Research Article |
Corresponding author: Peter Mašán ( peter.masan@savba.sk ) Academic editor: Farid Faraji
© 2020 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 (2020) A new wood-inhabiting mite species of the genus Dendroseius Karg, 1965 (Acari, Mesostigmata, Rhodacaridae) from Central Europe (Slovakia). ZooKeys 984: 49-57. https://doi.org/10.3897/zookeys.984.57256
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A new rhodacarid mite of the genus Dendroseius Karg, 1965, D. reductus sp. nov., was described based on females found in wood detritus and under bark of dead and dying poplar trees in a flood-plain forest in South Slovakia. The new species is unusual among the known congeners in the specifically formed triramous epistome of which the central projection is reduced in length, truncate, and markedly shorter than lateral ones. In other congeneric species, the anterior margin of the epistome possesses three pointed projections of similar size. A dichotomous key for identification of females of the world species classified in the genus Dendroseius is provided.
Description, morphology, poplar tree, saproxylic habitat, systematics
Dendroseius was originally described as a subgenus of Dendrolaelaps Halbert, 1915 by Karg in 1965, and treated at the generic level by
Dendroseius is a small group of rhodacarid mites, currently includes only six known species, namely D. reticulatus Sheals, 1956 (= D. scotarius Sheals, 1958) distributed mainly in Western Europe (with sporadical findings in North Africa and Central Europe), D. badenhorsti (Ryke, 1962) from South Africa, D. gujarati Wiśniewski & Hirschmann, 1989 from India, D. congoensis Wiśniewski & Hirschmann, 1992 from under bark of a tree imported to Poland from Africa, D. amoliensis Faraji, Sakenin-Chelav & Karg, 2006 from Iran, and D. vulgaris Ma, Ho & Wang, 2014 from China. Further species initially described under the subgeneric name Dendroseius, namely Dendrolaelaps (Dendroseius) fimetarius Karg, 1965 distributed in Central Europe, is now regarded as a member of the genus Oligodentatus Shcherbak, 1980 (see
Dendroseius species display a relatively wide spectrum of habitat specialization. Most original descriptions and subsequent reports are based on specimens found in heterogeneous soil detritus (D. amoliensis, D. reticulatus, D. vulgaris), wood substrates (D. congoensis, D. vulgaris), and manure or cow dung (D. badenhorsti, D. vulgaris) (
The purpose of this study is to describe a distinct new species of Dendroseius from Slovakia contributing thus to knowledge of Rhodacaridae European fauna. Our finding represents also a first record of the genus Dendroseius for Slovakia. An introduction of a new key to the identification of the world species based on females is a supplementary aim of this paper.
The mites were extracted from decomposing wood detritus by means of a modified Berlese-Tullgren funnel equipped with a 40-Watt bulb, and preserved in ethyl alcohol. Some specimens were collected by wet pincette from under loosen bark. Before identification, the mites were mounted onto permanent microscope slides, using Swan’s chloral hydrate mounting medium. A Leica DM 1000 light microscope equipped with a Leica EC3 digital camera was used to obtain measurements and photos. Measurements were made from slide-mounted specimens. Lengths of idiosoma and shields were measured along their midlines, and widths at their widest point (if not otherwise specified in the description), legs I–IV from coxal base but without the pretarsal ambulacrum. Idiosomal setae were measured from the bases of their insertions to their tips. Measurements are mostly presented as ranges (minimum to maximum). The terminology of dorsal and ventral chaetotaxy follows
Holotype female: SW Slovakia, Podunajská Rovina Flatland, Bratislava Capital, Rusovce Settlement, hard-wood flood-plain forest (Fraxino-Ulmetum carpinetosum) with poplar (Populus sp.), 135 m a.s.l., March 7, 2020, detritus from a hollow of old and dying poplar tree. Paratype females: one specimen, with the same data as for holotype; three specimens, the same locality as in holotype, May 19, 2004, under bark of dead poplar tree. The type material is deposited at the Institute of Zoology, Slovak Academy of Sciences, Bratislava, Slovakia.
(Female). Dorsal idiosoma (Figs
Ventral idiosoma (Figs
Sperm induction system (Fig.
