Oribatella calcarata (CL Koch, 1835 )

Seniczak, Stanisław & Seniczak, Anna, 2013, Differentiation of external morphology of Oribatella Banks, 1895 (Acari: Oribatida: Oribatellidae), in light of the ontogeny of three species, Journal of Natural History 47 (23 - 24), pp. 1569-1611 : 1589-1603

Oribatella calcarata (CL Koch, 1835)

( Figures 15–22 )

Oribates calcaratus CL Koch, 1836 .

sexdentata , Oribatella canadensis , Oribatella metzi and Oribatella nortoni .

Oribata calcarata ( Michael, 1898) .

Oribatella decumana Berlese, 1910 .

Oribatella calcarata: Jacot, 1937 ; Hammen 1952; Rajski 1968; Bernini 1975, 1977; Krivolutskiy 1975; Subías 2004; Weigmann 2006; Schatz 2008.

Diagnosis

Adults dark brown, lamellae broad, with small lateral dens, inner cusp longer than outer cusp. Females distinctly larger (574–670 µm) than males (450–526 µm), with subtriangular knoll located on posterior joint of lamella ( Figure 15A ), in males this knoll absent ( Figure 15B ). Seta le thicker than seta in, apical end of seta in not reaching that of seta le in dorsal aspect; seta le protruding beyond rostrum ( Figures 15A , 16A ). Notogaster almost spherical, usually with 10 pairs of setae, including c 2, rarely with smaller seta c 3 inserted unilaterally; all setae curved outward and ventrally, except raised seta h 1. Seta 4c thicker than other coxisternal setae ( Figure 16B ). Formula of setae and solenidia of legs as in O. quadricornuta . Seta l” on tibia I relatively thin, solenidion ω 1 on tarsus I slightly longer than ω 2, famulus ε short ( Figure 17A ). Tarsi tridactylous.

Juveniles light brown, similar to those of O. quadricornuta , with sensillus shorter than seta ex in larva, and of similar length in nymphs. Dorsocentral setae of nymphs longer than lateral setae. Nymphs usually with 13 pairs of setae (c 1 and dm lost), rarely with more setae. Nymphs do not carry the exuvial scalps.

Description of larva and tritonymph

Shape and colouration of larva, its setae, bothridium and sensillus similar to that in O. quadricornuta , and sensillus shorter than seta ex ( Figure 18 ). Gastronotum with 12 pairs of setae, including seta h 3 ( Figure 19A ) positioned lateral to medial part of anal opening. Shape of setae, and location of gland opening gla, and cupules ia, im, ip and ih as in O. quadricornuta .

Nymphs more stocky than larva, and with long ( Table 1), rather thick, curved and barbed prodorsal and gastronotal setae. Tritonymph ( Figures 19B , 20 ) with setae h 1 and p -series shorter than other gastronotal setae, and pair dp inserted more than twice as wide as pair da. Gland opening gla and cupules ia, im, iad, ips and ih located as in O. quadricornuta . Sensillus approximately as long as seta ex. Most nymphs with 13 pairs of gastronotal setae (c 1 and dm lost), rarely with more setae, often present unilaterally ( Figures 21 , 22 ). Shape and location of setae and solenidia on tibia I and tarsus I of tritonymph ( Figure 17B ) as in O. quadricornuta , but seta l” shorter than in O. quadricornuta , and solenidia ω 1 and ω 2 of similar length.

Summary of ontogenetic transformations

The number, shape, location and ontogeny of setae in O. calcarata are similar to those in O. quadricornuta . However, the protonymph usually loses setae c 1 and dm, and these setae remain absent in the next instars; if they are present, they are shorter than most other gastronotal setae. In the nymphs the dorsocentral setae are longer than lateral setae, and pair dp is inserted more than twice as wide as pair da. The adult usually retains 10 pairs of notogastral setae, including seta c 2, but rarely retains also seta c 3 unilaterally, similar to O. quadricornuta . The formula of coxisternal, genital, aggenital setae and segments PS–AN are similar to those in O. quadricornuta ( Table 2). All formulae of setae are consistent with those of Grandjean (1949), except for formulae of gastronotal setae ( Table 2).

