Maxinia, Lindquist, Evert E. & Makarova, Olga L., 2012

Lindquist, Evert E. & Makarova, Olga L., 2012, Review of the mite subfamily Arctoseiinae Evans with a key to its genera and description of a new genus and species from Siberia (Parasitiformes, Mesostigmata, Ascidae), ZooKeys 233, pp. 1-20 : 2-4

Maxinia gen. n.

Type species.

Maxinia arctomontana new species. Monotypic. Genus based on adult female and male material representing one newly described species.

Diagnosis.

Adults of Maxinia are immediately distinguished from those of other arctoseiinae genera by having a broad, robust dorsal shield; by the female having an apomorphically expansive ventrianal shield that encompasses the metapodal plates anterolaterally and includes setae JV1 anteriorly; and by the male having an expansive sternitigenital shield that is fully consolidated with the endopodal strips beside coxae III–IV and abuts an expansive ventrianal shield. In addition, apomorphically, the subcapitulum has a narrow deutosternal groove, and the opisthogaster lacks a setal pair ZV1. None of the setae on tarsi II to IV are conspicuously differentiated by thinness, elongation, or curved shape. As in Arctoseius Thor, 1930 and Iphidozercon Berlese, 1903, genu III carries only seven setae (lacking pv-1) on adults; however, adults of those genera have less robust, parallel-sided dorsal shields, retain opisthogastric setae ZV1, and their females have free metapodal plates and an anal shield. As in Zerconopsis Hull, 1918, adults have robustly sclerotized dorsal and ventral shields. However, adults of Zerconopsis have two to several pairs of dorsal shield setae (at least s4 and Z5) uniquely paddle-like in form, retain opisthogastric setae ZV1, eight setae (including pv-1) on genu III, and the female ventrianal shield is never expansive enough to include the metapodal plates and setae JV1; also, their tarsi II to IV have dorsal proximal setae ad-2, pd-2 conspicuously elongated and curved.

Description.

Idiosomal dorsum. Dorsal shield relatively broad, entire, without lateral incisions, well sclerotized; surrounding soft integument smoothly striate; all dorsal shield setae simple, undifferentiated in form; opisthonotal region lacking setae S2 (Fig. 9). Dorsal shield with complement of 20 pairs of discernible pore-like structures, of which 4 pairs superficially appear secretory (glandular). Marginal r-R series of setae on soft integument in female (Fig. 12), but on dorsal shield edge in male (Fig. 22); r-series lacking r6, R-series with R1-6; submarginal UR-setae absent. Peritrematal shields uniting with dorsal shield anteriorly and pericoxal strip beside coxa IV posteriorly (Fig. 10). Peritremes somewhat reduced in length.

Idiosomal venter.Tritosternum with laciniae free for most of length (Fig. 17). Ventral shields well sclerotized and ornamented (Figs 1, 2, 12, 22). Female sternal shield entire, continuous with well developed endopodal extensions between coxae I–II, but free from those between coxae II–III (Figs 13-16); endopodal extension between I–II with gland pore apically where approaching or abutting exopodal strip; sternal shield with three pairs of sternal setae and three pairs of poroids; setae st4 isolated on soft cuticle. Female with well developed endopodal strips alongside coxae III–IV. Female epigynal shield widened behind level of setae st5, its posterior margin broadly convex and nearly abutting ventrianal shield; setae st5 and paragenital poroids iv5 on soft cuticle; postgenital furrow with two pairs of small platelets. Female with expansive ventrianal shield encompassing metapodal plates anterolaterally and including setae JV1 anteriorly, along with other opisthogastric and circumanal setae, except JV5, ZV4 on soft cuticle; ventrianal shield with paranal setae inserted at level of anterior margin of anus, with gland pores gv3 on posterolateral margins, and with cribrum formed as partitioned strip behind level of postanal seta. Male with expansive sternitigenital shield consolidated with presternal platelets and endopodal strips alongside coxae I–IV and abutting expansive ventrianal shield. Male ventrianal shield similar in expansiveness, setation, and other structure to that of female (Fig. 22); setae JV5, ZV4 on soft cuticle, ZV5 absent. Peritrematal shield consolidated with exopodal strips behind coxae IV, with two poroids and one gland pore in area behind stigma, and a gland pore and poroid at level between coxae II–III; exopodal strip alongside coxae II–III usually fragmented.

