Cosmochthonius reticulatus Grandjean, 1947

Seniczak, Stanisław, Penttinen, Ritva & Seniczak, Anna, 2011, The ontogeny of morphological traits in three European species of Cosmochthonius Berlese, 1910 (Acari: Oribatida: Cosmochthoniidae), Zootaxa 3034, pp. 1-31 : 2-12

Cosmochthonius reticulatus Grandjean, 1947 ( Figs 1–7 , 8 A, 9A, 10A)

Cosmochthonius reticulatus: Grandjean 1947b ; Travé 1956, 1984; Grandjean 1962; Balogh and Mahunka 1983; Pérez-Iñigo and Peña 1995; Mahunka and Mahunka-Papp 2003, 2010; Karasawa and Hijii 2004a, 2004b; Subías 2004, 2011; Karasawa et al. 2005; Penttinen and Gordeeva 2005, 2009.

Cosmochthonius trivialis Sergienko, 1991 : Sergienko 1994.

Diagnosis. Adult small (266–340 µm), light brown, with typical characters of Cosmochthonius (for adult see also Penttinen & Gordeeva 2005). Seta c 3 inserted on lateral border of plate Na ( Figs 1 , 2 ). Setae of e -series with 12–13 pairs of cilia, those of f -series shorter ( Table 1), with 10–11 pairs of cilia. Whole body covered with reticulate, porous cerotegument, cerotegumental collar absent. Cuticle with polygonal or hexagonal foveae in SEM micrographs, reticulate in light microscopy ( Fig. 2 ). Genital plate larger than anal plate, with 10 pairs of setae, six of which inserted on inner border of plate ( Fig. 3 ). Formulae of setae (+solenidia) of legs (trochanter to tarsus) as follows: I – 0-5-5-(6+1)-(19+1), II – 1-6 -5-(6+1)-(17+1); III – 2-3 -4-(4+1)-15; IV – 2-3 -4-(4+1)-14. Tarsus I bidactyle, tarsi II–IV tridactyle.

Larva unpigmented, nymphs light brown. Most prodorsal setae bushy, sensillus with long, barbed head. Gastronotum with three transverse scissures. Larva with 14 pairs of gastronotal setae, nymphs with 16 pairs. Setae of e - and f -series hypertrophied, and pinnate; other setae distinctly shorter and barbed. Hypertrophied setae of larva with 6–7 pairs of cilia, those of nymphs with 8–9 pairs. Other morphological characters of juveniles given in Table 2 .

Description of larva and tritonymph: Larva small ( Table 1), unpigmented, often distended in alcohol samples. Prodorsum relatively long, subtriangular, with wide rounded rostrum, with small, thin fenestrate areas ( Fig.

4). Prodorsal setae ro, le, in and exs bushy, curved, usually uniramous, spines single or bifurcate; seta exi distinctly shorter and rather smooth ( Fig. 5 A). Bothridium rounded, sensillus slightly curved, and with long, narrow, barbed head.

Species Morphological characters L PN DN TN AD

C. reticulatus Body length 160 243 264 330 330 Body width 96 120 136 182 173 Length of: sensillus 48 51 58 65 67 seta c 1 22 24 38 43 50 seta c 3 21 16 32 42 45 seta cp 25 32 45 52 53 seta d 1 17 13 15 17 31 seta d 2 23 22 22 23 35 seta e 1 63 73 103 144 176 seta f 1 54 64 92 136 162 genital opening Nd 22 35 48 82 analopening 23 30 42 55 50

C. foliatus Body length 149 182 198 231 297 Body width 88 102 112 120 152 Length of: sensillus 48 51 62 72 65 seta c 1 22 24 37 42 39 seta c 3 22 17 30 33 39 seta cp 25 17 41 51 57 seta d 1 17 15 15 21 29 seta d 2 25 22 25 27 39 seta e 1 60 75 103 126 168 seta f 1 51 65 83 112 146 genital opening Nd 21 32 40 70 analopening 20 32 39 45 54

