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181.
MECHANICS OF CILIARY LOCOMOTION 总被引:6,自引:0,他引:6
182.
CHRISTOPHER HASSALL CHRIS D. LOWE IAN F. HARVEY PHILLIP C. WATTS DAVID J. THOMPSON 《Ecological Entomology》2010,35(4):514-522
1. The extent to which individuals are parasitised is a function of exposure to parasites and the immune response, which in ectotherms may be associated with temperature. 2. We test the hypothesis that seasonal variation in ectoparasite burden is driven by temperature using an extensive mark‐release‐recapture study of adult Coenagrion puella (L.) (Zygoptera) as a model system. Mite counts were taken both at capture and on a subset of subsequent recaptures over two entire, consecutive breeding seasons. 3. Emergence date was the most significant factor in determining individual differences in mite burden, and mean counts for individuals emerging on the same days showed strong unimodal relationships with time of season. Subsequent recounting of mites on a subset of individuals showed that patterns of loss of mites were similar between seasons. 4. While temperature did not significantly affect mite burdens within seasons and ectoparasite prevalence was very similar across the two seasons, intensity of infection and rate of mite gain in unparasitised individuals were significantly higher in the cooler season. 5. We demonstrate that, while temperature may modulate the invertebrate immune response, this modulation does not manifest in variations in mite burdens in natural populations. 相似文献
183.
Development in the Floating World: Defenses of Eggs and Embryos Against Damage from UV Radiation 总被引:2,自引:0,他引:2
EPEL DAVID; HEMELA KATHERINE; SHICK MALCOLM; PATTON CHRIS 《Integrative and comparative biology》1999,39(2):271-278
Eggs and embryos of many aquatic organisms develop in the watercolumn and can experience ultraviolet radiation with potentiallydeleterious effects. This is especially vexing for floatingembryos that develop in the surface or neuston layer. Radiationdamage can be a particular problem for these embryos since thecell division cycle during the cleavage period is quite shortand often these cycles do not have mitotic checkpoints to insurefaithful transmission of DNA to the daughter cells. This couldresult in cell division with unrepaired DNA in the blastomeres,which could impact embryogenesis and the transmission of thegenome through the germ line. Described strategies to restrictradiation damage include mechanisms to limit oxidative damageand the use of sunscreens such as the mycosporines to curb radiationto sensitive targets. We describe a particularly ingenious useof sunscreens in the tunicate embryo, the use of extra-embryoniccells to shield the embryo from potentially harmful UV-A andUV-B radiation. We also raise questions regarding the natureof UV damage to embryos (is it DNA or also protein) and thecharacteristics of DNA repair in such embryos. It is likelythat unique mechanisms are present in floating embryos thatdevelop in this air-water interface to assure that cell andgenomic integrity are maintained in this challenging environment. 相似文献
184.
The ectoparasitic snail Sayella laevigata was first describedby
Orbigny (1842) and first placed in the genus Sayella by Odé
(1994) without discussion. This study provides justificationfor this
assignment to the genus Sayella Dall, 1885 and to the
subfamilySayellinae Wise, 1996. Sayella laevigata
possesses an elongatepenis, with subapical swelling tapering to a
short terminalnipple, that is characteristic of the genus. 相似文献
185.
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188.
Evergreen leaf respiration acclimates to long-term nocturnal warming under field conditions 总被引:1,自引:0,他引:1
DAN BRUHN JOHN J. G. EGERTON BETH R. LOVEYS MARILYN C. BALL 《Global Change Biology》2007,13(6):1216-1223
Acclimation of plant respiration rates (R) to climate warming is highly variable and many results appear contradictory. We tested the recently suggested hypotheses that pre‐existing, long‐lived leaves should exhibit a relatively limited ability for R to acclimate to climate warming, and that acclimation would occur via changes in the short‐term temperature sensitivity of respiration. Seedlings of a subalpine, evergreen tree species (Eucalyptus pauciflora) were grown under naturally fluctuating conditions within its natural distribution. We used a free air temperature increase (FATI) system of infra‐red ceramic lamps to raise night‐time leaf temperatures by 0.3±0.1, 1.3±0.1, and 2.2±0.1 °C above ambient for 1 year. Light‐saturated assimilation rates and plant growth did not change with nocturnal FATI treatments. Leaf R measured at prevailing temperatures did not differ between FATI treatments. Within each FATI treatment, nocturnal leaf R was highly sensitive to artificial temperature changes within minutes, and also correlated strongly with natural nocturnal and seasonal temperature variation. The corresponding values of Q10 of R varied according to time scale of measurements, but did not vary between FATI treatments. Instead, acclimation of R to nocturnal FATI occurred through changes in the base rate of respiration. 相似文献
189.
MIAO MIAO WEIBO SONG JOHN C. CLAMP KHALED A.S. AL-RASHEID ABDULAZIZ A. AL-KHEDHAIRY SAUD AL-ARIFI 《The Journal of eukaryotic microbiology》2009,56(3):244-250
ABSTRACT. The systematic relationships and taxonomic positions of the traditional heterotrich genera Condylostentor, Climacostomum, Fabrea , Folliculina, Peritromus , and Condylostoma , as well as the licnophorid genus Licnophora , were re-examined using new data from sequences of the gene coding for small subunit ribosomal RNA. Trees constructed using distance-matrix, Bayesian inference, and maximum-parsimony methods all showed the following relationships: (1) the "traditional" heterotrichs consist of several paraphyletic groups, including the current classes Heterotrichea, Armophorea and part of the Spirotrichea; (2) the class Heterotrichea was confirmed as a monophyletic assemblage based on our analyses of 31 taxa, and the genus Peritromus was demonstrated to be a peripheral group; (3) the genus Licnophora occupied an isolated branch on one side of the deepest divergence in the subphylum Intramacronucleata and was closely affiliated with spirotrichs, armophoreans, and clevelandellids; (4) Condylostentor , a recently defined genus with several truly unique morphological features, is more closely related to Condylostoma than to Stentor ; (5) Folliculina, Eufolliculina , and Maristentor always clustered together with high bootstrap support; and (6) Climacostomum occupied a paraphyletic position distant from Fabrea , showing a close relationship with Condylostomatidae and Chattonidiidae despite of modest support. 相似文献
190.
JOHN P. THORPE 《Biological journal of the Linnean Society. Linnean Society of London》1989,37(4):335-344
Published data on mean rates of genetic divergence for a substantial number of protein molecules is used to examine the hypothetical effect of variations in these rates upon the expected relationship between evolutionary time and Nei's (1972, American Naturalist, 106: 283) genetic distance, D. Results indicate that at higher values D can be expected to deviate significantly from stochastic linearity with time. However, over the sort of time scale over which D values are normally estimated, deviation is slight and likely to be insignificant when compared to other potential sources of error. It is concluded that for most practical purposes interprotein differences in mean rates of amino acid substitution need not be taken into account when calibrating genetic distance estimates against evolutionary time. 相似文献