Mycomelichares Mašán & Joharchi, 2021

Mašán, Peter, Joharchi, Omid & Abramov, Vladimir V., 2021, A new genus and two new species of melicharid mites (Acari: Mesostigmata) associated with wood-decaying fungi and mycophagous erotylid beetles (Coleoptera: Erotylidae) in Europe, Zootaxa 4980 (1), pp. 157-173 : 158-160

Mycomelichares Mašán & Joharchi gen. nov.

( Figs 1–32 )

Type species: Mycomelichares polypori Mašán & Joharchi sp. nov.

Other included species: Mycomelichares reductus Mašán & Joharchi sp. nov., Mycomelichares cyllodi ( Samšiňák, 1960) comb. nov., and Mycomelichares slovacus ( Mašán, 1998) comb. nov.

Diagnosis and description (Adults)

Female idiosoma oval to widely oval, with all legs shorter than dorsal shield. Dorsal shield with normal (42 pairs) to decreased number of 38 or 32–33 pairs of setae (setae z1, z3, r2, r5, S1, R1, R3, R5 may absent; setae R5 always on soft integument if expressed; R1–R4 and r6 sometimes situated on soft integument beside lateral margins of the shield); podonotal plate of the shield with 19, 21 or 23 pairs of setae, opisthonotal plate with 14, 17 or 19 pairs of setae. Idiosomal setae simple and smooth, needle-like, except setae Z5 mostly short to very short, usually with their tips not reaching half the distance to the bases of following setae; male dorsal setae conspicuously longer than those of female. Female tritosternum robust, enlarged, brush-shaped, with shortened, thickened and densely pilose laciniae; male tritosternum relatively small, with short base, thin and sparsely pilose laciniae. Dorsal shield and all ventral shields in female entirely, densely and strongly reticulate on their surface; in male, reticulation of sternitogenital and ventrianal shield less defined, weakly developed. In female, metasternal setae (st4) and associate lyrifissures situated on soft integument, or on small platelets. Peritremes normal or moderately shortened, with anterior ends reaching close to paravertical setae (z1), or the level between setae s1 and s2. Sternal shield wider than long, epigynal shield with short hyaline portion reaching at most the level of lyrifissures iv2. Anus small, postanal seta (pa) shorter than setae JV5. Female with submarginal setae (UR) strongly reduced, its soft integument with JV1–JV5, ZV1– ZV5 (ZV3 may be absent), SV2 present or absent, 1 x UR, sometimes R1–R5; submarginal setae on soft integument at level of coxae IV not expressed, absent. Ventral surface of hypostome with normal (seven rows) or with increased number of nine transverse rows of denticles; anteriormost rostral setae (h1) longest, enlarged, thickened in basal part and slightly spatulate in distal part in female (not modified in male); other setae on hypostome simple, needle-like. In female, chelicera with relatively short and wide digits, denticles relatively robust, long and sharp, usually sligthly curved; fixed digit almost dish-shaped, with 5–9 denticles in addition to bifurcate terminal hook; male spermatodactyl narrowed terminally, nearly as long as fixed digit. Gnathosomal corniculi horn-like, well spaced and less or more convergent. Internal malae tubular, and finely ciliated, longer or as long as corniculi. Palp apotele 2-tined. Leg chaetotaxy typical of Melicharidae (tibiae I–IV with 13, 10, 8, 10 setae; genua I–IV with 13, 11, 9, 9 setae; and femora with 12, 11, 6, 6 setae), or modified and with number of setae significantly reduced (tibiae I–IV with 10, 7, 7, 7 setae; genua I–IV with 10, 7, 7, 9 setae; and femora with 12, 9, 6, 6 setae); some of dorsal setae on trochanters and femora thickened, spur-like; male leg II not armed by spurs.

Etymology

The name is derived from the valid generic name Melichares and the Ancient Greek words μύκης (mukēs), meaning “fungus”, and used as a prefix. It refers to the specific association of all the members with the wood-decaying fungi, and the fact, that the type species is similar to Melichares by the placement of the posterior marginal setae (R1–R5) on soft integument.

Taxonomic notes

Based on our observations on Mycomelichares , and from comparison with other melicharid genera and species, we conclude that the following female characteristics should be considered as apomorphic for the genus: (1) tritosternal base and laciniae enlarged and thickened, laciniae fused basally and shortened distally, with long and dense pilosity forming a typical brush-shaped form; (2) rostral setae negligibly flattened distally, paddle-shaped; (3) cheliceral denticles conspicuously long, narrow, sharp and often slightly curved. Such a form of tritosternum and cheliceral dentation cannot be detected in any other species of Melicharidae .