Gnathosomal structures (Figs
Legs. All legs with well-developed pretarsus and ambulacral apparatus (including pulvillus and two claws), shorter than idiosoma: legs I 290–310 μm, legs II 210–230 μm, legs III 180–200 μm, and legs IV 260–285 μm long. Leg segments not spurred ventrally, with normal chaetotactic pattern for the genus: leg I – coxa 0-0/1, 0/1-0 (2), trochanter 1-1/1, 0/2-1 (6), femur 2-3/2, 2/2-2 (13), genu 2-3/2, 2/1-2 (12), tibia 2-3/2, 2/1-2 (12); leg II – coxa 0-0/1, 0/1-0 (2), trochanter 1-0/1, 0/2-1 (5), femur 2-3/1, 2/2-1 (11), genu 2-3/1, 2/1-2 (11), tibia 2-2/1, 2/1-2 (10); leg III – coxa 0-0/1, 0/1-0 (2), trochanter 1-1/1, 0/2-0 (5), femur 1-2/1, 1/0-1 (6), genu 2-2/1, 2/1-1 (9), tibia 2-1/1, 2/1-1 (8); leg IV – coxa 0-0/1, 0/0-0 (1), trochanter 1-1/1, 0/2-0 (5), femur 1-2/1, 1/0-1 (6), genu 1-2/1, 2/0-1 (7), tibia 1-1/1, 2/1-1 (7); tarsi II–IV – 18 setae each. Leg setae uniform and similar in length, smooth and needle-like.
The specific name is derived from the Latin word reductus (reduced) and expresses an important feature of the species ‒ an unusual shape of epistome, a fine flat structure situated on upper surface of gnathosoma, with partly reduced central projection on its anterior margin.
The triramous epistome of the new species, with remarkably shortened central projection, is unique and quite unlike any other known species in the genus Dendroseius. In other congeners, this central projection is much longer and more acuminate in the terminal part, reaching to (in D. amoliensis) or slightly beyond the level of the adjacent lateral apices (in all other congeners, including two species exclusively based on deutonymphs and not included in the key below). Nevertheless, the new species is most similar to D. vulgaris distributed in China (
1 | Ventrianal shield subtriangular in shape, with posterior margin convex, and four pairs of pre-anal setae (JV1–JV3, ZV2; ZV3 situated outside the shield); peritremes relatively shorter, reaching about the middle of coxae III; length of idiosoma: 367 µm [Iran] | Dendroseius amoliensis Faraji, Sakenin-Chelav & Karg, 2006 |
− | Ventrianal shield subquadrate or subrectangular in shape, with posterior margin only moderately curved, and five pairs of pre-anal setae (JV1–JV3, ZV2, ZV3); peritremes relatively longer, reaching coxae II | 2 |
2 | Podonotal soft integument with at most two pairs of setae (r4, r5; r2 situated on dorsal shield); length of idiosoma: 364 µm [South Africa] | Dendroseius badenhorsti (Ryke, 1962) |
− | Podonotal soft integument with at least three pairs of setae (r2, r4, r5; sometimes s1) | 3 |
3 | Dorsal shield setae shorter (J1–J4 normally less than 15 µm in length); setae r5 and Z5 similar in length (26–32 µm); ventrianal shield wider than long (L 95–100 µm; W 120–135 µm), dish-shaped; smaller species, length of idiosoma: 260–290 µm [Europe, North Africa] | Dendroseius reticulatus (Sheals, 1956) |
− | Dorsal shield setae longer (J1–J4 normally more than 18 µm in length); setae r5 1.5–2 times shorter than Z5 (r5 23–28 µm, Z5 35–55 µm); ventrianal shield similar in width and length (L 105–143 µm; W 112–135 µm), cup-shaped; larger species, length of idiosoma: 315–375 µm | 4 |
4 | Central process of epistome shortened, about two times shorter than those on lateral margins; dorsal shield setae generally shorter: J4≈1/2×J4–J5, S1≈1/2×S1–R2, S2≈1/2×S2–S3, S3≈1/2×S3–S4 (j5 17–20 µm, J1–J4 19–23 µm, J5 17–19 µm, Z5 35–40 µm); ventrianal shield slightly wider than long (L 105–115 µm; W 112–130 µm); length of idiosoma: 315–345 µm [Slovakia] | Dendroseius reductus sp. nov. |
− | Epistome with three well-developed prongs, central process slightly longer than lateral ones; dorsal shield setae generally longer: J4≈J4–J5, S1≈S1–R2, S2≈S2–S3, S3≈S3–S4 (j5 25–30 µm, J1–J4 23–42 µm, J5 26–38 µm, Z5 48–55 µm); ventrianal shield slightly longer than wide (L 131–143 µm; W 128–135 µm); length of idiosoma: 353–375 µm [Taiwan] | Dendroseius vulgaris Ma, Ho & Wang, 2014 |
This study was fully supported by the Scientific Grant Agency of the Ministry of Education of Slovak Republic and the Academy of Sciences [VEGA Grant No. 2/0036/18: Systematics, ecological requirements and chorology of saproxylic mites (Acari: Mesostigmata) phoretically associated with woodboring insects in Europe].