Studies on the function of the tritosternum in selected Gamasida (Acari)

Abstract

Observations on the feeding behavior of Parasitus coleoptratorum (L.) and Glyptholaspis americana (Berl.) revealed that the tritosternum functions in concert with the capitular groove of the gnathosoma as a fluid transport and grooming mechanism. Excess prey fluids overflowing into the postcapitular channel are redirected to the prebuccal region between the tritosternal laciniae and the capitular groove, preventing loss of food material.Surgical removal of the tritosternum results in an overflow of fluids from the region behind the tritosternal remnant onto the sternal area. Feeding efficiency studies on normal and tritosternectomized P. coleoptratorum showed that mites which lack a tritosternum feed on significantly more prey than do normal individuals. It is postulated that this increase reflects impairment of feeding efficiency and resultant food loss during each feeding episode.Grooming of the capitular groove is accomplished through the combined raking action of the lacinial pili and the deutosternal denticles. Substantial accumulations of debris were observed only in the capitular grooves of tritosternectomized mites.

Some noteworthy features of the chelicerae and subcaptulum of Phytoseiulus longipes Evans (Acari: Mesostigmata: Phytoseiidae), with observations on the preoral channel in the Phytoseiidae

“…The number of denticles (up to 5, frequently 4) per scale in P. Iongipes is also unusual in the Phytoseiidae, which more commonly have 2 or 3, but this is still a relatively small number of denticles and a relatively narrow groove for the free-living Mesostigmata in general. These features may be consistent with the apparent absence of excess flow of liquid food during the feeding process of phytoseiids (Flechtmann and McMurtry, 1992a) in contrast with species of Mesostigmata which induce much liquid flow from their prey and apparently are able to redirect to the mouth area significant portions of this excess liquid food (Wernz and Krantz, 1976). …”

Observations on pollen processing byPneumolaelaps longanalis (Acari: Laelapidae), a mite associate of bumblebees

“…Based on earlier research on feeding mechanisms in gamasid mites (Wernz and Krantz, 1976), it appears that these substances are dissolved by salivary secretions that are directed over the rotating pollen-grain surface, and then recaptured and redirected to the preoral cavity via the fluid transport system formed by the capitular groove (Fig. la, cg) and overlying tritosternum (tr).…”

Gross morphology, histology, and ultrastructure of the alimentary system of Ricinulei (Arachnida) with emphasis on functional and phylogenetic implications

“…The latter were important to define the different types of acarine gnathosomata (e.g., Hammen,1979,1989; Alberti and Coons,1999; Alberti,2006). Nothing is known about the functional relevance of the infracapitular gutter of Ricinulei, which is known to be involved in the feeding process in Gamasida (see Wernz and Krantz,1976). Without data about these characters in ricinuleids, final considerations about homology concepts are not possible so far.…”