Chemical alarm and defence in the oribatid mite Collohmannia gigantea (Acari: Oribatida)

Abstract

The multicomponent oil gland secretion of Collohmannia gigantea, a middle-derivative mixonomatan oribatid mite, is demonstrated to possess alarm pheromonal and allomonal properties. Four components of the secretion, namely the monoterpenes neryl formate, neral, geranial and the aromatic 2-hydroxy- 6-methyl-benzaldehyde (2,6-HMBD), showed moderate to strong alarm pheromonal activity in adult mites. Naturally elicited response is due to neral (about 50% of the secretion) and probably 2,6-HMBD (only 5% of the secretion, but strong alarm pheromonal activity). This is the second report of an alarm pheromone in Oribatida. Tridecane and pentadecane (=the hydrocarbon fraction of the secretion) did not evoke evident behavioural reactions, and most likely serve as solvents and spreading agents for the pheromonal-active components. Alarm reactions were characterized by a short recognition phase (waving movements with legs I), followed by shrinking back and panic escape from the scent source. In addition, all six components of the oil gland secretion, including the hydrocarbons, exhibited strong allomonal properties against a model oribatid predator, the scydmaenid beetle, Euconnus (Tetramelus) oblongus. Considering the widespread semiochemical properties of oil gland secretions in astigmatid mites (=a highly derivative oribatid group), these results furnish evidence for a phylogenetically early origin of defensive and communicative roles of oil gland secretions in oribatids. These roles include alarm communication, defence and the production of anti-fungal compounds.

Oribatid mites and skin alkaloids in poison frogs

“…These glands are present in all but the most primitive oribatid mites and constitute their main exocrine system. Their secretions appear to be taxon-specific, as shown by the large amount of chemical data compiled in the last 15 years [4][5][6][7][8][9][10][11][12][13][14][15].…”

Morphological analysis of the oribatid mite species Scutovertex pannonicus Schuster and description of its juvenile stages (Acari: Oribatida: Scutoverticidae)

“…The subject of aggregation is already known in many other species like Phauloppia lucorum (Oliveira et al 2007), Fortuynia atlantica (Krisper & Schuster 2008), Collohmannia gigantea (Raspotnig 2006) or in some Ameronothridae (Søvik 2004).…”

Storage and release of hydrogen cyanide in a chelicerate ( Oribatula tibialis )

“…The large oil glands, which represent the major exocrine system in oribatid mites and which secrete MNH in O. tibialis, are potent organs for chemical defense, thus playing an important role in the structuring of feeding interactions in soil food webs (24)(25)(26). As with arthropod defensive compounds in general, most known oil gland secretions of oribatid mites-mainly hydrocarbons, terpenes, aromatics, esters, and alkaloids-are probably "class II compounds" (38); i.e., they irritate or repel potential predators without substantial harm (22)(23)(24)(25)(26)(27)(28). By contrast, benzoyl cyanide and HCN are "class I compounds" (38), true and harmful toxins (3,6,39,40).…”

“…Here, we demonstrate cyanogenesis in a mite of the order Oribatida, a diverse and mostly soil-dwelling group of decomposers that discharge myriad defenserelated semiochemicals from a pair of large exocrine opisthonotal oil glands (22)(23)(24)(25)(26)(27)(28). The common and widespread species Oribatula tibialis stores HCN as the natural product mandelonitrile hexanoate (MNH) and releases HCN upon disturbance via two different chemical pathways.…”