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Aribatidae, a new myrmecophilous oribatid mite familyfrom JavaJun-ichi Aoki a , Gen Takaku b & Fuminori Ito ca Institute of Environmental Science and Technology, Yokohama National University,Yokohama, 240, Japanb Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo,060, Japanc Biological Laboratory, Faculty of Education, Kagawa University, Takamatsu, 760, Japan

Version of record first published: 17 Mar 2009.

To cite this article: Jun-ichi Aoki, Gen Takaku & Fuminori Ito (1994): Aribatidae, a new myrmecophilous oribatid mite familyfrom Java, International Journal of Acarology, 20:1, 3-10

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Vol.20, No.1 Internat. J. Acarol. 3

ARIBATIDAE, A NEW MYRMECOPHILOUS ORIBATID MITE FAMILY FROM JAVA

Jun-ichi Aoki, 1 Gen Takaku 2 and Fuminor i Ito 3 1. Institute of Environmental Science and Technology, Yokohama National University, Yokohama 240, Japan. 2.

Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060, Japan. 3. Biological Laboratory, Faculty of Education, Kagawa University, Takamatsu 760, Japan.

ABSTRACT - A new oribatid mite, Aribates javensis gen. et sp. nov., is described from ant nests in West Java, Indonesia. It is quite peculiar in lacking sensilli as well as in the variable number of anogenital setae. A new family, Aribatidae, is erected for this species. An interesting mutualistic relationship is found between the mite and the ant Mynnecina sp.

INTRODUCTION

In 1993, one of the authors, F. Ito, found a curious species of oribatid mite in the nests of ants in Bogor, West Java. The soft-bodied and slowly moving mites inhabit only the nests ofMyrmecina sp. and a mutualis- tic relationhip is found between them (Ito and Takaku, in press). The mite is morphologically unique and is described below as a new species representing a new genus and a new family.

Aribatidae fam. nov.

Diagnosis - Adult with rounded body, strongly swollen and very weakly sclerotized. Prodorsum with rostral, lamellar and exobothridial setae but without lamellae, sensilli and also often without interlamellar setae. Bothridia absent or vestigial, concealed under the body surface. Notogaster with 10 pairs of long, simple setae. Neither areae porosae nor sacculi present. Pteromorphae absent. Genital and anal aper- tures widely separated. In most cases, 7-8 pairs of geni- tal setae, 3-4 pairs of anal setae and 4-5 pairs of adanal setae. Only 2 pairs of genital papillae present. All legs monodactyle.

Type genus -Aribates gen. nov. Remarks - As to the systematic position of

Aribatidae, it is only clear that it belongs to Ap- terogasterina of Brachypylina. In this group the ab- sence of scnsilli occurs very rarely, only in some genera of the family Ameronothridae. The anogenital chaetotaxy in the family Ameronothridae is, however,

usually 6-1-2-3, not as numerous and variable as in the new family. In other families of the apterogasterine oribatids the number of genital setae is at most 6 pairs but exceptionally 7 pairs in the families Gymno- damaeidae, Plateremaeidae, Hermanniellidae, Phero- liodidae, Idiodamaeidae, Pedrocortesellidae, Lyrifis- siellidae and Liodidae and 8 pairs in Nooliodidae. Ap- terogasterine oribatids bear usually at most 2 pairs of anal setae but exceptionally have 3 pairs in Herman- niellidae, Liodidae, Idiodamaeidae, Pheroliodidae, Nooliodidae and Eremaeidae, 4 pairs in Platere- maeidae, 5 pairs or more in Plateremaeidae, Carabo- didae (genus Carabodella) and Eremaeidae (Balogh and Balogh, 1992). However, all these families have distinct bothridia with sensilli, a less swollen hysterosoma and more strongly sclerotized cuticle.

All measurements are given in micrometers.

Aribates gen. nov.

