Scutacarus tyrrhenicus Ebermann, 1986

Jagersbacher-Baumann, Julia & Ebermann, Ernst, 2016, Support for the underrepresented sex: new descriptions of scutacarid males (Acari, Heterostigmatina), Zootaxa 4179 (3), pp. 371-409 : 401-405

Scutacarus tyrrhenicus Ebermann, 1986

( Figs. 1 , 3 , 22–24 ).

MALE. Idiosoma length 140–210, n = 5.

Gnathosoma ( Fig. 1 j) extended, tube-shaped. One pair of finger-shaped solenidia, two pairs of dorsal setae ch 1 and ch 2 and one ventral pair of ventral setae su, thin, smooth. One pair of short tube-like accessory setigenous structures distally.

Dorsum ( Fig. 22 a). Idiosoma with four sclerotized plates, plates finely dotted. Most posterior plate forms dorsal cover for genital capsule. Length of dorsal setae: v about 13, sc 1 10, sc 2 36, c 1 36, c 2 38, d 38, e 20, f 51, h 1 8. Setae v, sc 1 smooth, pointed, all other dorsal setae barbed, blunt-ended. h 1 and h 2 smooth, blunt-ended, h 2 minute. Distance between dorsal setae: v–v about 12, sc 1 –sc 1 33, sc 2 –sc 2 26, c 1 –c 1 42, c 2 –c 2 84, d–d 62, e–e 45, f–f 21, h 1 –h 1 23, h 2 –h 2 21.

Genital apparatus ( Figs. 3 j, 3k, 22a). Segments H and PS fused, form genital capsule. Length of genital plate (tergite H) about 61. Posterior edge of plate narrowed, long genital plate (ratio length: width of genital plate = 1: 0.37). Area posterior of h 1 soft-skinned, with roundish- hexagonal, sucker-like structures or cavities. Aedeagus like in I. dispar .

Venter ( Fig. 22 b). Sternal plates finely dotted. Ap1 clearly sclerotized, prosternal ap continuous from ap1 to sejugal ap; ap2, ap3, ap4 and ap5 complete; ap2 and ap5 strongly sclerotized, sejugal ap, ap3 and ap4 weakly sclerotized; anterior part of poststernal ap incomplete, present between ap4 and ap5. Length of ventral setae: 1 a about 11, 1 b 13, 2 a 12, 2 b 13, 3 a 12, 3 b 12, 3 c 13, 4 a 10, 4 b 13, 4 c 11, ps 1 minute, ps 2 9. All ventral setae smooth, short, pointed. Distance between ventral setae: 1 a –1 a about 15, 1 b –1 b 46, 2 a –2 a 21, 2 b –2 b 44, 3 a –3 a 23, 3 b –3 b 38, 3 c –3 c 64, 4 a –4 a 16, 4 b –4 b 10, 4 c –4 c 53, ps 1 –ps 1 15, ps 2 –ps 2 18.

Leg I ( Fig. 23 a). Setal formula: Tr1–Fe3–Ge4–Ti6(2)–Ta13(2). Ta with one small padded claw. Sol ω1 thin, sol ω2 thick, both finger-shaped, sol ϕ1 slightly club-shaped, sol ϕ2 finger-shaped. Length of solenidia: ω1 about 13, ω2 27, ϕ1 8, ϕ2 18. Eupathidia tc’ and tc’’ situated on a low process. Eupathidia p’, p’’, tc’, tc’’ and ft’, setae u’, u’’, s, v’Ti, dTi, v’’Fe and v’Tr smooth, all other setae barbed, most only sparsely. Seta dTi blunt, all other setae pointed.

Leg II ( Fig. 23 b). Setal formula: Tr1–Fe3–Ge3–Ti4(1)–Ta7(1). Ta with two small claws and tiny empodium. Sol ω thick, sol ω and ϕ finger-shaped, sol ω 21, sol ϕ 7. Eupathidia tc’ and tc’’, setae u’, u’’, pv’, dTi and l’Ti smooth, all other setae barbed, most only sparsely. Eupathidion tc’ and seta l’Ti blunt, all other setae pointed.

