ON NEWLY DISCOVERED DEUTONYMPHAL STAGE OF Stigmaeus kumalariensis Akyol & Koç (ACARI: STIGMAEIDAE) FROM TURKEY, WITH NUMERICAL AND STRUCTURAL VARIATIONS IN ADULTS

Deutonymph of Stigmaeus kumalariensis Akyol & Koç (Acari: Stigmaeidae) is herein described and illustrated based on specimens collected from litter and soil from Ekşisu marsh, Erzincan (Turkey). This is the first record of deutonymphal stage of S. kumalariensis. In addition, variations in the number of aggenital setae and structure of the median zonal shields in some adult specimens of the species are reported.


Introduction
Stigmaeidae is one of the most diverse mite families in Raphignathoidea with 33  It is important to know morphological features of immature stages of mites as in many organisms for understanding history of developmental morphology. Most mite species are known only with adults, although immature instars show a diversity of characters and possess remarkable features potentially useful for understanding mite taxonomy, phylogeny and biology (Zhang 2018

Materials and Methods
Specimens of S. kumalariensis were collected from litter and soil in Ekşisu, Erzincan located 11 km to the east of Erzincan Province. The specimens were extracted by using Berlese-Tullgren funnels, cleared in 60% lactic acid and mounted on microscopic slides in Hoyer's medium. The specimens were examined by using a Leica DM 4000B phase-contrast microscope. The photographs of the specimens were taken by an Olympus BX63-CBH DIC microscope. Measurements of the deutonymphs (four specimens) identified within the sampled material were taken in micrometers (µm) with the aid of the Leica Application Suite (LAS) Software Version 3.8. The mean values followed by the range values in paranthesis were given. Dorsal idiosomal and leg setal designations follow Kethley (1990) and Grandjean (1944), respectively. Specimens examined are deposited in Acarology Laboratory of Erzincan Binali Yıldırım University, Erzincan, Turkey.

Variation
In the present study, a total of 46 specimens (36 females, 6 males and 4 deutonymphs) of S. kumalariensis were examined and variations in some adult specimens were found. The variations were determined in the structure of median zonal shields of one adult female (Fig.  9) and one adult male (Fig. 10), and in the number of aggenital setae (ag) of two adult females (Fig. 7). The median zonal shield in S. kumalariensis is normally divided (Fig. 8), and symmetrically three pairs of aggenital setae are present (Fig. 6). In the abnormal specimens examined, the median zonal shield is undivided (Figs 9, 10) and one aggenital seta on the left side of aggenital shield is absent (Fig. 7). This unilateral absence of the seta is a form of asymmetry.

Remarks
Stigmaeus kumalariensis was first discovered in Afyonkarahisar (type locality), and later reported from Hakkari and Erzincan in Turkey. Until now, female and male of this species have been known. The deutonymphal stage of the species is described for the first time in this study. Deutonymph specimens resemble adult females. Dorsal idiosoma and setae as in adult female. Ventral idiosoma similar to adult female, but genital setae absent (Figs 2, 5), with fewer setae on segments of the legs (trochanter IV and femur II) than those of adult female. Also, famulus κ is present on genu I and II in both adult female and male specimens as in Hakkari male specimens of the species (Uluçay 2015a), but in Afyonkarahisar specimens genu II lacks famulus κ (Akyol & Koç 2007).
No variation was reported so far for S. kumalariensis (Akyol & Koç 2007, Uluçay 2015a). In the present study, variations in the structure of median zonal shields and in the number of aggenital setae were observed. In some studies, variations in the genus Stigmaeus  Unilateral absence of aggenital setae observed in S. kumalariensis is a common variation in Stigmaeus, but variation in structure of the median zonal shields is reported for the first time with this study. Entire or divided median zonal shields for identification of the species are considered to be an important character in the genus Stigmaeus. This variation was observed in only 2 adult specimens of all examined specimens. We consider that the fusion of median zonal shields in this species is a rare, but an important variation. Such variations among individuals of the same species can lead to misidentifications.
There is no certain explanation about what factors causes the variation. Observed asymmetric and structural variations may be the result of the interactions of genetic and environmental factors (Bingül et al. 2017b(Bingül et al. , 2018.