Trhypochthonius tectorum ( Berlese, 1896 )

Weigmann, Gerd & Raspotnig, Günther, 2009, Comparative morphological and biometrical studies on Trhypochthonius species of the tectorum species group (Acari: Oribatida: Trhypochthoniidae), Zootaxa 2269 (1), pp. 1-31 : 5-8

Trhypochthonius tectorum ( Berlese, 1896)

( Figs. 2 , 4a , 5a , 9a )

Hypochthonius tectorum Berlese, 1896 : AMS 78.8.

Trhypochthonius tectorum: Berlese (1904: 27) ; Willmann (1931: 103); Hammer (1952: 96); Schweizer (1956: 231);

Pérez-Iñigo (1968: 229); Kunst (1971: 553); Weigmann (1997a: 200; 2006: 145).

Nothrus tectorum: Warburton & Pearce (1905: 567) .

Tumidalvus mutsalpina Kishida, 1931 : after Fujikawa et al. (1993).

Trhypochthonius tectorum congregator Grandjean, 1940 : Subías (2004: 60).

Trhypochthonius spinosus Kulijev, 1968: 84 .

Trhypochthonius tectorum spinosus Kulijev, 1968 : Subías (2004: 60).

Diagnosis. Body length about 600–700 µ m. Most notogastral setae with spinose setulae and distally broadened (except d 2, p 2-3); seta c 2 as long as c 3 (about 50 µm), c 1 and d 1 smaller (about 30 µm), d 2 smallest (about 20 µm), p 1 longest (about 70–100 µm), weakly broadened; p -setae acuminate and sparsely spinose. 7– 11 pairs of genital setae. Notogaster without distinct posterior boss.

General characters. Mean body length 643 µm (addition of prodorsum and notogaster lengths); range 599-694 µm; mean length of notogaster 456 µm, mean width 378 µm (n=27).

Prodorsum. Rostral seta about 75 µm long, acuminate, with setulae (seta type 3: cf. Fig. 1a ); lamellar (le) and interlamellar (in) setae bacilliform with setulae (type 4), le about 90 µm, in about 100 µm.Sensillus (ss)

with fusiform head with strong spiculae ( Fig. 2 ).

Notogaster. Detailed length of all setae in table 1; shapes of setae in Figs 4a and 9a . Normally, smooth ventral postanal area paa in fig 2c not reaching posterior notogastral edge (in some specimens rarely extending notogaster edge, forming small “boss”, i.e. round projection).

Ventral region. As typical for the genus. In one specimen two anal setae on the right anal plate. Genital setation ( Fig. 5a ) slightly variable from population to population and often asymmetrically expressed in the specimens; the range from 8 to 11 pairs, median number 10 (one specimen on one side 7). Mostly posterior edge of the postanal area ( Fig. 2 : paa) not reaching the edge of the notogaster.

Legs. Tarsus I with solenidion ω 1 normally in dorsal position, ω 2 long, anterolateral position near seta p ”, ω 3 short, mediolateral; in T. tectorum var. congregator ω 3 is long and near ω 2 ( Grandjean 1940). The studied specimens (n=3) represent the typical form. Leg setation formulas for trochanter, femur, genu, tibia, tarsus (+solenidia) (after Weigmann 1997b):

Leg I: 1–6–5(+1)–5(+2)–16(+3); leg II: 1–6/7–5(+1)–13(+2);

leg III: 2–4 3(+1)– (+1)–12; leg IV: 1–2–3–3(+1)–12.

Material examined.

(1) Slides in Berlese collection, especially slide 23/48 ( Fig. 1b in Weigmann 1997b). Genital setation recontrolled by Dr. R. Nannelli, Florence, pers. comm.

(2) Austria, Eastern-Tyrol, Virgental; leg. Heinrich Schatz ( Fig. 1a in Weigmann 1997b).

(3) Austria, Carinthia, Ferlach; leg. G. Raspotnig. 21.7.200 7, from moss on a roof.

(4) Austria, Styria, City of Graz; leg. G. Raspotnig 10.3.200 9, from moss on street pavement.

(5) Austria, Styria, Bachsdorf near Graz; leg. G. Raspotnig 12.6.200 7, from moss on a roof.

The latin etymology “ sphagnicola “ or “ cladonicola ” is used attributively in male gender, analogous to the latin word “agricola” (= colonizer of farmland)

(6) Northern Italy, near Reschen; leg. Heinrich Schatz 2008; poor grassland; 1570 m a.s.l.

(7) Austria, Tyrol, Kaunerberg; leg. Heinrich Schatz 31.8.2005; dry meadow, 1350 m a.s.l.

(8) Austria, Tyrol, Fragenstein near Zirl; leg. Heinrich Schatz; dry meadow, 750 m a.s.l.

(9) Germany, Milseburg near Fulda; leg. G. Weigmann, 4.6.199 4, from dry moss on stones.

(10) South-West Germany, Black Forest Mountains, Schauinsland; leg. 1986, Boris Schnebele, Freiburg; from lichens on tree bark.

