Research Article |
Corresponding author: Peter Mašán ( peter.masan@savba.sk ) Academic editor: Farid Faraji
© 2022 Peter Mašán.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Mašán P (2022) A new digamasellid mite of the subgenus Longoseiulus Lindquist (Acari, Mesostigmata) from Slovakia. ZooKeys 1131: 59-70. https://doi.org/10.3897/zookeys.1131.95246
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A new digamasellid mite, Longoseius (Longoseiulus) disparisetus sp. nov., was described from females found in the wood detritus of tree cavity of freshly felled elm (Fraxinus sp.) in a park in southwestern Slovakia. The new species differs from known congeners by the number of setae on some leg segments (genu II with eight setae, tibiae II and III with seven and six setae, respectively) and by the unusual presence of three pairs of conspicuously shortened setae (J3, J4, and Z3) on the posterior dorsal shield. In other known Longoseiulus species, the genu II has 11 setae, the tibiae II and III have 10 and seven setae, respectively, and almost all dorsal setae are of similar length (except for the elongated Z4 and S4), none of which is formed as a microseta. A dichotomous key for females is provided to identify species classified worldwide in Longoseiulus.
Description, Digamasellidae, Fraxinus, morphology, saproxylic habitat, systematics
Longoseiulus was originally described by
The concept of Longoseiulus adopted here is largely based on the diagnosis of
The subgenus Longoseiulus Lindquist, 1975 is a small group of digamasellid mites and currently includes only seven known species from Europe (aberrans, longuloides, longulus, ornatus), Asia (nobilis, ornatosimilis), and North America (brachypoda), which are almost always found in saproxylic habitats, especially in decomposing wood of various coniferous and broad-leaved deciduous trees, and in subcortical spaces associated with galleries of bark- and wood-boring beetles. Phoretic activity of deutonymphs is common in many xylophagous beetles such as Cerambycidae, Cleridae, Elateridae, Scolytinae, and Pyrochroidae (
The aim of this study is to describe a new species of the subgenus Longoseius (Longoseiulus) from Slovakia and thus to contribute to the knowledge of the fauna of Digamasellidae in Europe. This work is part of a project aimed at increasing our collective knowledge of the mite fauna of Slovakia. In this sense, the finding of the new species also represents a first record of the genus Longoseius for Slovakia.
Mites were extracted from decomposing wood detritus using a modified Berlese-Tullgren funnel equipped with a 40-W lamp and preserved in ethyl alcohol. For identification, the mites were mounted on slides with Swan’s medium (gum arabic/chloral hydrate). A Leica DM 1000 light microscope with a Leica EC3 digital camera was used for measurements and micrographs. The photomicrographs were processed using Adobe Photoshop Elements 8 software. Measurements were made on specimens mounted on a microscope slide. Idiosoma and shield lengths were measured along their midlines, and widths were measured at their widest point (unless otherwise noted in the description). The lengths of the ventral idiosomal shields are midline, from the anterior to the posterior margin of each structure, including the hyaline anterior extension of the epigynal shield and excluding the posterior cribrum of the anal shield. Legs were measured excluding the ambulacral apparatus. Setae were measured from the bases of their attachments to their tips. The dimensions of the structures are given as ranges (minimum to maximum). The number of teeth on the cheliceral digits does not include the apical hook. Setal notation symbols for the idiosoma follow
Holotype female: SW Slovakia, Podunajská Rovina Flatland, Bratislava Capital, Petržalka Settlement, Sad Janka Kráľa Park (48°08'N, 17°06'E), elev. 135 m, 25 October 2020, wood detritus from a cavity in the trunk of an old and freshly felled elm (Fraxinus sp.), colonised by an unidentified ant species (Hymenoptera: Formicidae). Paratypes: five females, with the same data as the holotype. The type material is deposited in the Institute of Zoology of the Slovak Academy of Sciences, Bratislava, Slovakia.
(female). The presence of three pairs of microsetae (J3, J4, and Z3) on the posterior dorsal shield of the new species is unique and distinctly different from all other known species of the subgenus Longoseiulus. Some displacement of J3 toward the bases of J4, making the bases of J3 and Z3 almost transversely aligned, also makes the idiosomal chaetotaxy of Longoseius (Longoseiulus) disparisetus sp. nov. peculiar. Most of the dorsal setae are of approximately equal length in all other congeneric species, with the exception of Z5 and S5, which are conspicuously long in most representatives of the family and are located at the posterior margin of the opisthonotum.
