Ameroseius Berlese, 1904

Masan, Peter, 2017, A revision of the family Ameroseiidae (Acari, Mesostigmata), with some data on Slovak fauna, ZooKeys 704, pp. 1-228 : 1

Genus Ameroseius Berlese, 1904

Ameroseius Berlese, 1904: 258. Type species: Seius echinatus C. L. Koch, 1839 (= Acarus corbicula Sowerby, 1806), by original designation. Synonymy by Vitzthum (1942).

Cornubia Turk, 1943: 858. Type species: Cornubia ornata Turk, 1943 (= Acarus corbicula Sowerby, 1806), by original designation. Synonymy by Turk (1953).

Ameroseius . - Evans 1963a: 230.

Diagnosis (adults).

Dorsal shield strongly sclerotised and coarsely sculptured, rugose, callous or ornamented with a series of depressions or interconnecting ridges, and normally with 29 pairs of setae (in Ameroseius magnisetosus group, the shield delicately reticulated and with only 26-27 pairs of setae). Dorsal setae similar or differently formed, variously modified, thickened and lengthened, lanceolate or oblanceolate to slightly claviform (plumose, pilose, serrate or spinate on surface), rarely short, smooth and needle-like, and not sexually dimorphic (except Ameroseius fungicola group). In female, st1 and st2 on sternal shield, st3 on small pseudo-metasternal platelets or soft integument and st4 on soft integument; ventral shields usually well reticulate on surface; genital poroids outside the epigynal shield. Anal shield having three circum-anal setae in female, only rarely bearing an extra pair of opisthogastric setae (JV3) close to its anterolateral edges; male with expanded ventrianal shield having usually three pairs of opisthogastric setae: JV2, JV3, ZV2 (in Ameroseius dendrovagans , the shield less expanded to capture only two pairs of opisthogastric setae: JV2, JV3). Peritrematal shields with anterior ends connected to dorsal shield. Opisthogastric soft integument with five or six pairs of setae in female (JV4 sometimes absent); male never with JV4 developed, with five pairs of opisthogastric setae (JV1-JV3, JV5, ZV2). Corniculi normally horn-like, relatively broad and parallel, with splitted and pointed apex (in Ameroseius fungicola group, corniculi membranous, hyaline, undivided and directed laterally). In female, fixed digit of chelicera normally tridentate on proximal masticatory area (bidentate in Ameroseius fungicola group); movable digit edentate, at most with subapical denticle, and provided with short spermatodactyl in male. Epistome usually subtriangular, with curved apex, with smooth or denticulate anterior margin. Palptarsal apotele usually three-tined. Genu III and tibiae III-IV with two anterolateral and one posterolateral setae. Tarsi I-IV each with well developed empodium and claws. Insemination apparatus with barely discernible structures.

Remarks.

Ameroseius is the most speciose genus of Ameroseiidae . In this paper, it comprises 50 valid species having their type specimens reported from almost all continents: 13 species each from Africa and Asia, 12 species from Europe, five species each from North and South America, and two species from Australia. In Slovakia, this genus is represented by 13 recorded species. Mites of this genus are apparently fungivorous living in a wide variety of habitats such as wood substrates, wood-destroying fungi, decomposing plant material and humic soils. Most of them belong to highly specialised species, each adapted to a particular environment. There are species associated with bark beetle galleries, or wood-boring beetle galleries, in subcorticolous habitats, and feeding on a specific diet of ambrosia fungi, and phoretically active on xylophagous insects (mostly Cerambycidae ). Some African species are phoretically associated with wasps and bees. In Slovakia, most species can be easily found on bracket fungi, especially on a lower fertile surface of the sporocarp (fruiting body).

Some authors ( Bregetova 1977, Evans and Till 1979) attempted to clarify the general concept of Ameroseius by removing some species that obviously belong to other genera ( Ameroseiella , Kleemannia ). In this paper I refine the concept of the genus further, by establishing a new genus based on Ameroseius michaelangeli Moraza, 2006, removing all species that belong to Kleemannia and Asperolaelaps and that were previously placed in Ameroseius , and introducing two species groups based on Ameroseius magnisetosus and Ameroseius fungicola (see below). The process of clarifying the genus should continue, especially with regard to some characters inconsistent with Ameroseius in the species from Africa described by Elsen (1973). His African species show some atypical characters for Ameroseius , for example: (1) cheliceral digits distally curved, fixed digit with five proximal denticles in Amerosieus megatritosternum , or with only one very robust medial tooth in Ameroseius bembix , Ameroseius gabonensis and Ameroseius leclercqi ; (2) peritremes and peritrematal shields densely spinate, especially the outer posterior margin of peritrematal shields with large spines; (3) dorsal shield setae relatively short and stout, brush-shaped; (4) anterior margin of epistome deeply dentate; (5) setae JV5 similar to those on dorsal shield, brush-shaped; (6) strong sclerotic incrustation of soft integument on opisthogastric surface. Generally, the border between Ameroseius and Neocypholaelaps is weak, based on a few diagnostic features of gnathosoma. The species of Elsen (1973) appear to have an intermediate position between these two genera because, in some respects, they exhibit certain similarities with Neocypholaelaps , whose members are also associated with bees and wasps (form of cheliceral digits and dorsal setae, and additional sclerotization of soft integument).

