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Background: The aquatic Acari are known as water mites and occupy a wide range of habitats. The freshwater mites, Unionicola aegyptiaca, were collected from the freshwater mussel, Caelatura aegyptiaca, River Nile, Sohag, Egypt. The present paper focuses on the structure of the cuticle and musculature of freshwater mite, U. aegyptiaca. Results: Histologically, the cuticle consists of two main layers: epicuticle and procuticle. The latter divided into two sublayers, exocuticle (exo) and endocuticle (en). The musculature of the present species, U. aegyptiaca, is divided into three regions: gnathosoma, idiosoma, and legs. The muscles of the body are classified according to their position and function. Conclusion: Details of muscles of gnathosoma, coxal epimerae, genital field, and legs were all described and discussed. The cuticle and musculature of U. aegyptiaca were studied by using the light microscope, and the drawings were down with the help of a camera Lucida. It is likely to note that the cuticle and musculature of freshwater mite, U. aegyptiaca, were described and discussed for the first time in Egypt. [ABSTRACT FROM AUTHOR]

The mitochondrial genome of Unionicola parkeri is a 14,734 bp circular DNA molecule. The sequence and annotation revealed a unique gene order, related to but distinct from the gene order in the closely related species U. foili. Mitochondrial tRNA sequences annotated in this genome predict non-canonical secondary structures for these molecules. The continuing patterns of unique gene orders and unusual tRNA structures in the Trombidiformes in general and Unionicola in particular support the use of phylogenetic approaches that use these types of molecular features as shared, derived character states. Further progress in using these molecular character states to reconstruct phylogeny will depend on careful annotation, especially of tRNA genes. [ABSTRACT FROM AUTHOR]

The mitochondrial genome of Unionicola foili is circular, 14,738 bp in length, and contains several notable features. The sequence and annotation revealed a unique gene order, continuing a pattern of highly rearranged mitochondrial genomes in the Trombidiformes. U. foili mitochondrial tRNA sequences predict non-canonical secondary structures for these molecules, and our annotation suggests an in-frame fusion between the nad4L and nad5 genes in this genome. The unique gene order and unusual tRNA structures could serve as idiosyncratic characters and have the potential to be phylogenetically informative. [ABSTRACT FROM AUTHOR]

Examines the georesponses and photoresponses of larval Unionicola foili to chemical substances from chironomids and mussels. Responses of larval Unionicola foili to light and gravity during larval ontogeny; Exhibition of host-induced negative photoaxis; Pattern of larval Unionicola foili responses.

Unionicolid water mites inhabit freshwater unionid mussels during the nymphal and adult stages of their life-cycle. Regular sampling of mussels from two sites in St. Mark's River, Fl. established that each of four species of water mite ( Unionicola abnormipes, U. fossulata, U. serrata and U. formosa) occurred mainly in one or two of the mussel species available at each site. The role of preference for particular mussel species during host location was assessed for the first three mite species by choice experiments, in which mites were offered different mussel species simultaneously. In five out of six experiments, mites entered normally unused mussels as often as they did normally used ones. Additionally, a sexual difference in choice was found for U. fossulata, with males preferring one mussel species and females showing no preference. One mussel species, ( Anodonta imbecilis), normally unused but chosen by mite species during the lab. experiments, is inhabited exclusively by the fourth mite species, U. formosa, in the field. An experiment showed that U. formosa excludes other mite species aggressively from Anodonta imbecilis. The results illustrate the sometimes misleading nature of simple sampling data as an indication of host specificity or host preference in parasites. They suggest also that the population dynamics of some parasites might be more fruitfully compared to unrelated, free-living species than to other parasites. [ABSTRACT FROM AUTHOR]