. (2008). All measurements are in micrometres (μm), provided for paratypes in parentheses, and were taken as follow: body length = the total length from the anterior extremity of the prescapular shield in listrophorids or the palpal extremites in myobiids to the posterior border of the body; body width = width at the level of setae se in listrophorids and setae c2 in myobiids; length of dorsal shields(listrophorids) = maximum length, measured along the median line of the shields; length of opisthosoma (listrophorids) = length from the posterior margins of trochanter IV insertions to the posterior border of the opisthosoma; length of the posterior legs (listrophorids) = length from the most basal point of the trochanter to the apex of the tarsus, excluding pretarsus; tarsal length was measured without pretarsus. Host systematics follows Musser and Carleton (2005).

Radfordia mirabilis
Etymology. This epithet refers the unusual external morphology of this speciesmirabilis (Latin, wonderful).
Differential diagnosis. The subgenus Radfordia is separated onto two species groups, "ensifera" (setation of coxae II-IV 3-2-2) and "lancearia" (3-1-2) (Bochkov and Fain 2003;Bochkov 2009). The new species distinctly differs from all known species of both groups by the setation of coxae II-IV(4-2-2), position of setae f2 on the lateral margins of the opisthosoma (vs. distant from the lateral margins in all other species) and the bases of f1 and e2 which are situated close to each other (vs. distant in all other species). Therefore, we establish for this new species a new species group mirabilis.

Discussion
The phylogenetic position of Hapalomys is still unclear because of the scarcity of museum specimens. Usually the genus is placed within Micromys division of the large muroid subfamily Murinae (Musser and Carleton 2005). Other authors suggested a close link between Hapalomys and Chiropodomys (Misonne 1969;Musser and Newcomb 1983;Chaimanee 1998;Musser and Carleton 2005). The both mite species from Hapalomys described herein strongly differ from the respective congeners described from rodents of the genus Chiropodomys Peters (Fain 1970(Fain , 1976Bochkov and Fain 2003). Afrolistrophorus chiropodomys Fain, 1970 described from Chiropodomys major Thomas and A. hapalomys sp. n. belongs to the same species group "apodemi" but in the limits of this group they strongly differ from each other by the ornamentation of the dorsal shields in both sexes. Radfordia chiropodomys Fain, 1976 described from Chiropodomys gliroides (Blyth) is the typical representative of the species group "ensifera" (Bochkov and Fain 2003), whereas R. mirabilis sp. n. is a sole representative of a separate species group and morphology strongly different from all other representatives of this subgenus (see description). Based on morphological evidences, we conclude that species of both mite genera associated with Hapalomys Blyth do not demonstrate clear phylogenetic links with respective congeners from rodents of the closest genus Chiropodomys.