There are three Asian Ameroseius species ( Ameroseius denticulatus , Ameroseius magnisetosus and Ameroseius submagnisetosus ) representing a specific group of closely related (if not identical) congeners characterised especially by a combination of the following character states: (1) dorsum with deficient chaetotaxy, having only 26-27 pairs of setae; (2) dorsal shield lacking coarse sculpture, with only delicate reticulate pattern; (3) in female, st3 on soft integument due to the absence of pseudo-metasternal platelets; (4) in male, st4 on soft integument, outside the sternogenital shield (5) five pairs of opisthogastric setae present (JV4 absent), of which JV3 on (ventri)anal shield, and JV5 similar to other setae on ventral surface. The above enumerated species are here referred to as the Ameroseius magnisetosus group. Unfortunately, I have examined no representative of this peculiar group to confirm reduced number of dorsal setae and other features as stated above.

There is a combination of diagnostic characters to recognise the newly designated Ameroseius fungicola species group, namely (1) fixed digit of chelicera bidentate, the two teeth small and similar in size; (2) corniculi unsclerotised, membranous, hyaline, medially curved, with tapered and undivided apex directed anterolaterally; (3) conspicuous dimorphism of dorsal chaetotaxy: in males, centrally situated setae strongly reduced in length when compared with those in females; (4) male with anal shield bearing only three circum-anal setae; (5) setae z5 minute; (6) absence of postgenital slit-like sclerites; (7) anus close to anterior margin of anal shield; (8) cheliceral digits relatively small; (9) legs I relatively short and thick (especially tarsi); (10) in male, legs I and palptrochanters with some setae thicker and spiniform when compared with those in female; and (11) empodium and claws of tarsi I-IV well developed, relativelly large; (12) in males, tarsal claws of legs II apparently larger than in other legs. This group contains only two described species ( Ameroseius fungicola , Ameroseius callosus ), and it can be characterised by several peculiar characters (see points 1-4, 12), unique or rarely expressed in Ameroseiidae . From a phylogenetic point of view, presence of these characters might support the idea of the justified existence of a separate ameroseiid taxon based on A. fungicola and A. callosus .

Narita et al. (2015) constituted a separate species group for 21 species of Ameroseius , referred to as the Ameroseius sculptilis group, with the following character states: (1) dorsal shield with ridges and pit-like depressions combined with a reticulate pattern of simple lines; (2) dorsal shield with 29 pairs of mostly stout and serrate setae; (3) posterior ventral surface with five or six pairs of opisthogastric setae; (4) ventrianal shield with 0-2 pairs of setae (in addition to three circum-anal setae). However, all these character-state arguments are weak, based on greatly variant and vague features, and not suitable for correct separation of the species, even at least at the level of Ameroseius / Kleemannia species as understood in this paper. So, I here did not follow Narita et al. (2015) in their concept of Ameroseius sculptilis as a separate and reasonably derived species group of Ameroseius .

Key to species of Ameroseius occurring in Europe (females)

European species of Ameroseius can be identified using keys from Westerboer and Bernhard (1963), Karg (1971a, 1993) and Bregetova (1977). In their keys, these authors included six, eight or nine species, respectively. A smaller part of the world species of Ameroseius (17 species) can be identified using keys of Narita et al. (2015), but better portion of congeners should be exclusively identified using the primary species descriptions. A new key presented here contains 13 species considered to be of the European origin, including recently described species ( Ameroseius callosus , Ameroseius fungicola and Ameroseius lehtineni ), and a new species described in this study.

