Oribatida

Roczen-Karczmarz, M. & Tomczuk, K., 2016, Oribatid mites as vectors of invasive diseases, Acarologia 56 (4), pp. 613-623 : 616

Oribatida - Biological and morphological requirements for vectors

The efficiency of mites as vectors (alternate hosts of tapeworms) is limited by several factors. They are regarded to be morphological and biological factors ( Shaldybina 1953; Kassai and Mahunka 1965). The biological ones are feeding habits, hygrophily, xe- rophily (these factors are discussed in Conditions affecting Oribatida distribution). The morphological factors are body size, the size of the mouth opening and the structure of the mouth parts. The lower limit of this vector’s size varies between 300 and 400 µm ( Kassai and Mahunka 1965; Graber and Gruvel 1969; Denegri 1989). The representative genus Scheloribates usually has a minimum length of 500 µm, so they are often used in studies of Oribatida as intermediate hosts in tapeworms. This finding was confirmed by the research undertaken by Akrami et al. (2007). The species of 400 and 465 µm in size ( Scheloribates fimbriatus and Galumna iranensis , respectively) contained only 1 cysticercoid in their bodies while the species of a larger size (540 – 567 µm Galumna karajica ) contained up to 7 cysticercoids ( Akrami et al. 2007). Those mites that have less chitin cuticle and a more flexible body, they are capable of swallowing tough food. In such creatures, pollen of similar size to the one of a parasite egg was observed ( Żbikowska-Zdun and Koczara 2013). Schuster et al. (2000) observed that oncosphere in larger mites (in their research Galumna racilis , Kilimabates sp. ) are not developed in such a degree as in the smaller ones ( Scheloribates fusifer, Ceratozetoidea immatures, Muliercula ngoyensis , Zygoribatula undulata ). This may be due to the fact that in larger species ingested eggs pass through the alimentary tract before the oncosphere have hatched ( Ebermann 1976). Trowe (1997) reported that the size of tapeworm larvae decreases with a rising burden of cysticercoids. It is due to the presence of a hard exoskeleton in oribatid mites, preventing a body cavity from expanding. This has been described for cysticercoids of four anoplocephalid cestodes: M. expansa , M. benedeni , A. perfoliata , A. mamillana that were experimentally grown in both Scheloribates laevigatus and S. latipes ( Trowe 1997) . The calculated average volume for cysticercoids of A. perfoliata and A. mammillana were the largest (1.97 and 2.27 × 106 µm 3) for single cysticercoids, less (1.63 and 1.61 × 106 µm 3) for two cysticercoids and the least for three cysticercoids per a mite (1.47 and 1.35 × 106 µm 3) ( Trowe 1997). Schuster and Coetzee (2012) in their experiments used Scheloribates pallidulus as an intermediate host for A. magna and achieved 1.23 × 106 µm 3 for the volume of one cysticercoid per a mite and 0.872 × 106 µm 3 for two and 0.684 × 106 µm 3 of three cysticercoids per a mite. The smaller dimensions of cysticercoids are due to the smaller size of S. pallidulus .