Remarks. If not mentioned converse, in the following T. tectorum refers to the typical subspecies. The most specific diagnostic character of T. tectorum is the length of notogastral seta c 2 (as long as c 3: about 50 µm) and the equal length of seta e 1 (it seems shorter in Fig. 2a because of parallax projection). By contrast, in two other European species of the tectorum group, as described below, setae c 2 and e 1 are distinctly smaller. Secondarily, the lack of a distinct posterior boss of the notogaster, the genital setation of 8-11 pairs, the numerous distally broadened notogastral setae with spinose setulae, and the body size of 600-700 µm length are of diagnostic importance.

A study of published descriptions and figures of “ T. tectorum ”, suggests that only some fit these notogastral setation characteristics, which are clearly present in the original description of Berlese (1896) as well as in specimens of his collection (see Fig. 1b in Weigmann 1997b): Warburton & Pearce (1905), Willmann (1931), Schweizer (1956), Pérez-Iñigo (1968), Kunst (1971), Weigmann (1997a, 2006). Probably Trhypochthonius spinosus Kulijev, 1968 , is a synonym, but the description is very short and there is no indication about the genital setae.

Aoki (2000) presented an accurate drawing of the dorsal aspect and the ano-genital region of his “ T. tectorum ”: because of the six pairs of genital setae it resembles more probably T. americanus than the European T. tectorum (discussed also in the section on T. americanus below). The figured “ T. tectorum ” in Hammer (1952) from North Canada also may be T. americanus , as redescribed below, but this can not be verified without at least knowing the genital setation. Kamill et al. (1986) described and figured a “ T. tectorum ” specimen from New Mexico ( USA) which has large c 2 -seta as is present in T. tectorum Berlese and in T. americanus (cf. next section); the genital setation with 6-7 pairs agrees with T. americanus , but it differs from both by large d 2 -setae (the distincly smaller d 2 -seta in comparison with d 1, c 1, c 2 and c 3 is one of the most important diagnostic characters of both T. tectorum and americanus ), and the body length with 545-605 µm is less than in the two other species. The New Mexico specimen needs to be restudied.

Regarding the notogastral setation of the c-e rows, especially the very short setae c 1, c 2, d 1, d 2, it seems certain that the following studies and illustrations of “ T. tectorum ” do not represent Berlese’s species: Balogh (1972: pl. 8, Fig. 13 ); Gilyarov & Krivolutsky (1975: Fig. 140—redrawn from Balogh 1972); Hammer (1961: pl. 2, Fig. 6 —from Peru); Balogh & Balogh (1992: pl. 57C—redrawn from Hammer 1961); Seniczak (1992: 416).

Fujikawa (2000) described two Japanese species similar to T. tectorum . Trhypochthonius fujinitaensis and T. stercus differ from T. tectorum in details of the notogastral setation (cf. Fig. 4a ): c 1 and d 1 shorter, h 3 longer. The possible taxonomical relation of these species is discussed below.

Distribution and ecology. In summary, all references to Berlese’s Trhypochthonius tectorum from outside Europe are questionable or clearly belong to different species. North American findings (as pictured by Hammer 1952) need reinvestigation. Provisionally, T. tectorum must be regarded as a European species with probable extensions to the Caucasus. In ecological respects, the species prefers dry to very dry habitats, like moss cushions on roofs, walls and trees and dry grassy areas.

Figures

FIGURE 1. a—Shape types of notogastral setae in the Trhypochthonius tectorum species-group; b—Length measures of notogaster (L NG) and of prodorsum (L PD) on a shrunken specimen; c—the same on a swollen specimen.

FIGURE 2. Trhypochthonius tectorum. a—Dorsal view, legs omitted; b—sensillus; c—anal area, ventral view. Scale bar 100 µm for a and c. Abbreviations: paa—postanal area; gla—opisthonotal gland; in—interlamellar seta; le—lamellar seta; ro—rostral seta; ss—sensillus; ia, im—lyrifissures; further abbreviations refer to notogastral setae.

FIGURE 4. Profiles of all notogastral setae. a—Trhypochthonius tectorum; b—T. americanus; c—T. silvestris; d—T. silvestris europaeus subsp. nov.; e—T. japonicus forma occidentalis.

FIGURE 5. Genital plates. a—Trhypochthonius tectorum; b—T. americanus; c—T. silvestris; d—T. silvestris europaeus subsp. nov.; e—T. japonicus forma occidentalis. Scale bar 100 µm.

FIGURE 6. Trhypochthonius silvestris, dorsal view, legs omitted. Scale bar 100 µm.

FIGURE 9. SEM pictures. a—Trhypochthonius tectorum, dorsal view; b—Trhypochthonius japonicus forma occidentalis, dorsal view.—T. silvestris europaeus subsp. nov. c – Opisthonotal gland opening and seta f2 in dorsolateral view; d—Dorsal view; e—ventral view with anogenital region.

FIGURE 13. Ranges of length-values of notogaster setae (a, c) and individual length-values plotted against notogaster lengths (b, d) of Trhypochthonius species. a, b—c1 setae; c, d—c2 setae. Abbreviations of species at plots: see fig. 12.