Intraspecific variations and additional information about Cheletomimus (Hemicheyletia) wellsi (Baker, 1949) (Trombidiformes: Cheyletidae) from Brazil

In this paper, we presented additional information to the description of Cheletomimus (Hemicheyletia) wellsi (Baker, 1949) (Acari: Cheyletidae) collected on Vitis vinifera L. (Vitaceae), Ruellia angustiflora (Ness) Lindau ex Rambo (Acanthaceae) from Dois Lajeados, Marques de Souza and Pantano Grande municipalities in Rio Grande do Sul state, and on Malus domestica Borkh (Rosaceae) in Campo do Tenente municipality, Paraná state, Brazil. The specimens examined presented intraspecific variations from those described previously. These variations will be discussed herein. A key to the known Brazilian species of the genus is provided.

The family Cheyletidae Leach, 1815 (Trombidiformes: Cheyletoidea) includes over 440 species in 75 genera (Bochkov & Abromov 2016;Salarzehi et al. 2018). This family comprises species that are free-living predators, parasites of birds and mammals and some of them can be both (Bochkov & Fain 2001;Bochkov 2009;Walter et al. 2009). One of the most representative genera within Cheyletidae is Cheletomimus, which was erected by Oudemans (1904) who designated Cheletes berlesei Oudemans as type species (Baker 1949;Summers & Price 1970;Fain et al. 2002). This genus comprises 36 species that can be found on plants playing an important role in pest control (Fain et al. 2002). They are known from all the continents, except Antarctica, but mostly from the warmer climatic regions (Fain et al. 2002;Bochkov & Sidorchuk 2016). Fain et al. (2002) reduced Hemicheyletia and Philippicheyla Corpuz-Raros to a subgenus of Cheletomimus. Thus, the genus Cheletomimus now consists of three subgenera, namely Philippicheyla, Hemicheyletia and Cheletomimus s.str. These subgenera differ from each other by: Hysteronotum with a pair of lateral shields in Cheletomimus s.str; hysteronotum with a single shield in Hemicheyletia; and hysteronotum without shield in Philippicheyla.
The genus Cheletomimus can be easily distinguished by the following characteristics: Palp: palpal tarsi with 4 setae and a short solenidia: 2 dorsal comb-like setae with numerous teeth and 2 sicklelike ventral setae; palpal claw with teeth in the basal part; palpal tibia with 3 setae, dorsal and outer ventral setae variable in shape from hairlike to serrate lanceolate, inner seta always fine, hair-like; peritremes arch-like. Dorsum: with eyes present; propodonotal shield present, granulated; hysteronotal shield present or lacking, variable in shape; all dorsal setae homeomorphic (fan-like or lanceolate) or median setae aberrant, staghorn-like, bulb-like, cloud-like, dendrite-like; number and shape of median setae variable. Genital: genital region with three aggenital, two genital and three pseudoanal setae respectively. Legs: tibia I with four or five setae; tarsus I with elongate solenidium.
The diagnosis of the examined species is as follows: Female (n=6) (

