First record of the genus Tanytydeus (Acari: Paratydeidae) from South America with description of a new species from the Patagonian forests of Argentina

All active stages of Tanytydeus nothofagi n. sp. are described from northwestern Patagonian forests in Argentina where it was collected on bare tree bark of Nothofagus dombeyi. The genus Tanytydeus is recorded from South America for the first time.


Introduction
The Paratydeidae comprises three genera, Scolotydaeus Berlese 1910, Tanytydeus Theron et al. 1969and Neotydeus Baker 1950, and 20 extant and 2 fossil species, distributed worldwide (Klimov et al. 2020). Previous reports of paratydeid mites indicate this group lives in edaphic and arboreal habitats such as litter, moss, rotten wood and under tree bark, but also taking shelter in bird nests (Theron et al. 1969; Price 1973; Delfinado & Baker 1974; Seeman & Walter 1999; Dönel et al. 2012 or termite nests (Khaustov et al. 2019). Species of Paratydeidae with eyes such as those belonging to Scolotydaeus apparently thrive on exposed habitats such as bark, moss, or litter while the blind genus Tanytydeus is generally found in soil excepting T. lamington.
The sickle-shaped chelicera of Paratydeidae could advocate for a predatory way of life, but some mites with a similar shape of chelicerae are suspected to be moss feeders such as the genus Eustigmaeus (Stigmaeidae) (Flechtmann 1985).
This study presents the description of a new species of Tanytydeus representing the first record of this genus in South America and the first record of the Paratydeidae from Argentina. path to Puente Romano and from Parque Nacional Nahuel Huapi, Villa Los Coihues near the path to Cascada Los Duendes. Mites were extracted during ten days in Tullgren funnels, at 20°C , cleared one day in Nesbitt's fluid, mounted in Hoyer's medium, dried, measured, identified and drawn with Olympus CH5-260 and Zeiss BX40 microscopes. The latter was equipped with a drawing tube and phase contrast (PH) and Differential Interference Contrast objectives and was used for detailed analysis and PH micrographs. Measurements were made with an ocular eyepiece provided with a grid and calibrated with a stage micrometer. Photos were made with a 12-megapixel Sony Camera model SS adapted to the microscope tube. Drawings were made with nanoCAD 5.0 with micrographs as a background. The notation applied to the body and leg setae follow that of Grandjean's system, overviewed by Kethley (1990) and Norton (1977), respectively, and the palpal setation follows Grandjean (1946).
Ventral idiosomal setal designation follows the epimeral setation of Grandjean (1934). All measurements are given in micrometers (µm). Legs were measured from the base of trochanters to the tip of the tarsi without considering the claws.
The female holotype and 4 paratypes (1 male, 1 tritonymph, 1 deutonymph, and 1 protonymph) are deposited in the Museo Nacional de La Plata and remaining paratypes in the Laboratorio de Zoología del Centro Regional Universitario Bariloche de la Universidad Nacional del Comahue.
Idiosomal dorsum (Fig. 2B). Prodorsum with linear crista-like shield and 3 pairs of setae: long simple trichobothria sci, located on shield margin and simple setae ve and sce, on striated cuticle, supracoxal peg-like setae, ep and pl on dorsal palpcoxae and coxae I. Prodorsum lacking eyes but with 1 pair of subcuticular eyespots (Fig. 1A) located between second legs and trichobothrial setae sci represented by subdermal dark violet pigmented granules, each granule rounded to elongated 2 to 5 microns diameter. Hysterosoma with 4 transverse dorsal furrows between setal rows C and D, D and E, E and F and H and PS; furrows between E and F and H and PS incomplete not reaching hysterosomal margin. Furrow between setal rows C-D divides hysterosoma into anterior and posterior hysterosomal regions, anterior margin of latter overlaps caudal margin of anterior hysterosomal region. All dorsal setae smooth, pointed. Cupules im situated anterolaterally to setae e near lateral margin, cupules ip situated posteriad setae f1, anteromedially to setae f2.
Idiosomal dorsum. Prodorsum as in female. Hysterosoma with furrow between setal rows C and D present. Cupules ia situated anteriad to setae c 2 .
Idiosomal venter. Claparède organs between coxae I and II. Genital area without setae only represented by a sinuate middle slit between two flanking parallel linear folds.
Idiosomal dorsum (Fig. 8B). Hysterosoma with incomplete furrows not reaching hysterosomal margin between the E and F and F and PS setal rows present.

Differential diagnosis
Tanytydeus nothofagi n. sp. may be unique in Tanytydeus by the presence of subdermal eyespots which are not reported in the genus. The presence of 3 pairs of genital acetabulae (instead of 2 in the adult) places this species in a group comprising T. beyzavii, T. kakadu, T. lamington , T. simplex and T. theroni (Delfinado and Baker 1974, Seeman and Walter 1999, Khanjani et al. 2014, Khaustov et al. 2019. T. nothofagi n. sp. differs from T. beyzavii, T. kakadu and T. theroni by the presence of 8 setae on femur I, from T. simplex by the presence 3 setae on Fe II and 6 setae on Ta II, from T. lammingtoni by the presence of 7 setae on Ge I, 2 setae on Ge II, 4 setae on Ti II, 5 setae on Ta III.

Remarks
Species of Paratydeidae with eyes as those belonging to genus Scolotydaeus apparently live on exposed habitats such as bark, moss, or litter while the blind genus Tanytydeus is generally found in soil excepting T. lamington. The finding of T. nothofagi n. sp. living on bark instead of soil poses the question if the presence of eyespots could be a mild adaptation for the perception of shifts in light intensity which is an advantageous ability for surviving in a light exposed habitat.

Etymology
The species is named after Nothofagus dombeyi, the tree on which the mites were collected.