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At least 181 records · Page 10Linked to original sources
PubMed1980

DNA-content in isolated nuclei of postembryonic stages of progeny from normal and irradiated males of Tetranychus urticae Koch (Acari, Tetranychidae).

The 1C DNA-content of isolated nuclei of postembryonic stages of Tetranychus urticae stained with the classic and a modified Schiff's reagent was cytophotometrically estimated as 0.1 pg, a low value in animals. For many tissues of this arrhenotokous species the ploidy ratio between males and females is 1:2, indicating the absence of sex-related differences in ploidy.--In addition, DNA measurements were performed to evaluate irradiation-experiments, starting with X-irradiation of mature sperm in males with doses known from previous work to induce chromosomal fragments that are subject to loss and missegregation in the embryonic mitotic stages of the female progeny despite the presumed holokinetic nature of the chromosomes. The DNA-content of the nuclei of the surviving postembryonic preadult stages did not indicate the occurrence of nuclei with in-between male/female values, ruling out loss and missegregation of fragments as important factors in postembryonic lethality. Abnormally low DNA-values in some adult females could be attributed to development of embryos before oviposition caused by radiation-induced effects.

Acari↗
PubMed1992

Molecular approach in spider mites (Acari: Tetranychidae): preliminary data on ribosomal DNA sequences.

DNA sequence data were used to examine phylogenetic relationships between six species of economically important Tetranychidae mites: Eotetranychus carpini (Oudemans), E. pruni (Reck), Tetranychus pacificus McGregor, T. mcdanieli McGregor, T. turkestani Ugarov & Nikolski and T. urticae Koch. With primers directed toward conserved elements flanking the target region, the Polymerase Chain Reaction was used to amplify the ITS2 spacer of the ribosomal DNA molecule. The nucleotide sequence of a 300-bp fragment of the ITS2 was determined by direct sequencing and nucleotide divergence used for intra-generic comparison in mites. The resulting phylogenetic tree expressing interspecific relationships in genus Tetranychus agrees with morphological data. The study demonstrates the usefulness of the approach in the assessment of the systematics and evolution of the group.

Acari↗
PubMed2006

Microhabitat selection in the simple oribatid community dwelling in epilithic moss cover (Acari: Oribatida).

The moss cover of a roof was studied as the model of a simple habitat divided into microhabitats by the members of a community of saprophagous mites. This community consisted of two species of oribatid mites: Scutovertex minutus and Trichoribates trimaculatus. They were extracted from moss onto moist paper, and subsequently, their mobility, responses to moisture fluctuation, and food selection were tested in laboratory experiments. For the nutritional biology, the microanatomy of their alimentary tract was examined according to the system of histological characteristics formulated in the laboratory of the author (type of food, digestive activity of gut walls, etc.). The paraplast sections of the mites were stained by Masson triple stain for these purposes. Moreover, the enzymological tests (chitinase and cellulase activities) were performed to detail the digestive processes. Such an approach was applied to field-sampled specimens as well as to those in the laboratory experiments. These above-mentioned data were discussed with respect to microhabitat selection, vertical and horizontal distribution, and dispersal ability of these two oribatid mites sharing this habitat. These two species differ in several characteristics from each other and these differences resulted in their different microhabitat choices and role in the habitat as a whole.

Acari↗
PubMed2005

Oribatid mite (Acari, Oribatida) feeding on ectomycorrhizal fungi.

The coexistence of a large number of soil animals without extensive niche differentiation is one of the great riddles in soil biology. The main aim of this study was to explore the importance of partitioning of food resources for the high diversity of micro-arthropods in soil. In addition, we investigated if ectomycorrhizal fungi are preferentially consumed compared to saprotrophic fungi. Until today, ectomycorrhizal fungi have never been tested as potential food resource for oribatid mites. We offered six ectomycorrhizal fungi [Amanita muscaria (L.) Hook., Boletus badius (Fr.) Fr., Cenococcum geophilum Fr., Laccaria laccata (Scop.) Fr., Paxillus involutus (Batsch) Fr. and Piloderma croceum J. Erikss. & Hjortstam], one ericoid mycorrhizal fungus [Hymenoscyphus ericae (D.J. Read) Korf & Kernan] and three saprotrophic fungi [Agrocybe gibberosa (Fr.) Fayod, Alternaria alternata (Fr.) Keissl. and Mortierella ramanniana (A. Møller) Linnem.] simultaneously to each of the mainly mycophagous oribatid mite species Carabodes femoralis (Nicolet), Nothrus silvestris Nicolet and Oribatula tibialis Nicolet. The ericoid mycorrhizal fungus H. ericae and the ectomycorrhizal fungus B. badius were preferentially consumed by each oribatid mite species. However, feeding preferences differed significantly between the three species, with O. tibialis being most selective. This study for the first time documented that oribatid mites feed on certain ectomycorrhizal fungi.

Acari↗
PubMed2005

Influence of selected fruit tree pollen on life history of Euseius stipulatus (Acari: Phytoseiidae).