Gnathosoma. Gnathotectum with basically but variably triramous anterior margin (Figs 4-7, 26-28); dorsal face without punctate fields. Chelicerae without any conspicuous process along antiaxial or paraxial lateral surfaces basal to digits (Figs 19, 20, 23); fixed digit with small, setiform pilus dentilis and series of teeth along distal half of masticatory surface; movable cheliceral digit bidentate on female (Fig. 19), unidentate on male (Fig. 23), with arthrodial envelope margin fimbriate; male spermatodactyl simple, digit-like, not recurved basally. Deutosternal groove narrow (Fig. 8), with seven transverse rows of denticles of similar width, rows variably denticulate (2-7 denticles), all rows connected by lateral margins. Corniculi normal in form, parallel in anterior projection from base to apex; internal malae normal in form, similar in length with corniculi or somewhat longer. Subcapitular setae smooth, not greatly disparate in length, hp1 not elongated. Palpi with normal setation as described for Gamasina by Evans (1964); palpfemoral seta al and palpgenual setae al-1 and al-2 more or less spatulate distally; palptarsal apotele two-tined.

Legs. Legs I to IV with ambulacrum bearing paired claws without basal swelling (Fig. 3), with paradactyli and rounded pulvilli, ambulacrum I smaller than ambulacra II–IV; legs I–IV similar in thickness, and not disparate in length. Legs II–IV with tarsus (excluding ambulacrum) less than twice as long as tibia. Tarsus I without a sensilla distinguishable as s by apically lanceolate form (as found in most other members of subfamily), and without markedly elongated setae apically, but with seven finger-shaped sensillae of different lengths. Tarsi II–IV with apical setal processes inconspicuous, shorter than ambulacrum (to base of claws), and with acutely triangular apical process ventrally. Complement of setae on segments of legs I–II–III–IV typical for Arctoseiinae as presented by Lindquist and Evans (1965): femora (2-5/3-2) (2-5/3-1) (1-3/1-1) (1-3/1-1) [Setation of femur III was mistakenly presented as 1-4/1-0 in Lindquist and Evans 1965 (see Evans 1963).]; genua (2-3/2, 2/1-2) (2-3/1, 2/1-1) (1-2/1, 2/0-1) (1-2/1, 2/0-1); tibiae (2-3/2, 2/1-2) (2-2/1, 2/1-1) (1-1/1, 2/1-1) (1-1/1, 2/1-1); in transformation from proto- to deutonymph, seta pd-3 not added to genu and tibia I, pv-1 but not pl-2 added to genu II, and al-2 not added to genua and tibiae III–IV (this combination of hypotrichy is apomorphic for subfamily). Leg setae collectively smooth; none of setae on tarsi II–IV conspicuously differentiated by thinness, elongation, or curved shape. Legs of male without dimorphically modified setae.

Etymology.

The name of the genus is tribute to the first author’s spouse, Maxine Lindquist. Together with him for 55 years, she supported his acarological endeavors, accompanied him in field work throughout North America, and hosted many visiting colleagues at home. The name is feminine in gender.

Remarks.

Among some of the characteristics that distinguish them from other taxa of Arctoseiinae , adults of Maxinia resemble those of the genus Neojordensia Evans, 1957, Ascinae , e.g., the relatively broad, well sclerotized dorsal shield, expansive ven trianal shield encompassing the metapodal plates and insertions of setae JV1, absence of setae ZV1, expansive male sternitigenital shield, and the narrow rows of deutosternal denticles. However, adults of Neojordensia present dorsal shield setation and leg chaetotactic attributes typical of the subfamily Ascinae , and are characterized by different distinctive attributes, including absence of paravertical setae z1, absences of setae av-2 on genu I and ad-2 on tibia II, gnathotectum with convex, smooth anterior margin, female with most or all of r-R marginal series of setae on margins of dorsal shield, female sternal region with setae st1 on separate presternal plates, and female epigynal shield apomorphically widened to include the paragenital poroids as well as setae st5 ( Lindquist and Evans 1965, Athias-Henriot 1973).