Leg III ( Fig. 23 c). Setal formula: Tr1–Fe2–Ge2–Ti4(1)–Ta7. Ta with two small claws and tiny empodium. Sol ϕ 7, finger-shaped. Seta pl’’ spine-like; eupathidion tc’ ’, setae u’, u’’, pv’’, and dTi smooth, all other setae barbed, most only sparsely; all setae pointed.

Leg IV ( Fig. 23 d, Table 1 ). Setal formula: Tr1–Fe2–Ge1–Ti4(1)–Ta6. Distal Ta with two adhesive pads of differing size. Tarsal setae tc’, tc’’ are longest, length tc’ about 81, tc’’ 55. Seta v’’Ti spine-like, smooth, bluntended; seta pl’’ hook-like, smooth; setae dTi, pv’’, and u smooth, all other setae barbed, pointed; u small. Sol ϕ 13, thin, finger-shaped.

Differential diagnosis. Males of S. tyrrhenicus can be differentiated from Archidispus , Heterodispus and Imparipes by the presence accessory setigenous structures on the gnathosoma. They can be separated from all other males by their setation. Being morphologically most similar to S. tackei , the two species can be separated by size differences (idiosoma length about 120µm in S. tackei versus 165µm in S. tyrrhenicus ) and by the absence of barbed ventral setae in S. tyrrhenicus while S. tackei possesses slightly barbed ventral setae 1 a, 1 b, 2 a, 2 b and 3 c. Scutacarus tyrrhenicus also shows certain similarity to S. deserticolus , but it is larger (idiosoma length about 145µm in S. deserticolus versus 165µm in S. tyrrhenicus ), and possesses smooth dorsal setae v and sc 1 which are barbed in S. deserticolus . Moreover, the setation of leg IV differs between the three species ( Table 1 ).

Material examined. 5 males from laboratory cultures based on females from a layer of pine needles on sandy ground; ITALY : Island of Elba / Madonna delle Grazie, 42°44'24.9"N, 10°22'06.3"E, 1987, leg. Ebermann .

Deposition of material. 2 males: Natural History Museum Vienna, Austria ( NHMW 27.647 ) ; 2 males: Institute of Zoology , University of Graz, Austria ; 1 male: Museum of Natural History of the City of Geneva, Switzerland .

Remarks. In the laboratory cultures, small (idiosoma length around 140µm) and large (idiosoma length around 200µm) males of S. tyrrhenicus could be found. Between them, allometric effects were recognisable: First, the shape of the genital plate was affected ( Figs. 3 j, 3k): it appeared slightly longer in large males than in small males (ratio length: width of genital plate = 1: 0.39 in large males versus 1: 0.36 in small males). Second, the shape of tibia and tarsus on leg IV differed between small and large males ( Fig. 24 ). There is a broad, spine-like process on the dorsal side of the tarsus which is pronounced in relation to the tarsus in large individuals and minute in small ones. Another roundish process can be found on the dorsal side of the tibia, and again it is pronounced in large and minute in small males.

Figures

FIGURE 1. Dorsal view of the male gnathosoma: a. Heterodispus foveatus, b. Imparipes dispar, c. Lamnacarus ornatus, d. Scutacarus acarorum, e. S. deserticolus, f. S. ellipticus, g. S. longipes, h. S. longitarsus, i. S. tackei, j. S. tyrrhenicus. Abbreviations: ass = accessory setigenous structures.

FIGURE 3. Dorsal view of the genital plates of: a. Heterodispus foveatus, b. Imparipes dispar, c. Lamnacarus ornatus, d. Scutacarus acarorum, e. S. deserticolus, f. S. ellipticus, g. S. longipes, h. S. longitarsus, i. S. tackei, j. S. tyrrhenicus large male (idiosoma length 200 µm), k. S. tyrrhenicus small male (idiosoma length 140 µm).

FIGURE 22. Scutacarus tyrrhenicus male: a. dorsal view, b. ventral view.

FIGURE 23. Scutacarus tyrrhenicus male: a. leg I, b. leg II, c. leg III, d. leg IV.

FIGURE 24. Scutacarus tyrrhenicus male leg IV: Allometric effects between a. a large male (idiosoma length 200 µm) and b. a small male (idiosoma length 140 µm). Abbreviations: taP = tarsal process, tiP = tibial process.