Diagnosis - Same as that of the family. Type species -Aribates javensis sp. nov. Etymology - The name Aribates is constituted of

"Ari," the Japanese word meaning ant, and Oribates.

Aribates javens is sp. nov.

(Figs. 1-24)

ADULTS : Measurement - Body length 660 - 710 (685), width

430 - 580 (511), height 450 - 580 (545) (numbers repre-

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Vol.20, No.1 Internat. J. Acarol. 5

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Figs. 6-8. Aribates javensis sp. nov. - 6. leg IV, 7. leg I, 8. lateral view of mite.

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Figs. 9-14. Photos by SEM ofAribates javensis sp. nov. - 9. dorsal view of mite, 10. lateral view of mite, 11. dorsal view of prodorsum, 12. dorsal view of rostrum (R- rostral tip, ro - rostral seta, rm - flat rim of rostrum), 13. laterodorsal view of prodorsum showing vestigial bothridium (vb) and exobothridial seta (ex), 14. laterodorsal view of notogaster showing lyrifissures ( im) and lateroabdominal gland opening (gla).

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Figs. 15-20. Photo by SEM ofAribates javensis sp. nov. - 15. ventral side of mite (G- genital opening, A - anal opening), 16. genital opening (arrow showing anterior direction), 17,18. ovipositor (ov) protruding from genital opening, 19. anal opening (arrow showing anterior direction), 20. lateral view of posterior part of body.

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Figs. 21-24. Photo by SEM ofAribates javensis sp. nov. - 21. ventral view of gnathosoma, 22. epimeral region, 23-24. leg I.

Table. 1. Variation in the number of setae in anogenital region ofAribates javensis sp. nov. The figures show the number of setae on the left and the right sides of individual adult mites.

Genital setae Aggenital setae Anal setae Adanal setae L - R L - R L - R L - R

11-8 2-3 6-4 5-5 10-7 2-2 4-6 5-5 9-8 2-2 4-4 5-5 8-8 2-2 4-4 5-4 8-8 2-1 4-3 4-5 7-9 2-1 4-3 4-5 8-7 2-1 4-3 4-5 7-8 2-1 3-4 4-4 7-7 1-2 2-4 4-4 7-5 1-1 2-4 4-4

1-1 3-3 4-4 1-1 3-3 3-4 1-1 2-3 1-1 1-1 1-1

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sent a range with an arithmetic mean in parentheses based on measurement of 20 females and males).

Integument and color - Entire cuticle weakly sclerotized. Texture weakly and finely wrinkled (Fig. 9), with dense, minute, porosity. Integument color light yellow-brown.

Prodorsum - Rostrum pointed, with a fiat rim on each side (Figs. 1, 12). Rostral, lamellar and ex- obothridial setae thin and simple; ro a little longer than their mutual distance; le twice as long as ro; right and left le often located asymmetrically, one seta anterior to the other (Fig. 1); ex shorter than ro. Interlamellar setae absent (totally absent without alveolar vestige) in most cases (Fig. 11), rarely present as very short setae (Fig.l). Bothridia vestigial, discernible only as a low knot of irregular shape (Figs. 4,5,13), or completely absent. Sensilli completely absent. Neither lamellae nor costulae found on prodorsum.

Notogaster - Nearly hemispherical (Fig. 10). Anteriorly protruding very strongly like a "beret." Usually with 10 pairs of notogastral setae, sometimes additional seta (or setae) present haphazardly in dor- socentral region (Fig. 1). Setae of t- series, m s and r- series nearly equal in length, those of p- series being somewhat shorter. RLN (relative length to notogaster) of notogastral setae: ta 41-43, te 40-43, ti 41-43, m s 42-45, ri 42-44, r2 38-42, r3 36-44,pl 33-39, p2 33-38, p3 26-31. Orifice of lateroabdominal gland (gla) lo- cated posterior to te and lyrifissure im present as a small pore anterolateral to te (Figs. 8,14).