Scientific Note
shield 125 (113-128) long and 157 (127-157) wide measured at level of setae e2. All the propodonotal dorsolateral setae are fan-like and subequal in length and width, 22 (21-23) long and 13 (12-14) wide, while the fan-like setae on the hysteronotal shield are 16 (16-20) long and 12 wide. All specimens with four lateral fan-like and four median pairs of staghorn-like setae on the propodonotal shield, and four pairs of lateral fan-like setae and two median pairs of staghorn-like setae on the hysteronotal shield. Setae h3 situated off the hysteronotal shield as well as c2 and d2. Setae c2 and d2 21 (20-21) and h3 18 (18-20) are on individual plates. Dorsal shields are well punctuated and interscutal areas are striate-granulate. The ornamentation between median setae on propodonotal shield varies between punctuated and bands of dashes (Fig. 1C, D). Venter (Fig. 1B). With three setaceous pairs of setae (ic1, ic3 and ic4) subequal in length, 21 (20-23). The ventral cuticle is finely striated. Pseudoanal setae ps1 6 (5-8), ps3 6 (5-8) that may appear smooth or slightly serrated, and smooth ps2 8 (7-11), genital g1 and g2 7 (6-8) and aggenital setae ag1, ag2 and ag3 smooth 11 (10-14). Gnathosoma 151 (129-165) long. Peritreme form an inverted U with six pairs of links, the first link is curving outward. Palptarsus with two comb-like setae, outer comb. with 15 to 18 teeth and 52 (46-54) long, inner comb. with 18 to 22 teeth and 25 (25-32) long, two smooth sickleshape setae and one small solenidia. Palptibia claw with 6-7 teeth, with one thick serrated seta dorsally and one outer ventral setae serrated; palptibia may present an inner lobe or not (Fig. 1E, F). Palpfemur has two fan-like setae dorsally, two smooth setae ventrally on a shield-like area. Palpfemur shield is striated and granulated. Gnathosoma with three pairs of ventral setaceous setae (n, ro1 and ro2). Legs. Leg I with claws smaller than those of other legs; empodium is present in all legs (Fig. 1A) Another confusing topic is the number of dorsomedian setae. Baker (1949) and Fain et al. (2002) observed that the number of dorsomedian setae is variable and cannot be used to differentiate species. In C. (H.) wellsi description, the number of dorsomedian setae on the propodonotal shield can vary from one to five pairs. In Baker's additional material, namely, the two specimens from Puerto Rico, one of them has one pair of setae and the second has two pairs, while in two specimens from Mexico, one has three pairs and the other one has four pairs of setae. In the original description of C. (H.) wellsina, it is mentioned that the propodonotal shield has two to three pairs of dorsomedian setae, this is also mentioned in Fain et al. (2002). In all six specimens analyzed here, the palptibia has three setae, a ventral smooth setae, an outer ventral and a dorsal setae serrated; also all presented four pairs of dorsomedian aberrant setae on the propodonotal shield. Thus, it is difficult to determine if the analyzed species are C. (H.) wellsi or C. (H.) wellsina. First, because there are no records of C. (H.) wellsina with four pairs of dorsal median setae on the propodonotal shield (only one to three) and two pairs of median setae on the hysteronotal shield (only one), and secondly, because in Fain et al. (2002) they describe the ventral palpaltibia setae as smooth, while in Baker (1949) as serrated. It seems as if the latter two observations may contradict each other and thus need further investigation if the shape of the ventral setae is strong enough to separate these two species.
In our examined material, the palptibial claw bears 6-7 teeth, outer comb. with 15 to 18 teeth and 52 (46-54) long, inner comb. with 18 to 22 teeth and 25 (25-32) long while in Baker (1949), the palptibial claw can have up to eight teeth, outer comb with 15 and inner 20 teeth, respectively. The ventral palpaltibia seta in our individuals is thick and smooth, the outer ventral and dorsal setae are serrated; in Baker (1949) it is described the same shape for the palptibia setae. All specimens with four pairs of dorsomedian setae on the propodonotal shield and the hysteronotal shield have two pairs of median setae; on the other hand, the propodonotal shield may have up to five pairs of dorsomedian setae (can vary from one to five) in Baker (1949). Pseudoanal setae are simple, smooth to slightly serrated and the same is given in the original description. Dorsal body with 350 long and solenidium 22, and in Baker (1949) is 363. Later, Summers & Price (1970) described the length of dorsal body 407, and the pattern of the microtubercles on the propodonotal shield as preponderantly of one size with a few microtubercles in the central area becoming elongated and forming several whorls of "dotted" striae, more transverse than longitudinal, but in our examined material the specimens were presented with more longitudinal pattern than transverse.
If the number of dorsomedian setae are not strong enough to determine species as given in Baker (1949) and Fain et al. (2002) due to their variation among specimens collected, why the shape of ventral palpaltibia setae could be? Can the shape of this setae vary as well? They clearly can vary in the genital region sometimes? If yes, C. ) bregatovae] and also by two hysteronotal setae that are 'narrower' than on the propodonotal shield in C. (H.) greenwoodi. This shape of setae can be seen in our material as well and may be due to the mounting process. In this publication we refrain from considering these species as synonyms until the examination of the type specimens and collect the information on the degree of intraspecific variability of those characteristics.
From females collected in southern Brazil, the present study contributes to the original description and illustration of C. (H.) wellsi. Different morphological characteristics were analyzed, such as variations related mainly to the ventral palptibial setae and the number of dorsomedial setae. It is extremely important that researchers, when describing or redescribing species, provide drawings and measurements of all mite structures. This information, when present, helps taxonomists to identify species more accurately and also to determine intraspecific variations when present. Clearly, individuals of the genus Cheletomimus may present intraspecific variations, whether in terms of size or shape in some cases. One of the solutions to solve these taxonomic problems would be to do molecular analysis with species from around the world and see the level of similarity between them. Key