1	Setae JV3 on (ventri)anal shield close to its anterolateral margins; soft integument between pseudo-metasternal platelets with a pair of rounded platelets; lateral margins of epistome produced into elongate, narrow, rounded and deeply dentate apex; movable digit of chelicera terminally with short and rounded hyaline appendage	Ameroseius furcatus Karg, 1971 (Plates 14 - 16 )
-	All opisthogastric setae on soft integument, anal shield with only three circum-anal setae; a pair of rounded platelets between pseudo-metasternal platelets absent; epistome relatively flat, with anterior margin smooth or delicately serrate; cheliceral digits terminally with no hyaline appendages	2
2	Dorsal setae relatively shorter and subequal: j6 with their tips reaching between bases of j6 and J2, J2 reaching between bases of J2 and J4, and J4 clearly not reaching posterior margin of dorsal shield	3
-	Dorsal setae relatively longer, well differing in length: j6 and J2 reaching or overlapping bases of following setae, and J4 reaching or overlapping posterior margin of dorsal shield	8
3	Five pairs of opisthogastric setae present (JV4 absent); setae j1 conspicuously expanded, apically curved, apparently otherwise formed as other dorsal setae; vertex with a pair of horn-shaped structures between bases of j1	Ameroseius corniculus Karg, 1971 (Plates 9 , 10 )
-	Six pairs of opisthogastric setae present, including JV4; setae j1 progressively narrowed towards their tips, at most moderately thickened, similar to other dorsal setae; vertex without a pair of horn-shaped structures between j1 (at most an unpaired process present)	4
4	Setae z5 strongly reduced in length, minute, several times shorter than z6; fixed digit of chelicera with proximal masticatory area bidentate; corniculi hyaline, curved and directed laterally	5
-	Setae z5 and z6 subequal in length; fixed digit of chelicera with proximal masticatory area tridentate; corniculi well sclerotised, straight and directed forward	6
5	Dorsal setae relatively shorter: j6 with tips reaching between bases of j6 and J2; posterior dorsal surface between J2 and J4 rugose	Ameroseius fungicola Mašán, 1998 (Plates 11 - 13 )
-	Dorsal setae relatively longer: j6 almost reaching bases of following setae J2; posterior dorsal surface between J2 and J4 coarsely reticulate	Ameroseius callosus Mašán, 1998 (Plate 3 )
6	Medial dorsal surface between j6 and J2 with subtriangular sculptural pattern; anal shield subpentagonal, coarsely reticulate on surface; metapodal platelets enlarged and rounded	Ameroseius sculptilis Berlese, 1916 (Plates 26 , 27 )
-	Medial dorsal surface between j6 and J2 otherwise sculptured; anal shield suboval, with delicate reticulation on surface; metapodal platelets small, elongate and narrow	7
7	Setae Z5 and S5 progressively narrowed towards their tips, lanceolate; vertex with finely serrate horn-like process on each side and between bases of j1; setae j5 thinner and shorter than j6; anal shield with smaller suboval anus situated in posterior portion of the shield	Ameroseius lidiae Bregetova, 1977 (Plates 20 , 21 )
-	Setae Z5 and S5 progressively broadened towards their tips, oblanceolate; vertex densely denticulate; setae j5 and j6 similar in length and form; anal shield with larger elongate anus having central position on the shield	Ameroseius ulmi Hirschmann, 1963 (Plate 28 )
8	Coarse dorsal shield sculpture additionally ornamented with plentiful tubercles arranged in rows and clusters; setae j5 shorter, with tips not reaching bases of j6; three pairs of setae (s2, r3, r4) on anteromarginal dorsal surface markedly reduced in length, minute	Ameroseius lehtineni Huhta & Karg, 2010 (Plate 19 )
-	Coarse dorsal shield lacking tubercles on it surface; setae j5 longer, reaching or overlapping bases of j6; minute setae on dorsal surface absent, or their number and arrangement otherwise	9
9	Five pairs of opisthogastric setae present (JV4 absent); setae j1 conspicuously expanded and denate, apparently otherwise formed as other dorsal setae; dorsal setae notably robust	Ameroseius corbiculus (Sowerby, 1806) (Plates 6 - 8 )
-	Six pairs of opisthogastric setae present, including JV4; setae j1 progressively narrowed towards the tip, lanceolate, almost similar to other dorsal setae; dorsal setae normal in thickness	10
10	Dorsal setae extremely differing in length; setae j4, z5, z6, Z1-Z3 strongly reduced in length, subequal, smooth and minute; setae Z2 and Z3 similar in length; most dorsal setae greatly lengthened: J2 with tips reaching beyond posterior margin of dorsal shield	Ameroseius georgei (Turk, 1943) (Plates 17 , 18 )
-	Dorsal setae less obviously differing in length; setae j4 reaching or overlapping bases of j5; setae Z2 and Z3 never similar in length; setae J2 never reaching beyond posterior margin of dorsal shield	11
11.	Setae z5 and z6 longer: z5 with tips reaching or overlapping bases of j6, z6 reaching or overlapping bases of Z1; setae JV5 less lengthened, with tips reaching between bases of JV5 and anus	Ameroseius cavernosus Westerboer, 1963 (Plates 4 , 5 )
-	Setae z5 and z6 shorter: z5 reaching between bases of z5 and j6, z6 reaching between bases of z6 and Z1; setae JV5 more lengthened, with tips reaching to or beyond anus	12
12.	Setae z5, z6, Z1 and Z2 similar in length, short; setae Z2 apparently shorter than Z3, with tips reaching between bases of Z2 and Z3	Ameroseius longitrichus Hirschmann, 1963 (Plates 22 , 23 )
-	Setae z5, z6, Z1 and Z2 becoming progressively longer posteriorly; setae Z2 lengthened, markedly longer than Z3, reaching far beyond bases of Z3	Ameroseius renatae sp. n. (Figure 2 , Plates 24 , 25 , 76G )