Anogenital region - Genital and anal openings widely separated, nearly of the same size. Genital open- ing narrow anteriorly, and anal opening narrow posteriorly (Fig. 15). Number of setae on anogenital region highly variable as shown in Table 1. Genital plate usually with 7 or 8 setae, posterior setae distinctly longer than anterior setae (Figs. 2,16); number of geni- tal setae variable from 5-11, often differing on left and right sides. Only 2 pairs of genital papillae present. Ovipositor short and thick, with 3 triangular projections each with 2 long setae. Anal plate usually with 3 or 4 thick, long setae, also variable from 2-6 (Figs. 3,19). Aggenital and adanal setae also variable in number, the former usually 1 or 2 (rarely 3) and the latter usually 4 or 5 (rarely 3) on one side. Ventral plate strongly convex like notogaster, the surface with fine wrinkles.

Epimeral region - Left and right epimeral plates fused together on epimerata I and II, those of epimerata III and IV separated by a distinct longitudinal furrow. Epimerata III and IV on each side fused together into a single plate. Setal formula of epimerata: 3-1-3-4. Setae la, lc and 2a very short, while other setae long and prominent.

Mouth parts - Hypostomal setae (h) long, straight and thick, 0.6-1.2 x as long as their mutual distance.

Infracapitular setae, a pair of a and 2 pairs of m, short and spine-like, especially setae a very small. Chelicera small, 1/7.2- 1/7.6 as long as body, anterior portion slender, half as thick as posterior portion. Seta cha twice as long as chb. Tip of movable digit extending slightly beyond tip of immovable digit. Palp 5- seg- mented, palpal tarsus nearly as long as femur. Chaetotaxy: 0-2-1-2-7.

Legs - Femora I and II longer than femora III and IV, other segments (genua, tibiae, tarsi) mostly similar in length in legs I, II, III and IV. Ta > Fe > Ti > Ge. Leg chaetotaxy (Tr-Fe-Ge-Ti-Ta): I (2-5-3-5-12), some- times (1-5-3-5-12), (2-4-3-5-12), (2-5-3-5-13); II (3-5-3- 4-10), sometimes (4-5-3-4-10), (3-4-3-4-10), (3-5-3-4- 11); III (1-3-2-4-9), sometimes (1-3-2-4-11); IV (1-2-2- 4-11), sometimes (2-2-2-4-11), (1-2-2-5-11), (1-2-2-4- 10). Solenidiotaxy: I (0-0-1-2-2), II (0-0-1-1-2), III (0- 0-1-1-0), IV (0-0-0-0-0), sometimes (0-0-0-1-0). All legs monodactyle, claws broadened in apical half in dorsal view. Solenidia on tibia I inserted close together, side by side (Fig. 23).

IMMATURES: Only i nymph and 4 larvae are available for des-

cription. The specimens are not in good condition and the number is insufficient to make a complete descrip- tion. Only a short note of observation is given here.

NYMPH - Body length 538, width 370. Prodor- sum with 4 pairs of setae. Lamellar setae short, straight, rather blunt at tip, a little shorter than their mutual distance. Rostral setae as long as le but thinner and pointed at tip. Interlamellar and exobothridial setae minute, spine-like, 1/4 as long as le. Bothridia absent. Notogaster with 7 pairs of setae. Genital aperture wrinkled longitudinally, with 3 pairs of setae of which anteriormost pair longer than others. A pair of genital papillae. Anal aperture with 5 setae on right plate and 4 on left. A pair of small aggenital setae. Three pairs of adanal setae, ad3 shorter than ad2 or adl. Only one pair of genital papillae (the nymph is considered a protonymph).

LARVA - Body length 380-385, width 297-310. Prodorsum with 4 pairs of setae. Interlamellar and ex- obothridial setae very short, spine-like, 3/8 as long as lamellar seta. Rostral seta a little thinner and shorter than lamellar seta. One of le often located anterior to others. Bothridia absent. Border between propodo- soma and hysterosoma indistinct. Hysterosoma with 6 pairs of setae. No setae on anal aperture.