C. ugamaensis Bodylength 159 211 244 310 304 Body width 96 125 144 188 153 Length of: sensillus 49 56 63 64 63 seta c 1 17 27 33 45 50 seta c 3 20 15 29 37 49 seta cp 27 27 39 48 55 seta d 1 17 18 20 23 31 seta d 2 18 20 25 32 46 seta e 1 60 87 95 133 155 seta f 1 49 70 87 109 143 genital opening Nd 20 28 51 70 analopening 22 26 35 46 54

1 According to Seniczak and Seniczak (2009a) Gastronotum with 14 pairs of setae ( Figs 4 , 5 A), including inguinal seta h 4 positioned anterior to paraproctal valves (segment PS). Gastronotum with three transverse scissures, which divide it into four parts. Plate Na with four pairs of setae: c 1– c 3 in anterior row, cp in posterior row; all setae rather long, and barbed. Plate Nm 1 with two pairs of setae (d 1, d 2), shorter than c -series. Setae of e - and f -series hypertrophied, pinnate, inserted on intercalary sclerites between plates Nm 1 and Nm 2, and Nm 2 and pygidium (Py), respectively; each seta with 6–7 pairs of cilia. Pygidium weakly developed, with four pairs of slightly curved and barbed setae of h -series, length decreasing from h 1 to h 4 ( Figs 5 A, 6A). Seta h 1 with 4–5 cilia, other setae barbed. Paraproctal valves with four pairs of barbed setae, similar in shape to h 4. Cupule ia posteroventral to seta c 3, cupule im posteroventral to seta cp, cupule ip between setae f 2 and h 3, cupule ih posterior to seta h 4 ( Fig. 6 A). Ventral parts of gastronotum weakly striated.

Prodorsum of tritonymph ( Fig. 7 ) relatively smaller, and Py longer than in larva. Rostrum with small dens and two transverse rows of small, thin fenestrate areas. Prodorsal setae ro, le, in and exs bushy, biramous, with longer single, and bifurcate spines than in larva; seta exi barbed. Bothridium and sensillus as in larva. Gastronotum with 16 pairs of setae, including hypertrophied, and pinnate setae of e - and f -series, inserted on intercalary sclerites, and curved posterior ( Fig. 5 B); other setae distinctly shorter and barbed. Hypertrophied setae with 8–9 pairs of cilia ( Fig. 8 A), basal cilia of f -series longer than those of e -series; length of cilia decreasing from basal to distal part of setae. Seta c 3 bushy and shorter than other pinnate setae of c -series, setae of d -series shorter than c 3, and pinnate (Fig. 9A). Pygidium with setae of h - and p -series; all curved and heavily barbed, but p 1 and h 1 thicker than h 2 and h 3 ( Fig. 10 A). Setae of ad -series barbed, ad 1 approximately as long as p 2, length decreasing from ad 1 to ad 4 ( Fig. 6 B). Paraproctal valves with four pairs of barbed setae, slightly shorter than ad 4. Cupules ia and im as in larva, cupule ip posterolaterally to seta h 2, cupule iad lateral to anterior part of anal valves, cupules ips and ih displaced laterally from cupule iad ( Fig. 5 B). Ventral parts of gastronotum weakly striated. Shape of tibia and tarsus I, solenidia φ and ω, and famulus ε similar to that of C. ponticus (see Seniczak & Seniczak 2009a).

Summary of ontogenetic transformations: The ontogeny of C. reticulatus is similar to that of C. ponticus , which was described earlier ( Seniczak & Seniczak 2009a). The number of prodorsal setae is constant during ontogeny (six pairs, including the sensillus), and the shape of setae remains similar in all instars. In contrast, the number of gastronotal setae increases in ontogeny, from 14 pairs in larva to 16 pairs in protonymph (h 4 lost, p -series gained), and these setae remain in the nymphs and adult. All instars have three transverse scissures on the dorsal part of hysterosoma, and hypertrophied and pinnate setae of the e - and f -series, which are positioned on intercalary sclerites. Aggenital setae are absent throughout. The formulae of setae are as follows: gastronotal setae – 14-16-16- 16-16 (larva to adult); segments PS–AN – 43333-4444-444; genital setae – 1-2-7-10 (protonymph to adult); and coxisternal setae – 3-2-2 (larva), 3-2-2-1 (protonymph), 3-2-3-3 (deutonymph) and 3-2-3-4 (tritonymph and adult). All formulae are consistent with patterns presented by Grandjean (1949). In the larva seta 1c is scaliform and covers Claparéde’s organ.