There are other important diagnostic characters for this new species: (1) the absence of dorsal setae r5 (these setae are present on the soft cuticle in females of the related species whose setae Z3 are prominent and moderately elongate), (2) the absence of many leg setae that
Number of setae on selected leg segments of Longoseius [based on
Leg segment | Taxon | Number of setae | |||
---|---|---|---|---|---|
Leg I | Leg II | Leg III | Leg IV | ||
Femur | subgen. Longoseius | 10 | 10 | 5 | 6 |
disparisetus sp. nov. | 12 | 10 | 6 | 6 | |
subgen. Longoseiulus | 12–13 | 10 | 6 | 6 | |
Genu | subgen. Longoseius | 8 | 5 | 4 | 3 |
disparisetus sp. nov. | 11 | 8* | 7 | 7 | |
subgen. Longoseiulus | 11–12 | 11 | 7 | 7–8 | |
Tibia | subgen. Longoseius | 9 | 7 | 7 | 7 |
disparisetus sp. nov. | 12 | 7* | 6** | 7 | |
subgen. Longoseiulus | 12 | 10 | 7 | 7 | |
Telotarsus | subgen. Longoseius | – | 11 | 10 | 10 |
disparisetus sp. nov. | – | 11* | 11* | 12 | |
subgen. Longoseiulus | – | 12 | 12 | 12 |
(female). Dorsal idiosoma (Figs
Ventral idiosoma
(Figs
Sperm induction system
(Fig.
Gnathosomal structures
(Figs
Legs
(Fig.
Among the closest relatives with known chaetotaxy of the legs, the new species is easily recognised by the specific number of setae on several leg segments (see Table
The specific name is derived from the Latin words dispār (unequal or dissimilar) and sēta (bristle or hair) and refers to the striking differences in length between the setae on the opisthonotal shield of the female of this new mite (three pairs of setae are greatly reduced and formed as microsetae).
Longoseiulus includes seven described species, all known from the Holarctic. Only Longoseius (Longoseiulus) aberrans Hirschmann, 1960 is not included in the following key because its description is based solely on the male stage (it is one of the species with 21 pairs of setae on the anterior dorsal surface, including r5). It is not possible to reliably subdivide the individual species of Longoseiulus known to date based on literature data alone, without examining the type specimens. They should be thoroughly revised, redescribed, and compared in future studies to obtain a more accurate and reliable identification key than the one presented in this study. The original descriptions of most Longoseiulus species were not elaborated with the necessary precision (for example, they lack information on the chaetotaxy of the legs or on the measurement of important setal or scutal structures). Therefore, it is not currently possible to define and delimit some species morphologically on the basis of reliable characters. It is likely that a future revision will reveal the conspecificity of some species now placed in this subgenus.
1 | Anterior dorsum with 20 pairs of setae, including two pairs of marginal setae on peritrematal shields (r3) or soft cuticle (r4); setae Z3 short (Z3≤Z2, Z3≤j5), never reaching beyond posterolateral margins of opisthonotal shield; idiosoma relatively small, 290–335 µm long | 2 |
– | Anterior dorsum with 21 pairs of setae, including three pairs of marginal setae on peritrematal shields (r3) or soft cuticle (r4, r5); setae Z3 long (Z3≥2×Z2, Z3≥2×j5), reaching beyond posterolateral margins of opisthonotal shield; idiosoma relatively large, 330–390 µm long | 3 |
2. | Three pairs of opisthonotal setae (J3, J4, and Z3) conspicuously shortened, formed as microsetae (2–4 µm long), at least twice shorter than other dorsal setae; inner pair of sclerotic nodules on hexagonal dorsal area with anterior position as outer pair; tibia III with 6 setae (without posterolateral setae) | Longoseius (Longoseiulus) disparisetus sp. nov. [Slovakia] |
– | Three pairs of opisthonotal setae (J3, J4, and Z3) never shortened and almost as long as other dorsal setae (except Z5 and S5); two pairs of sclerotic nodules on hexagonal dorsal area in a transverse row; tibia III with 7 setae (with one posterolateral seta) | L. (L.) longulus (Hirschmann, 1960) [Germany]. L. (L.) longuloides Hirschmann & Wiśniewski, 1982 [Ukraine] |
3 | Ventrianal shield with three pairs of preanal setae (JV1, JV2, and ZV2) | L. (L.) ornatus (Hirschmann, 1960) [Germany] |
– | Ventrianal shield with four pairs of preanal setae (JV1–JV3 and ZV2) | L. (L.) brachypoda (Hurlbutt, 1967) [U.S.A., Louisiana]. L. (L.) ornatosimilis (Shcherbak, 1980) [Russia, Buryat]. L. (L.) nobilis (Barilo, 1989) [Uzbekistan] |
This work was fully supported by the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Academy of Sciences [VEGA grant no. 2/0007/22: Mesostigmatic mites associated with subcorticolous habitats and wood-destroying insects in Slovakia – taxonomy, ecology and chorology of the species of Digamasellidae (Acari: Parasitiformes)].