It is worthy of notice that the adults have only two pairs of genital papillae because oribatid adults usually have 3 pairs. Although it is uncertain at the present moment but it is possible that A. ]avensis has only one

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nymphal stage (protonymph) and the adults with only 2 pairs of genital papillae correspond to deutonymphs of other oribatid mites sugesting a kind of "neoteny." A further study will explain this very interesting problem.

Type series - Holotype, female, Bogor, West Java, Indonesia, from nest of ant, Myrmecina sp., 22 February 1993, coil- F. Ito. Paratypes, 31 female, male, 1 nymph and 4 larvae, with same data as holotype. Holotype (NSMT-Ac 10483) and 19 paratypes (NSMT- Ac 10484-10493) including 1 nymph and 2 larvae deposited in National Science Museum, Tokyo; 5 paratypes (ZIHU-984) in the Division of Biological Sciences, Hokkaido University; 7 paratypes including 2 larvae in Natural History Museum, London; and 5 paratypes in the Zoological Museum, Bogor, West Java, Indonesia.

BIOLOGY

Ito and Takaku (in preparation) showed that the oribatid mite described in this paper was an obligate myrmecophile of a myrmicine ant, Myrmecina sp. The following is an outline of the bionomics of Atibates javensis which are discussed by them.

Aribates javensis was found only in the nests of a myrmicine ant, Myrmecina sp. Of 30 nests examined, all contained a number of eggs, nymphs and adults of A. javensis. The mites were not found in the samples of soil arthropods collected by hand sorting and Tullgren methods from soil near the ant nests. Also, these mites were never found in the nests of other ant species. In the ant nests, the mites are remarkably inactive. Although their legs are well developed, they never walk alone on the nest floor. The mites are usual- ly deposited on the nest floor within a brood cluster of ants but some mites are attached to decomposing leaves in the ant nests. Mites are often groomed by ant workers in the nests. Ant workers also help oviposition of the mites. The workers pickup mite eggs from the ovipositor and the eggs are deposited on an egg cluster of ants. The mite eggs are often licked by the ant workers along with ant eggs. Mites cannot survive

without ant attendance since they cannot walk by them- selves and they alone, therefore, become infested by fungi.

A few species of the genus Myrmecina specialize in some degree on oribatid mites as prey (Masuko, 1994). Workers of the Japanese ant, M. graminicola nipponica, hunt and bring some species of oribatid mites into their nests and feed them to their larvae. In the case of the Indonesian Myrmecina sp., workers and larvae rarely feed on living A. javensis. However, A. javensis artificially killed were immediately eaten by ant workers, including that the ants feed onA. javensis after their death. In other words, A. javensis give their body as a reward to ants in return for ant care. The relation- ship between the ants and the oribatid mites seems to be mutualistic.

ACKNOWLEDGEMENTS

We thank K. Nakamura, H. Katakura, S. Wirjeat- modjo and the members of the Bogor Zoological Museum for various help in the collection of the mites and LIPI (Indonesia Institute of Science) for permis- sion to conduct this study in Indonesia. The collection of mites by F. Ito was supported in part by the Grant-in Aid for International Scientific Research Program (No. 02041033) from the Japanese Ministry of Education, Science and Culture.

REFERENCES

Balogh, J. and P. Balogh. 1992. The oribatid mite genera of the world. Vol. 1:263 pp and Vol. 2: 375 pp. Hungarian Natural History Museum, Budapest.

Ito, F. and G. Takaku. 1994. Obligate myrmecophily in an oribatid mite: novel symbiont of ants in the Oriental tropics. Naturwissenschaften (in press).

Masuko, K. 1994. Specialized predation on oribatid mites by the ant genus Myrmecina (Hymenoptera: Formicidae). Psyche (in press).

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