Distribution and ecology: Cosmochthonius reticulatus is a Mediterranean occidental species ( Subías 2004, 2011), with type-locality in Périgueux city, north-west of Bordeaux, France ( Grandjean 1947b). According to Travé (1956, 1984) this species prefers warm, south-slope biotopes in pine forests ( Pinus alepensis Mill. ), but it is not very common. Pérez-Iñigo and Peña (1995) found it in soil with mosses, while Mahunka and Mahunka-Papp (2003, 2010) recorded C. reticulatus from dead tree trunk and oak forest. Penttinen and Gordeeva (2009) found this species more frequently in litter under juniper [ Juniperus macrocarpa (Sibth. & Sm.) ] in Lesvos ( Greece), and under cypress ( Cupressus sempervirens L.) and oak trees ( Quercus coccifera L.) in Rhodes ( Greece), and also under juniper ( Juniperus excelsa Bieb ) in Ukraine, and considered it common in the eastern Mediterranean area. Karasawa and Hijii (2004a) found C. reticulatus on tree branches in a typical mangrove forest about 4.5 m high, with dominant Bruguiera gymnorrhiza (L.) Lam. and rare Rhizophora stylosa Griff in the Ryukyu Islands ( Japan). Interestingly, these adults were slightly smaller ( Karasawa & Hijii 2004b) than those investigated here. Karasawa et al. (2005) also found C. reticulatus in window traps mounted above the soil and at canopy level. This species was abundant in cypress tree litter near Villa del Casale (Central Sicilia, Italy, N37°21’ 52, E14°20’ 04, 538 m a. s. l.), achieving on May 27 of 2009 a density of 1,903 individuals per 500 cm 3, with a large fraction of juveniles (62.7% of population), including larvae (27.5% of juveniles).

Figures

FIGURE 1. Cosmochthonius reticulatus, adult with cerotegument, dorsal aspect, legs partially drawn, scale bar 50 μm.

FIGURE 2. Cosmochthonius reticulatus, adult. (A) Notogaster, cerotegument removed, scale bar 50 μm; (B) fragment of pygidium.

FIGURE 3. Cosmochthonius reticulatus, adult, anogenital region, legs partially drawn, scale bar 50 μm.

FIGURE 4. Cosmochthonius reticulatus, larva, dorsal aspect, legs partially drawn, scale bar 50 μm.

FIGURE 5. Cosmochthonius reticulatus, lateral aspect, legs partially drawn, scale bars 50 μm. (A) Larva; (B) tritonymph.

FIGURE 6. Cosmochthonius reticulatus, scale bars 50 μm. (A) Anal region of larva; (B) anogenital region of tritonymph.

FIGURE 7. Cosmochthonius reticulatus, tritonymph, dorsal aspect, legs partially drawn, scale bar 50 μm.

FIGURE 8. Hypertrophied setae of tritonymph, scale bars 50 μm. (A) Cosmochthonius reticulatus; (B) C. foliatus.

FIGURE 10. Posterior margin of gastronotum, scale bar 20 μm. (A) Cosmochthonius reticulatus; (B) C. foliatus; (C) C. ugamaensis; (D) C. ponticus.

Tables

TABLE 2. Selected morphological characters of Cosmochthonius reticulatus, C. foliatus, C. ugamaensis, and C. ponticus.

Morphological char- C. reticulatus acters	C. foliatus	C. ugamaensis	C. ponticus 1
Adult:
Pairs of cilia on e - 12–13 series setae	23–25	16–18	13–14
Pairs of cilia on f - 10–11 series setae	22–24	13–14	10–11
Form of cerotegument Thick	Thick	Thin, granular	Thin, granular
Presence of cerotegu- Absent mental collar	Present	Absent	Absent