Figures

Figure 2. Ameroseius renatae sp. n., female. A Dorsal idiosoma B Ventral idiosoma. Not scaled.

Plate 3. Ameroseius callosus, female, dorsal idiosoma.

Plate 4. Ameroseius cavernosus, female, dorsal idiosoma.

Plate 5. Ameroseius cavernosus, female. A Dorsal idiosoma with legs B Epigynal and anal shield C Dorsal shield sculpture, posterolateral view D Setae j 1.

Plate 6. Ameroseius corbiculus, female, dorsal idiosoma.

Plate 8. Ameroseius corbiculus, female. A Dorsal idiosoma with legs B-C Setae j 1, variant forms D Ventral shields.

Plate 9. Ameroseius corniculus, female, dorsal idiosoma.

Plate 10. Ameroseius corniculus, female. A Dorsal idiosoma B Ventral shields C Dorsal idiosoma with legs D Setae j 1 and dentation of vertex.

Plate 11. Ameroseius fungicola, female, dorsal idiosoma.

Plate 13. Ameroseius fungicola, female. A Dorsal idiosoma with legs B Sternal and epigynal shield C Hypostome, ventral view D Anal shield E Chelicera, lateral view F Epistome.

Plate 14. Ameroseius furcatus, female, dorsal idiosoma.

Plate 16. Ameroseius furcatus, female. A Dorsal idiosoma with legs B Setae j 1 C Epistome D Sternal shield and metasternal area E Ventrianal shield F Posterior margin of dorsal shield.

Plate 17. Ameroseius georgei, female, dorsal idiosoma (pressed specimen).

Plate 18. Ameroseius georgei, female, dorsal idiosoma.

Plate 19. Ameroseius lehtineni, female (holotype, from Finland), dorsal idiosoma.

Plate 20. Ameroseius lidiae, female, dorsal idiosoma.

Plate 21. Ameroseius lidiae, female. A Dorsal idiosoma with legs B Sternal and epigynal shield C-D Anal shield, variant forms E Hypostome, ventral view F Epistome G-H Setae j 1 and dentation of vertex.

Plate 22. Ameroseius longitrichus, female, dorsal idiosoma.

Plate 23. Ameroseius longitrichus, female. A Dorsal idiosoma with legs B Sternal and epigynal shield C Posterior dorsal shield D-E Anal shield, variant forms.

Plate 24. Ameroseius renatae, female, dorsal idiosoma.

Plate 25. Ameroseius renatae, female, dorsal idiosoma (pressed specimen).

Plate 26. Ameroseius sculptilis, female, dorsal idiosoma.

Plate 27. Ameroseius sculptilis, female (A-D a specimen from Germany). A Dorsal shield sculpture, medial area B Dorsal idiosoma C Setae j 1 D-E Anal shield, variant forms.

Plate 28. Ameroseius ulmi, female, dorsal idiosoma.

Plate 76. Ameroseiidae spp., female. A-E Structures of sperm access system. A Kleemannia delicata, sperm induction pores (solenostomes) associated with inner margin of coxae III B and D Kleemannia plumigera, solenostomes associated with inner margin of coxae III C Epicriopsis suedus, sacculus foemineus and associated tubuli annulati E Sertitympanum nodosum, tubuli annulati F-H Chelicera. F Asperolaelaps rotundus G Ameroseius renatae H Kleemannia delicata.