Functional morphology of the gnathosoma in the quill mite Syringophilopsis fringilla Fritsch (Acari: Prostigmata: Syringophilidae).

Abstract: The mouthparts of Syringophilopsis fringilla Fritsch have been studied using light and electron microscopy (TEM, SEM). The chelicerae are two-segmented, each comprising the cheliceral body and the movable digit in a form of a piercing stylet. The cheliceral fixed digits are strongly reduced to small projections covering the distal part of the stylets from the dorsal plane. The two cheliceral bodies are completely fused into a stylophore, which is proximally coalesced with the infracapitulum to form a gnathosomatic capsule. At the tip of the gnathosoma, the malapophyses (endites of the palpal coxae) enclose both the stylets and the fixed digits forming a tube-like prelabral cavity. Posteriorly, the labrum divides the internal space of this cavity into the ventrally located preoral groove and dorsally located supralabral cavity. The latter is continuous posteriorly with the median salivary duct containing the secretory product of the coxal glands only. The duct of the unpaired tracheal gland runs dorsally inside the median septum to the tip of the stylophore. The labrum, provided with a pair of muscles, appears to regulate the relationship between the food suction and discharging of saliva. The movement of the cheliceral stylets is realized by the action of both protractor and retractor cheliceral muscles, while the pharyngeal pump is activated exclusively by the dilators. Both food suction and salivary injection appear to be associated with the protraction of the stylets, which apparently form a semi-closed intercheliceral channel but do not show interlocking mechanism. Special features of syringophilid gnathosoma are discussed comparing to those in related Acari. [Copyright &y& Elsevier]