Mideopsis orbicularis

Pešić, Vladimir, Bańkowska, Aleksandra, Zawal, Andrzej, Rewicz, Tomasz & Smit, Harry, 2023, Molecular diversity and species delimitation in the genus Mideopsis Neuman, 1880 in Europe (Acari, Hydrachnidia, Mideopsidae), Ecologica Montenegrina 70, pp. 101-115 : 112

Mideopsis orbicularis Clade 2

Material examined — Netherlands: Ditch along E-side of Hoge Weg, Weerribben Prov. Overijssel, 52.80748° N 5.95947° E, 28.viii.2011 leg. Smit 1♂, dissected and slide mounted ( RMNH.ACA.537); Maarseveense Plas, Prov. Utrecht, 52.14403° N, 5.08472° E, 13.vi.2011, leg. Smit, 1♀, dissected and slide mounted ( RMNH.ACA.373) .

Compared material — Netherlands: Prov. Friesland, Tjeukemeer , E-side, 52.88561° N, 5.84033° E, 6.vi.1992 leg. Smit 2♂, dissected and slide mounted .

Remarks — Molecular data reveals that some of the specimens morphologically assigned to M. orbicularis (three from the Netherlands) and/or M. roztoczensis (two from Norway) form a unique BIN ACR9763. In this study, we examine two slides of Mideopsis specimens from the Netherlands belonging to the BIN ACR9763 which were tentatively morphologically attributed to M. orbicularis by the junior author (H.S). The examined female specimen (RMNH.ACA.373) from the Netherlands differs from M. orbicularis Clade 1, in anteriorly diverging lines of particularly faint fine porosity not evident on the dorsal shield ( Fig. 3C ) and comparatively wider and more sclerotized acetabula ( Figs. 3 H-I).

In the phylogenetic tree based on the COI dataset, the latter clade was placed as a sister clade to a clade containing specimens of M. milankovici Pešić & Smit, 2020 from Montenegro (see Fig. 1 ). The level of COI differentiation between these two species was estimated to be 16.7±2.0% K2P divergence indicating their long genetic isolation.

Unfortunately, the slide of a barcoded male (RMNH.ACA.537) from the Netherlands did not allow for an examination of the morphology of the ejaculatory complex. We examined two males from Lake Tjeukemeer from the Netherlands. The ejaculatory complex of the examined males from Tjeukemeer is characterized by a comparatively much smaller, wedge-shaped, anterior ramus (see Fig. 3O ), resembling that of M. milankovici (see Fig. 3N ), a species recently described from the Mediterranean part of Montenegro ( Pešić & Smit, 2020). Nevertheless, to clarify the taxonomic status of specimens from Lake Tjeukemeer and the status of the above-described M. orbicularis Clade 2, more specimens, including a male, need to be molecularly and morphologically analysed.

Figures

Figure 1. Maximum Likelihood tree (GTR+I model) of the Mideopsis spp. obtained from 71 nucleotide COI sequences. The results of the three species delimitation methods are indicated by vertical bars (BIN number given). The outgroup was removed from the figure. Only a bootstrap that supported more than 50% is reported.

Figure 3. A-D Photographs of dorsal shield: A – M. roztoczensis, ♂, CCDB38233 C11, River Zeta, Montenegro. B – M. orbicularis Clade 1, ♂, River Bukowa, Poland. C – M. orbicularis Clade 2, ♀, RMNH.ACA.373, Netherlands. D – M. orbicularis, ♂, Tjeukemeer, Netherlands. E-H Genital field: E – M. roztoczensis, ♂, CCDB38233 C11, Montenegro. F-G – M. orbicularis Clade 1, ♂: F – River Bukowa, Poland; G – RMNH.ACA.374, Netherlands. H-I – M. orbicularis Clade 2, ♀, RMNH.ACA.373, Netherlands. K-O Ejaculatory complex. K – M. roztoczensis, ♂, Roztocze, Poland (from Biesiadka & Kowalik 1979: fig. 10), inset: photograph of anterior ramus, CCDB38233 C11, Montenegro). L – M. orbicularis Clade 1, Roztocze, Poland (from Biesiadka & Kowalik 1979: fig. 12). M – M. orbicularis Clade 1, ♂, River Bukowa, Poland (inset: photograph of anterior ramus). N – M. milankovici, paratype ♂, Montenegro (from Pešić & Smit 2020). O – M. orbicularis, ♂, Tjeukemeer, Netherlands. Scale bars = 100 µm (for K-L = 50 µm).