Lasioseius helvetius Chant

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 : 14-16

Lasioseius helvetius Chant

( Figs 28–34 )

Lasioseius (Paragarmania) helvetius Chant, 1958: 384

Lasioseius saltatus Karg, 1980: 355 , new synonymy (see Remarks); Christian & Karg, 2006: 200.

Diagnosis: Adult females of this species resemble those of several other species (e.g., L. analis Evans 1958 , L. scapulatus (Kennett 1958) , L. bilineatus Karg 1976 , L. operculi Karg 1980 , etc.) in having a ventri-anal shield with 4 pairs of opisthogastric setae, and leg IV clearly longer than the dorsal shield and provided with several macrosetae on the genu, tibia, basitarsus and telotarsus, of which pd -3 on the basitarsus and pd -2 on the telotarsus are clearly longer than the tibia, and pd -2 on the tibia is slightly longer than that segment. It differs from those species in the dorsal shield lacking setae J4 (denoted as J3 by Karg 1980).

Adult female. Dorsal idiosoma ( Fig. 28 ): Dorsal shield 435–475 µm long, 275–310 µm wide at midlength level of setae s6, reticulate over entire surface, lacking puncta posteriorly between setae Z4-J5; with 21 pairs of setae (j1-j6, z1-z6, s1-s6, r2-r4) on anterior region and 14 pairs of setae (J1-J3, J5, Z1-Z5, S1-S5), lacking J4, on posterior region. Most setae on dorsal shield relatively long (40–65 µm), slightly longer than distance to insertions of next seta in series; z1, s1, s2, r2, r4 and J5 smooth, similarly short (12–19 µm) except s1 and r4 slightly longer (20–24 µm), r4 half as long as tricarinate seta s4 neighboring it medially; other dorsal shield setae stout, tricarinate, Z4 and Z5 also barbed. Lateral soft cuticle with 7 or 8 pairs of marginal setae (r5-r6, R1-R6, but R3 sometimes absent on one or both sides), these setae similarly short (15–20 µm), simple, except r5 slightly longer; submarginal setae absent.

Ve n t r a l idiosoma ( Fig. 29 ): Tritosternal laciniae free for ca. 60–75 µm of their length (ca. 90 µm). Presternal area lineate, sparsely microtuberculate, without platelets. Sternal shield sparsely punctate over most of surface, lineate along lateral margins, with pair of oblique lines extending from near midline of anterior margin to level between first and second pairs of sternal setae, sometimes with median groove but lacking patch of reticula anteromedially, and with 3 pairs of setae and 2 pairs of poroids. Metasternal plates subquadrate, with fourth pair of sternal setae and third pair of poroids. Endopodal strips normally formed alongside coxae III–IV. Genital shield punctate, nearly truncated posteriorly, with lateral margin markedly concave anterior to genital seta; paragenital pores in soft cuticle slightly behind level of genital seta. Postgenital strip divided into 4 weakly defined platelets (division incomplete or difficult to discern in some specimens). Metapodal plates divided into smaller narrow element (13–14 µm) and larger oval to subtriangular element (15–18 µm long, 10–11 µm wide). Ventri-anal shield wider (202–208 µm) than long (148–160 µm), with transverse lineation connected by few diagonal lines that are more numerous in anal region, lacking puncta in anal region; shield with usually 4, rarely 5, pairs of opisthogastric setae (JV1-JV3, ZV2, and sometimes asymmetrically one or symmetrically both of ZV3) plus 3 circum-anal setae of which para-anals (28–32 µm) slightly longer than post-anal seta (25–29 µm), all these setae simple, similar in length; anal opening slightly enlarged (length 35–40 µm). Ventral soft cuticle with usually 5 pairs of setae (ZV1, ZV4, JV4, JV5, and usually ZV3) around ventri-anal shield (ZV5 absent); most posterior pair (JV5) longer (36–40 µm), thicker, slightly tricarinate or not tricarinate. Exopodal plate a continuous strip alongside coxae II–IV.

Peritrematal shield and peritreme ( Figs 28–29 ): Peritrematal shields fused to dorsal shield at level of setae s1 and to exopodal plates at level of coxae IV; peritremes extending anteriorly nearly to bases of setae j1.

Spermathecal apparatus ( Fig. 30 ): With major duct leading to densely sclerotized, thick embolus and calyx with twisted base and short, cup-shaped apex (20–25 µm long, 18–20 µm wide); long, fine minor duct ending with slightly enlarged terminus.

Gnathosoma ( Figs 31–33 ): Anterior margin of tectum truncate or slightly convex, coarsely irregularly denticulate. Fixed cheliceral digit with short pilus dentilis, offset subapical tooth, and row of 18–22 evenly sized, closely spaced teeth; movable digit (length 45–47 µm) tridentate; lateral hyaline rim along paraxial face of digit smooth, lacking serration at level of base of movable digit. Deutosternum with 7 connected rows of denticles; anterior 5 rows each with 7–12 fine denticles, 6th row wider, with ca. 12–21 coarser denticles, 7th row narrow, with 7–11 coarser denticles. Hypostomatic setae h1 not elongated, ca. as long as h2 (30–35 µm); internal mala slightly longer than corniculus, with lateral margin finely fringed. Palptrochanter with internal seta subequally as long as external seta.

