Gamasellodes magniventris, De, Jeferson L., Lindquist, Evert E. & De, Gilberto J., 2009

De, Jeferson L., Lindquist, Evert E. & De, Gilberto J., 2009, Edaphic ascid mites (Acari: Mesostigmata: Ascidae) from the state of São Paulo, Brazil, with description of five new species, Zootaxa 2024, pp. 1-32 : 8-10

Gamasellodes magniventris sp. nov.

( Figs 11–15 )

Diagnosis: Adult females of this species are closely similar to those of Gamasellodes rectiventris Lindquist 1971 in having the anterior margin of the ventri-anal shield broad, nearly straight, seeming to cause an anterior displacement of seta ZV2 into nearly transverse alignment with JV1 and ZV1, and in having long peritremes that extend anteriorly to a level between the bases of setae s1 and z1. They are distinguished from the latter in having the anterior margin of the ventri-anal shield extending slightly more anteriorly so as to nearly touch the alveoli of setae JV1 and ZV2, and to incorporate a pair of sigillar platelets between and slightly behind the bases of setae JV1 and ZV1. They also differ in having several setae on the opisthonotal shield longer than in G. rectiventris , such that Z3 extends to the base of Z4, Z4 well surpasses the base of Z5, and S3 surpasses the base of S4. In contrast to G. rectiventris , the anterior extremities of the peritrematal shields abut but do not unite with the podonotal shield, and the slightly longer peritremes reach to the extremities of these shields alongside setae z1. Further, on tarsus IV, seta ad -2 is nearly 3 times as long as pd - 2, whereas these setae are similar in length in G. rectiventris .

Adult female. Dorsal idiosoma ( Fig. 11 ): Dorsal shields collectively 288 µm long, 128 µm wide at levels of setae j5 and J3, unornamented over entire surface except for an arched transverse line anteriorly between setae j2 and j3, and some markings posteriorly in region of setae J4-J5, including a posteriorly arched, crenulated transverse line between setae Z4 and a mostly longitudinal line on either side medial to Z4. Podonotal shield with 16 pairs of setae, opisthonotal shield with 15 pairs; 10 or 11 pairs of setae on lateral soft cuticle, including s1-s2 and r2-r5 anteriorly (r6 absent), and R1-R3, R5 and sometimes R4 posteriorly (R4 sometimes unilaterally or bilaterally absent, R6 absent). Most dorsal setae, including all on podonotal region, short (11–15 µm), clearly shorter than successive longitudinal distances between their bases; on opisthonotal shield J2 (14 µm) ca. 0.4 as long as alveolar interval J2-J3, J4 (17–18 µm) slightly longer than other members of J -series (13–15 µm), Z1-Z5 (15, 16, 20, 30, 42 µm, respectively) and S1-S5 (13, 16, 18, 20, 23 µm, respectively) sequentially slightly longer, Z1 slightly longer than interval Z1-S1, Z3 almost reaching base of Z4; all setae smooth except Z5 almost imperceptibly barbed. Setae j2 nearly transversely aligned with j1 and z1. Setae on lateral soft cuticle short (10–13 µm, except r3 16 µm), simple.

Ve n t ra l idiosoma ( Fig. 12 ): Tritosternum normal in shape, with trapezoidal base and slender, pilose laciniae fused along only basal one-tenth of their length (45 µm). Pre-sternal area weakly sclerotized, indistinctly lineate and microtuberculate, without platelets. Sternal shield ca. 82 µm in median length by 50 µm wide at narrowest width between coxae II, with 3 pairs of setae and 3 pairs of poroids; shield with anterior margin deeply emarginated medially, lineated along lateral margins, smooth over rest of surface, and with posterior margin gently, irregularly concave. Sternal setae st4 on soft cuticle; st4 and genital setae st5 slightly shorter (10–11 µm) than st1-st3 (13–14 µm). Endopodal plates formed as weak strips alongside coxae III–IV. Genital shield smooth anteriorly, but lightly reticulated posteriorly and widened at level of insertions of genital seta, with posterior margin truncate, and hyaline anterior margin broadly rounded, not overlapping posterior margin of sternal shield. Post-genital groove lacking platelets. Metapodal plates undivided, small, slender, ca. 12 µm long by 5 µm wide. Ventri-anal shield ca. 0.7 as long (90 µm) as wide (120 µm), with anterior margin nearly straight medially, incorporating a pair of sigillar platelets between and slightly behind the bases of setae JV1 and ZV1, nearly touching alveoli of setae JV1 and ZV2, and abruptly curving posterolaterally behind setae ZV2; shield unornamented in anterior half, lacking line between bases of setae JV2 and JV3, and sparsely punctate on post-anal region, with 4 pairs of ventral setae (JV2, JV3, JV4, JV5) plus 3 circum-anal setae, all simple; post-anal seta longest (38 µm), then JV5 (35 µm); JV3 inserted in lateral alignment with JV2 and shorter (11 µm) than JV2 (20 µm); para-anal setae (15 µm) ca. 0.4 as long as postanal seta. Four pairs of ventral setae (JV1, ZV1-ZV3) on soft cuticle antero-laterally of ventri-anal shield; ZV2 nearly aligned transversely with JV1 and ZV 1 in front of anterior margin of shield. Exopodal plate strip interrupted between coxae II and III, and between coxae III and IV, and free from peritrematal shield alongside coxae II–III, but integrated with it beside and behind coxa IV.