Other important characters to be considered, which could establish a separate position of the new genus from other melicharid genera, but which cannot be consistently detected in all congeners, are: (1) dorsal shield setae decreased in number due to their absence (z1, z3, r2, S1, R1, R3, and R5; in male also R1–R5), or their position on soft integument outside the shield in female (R1–R5, sometimes also r6); (2) sexual dimorphism of tritosternum and anterior pair of rostral setae h1 (in female tritosternum brush-shaped and h1 paddle-shaped, but male with these structures normal, not modified in a form); (3) metasternal setae and associated pores situated on soft integument; (4) strong hypotrichy of most leg segments; and (5) hypostome with unusually increased number of transverse rows of denticles (normally nine rows present).

Generally, the new genus as a whole shows relatively high diversity in external morphology, and it represents a group of morphologically heterogeneous species. The following character states were used to separate the Mycomelichares species into three species groups (see the identification key for the congeneric species below): (1) placement and expression of posterior marginal setae (completely situated on soft integument in polypori group, with anterior four pairs on lateral rims of dorsal shield in cyllodi group, and with only two expressed pairs (R2, R4) placed on the shield in reductus group); (2) expression of setae z1 and z3 (absent in polypori and reductus groups); (3) expression of setae r2, r5 and S2 (absent in polypori group); (4) leg setation (strongly hypotrichous in reductus group); (5) length of peritremes (shortened in polypori group); (6) number of transverse rows of denticles on ventral gnathosoma (increased in polypori group); (7) mutual position of corniculi (moderately adjacent and convergent distally in reductus group).

Regularly enlarged or thickened anterior rostral setae (h1) are found in both adult stages in a number of described species of Proctolaelaps , but their modified setae are never distally flattened as in members of the new genus, and usually are not the longest when compared with the three other pairs on ventral gnathosoma. Placement of all or some of the posterior marginal setae on soft integument due to the reduction of dorsal shield in posterolateral extent together with the presence of a unique, distal mucronate process on the fixed chela (missing in two congeners) was the basis for original proposition of a new genus Mucroseius by Lindquist (1962). Existence of Melichares is derived from similar lateral reduction of the dorsal shield, not capturing r- and R- row of marginal setae (although completely expressed), and some features of the gnathosoma. The genus Orthadenella Athias-Henriot , only recently excluded from phytoseioid Blattisociidae and transferred to ascoid Melicharidae by the presence of a laelapoid-type of sperm access system by Moraza & Lindquist (2011), may be especially recognised by the setiform instead of membranous pilus dentilis, and the presence of a ventrianal shield instead of an anal shield.

The two species previously described in Proctolaelaps were newly transferred to Mycomelichares , namely Mycomelichares cyllodi ( Samšiňák, 1960) comb. nov. and Mycomelichares slovacus ( Mašán, 1998) comb. nov. Both are known to be inhabitants of wood-decaying fungi, and associates of mycophagous beetles ( Samšiňák, 1960; Mašán, 1998). In his original descriptive paper on M. slovacus, Mašán (1998) correctly stated the number of 42 pairs of dorsal shield setae, but he did not illustrate one pair of podonotal setae (z3), and additionally illustrated one nonexistent pair between S- and R- setal rows on the opisthonotum.

Figures

FIGURES 1–6. Mycomelichares polypori gen. nov., sp. nov.: 1. Dorsal idiosoma, female; 2. Ventral idiosoma, female; 3. Ventral gnathosoma, female; 4. Epistome, female; 5. Epistome, male; 6. Chelicera, female, lateral view of distal part.

FIGURE 7. Dorsal idiosoma of Mycomelichares polypori gen. nov., sp. nov., female. Not to scale.

FIGURE 8. Ventral idiosoma of Mycomelichares polypori gen. nov., sp. nov., female, a specimen with partly abnormal, and asymmetrical setation of soft integument. Not to scale.

FIGURES 9–17. Mycomelichares polypori gen. nov., sp. nov.: 9. Ventral gnathosoma, female; 10. Chelicera, female, lateral view of distal part; 11. Epistome, female; 12. Tritosternum, female; 13. and 14. Epistomes, female; 15. Epistome, male; 16. Tritosternum, male; 17. Proximal part of sperm induction system, female. Not to scale.

FIGURES 18–22. Mycomelichares reductus sp. nov., female: 18. Dorsal idiosoma; 19. Ventral idiosoma; 20. Ventral gnathosoma; 21. Epistome; 22. Chelicera, female, lateral view of distal part.

FIGURES 23–26. Mycomelichares reductus sp. nov., female: 23. medial segments of leg I (trochanter, femur, genu, tibia); 24. leg II (except coxa); 25. leg III (except coxa); 26. leg IV (except coxa).

FIGURES 27–32. Mycomelichares reductus sp. nov., female: 27. Dorsal idiosoma; 28. Ventral idiosoma; 29. Ventral gnathosoma; 30. Palp; 31. Epistome; 32. Chelicera, lateral view.