Cosmochthonius (Nortonchthonius) oblongisetosus, Jorrin, 2014

Jorrin, J., 2014, Two New Arthronotic Mites From The South Of Spain (Oribatida, Cosmochthoniidae), With A New Subgenus And Species Of Cosmochthonius And One New Species Of Phyllozetes, Acarologia 54 (2), pp. 183-191 : 185-187

Cosmochthonius (Nortonchthonius) oblongisetosus n. sp.

Description Adult ( Figure 1 ) (n=2).

General aspect, measures and integument ( Figure 1 ) — Small oribatids, the length of the idiosoma is 259-264 µm; the maximum width, measured in the transect between the third pseudoanal setae is 0.62-0.64 times the length of the body. The sides of the body diverge in a front-to-back direction and the pygidium is straight from behind, giving the mites a triangular appearance. Very clear ochre cuticle, almost colorless. In the center of the third notogastral plaque (NM2) there are five finely dotted spongy areas, similar to those located on Cosmochthonius ponticus Gordeeva 1980 (Figure 2,1), the rest of the body integument is smooth, without any traces of sculpture.

Prodorsum ( Figure 1a ) —- The rostral tectum has a rounded margin and lies ventrally, the back shows elongated fenestrations in longitudinal rows composed of 1-3 alveoli. The proterosomatic setae show the arborescence and layout of the genus, with long pectinations with a spiniform appearance; the rostral setae (ro), anterior exobothridials (exa), posterior exobothridials (exp) and interlamellars (in) uniramous, lamellar setae (la) biramous, ro and la are the most robust; with muscular sigillae on both sides of the interlamellar region and in the posterior subbothridial region. Trichobothridium with a typical sensillum (ss), fusiform and moderately pubescent in the greater part of its length.

Notogaster ( Figure 1a ) — With four dorsal plates, the anterior (NA) is approximately 1.5 times thicker than the mid-anterior (NM1), 1.0 times the mid-posterior NM2 and 0.5 times the pygidium ( PYG). The series of setae in NA (c1, c2, c3 and cp) and NM1 (d1 and d2) are typical setiform, with relatively short narrow pectinations, each seta projects over the origin of the previous seta. Setae c1, c2, and d2 of similar length, shorter than c3 and posterior cp and somewhat longer and more robust than d. In NA, the first three setae are equidistant in the same row in the midst of the plaque and cp in the posterior corners; d- row originates in the fold or broad evagination of the first notogastral furrow (ar1) and the distance between setae d1 is approximately half the distance d1–d2. The erectile setae (row e: e1 and e2 and row f: f1 and f2) are large and rigid and they project beyond the hysterosoma in more than half the setal length. These setae have a ’palm leaf’ or ’fish spine’ appearance with a thick and rigid stem, continued bilaterally by long and large spiniform setulae and other very short spinulae interspersed throughout the stem. The intercalary sclerites of second and third scissures (ar2 and ar3) are narrow and long. The first setae of the segment H (h1) are very large setae of the foliar type, oblong or orbicular, concave towards the sagittal plane of the body and they overlap; each seta has a strong and short stem, the surface of the leaf shows a fine irregular grid and a finely denticulated leaf margin. The second and third setae of the h -series (h2, h3) and the three pseudoanal setae (ps1, ps2, ps3) are shorter and finer than the erectile setae and they curve over h1 .

Lateral View ( Figure 1c ) — Below plaque NA, the anterior pleural plate (PLa) is located with the anterior lyrifissure (ia). Below PLa and over the acetabulum III, is the humeral flap (hfl), a counterpart to that of Cosmochthonius reticulatus ( Grandjean, 1962: Figure 3A-B); over the acetabulum IV, there is an accessory plate (apl), auriculiform and prominent in the dorso-ventral; the middle pleural plate (PLm) has the median cupule (im).

Venter ( Figure 1b ) — Second apodemes (ap2) and sejugal (ap-sj) complete, third apodemes (ap3) not very pronounced; non-coalescing first and third epimeral plates (epI, epIII), unique second (epII) and the fourth one (epIV) separated by the major anterior growth of the genitalia; coxisternal formula 2-2- 3-4, the epimeral setae are long and they have fine, relatively large pectinations. Every genital valve has 10 genital setae similar to the epimeral setae, 6 on the medial longitudinal row, with one of the closer fourth or fifth setae somewhat displaced laterally and 4 lateral setae longer than the medial row. The anal plate is attached to the genital plate and with four setae on each valve, the three anterior pairs being similar to the genitals, the first posterior pair (an1) is thick and densely ciliated in a ’brush’ manner. Adanal plate undivided, U-shaped, with four pairs of setae, the posterior ones and the first adanal ones (ad1) of the orbicular type with a length approximately half of the abdomen and a thickness that is approximately 0.75 times its length, with a surface and margins similar to those of the h1 setae. The three anterior pairs of setiform adanal setae (ad2 to ad4) are setiform, stronger and longer than the anal ones.

Legs — All tarsi are polydactyl, tarsus I is bidactyl and tarsi II to IV have three claws and, in the lateral view of the pretarsi, the central claw is stronger than the laterals and with a ’sickle blade’ appearance.

Specimens examined — Two females in a simple from soil below the coverage of an olive tree in production in a parcel of an organic olive grove, holotype code 2715-Hol/M14-20120523 and paratype code 2715-Par/M14-20120523.

Etymology — The specific name ’ oblongisetosus ’ refers to the appearance of some setae on the posterior margin of the body. Remarks - The new and type species of the new subgenus Cosmochthonius (Nortonchthonius) oblongisetosus differs from the rest of species of Cosmochthonius by the morphology of the setae h1 and ad1.

Figures

FIGURE 1: Cosmochthonius (Nortonchthonius) oblongisetosus n. subgen. and n. sp.; a – dorsal view, b – ventral view, c – lateral view; gnathosoma and legs not illustrated. Scale bar = 100 micrometers.