A new species of Abacarus Keifer (Acari: Eriophyidae) from Brazil

Zoysiagrass is an important ornamental and turfgrass cultivated in different countries. Recently, damage to this plant, characterized by a type of witch’s broom and stunting were observed in southern Brazil, suggesting possible attack by mites. A detailed examination of these plants showed the presence of a new mite species, Abacarus zoysiae Flechtmann & Tassi sp. nov., as responsible for the damage. The objective of this publication is to describe that new species, based on adult females and males.


INTRODUCTION
Abacarus is a mite genus described by Keifer (1944), containing the type species A. hystrix (Nalepa, 1896) and over 60 species are currently placed in this genus, both from monocotyledonous and dicotyledonous plants, about 36 species in monocotyledonous (Amrine & Stasny, 1994, Amrine, pers. comm.). Abacarus hystrix has long been associated with a broad host range, an unusual characteristic for eriophyoid mites that have obligate interactions and long evolutionary relationships within their specific host plants (Oldfield, 1996).
Despite the direct damage to their hosts resulting in leaf discoloration or rusting, A. hystrix is known as the vector of rye grass mosaic virus and agropyron mosaic virus (Jeppson et al., 1975;Vacante, 2015). Due to this importance as a virus vector and the unusual host range, the identification of A. hystrix has been questioned and studied extensively, the reviews include mtDNA COI sequences analyses, morphometric analyses, and reproductive tests (Skoracka., 2002;Skoracka, 2008;Laska et al., 2018) which demonstrated the presence of cryptic diversity within the Abacarus genus and a pattern of host-associated differentiation within the complex (Skoracka, 2002;2008;Skoracka et al., 2012Skoracka et al., , 2013Skoracka et al., , 2018Miller et al., 2013;Navia et al., 2015;Cvrković et al., 2016;Laska et al., 2018, Duarte et al., 2019. As many other eriophyid groups, Abacarus is known for the wax-like material produced over its body which has been mentioned as important for protection against water loss at times of low relative humidity (Vacante, 2015). The presence of wax-like material is also considered important for increasing total surface drag, which is relevant for wind dispersed mites of wide host-range, as A. hystrix (Vacante, 2015). In some parts of Europe, this is one of the most common and widely distributed eriophyid mites on grasses (Skoracka, 2004).
Zoysia japonica Steud., also known as zoysiagrass, is an ornamental commonly cultivated in southern Brazil and in different parts of the world. Recently, plants of this species with irregular elongation of culms were observed in São Paulo state, in southeastern Brazil. The objective of this publication is to describe a new Abacarus species found in association with zoysiagrass causing specific symptoms.

MATERIAL AND METHODS
Examination of symptomatic plants under a stereomicroscope showed the presence of dozens of eriophyoid mites. These were collected and mounted in modified Berlese Medium (Amrine & Manson, 1996) on microscope slides. They were kept on a heating plate at circa 60℃ for a week, for clarification and drying. The mounted mites ISSN On-Line: 1807-0205 ISSN Printed: 0031-1049 ISNI: 0000-0004-0384-1825 were then examined using a phase-contrast microscope (Leitz Dialux 20), at 1,000 × magnification (plan-apochromatic lens) in immersion oil. Mites were identified to genus level according to Amrine et al. (2003). They were determined to constitute a new species, based on an examination of the world literature, as subsequently detailed, and hence they are here described.
Structures of taxonomic interest were measured using a graded eyepiece. Measurements are given in micrometers and unless otherwise specified correspond to the length of the structure. The terminology and description used for this mite follows mainly Amrine et al. (2003). For each female structure, the first number refers to the measurement of the holotype, which is followed (in parentheses) by the range of the paratype. For males, measurements of each structure refer to the range of the paratypes.
Dorsal annuli were counted from the first annulus behind the prodorsal shield rear margin; ventral semi-annuli, from the first annulus behind caudal end of genitalia. Line drawings were made with the aid of a lucid chamber.
Slides are deposited in the Mite Reference Collection of Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba, São Paulo, Brazil. Holotype position is marked on the slide.
For scanning electron microscopy (SEM) studies, additional mites were kept in 70% ethanol for 24 h, and transferred to stubs with a double carbon tape, dried at room temperature, sputter coated with gold in a Baltec SDC 050, and examined on a JEOL JSM IT300. Photomicrographs were recorded digitally.   Paratypes: 24 female, 10 males on 14 microscopic preparations, collected with holotype, same locality and collector as holotype.

Etymology:
The specific designation refers to Zoysia, the common and also genus name of the host plant.