Coccalicus clavatus Willmann, 1952

Coccalicus clavatus Willmann, 1952 ( Figure 1)

Diagnosis. The morphological characters of the Iranian specimen is similar to C. clavatus and C. lukoschusi but there are some variations in differential characters, which separate Willmann’s specimen, André’s C. lukoschusi and Iranian Coccalicus . Differences and variations are as follows:

Body size. Length of the idiosoma of tritonymph in the Iranian specimen is shorter than three paratype tritonymphs of C. lucoschusi (201 ± 14 μm) and C. clavatus (188 μm) tritonymph holotype. The length of the idiosoma is 135 ± 1 μm and the width 78 μm. This size is closer to C. clavatus .

The striation pattern. The striation pattern in this genus is very fine and difficult to discern. It is longitudinal on the prodorsum and transverse on the opisthosoma. The density of stria in C. lukoschusi is less than C. clavatus . According to André and Uusitalo (2006) in C. lukoschusi , the striation is slightly V-shaped between setae ( c1). Between setae ( d1), the striation is slightly transverse. In C. clavatus the striation is slightly transverse between setae ( c1). Between setae ( d1), the striation is slightly V-shaped. We compared their figures ( Figures 2A and 2B in André & Uusitalo, 2006) with our digital image ( Fig. 2) and did not find any significant difference between these three striations. In the Iranian specimen, as well as in the other two species of Coccalicus , the striation is slightly V-shaped between setae ( c1) and between setae ( d1), the striation is slightly reverse U-shaped.

Shape of bothridial setae. The two species are also separated by the prodorsal trichobothria. Overall, the trichobothria are clubbed in both species but according to André and Uusitalo (2006), those of C. clavatus seem to be more rounded. In the Iranian specimen left trichobotrium (22 ± 1 µm) is a little bit more rounded and the right one’s shape is near to the C. lukoschusi ( Fig. 3). However, the shape of trichobothria depends on species, the stase, the individual, specimen treatment (lactic acid or not...), pressure on the coverslip during mounting, the orientation, drawings and the artistic talent of the author. It seems that the position of the bulb in the microscope slide is also important to see its exact shape. Not only the trichobothria have different shapes, but also the density of barbules covering the bulb was reported greater in C. lukoschusi than in C. clavatus (Figure 4 in André & Uusitalo, 2006). A higher density of barbules was also observed in the adult of C. lukoschusi . The density of barbules in Iranian Coccalicus seems similar to C. clavatus . We took two images with different zooms from each bo seta of Iranian Coccalicus ( Fig. 3) and showed that the density of barbules seems different in various zooms. Checking this challenging character depends on the microscope’s quality and appropriate zoom.

The density of striae. The density of striae between lamellar setae ( la) counted 55 from figure 2 of André and Uusitalo (2006) for C. clavatus and 49 for C. lukoschusi . This number counted as 42 in the Iranian specimen ( Fig. 3E). It seems that this number is positively related to body size and varies in the different stages of life.

The relative position of prodorsal setae. The position of prodorsal setae is also reported as a differential character in two species. In C. clavatus , the distance between setae ( la) is greater than that between setae ( bo), while the ratio is reversed in C. lukoschusi (1.01 vs 0.97). In other words, setae la are in line with or exterior to bo in C. clavatus , whereas they are in a more internal position in C. lukoschusi ( André & Uusitalo, 2006) . In collected specimens from Gilanegharb, setae la are more or less in line with bo setae and have no internal nor external position to bo ( Fig. 3E). Also, the difference between these distances in two other collections (Willmann, and André) is negligible and difficult to concern.

Habitat. Both species are recorded from Western Europe, C. lukoschusi from Germany and C. clavatus from the Netherlands. However, C. clavatus was collected from old beach wrack after winter high floods, while C. lukoschusi was found on the Blue Tit, Parus caeruleus Linnaeus ( André and Uusitalo, 2006). The Iranian specimen was found in the soil of the riverside. Hence, Willmann’s specimen as well as our specimen are tritonymphs and each only one specimen whereas the collection from the Netherlands ( André, 1980) which has different stages and contains 13 specimens, has collected from the original habitat of mite that is related to Blue Tit. Specimens from Germany and Iran maybe had detached from the bird and fallen into the soil. Iran also is one of Blue Tit habitats and the location of the collected specimen has pure nature containing a river, trees, and shrubs and can be suitable for birds like that. Another possible hypothesis is that these mites can also live in soil or live on a creature that may be found in soil. The simple and small stylets (7 μm) in the Iranian specimen does not suggest being parasitic mite. Therefore, we rather propose to recognize the Iranian specimen as C. clavatus based on most morphological characters as well as habitat. There are some characters in this specimen which do not completely fit to previous records and show that the mentioned diagnoses between these species are small morphological variations ( Table 1) and in this case all of three collections refer to probably one species. Of course, this propose would be open until collecting more specimens of these mites.