Unguitarsonemus, Khaustov & Petrov & Kolesnikov, 2021

Khaustov, Alexander A., Petrov, Alexander V. & Kolesnikov, Vasiliy B., 2021, A new genus and two new species of Tarsonemidae (Acari: Heterostigmata) associated with bark beetles (Coleoptera: Curculionidae: Scolytinae) from Peru, Zootaxa 4966 (1), pp. 41-53 : 42-43

Genus Unguitarsonemus n. gen.

Type species: Unguitarsonemus paradoxus n. sp.

Diagnosis

Female. Gnathosomal capsule oval, completely covered by prodorsal shield; pharynx narrow, with well sclerotized walls and well-developed ovoid posterior glandular bodies. Stigmata located dorsally; dorsal setae not modified. Anterior margin of posterior sternal plate nearly straight, without lobes; two pairs of coxal setae on metapodosomal venter. Ambulacrum of leg I with single, typically uncinated claw; tarsal part of tibiotarsus I with only one attenuate seta pv’; tarsus II with three attenuate setae; seta pl” of tarsus II located on distinct protuberance and modified into large claw-like structure with thickened base.

Description (based on female)

Gnathosoma. Gnathosomal capsule oval, completely covered by prodorsal shield. Postpalpal setae (pp) present. Palpi short, with distinct rod-like dorsolateral setae dFe and dGe, ventrally with very small tibial claw and well developed round accessory setigenous structure (ass). Cheliceral stylets and their levers small, located anteriad bases of setae ch. Pharynx narrow, with well sclerotized walls and with well-developed prominent posterior ovoid glandular bodies.

Idiosoma. Rostral shieldlet widely semicircular. Stigmata small, round, located dorsally near posterolateral ends of rostral shieldlet; trachea long and narrow, without sclerotized atrium. Bothridia present, with capitate trichobothria sc 1 completely covered by prodorsal shield. Alveolar pits v 2 located anteromesad bases of setae sc 2. Dorsal setae not modified. Ventral shielding with apodemes 1 forming Y-shaped juncture with prosternal apodeme; apodemes 2 not fused with prosternal apodeme; prosternal apodeme not fused with sejugal apodeme; sejugal apodeme developed only laterally; apodemes 3 not extending laterad trochanters III, nor mesad setae 3a. Apodemes 4 narrow, not extending posterolaterad setae 3b, fused with poststernal apodeme with typical bifurcation anteriorly. Anterior margin of posterior sternal plate nearly straight, without lobes. Two pairs of coxal setae on metapodosomal venter; setae 3c, and 4a absent. Bases of legs IV moderately well-spaced, separated by interval of about two times of width of trochanter IV; tegula moderately long, rounded apically. Aggenital plate lacking setae. Pseudanal setae present.

Legs. Ambulacrum of leg I with single, typically uncinated claw. Ambulacra of legs II and III with empodium and well-developed, symmetrically paired claws. Femur I without apophysis; femur II without ventral flange. Legs I and II of moderate length, with none of segments unusually elongated. Tarsal part of tibiotarsus I with only one attenuate seta pv’ (pl” and pv” absent); tarsus II with three attenuate setae (pv” absent); seta pl” of tarsus II located on distinct protuberance and modified into unusually large claw-like structure with basal thickening; seta s of tarsus I spine-like; setae (u) of tarsus I present; seta u′ on tarsi II and III spine-like, with rounded tip. Seta u” on tarsi II and III not evident. Trochanter III of adult female elongate, subelliptical, plate-like, longer than femorogenu III. Leg IV elongate-cylindrical, about twice shorter than leg III, with femorogenu at least two times as long as tibiotarsus; trochanter no longer than tibiotarsus. Number of setae and solenidia on femur, genu, tibia, and tarsus, respectively: leg I: 3-4-6(2 φ) + 8(l ω); leg II: 3-3-4-5(l ω); leg III: 1+3-4-4.

Male and larva unknown.

Species included. The genus Unguitarsonemus includes one species, U. paradoxus n. sp.

Distribution and habitat. Unguitarsonemus paradoxus n. sp. is phoretic on the bark beetle Phloeotribus pilula ( Erichson, 1847) in Peru.

Etymology. The name of the new genus is a combination of two words, the Latin unguis meaning claw, and Tarsonemus , the type genus of the family Tarsonemidae and refers to the presence of the remarkably large, clawlike, modified seta pl” on tarsus II.

Differential diagnosis. The female of Unguitarsonemus n. gen. resembles that of Tarsonemus Canestrini and Fanzago, 1876 , especially of subgenus Schaarschmidtia Magowski, 2010 of the tribe Tarsonemini Canestrini & Fanzago, 1877, sensu Lindquist, 1986 in general appearance, in the gnathosoma having prominent posterior pharyngeal ovoid glandular bodies, and in lacking setae pl” and pv” on tarsi I and II, respectively. The new genus differs from Tarsonemus (Schaarschmidtia) by the absence of seta pv” on tibiotarsus I (present in Schaarschmidtia ) and by the form of unusually large claw-like seta pl” on tarsus II (spiniform or disc-shaped in Schaarschmidtia ). The female of the new genus is also similar with Lobotarsonemus Khaustov & Abramov, 2017 with shearing the following apomorphic characters: gnathosoma having posterior pharyngeal ovoid glandular bodies; tibiotarsus I with only one attenuate seta pv’; tarsus II with three attenuate setae. The new genus differs from Lobotarsonemus in having short palps (very long in Lobotarsonemus), straight anterior margin of posterior sternal plate (with three large lobes in Lobotarsonemus), seta v’Ge of femorogenu IV present (absent in Lobotarsonemus), and by the form of large claw-like seta pl” on tarsus II (spiniform in Lobotarsonemus).