Euseius stipulatus (Athias-Henriot) is a predatory mite widespread in the Mediterranean region considered to be important for the biological control of spider mites in citrus orchards. Development, survival and reproduction of this phytoseiid mite feeding on seven commercially obtained pollen were studied under constant laboratory conditions (20 +/- 1 degrees C, RH 65 +/- 5%, photoperiod 16L: 8D h). Mites were kept individually at rearing units with ample quantity of almond (Prunus amygdalus Batch), apple (Malus domestica Borkh), apricot (Prunus armeniaca L.), cherry (Prunus avium L.), pear (Pyrus communis L.), plum (Prunus domestica L.) and walnut (Juglans regia L.) pollen as food source. Developmental time from egg to adult varied between the several pollen tested from 8.38 +/-0.08 to 9.58 +/- 0.11 days for females and from 8.23 +/-0.12 and 9.07 +/-0.12 days for males. Female longevity varied from 11.53 +/- 1.22 to 51.38 +/- 2.45 days, while fecundity ranged from 22.84 +/- 2.30 to 43.61 +/- 3.78 eggs/female. The predator was unable to reproduce when feeding on walnut pollen. Data were submitted to life table analysis and values of the intrinsic rate of increase were derived, ranging from 0.079 to 0.146 (day(-1)). The cumulative Weibull function that was used to describe the age specific survival of females produced excellent fits to the survival data. Results show that almond, plum, cherry and apricot pollen possess higher nutritional value for E. stipulatus than pear and apple pollen and thus may contribute in sustaining and increasing the predator population in field conditions. Walnut pollen can be utilized by the predator only to survive during short periods of time when principal or alternative food sources are scarce.

Acari↗
PubMed2006

Biological cycle of Lorryia formosa (Acari, Tydeidae) on rubber tree leaves: a case of thelytoky.

Lorryia formosa Cooreman has been collected on many different host plants around the world. The biological cycle of this species was studied at 28 degrees C with mites collected from a rubber tree crop. The life table was constructed based on sixty individuals. The average lifetime was 37.43 +/- 20.23 (SE) days, and the r(m) was 0.08. The sex ratio was totally female biased, and unfertilized eggs developed into females. This is the first record of thelytoky in Tydeoidea proved by rearing.

Acari↗
PubMed2006

Side effects of five new acaricides on the predator Galendromus occidentalis (Acari, Phytoseiidae).

Contact and residual effects of etoxazole, spiromesifen, fenpyroximate, bifenazate, and acequinocyl on life parameters of Galendromus occidentalis (Nesbitt) were studied under laboratory conditions. Fenpyroximate reduced adult female longevity to <24 h, and no eggs were laid. Longevity of spiromesifen- and acequinocyl-treated adult females was reduced to 4 days, with observed reductions in fecundity and fertility. Etoxazole and bifenazate did not reduce adult female longevity, but progeny were not produced.

Acari↗
PubMed1995

Cuticular hydrocarbon variation and progeny phenotypic similarity between laboratory breeds of allopatric populations of Argas (persicargas) persicus (oken) (acari: argasidae).

Cuticular hydrocarbons of laboratory breeds of four Argas (Persicargas) persicus (Oken) population samples were studied by gas chromatography. Cuticular hydrocarbon patterns were used to determine Nei's genetic distances among populations, and their average heterozygosity. Sixteen n-alkanes, 37 monomethylalkanes and 26 dimethylalkanes were identified. Mostly quantitative differences were recorded between populations, rarely among males and females of the same population. A low genetic distance (0.0278-0.0781) together with a prominent degree of average heterozygosity (60.37-66.98%) were recorded in the population samples studied. When crossbreeds with adult specimens from the same or different geographical origins are performed, all larval progenies closely correlated within themselves and with their parents in hydrocarbon pattern. A slight matrocliny occurred in larvae coming from crosses of the same geographical source. From cross data it is postulated that hydrocarbons in A. persicus are inherited under a two dominant alleles hypothesis.

Acari↗
PubMed1979

Fate of fragments and properties of translocations of holokinetic chromosomes after X-irradiation of mature sperm of Tetranychus urticae Koch (Acari, Tetranychidae).

After irradiation of mature sperm in males of Tetranychus urticae, early cleavage stages were scored for chromosome fragments. As expected from the presumed holokinetic nature of the chromosomes, the majority (94.29%) of the fragments pass mitosis without difficulty. A minority of the fragments is affected by loss (4.76%) or missegregation (0.95%), leading to loss of fragments from cells in a large fraction of fragment-containing eggs after a few divisions. Lethality induced by the irradiation treatment can probably be ascribed to these losses. When meiotic configurations of F1 females are analysed, translocations turn out to be the most frequent type of aberration, often accompanied by recessive lethal mutations, thus adding an extra amount of lethality to the already high number of non-viable haploid offspring of heterozygous F1 females. The frequently occurring infecundity of the F1 females may be caused by mechanical problems in early stages of meiosis (before oviposition), when multivalents are not able to perform the specific turning movements typical for this type of chromosome. According to calculations, univalents in meiotic stages are thought to represent translocated chromosomes rather than independent fragments.

Acari↗