Distribution and ecology

Oribatella calcarata is a Holarctic species ( Subías 2004; Weigmann 2006), and its ecology is poorly known, because of its low density, and confusion of this species with O. quadricornuta and O. brevipila Bernini, 1977 ( Weigmann 2006) . It is a forest species ( Rajski 1968; Lebrun et al. 1989; Schatz 2008), which inhabits stems of trees and forest litter. Krivolutskiy and Lebedeva (2004) found O. calcarata on feathers of hooded crow ( Corvus cornix L.). This species is an intermediate host of tapeworm Moniezia expansa Rudolphi, 1810 ( Svadjian 1962) .

Near Duszniki Zdrój ( Poland, 50 ◦ 22.38’ N, 16 ◦ 22.77’ E; 729 m above sea level) O. calcarata was not abundant, occurring in 12 of the 102 samples of 500 cm 3 each. This species preferred spruce litter, rarely occurred in mosses and was absent from decaying wood. Its density was low (1–64 individuals per 500 cm 3), and in a total population of 177 individuals the juveniles dominated (58%), whereas the nymphs comprised 39% of the population. The sex ratio of females to males was 1.3: 1 .

Differentiation of morphology of species within Oribatella

The juveniles and adults of O. quadricornuta , O. superbula and O. calcarata investigated here, and those of O. sexdentata and O. berlesei investigated by Chistyakov (1983, 1984), O. canadensis investigated by Behan-Pelletier and Eamer (2010), and O. metzi and O. nortoni investigated by Behan-Pelletier (2011) well illustrate the differentiation of external morphology of Oribatella . The larvae and nymphs of all species look generally similar to each other, having long prodorsal and gastronotal setae, but they differ by the following morphological characters:

(1) Presence of seta h 3 in larva: most species have this seta, but O. nortoni lacks it ( Table 2).

(2) Length of sensillus in larva, compared to seta ex: some species have sensillus longer than ex ( O. sexdentata , O. superbula , O. nortoni ), other species have it shorter ( O. calcarata , O. quadricornuta ), and others have these setae of similar length ( O. berlesei , O. metzi ).

(3) Length of setae le, in and c 1 in larva is species specific ( Table 2).

(4) Number of gastronotal setae in nymphs: most species have 15 pairs of these setae, but O. metzi has 13 pairs, and O. calcarata usually has the same number, but the former species lacks setae dm and dp, whereas the latter species lacks setae c 1 and dm.

(5) Length of sensillus in nymphs, compared to seta ex: some species have sensillus longer than seta ex ( O. metzi , O. nortoni , O. sexdentata , O. superbula ), other species have it shorter ( O. berlesei , O. quadricornuta ), and others have these setae of similar length ( O. calcarata , O. canadensis ).

(6) Bearing the exuvial scalps by nymphs: most species carry these scalps, while O. calcarata does not.

The nymphs of most species of Oribatella , including O. quadricornuta and O. superbula carry the exuviae of previous instars in an original way, i.e. they form while moulting special muffs around the apical part of setae da to fasten the exuviae to these setae ( Grandjean 1953a; Behan-Pelletier and Eamer 2010). Therefore, the exuviae are held away from the body, as in O. berlesei and O. sexdentata investigated by Chistyakov (1983), and O. canadensis investigated by Behan-Pelletier and Eamer (2010), and O. nortoni investigated by Behan-Pelletier (2011). The muffs around setae da are darker than the setae themselves, and in the tritonymph it is possible to observe all muffs formed by the protonymph, deutonymph and tritonymph, as is demonstrated in Figure 5B , and in Grandjean (1953a) and Behan-Pelletier and Eamer (2010).

The exuviae borne by nymphs are located above setae dm and dp, and they probably change their shape or position, compared with the larva. For example, the nymphs of O. quadricornuta have pair dp in a more lateral position, in a similar way to O. berlesei and O. sexdentata investigated by Chistyakov (1983), and O. nortoni investigated by Behan-Pelletier (2011). In O. superbula pair dp is strongly reduced in size, but remains still thick and barbed, whereas in O. canadensis investigated by Behan-Pelletier and Eamer (2010), pairs dm and dp become minute. In O. metzi investigated by Behan- Pelletier (2011) these two pairs are lost in the protonymph, and are absent in the next instars, but setae da remain strong, which is typical of apopherederms.

The nymphs of O. calcarata investigated here differ distinctly from other species by their lack of exuviual scalps and most of them lack gastronotal setae c 1 and dm. From a total of 69 nymphs collected near Duszniki Zdrój ( Poland), all lacked exuviual scalps in alcohol samples, and most lacked setae c 1 and dm, except four nymphs; two of them retained seta dm unilaterally, one nymph retained a pair c 1 and one seta dm, and one nymph had all gastronotal setae, but these setae were usually shorter than most gastronotal setae. Hence the number of gastronotal setae in the population of nymphs of O. calcarata varied between 26 and 30 setae.