Peritrematal shield and peritreme ( Figs 11–12 ): Peritrematal shields abutting but not fused to dorsal shield at level of paravertical poroids and setae z1; peritremes extending to anterior extremities of peritrematal plates beside bases of setae z1.

Spermathecal apparatus: Not discernible in specimens at hand.

Gnathosoma ( Figs 13–14 ): Anterior margin of tectum smoothly triramous. Fixed digit of chelicera with short pilus dentilis and with offset subapical tooth followed by 4 teeth on apical half; movable digit 26–27 µm long, bidentate. Deutosternum with 7 connected rows of denticles, each narrow, with 2–4 denticles; corniculus normally formed, reaching to anterior margin of palptrochanter; internal mala finely fringed, extending nearly to tip of corniculus. Hypostomatic setae h1 similar in slender form and length (15 µm) with h2 (16 µm).

Legs ( Fig. 15 ): Legs I (223 µm) and IV (205 µm) shorter than length of the two dorsal shields. Coxa I with a dorsal ridge of denticles, and sparsely lineate ventrally; coxae II–III with one or two lines posteroventrally; coxa IV smooth. Legs I–IV with normally developed pretarsi (length ca. 10 µm) and claws. Tarsi II–IV with apical setal processes ad -1, pd -1 inconspicuous, short (ca. 5 µm). Leg IV with tarsus (61 µm) ca. 2.3 as long as tibia (26 µm); telotarsus IV with seta ad -2 (33 µm) 3 times as long as pd -2 (11 µm), and with av -1 (17 µm), av -2 (20 µm) and mv (14 µm) longer and thicker than pv -1 (11 µm) and pv -2 (12 µm) ( Fig. 15 ). Setation of femora of legs I-II-III-IV, respectively, 12-11-6-6; that of genua, 13-11-8-9; that of tibiae, 13-10-8-10; leg chaetotactic formulae normal for genus and tribe Ascini as presented by Lindquist & Evans (1965); leg setae generally slender, smooth.

Adult male: Unknown.

Material examined: Holotype female and 2 paratype females, 2.vii.1999, from litter of a patch of secondary forest, ESALQ-USP, Piracicaba, State of Sao Paulo, col. J.L. de C. Mineiro, deposited at ESALQ- USP. Two paratype females, same data as holotype, deposited at CNCI. One paratype female, 28.vi.1999, from soil of a bean field, same locality as holotype, col. J.L. de C. Mineiro, deposited at ESALQ-USP.

Remarks: These are the first records of a species of the genus Gamasellodes in Brazil. Our description of this species as distinct from Gamasellodes rectiventris is based in part on a re-examination of type material of the latter species, as well as study of material representing undescribed species from Costa Rica on loan in the Canadian National Collection of Insects and Arachnids. Our observations indicate that forms which seem to represent morphospecies are closely similar to one another in the genus Gamasellodes , and pose considerable problems in the distinction and description of species and their identification. Unless more careful descriptions and illustrations of these forms are made, including accounts of shield ornamentation, leg setation, and whatever spermathecal structures are evident, little progress will be made in understanding their distributions and ecological associations.

Etymology: The name magniventris refers to the characteristically broad ventri-anal shield of the new species here described.

Figures

FIGURES 11 – 15. Gamasellodes magniventris n. sp. Adult female, dorsal idiosoma (11), ventral idiosoma (12), tectum