Functional anatomy of oil glands in Collohmannia gigantea (Acari, Oribatida)

Abstract

Chemical and behavioural studies indicated that the oil glands of the Oribatida represented a central organ for protection and semiochemical communication.The hitherto unknown mode of action of these glands and their microscopic anatomy have been investigated in Collohmannia gigantea by histological and SEM techniques. The paired oil glands are located dorsolaterally in the hysterosoma and mainly comprise large intima-lined and sac-like reservoirs which are surrounded by glandular tissue. The reservoirs consist of a single-layered flat epithelium and probably serve for storage of the oil gland secretion only, but not for its production. Each reservoir opens to the body outside via a single pore. Externally, the pores appear as oval-shaped rings of smooth cuticle, moderately projecting from the surface of the notogaster. The pore orifices are supplied with trapdoor-like closing mechanisms, consisting of cuticular flaps which permit reservoir opening by muscles attaching to the posterior part of the reservoir and the inner side of the notogaster. These morphological data, especially the large intimalined reservoirs along with closing mechanisms under muscular control, are consistent with supposed biological roles of oil glands as defensive or alarm pheromonal organs.

Ontogenetic changes in the chemistry and morphology of oil glands in Hermannia convexa (Acari: Oribatida)

“…While in juveniles a clearly glandular active tissue is present, the rudimentary reservoir epithelium in adult oil glands most probably comprises intima-producing modified epidermal cells only. Comparably, the deposition of an intima is also the main function of the reservoir epithelium of oil glands in the large mixonomatan Collohmannia gigantea (Raspotnig et al 2003). However, in contrast to C. gigantea, no secretory tissue surrounding the oil gland reservoirs can be detected in adult H. convexa, and also oil gland pores are externally covered by cerotegument, corroboratively indicating oil gland degeneration, and, consequently, also a possible loss of function.…”

“…Apart from 1,8-cineole, all extracted compounds are well known oil gland secretion products of several species of Astigmata (Kuwahara 1991;Kuwahara et al 1995) and middle-derivative Oribatida Raspotnig et al 2001;Norton 2001, 2003). The occurrence of astigmatid compounds such as neral, geranial and c-acaridial in juveniles of H. convexa indicates that also the Hermannioidea -which are thought to be closely related to Brachypylida (e.g.…”

“…While the chemistry of oil gland secretions in Astigmata, and also the distribution of astigmatid compounds among the Astigmata, is well characterised by a considerable amount of chemical data (Kuwahara 1991;, the study of oil gland secretions in Oribatida has remained fragmentary. Among the potentially astigmatid compounds-possessing oribatid groups, chemical data are restricted to only two species of middle-derivative Mixonomata (Raspotnig et al 2001;Sakata and Norton 2001) and six species of Desmonomata Shimano et al 2002;Sakata and Norton 2003;Raspotnig et al 2004b). Even among the Desmonomata, a key-group in the phylogenetic systematics of Oribatida (Norton 1998), all chemical data hitherto available exclusively focus on oil glands of one superfamily, the Crotonioidea, leaving two other superfamilies, namely the Hermannioidea and Nanhermannoidea, completely uncharacterised.…”

“…Oribatida and Astigmata): oil glands lack in the nearbasal oribatid cohorts (Palaeosomata and Enarthronota) but are present in more-derivative Oribatida (Parhyposomata, Mixonomata, Desmonomata, Brachypylida) and also in astigmatid mites (Norton 1998). In detail, glandulate Oribatida and Astigmata share a common topography and morphological structure of oil glands, sufficiently justifying a position as homologous organs (Van der Hammen 1980), and, in addition, show a striking correspondence in the chemical composition of their secretions: Characteristically, oil gland secretions contain terpenes, aromatics and hydrocarbons in the form of species-specific combinations which are well-suited for chemotaxonomic studies (Leal et al 1989;Sakata et al 1995Raspotnig et al 2001;Norton 2001, 2003). In these investigations, it has become obvious that the evolutionary history of Oribatida and Astigmata is reflected in their oil gland chemistry: hydrocarbons that are widely distributed in oil gland secretions are regarded to represent phylogenetically old and plesiomorphic characters.…”

Oribatid mites as a major dietary source for alkaloids in poison frogs

“…Oribatid mites posses paired exocrine glands (34), called opisthonotal or oil glands, that secrete a wide range of organic compounds, including monoterpenes, sesquiterpenes, aromatics, aliphatic aldehydes, a ketone, fatty acids, fatty acid esters, an alkyl formate, and hydrocarbons (12,(35)(36)(37)(38)(39)(40)(41)(42). The functions of these compounds have been little studied but include alarm signals and chemical defenses (34,38). In the better-studied and closely related mite group Astigmata (not occurring in our samples), compounds from homologous glands also function as aggregation signals and sex pheromones (40).…”