From the adults of O. quadricornuta , O. superbula and O. calcarata investigated here, the most problematic is the last of these species, which is sometimes confused with O. quadricornuta and O. brevipila ( Weigmann 2006) . The adult O. calcarata investigated here are similar to those investigated by Bernini (1977), which was well redescribed by Bernini (1975) on topotypic material near Regensburg ( Germany). However, the Italian females and males were larger (length 630–670 µm and 450–475 µm, respectively) than those from Regenburg (length 610–630 µm and 445–450 µm, respectively), while the Polish females (length 585–637 µm) are similar, and the males are larger (length 452–526 µm) than those from Regenburg. In O. quadricornuta and O. superbula the sexual dimorphism is weakly expressed, and females are usually slightly larger than males, but in O. calcarata the females are distinctly larger than males, and have a subtriangular knoll located on the posterior joint of lamellae, which is absent from males. A distinct sexual dimorphism was also observed in adults of O. canadensis described Behan-Pelletier and Eamer (2010), and it concerns porose areas; females have four small pairs of porose areas, while males have only three pairs.

The adult O. calcarata from Poland differ from those investigated by Krivolutsky (1975), and Shtanchaeva and Subías (2009) by shorter seta in, but the length of this seta in dorsal aspect strongly depends on the angle of orientation of specimens on slides. The adults of species of Oribatella compared here differ from each other by the following morphological characters:

(1) Number of notogastral setae: most species have 10 pairs of these setae, including pair c 2, while O. quadricornuta and O. calcarata rarely retain also seta c 3 unilaterally.

(2) Length of lamellar cusps: most species have outer cusp longer than inner one ( O. quadricornuta , O. sexdentata , O. canadensis , O. nortoni , O. superbula ), O. calcarata has inner cusp longer then outer one, and O. berlesei and O. metzi have both cusps of similar length.

(3) Shape of sensillus: most species have it fusiform ( O. quadricornuta , O. superbula , O. canadensis , O. metzi , O. nortoni ), some species have it clavate ( O. berlesei , O. sexdentata ), while O. calcarata has it setiform.

(4) Length of notogastral setae: O. quadricornuta , O. calcarata , O. metzi have these setae relatively longer than other species.

These species differ also in body size, shape of coxisternal seta 4c, and shape of solenidia and some setae on legs. The ontogeny of leg setae and solenidia of O. sexdentata and O. berlesei was investigated by Chistyakov (1983, 1984), that of O. canadensis was given by Behan-Pelletier and Eamer (2010), and that of O. metzi and O. nortoni was investigated by Behan-Pelletier (2011). Generally, the number of setae on the legs of Oribatella is similar in larva and protonymph, but differs slightly in deutonymph and tritonymph, mainly on femora and tibiae II and IV, independently from geographic distribution of species ( Table 3).

Figures

Figure 5. Oribatella quadricornuta, lateral aspect, legs partially drawn, scale bars 100 µm. (A) Larva; (B) tritonymph.

Figure 15. Oribatella calcarata, adult. (A) Female, dorsal aspect, legs partially drawn, scale bar 100 µm; (B) male, fragment of prodorsum.

Figure 16. Oribatella calcarata, female, legs partially drawn, scale bars 100 µm. (A) Anterior part, lateral aspect; (B) anogenital region.

Figure 17. Oribatella calcarata, tarsus I, antiaxial aspect, scale bars 20 µm, some setae are not illustrated. (A) Female; (B) tritonymph.

Figure 18. Oribatella calcarata, larva, dorsal aspect, legs partially drawn, scale bar 50 µm.

Figure 19. Oribatella calcarata, legs partially drawn, scale bars 50 µm. (A) Anal region of larva; (B) anogenital region of tritonymph.

Figure 20. Oribatella calcarata, tritonymph, dorsal aspect, legs partially drawn, scale bar 100 µm.

Figure 21. Oribatella calcarata, protonymph with seta dm, scale bars 50 µm. (A) Lateral aspect, legs partially drawn; (B) dorsal aspect of gastronotum.

Figure 22. Oribatella calcarata, gastronotum of tritonymph with additional gastronotal setae, dorsal aspect, scale bar 100 µm.