Legs ( Fig. 34 ): Legs I slightly (1.1–1.2) and IV clearly (1.4–1.6) longer than dorsal shield (ca. 450–530 and 625–720 µm, respectively); pretarsus of leg I slender (22–24 µm), pretarsi of legs II–III similar in length (20–24 µm) and of IV longer (40–45 µm); tarsi II–IV with apical setal processes (7–8 µm) blunt, ca. 0.3 as long as pretarsi; pretarsi II–IV with paradactyli projecting to apices of claws. Genua and tibiae of legs I-II-III- IV with 13-11-9-9 and 13-10-8-10 setae, respectively, without deficiencies. Tarsi II–III without elongated setae. Tarsus IV (235–270 µm) ca. 1.4 as long as tarsi II (130–150 µm) and III (135–160 µm); leg IV with 6 more or less enlarged setae: genual pd -2 (73–85 µm) subequally as long as genu (80–88 µm), tibial ad -1 (75–90 µm) nearly and pd -2 (100–120 µm) equally as long as tibia (98–112 µm), basitarsal ad -3 (90–105 µm) slightly shorter and basitarsal pd -3 (150–175 µm) and telotarsal pd -2 (135–160 µm) longer than tibia; basitarsal seta pl -3 stiff, slightly stouter than al -3. All leg setae smooth.

Adult male: Unknown.

Material examined: Piracicaba – 1 female, 9.x.1998, 1 female, 5.iv.1999 and 15 female, 2.vii.1999, from litter of a patch of secondary forest.

Previous records: Originally recorded by Chant (1958) from two females collected from pear bark, Lausanne, Switzerland, and by Karg (1980) from one female from a soil probe, “Batuati” (probably Botucatu, State of São Paulo), Brazil.

Remarks: The above redescription and the following remarks are based in part on the study by one of us (EEL) of the holotypes of both L. helvetius and L. saltatus . In his world review of the genus Lasioseius in which L. saltatus was described as a new species, Karg (1980) did not account for Chant’s (1958) earlier description of L. helvetius , even though he did so for L. allii , which was described in the same paper. This oversight was perhaps due to errors and inconsistencies in Chant’s description and his placement of helvetius in Paragarmania , which hindered confirmation of helvetius as a member of the genus Lasioseius rather than Paragarmania , a taxon now placed under Blattisocius . Chant’s distinction of Paragarmania from Lasioseius was based on its members having “...only a few weak teeth on the fixed digit of the chelicera as compared with the multidentate condition of the latter”. Yet, Chant’s description of helvetius states, correctly albeit vaguely, “Chelicera with many teeth”. Even if Karg had accounted for helvetius in the genus Lasioseius , without access to its type material he would not have considered it to be closely similar to the form he described as L. saltatus because of the following inconsistencies in Chant’s description: dorsal shield with 36 pairs of simple setae, with J4 illustrated as present (the holotype has 35 pairs of mostly tricarinate setae, with J4 absent); metasternal plates absent (they are present); ventri-anal shield longer (140 µm) than wide (113 µm) (but wider (175 µm) than long (145 µm) on the holotype). We wonder whether Chant based his description and illustration of this species largely on the single paratype he had at hand, rather than the specimen selected as holotype, and whether that paratype was of a different species than the holotype. The paratype has not been found amidst Chant’s material deposited in the CNCI.

We have a few reservations about the synonymy of L. saltatus under L. helvetius . The spermathecal apparatus is not clear in the holotype of saltatus , because of its obfuscation by two spermatophores on one side and by an egg on the other side. What can be seen of it, however, is consistent with that observed in our Brazilian specimens; and in other respects the holotype matches our material completely, and it was collected from a similar substrate in the same country. On the other hand, the type material of L. helvetius is from a different substrate in a north-temperate country, and the holotype differs slightly from that of L. saltatus and other Brazilian material in having the dorsal shield slightly narrower (263 µm) relative to its length (460 µm) [ratio 0.57], compared to widths (288–310 µm) and lengths (448–475 µm) [ratio 0.65–.0.69] in Brazilian material, and the ventri-anal shield slightly less wider (175 µm) than long (145 µm) [ratio 1.2], compared to widths (203–208 µm) and lengths (148–160 µm) [ratio 1.3–1.4] in Brazilian material. However, its spermathecal apparatus appears to be the same in form.

Figures

FIGURES 28 – 34. Lasioseius helvetius Chant. Adult female, dorsal idiosoma (28), ventral idiosoma (29), spermathecal apparatus (30), tectum (31), chelicera (32), ventral gnathosoma (33) and genu, tibia and tarsus IV (34).