Pseudolaelaps calvescens, Mašán, 2017

Mašán, Peter, 2017, Two new species of the genus Pseudolaelaps Berlese, 1916 (Acari: Mesostigmata: Pseudolaelapidae) from Europe, with an updated key to known species, Journal of Natural History 51 (21 - 22), pp. 1183-1195 : 1185-1187

Pseudolaelaps calvescens sp. nov.

( Figures 1 and 3 (a))

Specimens examined

North Italy, Lombardy, Bergamo Province, coll. P. Mašán: holotype female − Bergamo City, Astino Valley, Bosco di Astino, broadleaved deciduous forest (with Quercus robur , Quercus petraea , Quercus cerris , Castanea sativa , Carpinus betulus , Robinia pseudoacacia , Betula sp. , Fraxinus sp. , Corylus avellana , Crataegus sp. , Viburnum lantana , Cornus mas , ao.), leaf litter and soil, altitude 265 m, 13 May 2015; paratypes − five females, with the same data as in holotype; one female, Bergamo City, Fenile Settlement, young broadleaved deciduous forest (with Quercus spp. , Carpinus betulus and Fraxinus sp. ), leaf litter and soil, altitude 580 m, 17 May 2015; three females, Bergamasque Alps and Pre-Alps, Cantoni D ’ Oneta Village, beech forest ( Fagus sylvatica ) with admixed maple ( Acer sp. ), leaf litter and soil, altitude 1140 m, 13 May 2015.

Diagnosis

The new species may be distinguished from the other congeners by the combination of the following characters: (1) dorsal shield with 24 pairs of very short and thin setae; (2) dorsal setae S5 markedly reduced in length, shorter than postanal seta; (3) lines of sternal and genitiventral reticulation straight, not undulate; (4) ventral setae JV3 shorter than dorsal setae J5; (5) setae JV2 and ZV2 inserted on genitiventral shield; (6) tibia I and genu I each with only two ventral setae, av1 and pv1 (av2 absent); genu II with only one ventral seta, pv1 (av1 absent); genu III with only one ventral seta, av1 (pv1 absent).

Description

Female. Dorsal idiosoma ( Figure 1 (a)). Dorsal shield 385 – 430 µm long and 295 – 320 µm wide, suboval (length/width 1.25 – 1.42), widely rounded anteriorly, delicately micropunctate on whole surface, lacking reticulate sculpture on entire surface, rarely with very weak and uneven polygonal reticulation on lateral or posteromedial surface. Dorsal shield with 24 pairs of setae; setae markedly reduced in length (especially those on posterior area),

minute and thin, smooth and needle-like; length of some selected setae as follows: j1 12 – 15 µm, j5 10 – 13 µm, J4 7 – 10 µm, J5 21 – 27 µm, and S5 4 – 8 µm.

Ventral idiosoma ( Figure 1 (b)). Presternal shields subtriangular, free, with inner margins contiguous with each other. Sternal shield subquadrate, subeqal in length and

width (78 – 90 µm long, 77 – 88 µm wide), with normal reticulate ornamentation and delicate punctation on surface; outlines of polygonal sculptural cells straight, not undulated ( Figure 3 (a)). Metasternal platelets subtriangular, relatively middle-sized (26 – 36 µm wide). Genitiventral shield relatively variable in proportions, mostly longer than wide (length 168 – 193 µm, width 160 – 188 µm, length/width 0.92 – 1.2), rounded anteriorly, well expanded and widely rounded posteriorly, concave laterally and posteromedially (posterior margin rarely regularly straight, truncate), abutting parapodal elements of peritrematal shields; shield finely punctate and reticulate throughout except posteromedially; sculptural lines straight, not undulate. Ventral setae JV2 and ZV2 inserted on genitiventral shield. Length of setae JV3 16 – 20 µm. Anal shield subtriangular, 43 – 56 µm long and 82 – 96 µm wide (length/width 0.51 – 0.61); length of postanal seta 15 – 20 µm. Peritrematal shields essentially smooth, with a few lineae in poststigmatic portion; peritremes slightly expanded close to stigma, with smooth or very delicately crenulate margins close to coxae II and III. Metapodal platelets minute, slightly elongate, suboval ( Figure 1 (b)).

Epistome ( Figure 1 (c)). Tricuspid, with denticulate anterolateral margins; medial cusp with smooth margin, slightly longer than lateral cusps or all cusps subequal in length.

Leg chaetotaxy ( Figure 1 (d)). Tibia I and genu I with 12 setae (2 – 3/1, 3/1 – 2); genu II with 10 setae (2 – 3/0, 2/1 – 2); genu III with eight setae (2 – 2/1, 2/0 – 1).

Male and developmental stages. Unknown.

Etymology

The name is derived from the Latin word calvesco (become bald), and it refers to an important feature of the new species ‒ the minute and hardly discernable setae on the dorsal shield.

Remarks

Pseudolaelaps calvescens sp. nov. has striking similarities to Pseudolaelaps brevipilis and Pseudolaelaps mirandus – very short setae on dorsal shield and sternal shield sculpture. They may be easily distinguished by the leg setation and dorsal and ventral chaetotaxy – in the new species, seta av1 on genu II is absent (expressed in P. brevipilis and P. mirandus ), dorsal setae J2 are absent (expressed in P. mirandus ), setae ZV2 are inserted on genitiventral shield (on soft integument in P. brevipilis ), and presternal shields are separate (fused in P. brevipilis and P. mirandus ). For other differential features see Table 1 and identification key below.

Figures

Figure 1. Pseudolaelaps calvescens sp. nov., female. (a) Dorsal idiosoma; (b) ventral idiosoma; (c) epistome, variant forms; (d) diagrammatic representation of chaetotaxy of selected leg segments (tibia I, genua I−III).

Figure 3. Pseudolaelaps spp., sternal shields of females. (a) Pseudolaelaps calvescens sp. nov.; (b) Pseudolaelaps schweizeri sp. nov.