Gabriele Thomas

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The role of volatile semiochemicals in mediating the location and selection within herds of Holstein-Friesian heifers by nuisance and disease-transmitting cattle flies was investigated using coupled gas chromatography-electrophysiology (GC-EAG), coupled gas chromatography-mass spectrometry (GC-MS), electrophysiology (EAG), laboratory behaviour and field(More)
Summer mastitis is an acute suppurative bacterial infection of the udder in heifers and dry cows. To ascertain the possible role of flies in the transmission of the disease, experimental exposures of recipient heifers to Hydrotaea irritans previously exposed to bacteria were carried out. Flies were allowed to feed on secretions from clinical cases of summer(More)
The distribution of horn flies, Haematobia irritans (L.) (Diptera: Muscidae), in herds of Danish Holstein-Friesian cattle was investigated in two studies conducted during two field seasons. In the first study, highly significant differences in fly distribution between the most and the least fly-susceptible heifers were observed. In one herd, the mean(More)
Many non-biting muscids (filth flies) are characterised by the habit of visiting manure or rotting organic material to feed and/or oviposit. As these flies also often have close associations with human beings, as well as human habitations and domestic animals, they are potentially both a nuisance and a contributory factor in the transmission of diseases.(More)
 The ”Dorsalorgan” of pentastomids is an embryonic gland. With respect to a general revision of the glandular equipment of pentastomids and its synonyms the term embryonic gland, first mentioned by Esslinger in 1968, or glandula embryonalis (original) appears to be most suitable. Thus, this terminology may no longer lead to confusion of these glands with(More)
The ultrastructure of accessory genital glands in Raillietiella sp. is described and their function is discussed. In females we assume that they reactivate sperm, which are stored in the receptacula seminis after copulation. In males we think they are primer-pheromone glands, which inject secretions into the female during copulation and stimulate the(More)
The midgut of Raillietiella sp. was investigated ultrastructurally in different ontogenetic stages from the intermediate (cockroach) and the final host (small lizards). In the embryo the midgut anlage is an accumulation of cells filled with glycogen granules. During embryogenesis the cells organize and form a narrow tube. During postembryogenesis the(More)
The ionic glands of Raillietiella sp. were investigated ultrastructurally in different ontogenetic stages. Modifications of the ultrastructure, number, and distribution of ionic glands were observed after the invasion of the primary larvae into the invertebrate intermediate host and after the invasion of the infective larvae into the vertebrate final host.(More)
In Raillietiella sp. larvae we discovered a gland whose duct pores shed their secretion caudally of the mouth onto the integument. This gland type, which we call the suboral gland, seems to be characteristic of all pentastomid species. We discuss its possible function in the invasion of the larvae into the intermediate host. Furthermore, we identified(More)