Responses of stem net photosynthetic rate (P^) to irradiance (/), temperature, vapor pressure, CO2 concentration, nitrogen content, and water potential were studied during early spring (March) and mid summer (latě July) in field populations of two stem photosynthesizing species introduced into Coastal California sites. Stem in Spartium junceum was inhibited in the summer compared with the spring due to low water potential and low tissue nitrogen content. Quantum yield decreased from March to July, along with a decrease in the demand fimction of the C, response curves. Stem conductance was lower at all vapor pressure deficits during the summer, but Cj at a Cg of 350 pmol moE* increased for S. junceum from spring to summer. The thermal optimum for stem did not change between the two seasons, but that of S. junceum was 5 °C higher than that for Cytisus scoparius. The demand function for the Cj curves of C. scoparius also decreased from spring to summer, but the Cj at a Cg of 350 pmol moT* remained unchanged between the seasons. Thus, the water use efficiency of S. junceum decreased in the summer compared with that of the spring while that of C. scoparius remained unchanged between seasons. There was little evidence for compensatory acclimation of stem F^ to changes in climatic conditions in these species.
The seasonal activities of the European pigeon tick, Argas reflexus, in Berlin were investigated (a) by trapping locomotory active ticks and (b) by determining the occurrence of tick-invasions into human habitations. Tick trapping was carried out in two tick-infested attics in 1988. Pigeons were available for ticks in one of the attics only, while a previously existing bird colony was expelled from the other. Ticks were trapped by means of smooth V- shaped metal gutters cemented to the attic walls. Trapped nymphal and adult ticks were marked and released into cracks of the attic wall inside the rectangular traps in two-weck-intervals. During the one-year-study a total of 2081 ticks was trapped, 83% of which were larvae, 10% nymphs, 4% females and 3% males. Only 4.4% of the 366 ticks marked were recaptured. There is strong evidence that locomotor activities of A. reflexus were restricted to host-seeking and returning to a resting-site after a blood meal. Activities of all postembryonic stages peaked from March through early June, irrespective of whether or not hosts were available to the ticks. The immature stages displayed another peak of activity in late summer/autumn. A total of 51 cases of A. reflexus-infested buildings was reported from the public to public-health offices in Berlin from April 1989 to March 1993, 45 of which represented tick invasions into human habitations. About 60% of them occurred in spring, thus largely confirming the results of seasonal trapping.
Ecosystem photosynthetic characteristics are of utmost importance for the estimation of regional carbon budget, but such characteristics are not well understood in alpine regions. We collected CO2 flux data measured by eddy covariance technique over an alpine dwarf shrubland on the Qinghai-Tibetan Plateau during years 2003-2010; and we quantified the temporal patterns of ecosystem apparent quantum yield (a), saturated photosynthetic rate (Pmax), and ecosystem dark respiration (RDe). Results showed that the strong seasonality of a and RDe was driven mainly by air temperature (Ta), whereas that of Pmax was much more determined by leaf area index rather than abiotic factors. Diurnal thermal fluctuation inhibited significantly the daytime photosynthetic capacity. Stepwise regression revealed that the seasonal deviations of a, Pmax, and RDe were significantly controlled by Ta. The annual a was regulated mainly by annual growing season Ta, which indicated that the response of ecosystem a was instant. The annual variations of Pmax correlated positively with soil temperature 5 cm below ground (Ts) of the annual nongrowing season and those of RDe related negatively with the annual nongrowing season precipitation. We suggested that a lagged response regulated the annual Pmax and the annual RDe. Annual deviations of a and RDe were both significantly controlled by annual Ts, and those of Pmax were marginally determined by annual PPFD. Thus, the future warming scenario, especially significant for nongrowing seasonal warming in the Qinghai-Tibetan Plateau, would favor ecosystem photosynthetic capacity in the alpine dwarf shrubland., H. Q. Li, F. W. Zhang, Y. N. LI, G. M. Cao, L. Zhao, X. Q. Zhao., and Obsahuje bibliografii
The seasonal changes of the nematode Camallanus anabantis Pearse, 1933, in the climbing perch (Anabas testudineus) from the freshwater swamps near Kalyani town, West Bengal, India were studied during the period from February 1988 to August 1989. The nematode exhibited a one-year cycle. Larvated females occurred in the fishes from October to February at a water temperature of 12“-29 °C. New infection of fishes occurred from February to May and occasionally in September. The fourth-stage larvae, the males, and the young females (without eggs), although irregularly, were found present throughout the year. Egg-laden females occurred in the fishes in August, October to February, and March.
Seasonal changes in leaf gas exchange, assimilation response to light and leaf area were monitored in bearing and nonbearing pistachio shoots. Shoot bearing status did not directly affect leaf photosynthetic rate. However, photosynthetic light-response curves strongly varied during the season demonstrating the dominant effect of the tree’s seasonal phenology on assimilation. Early in the season low photosynthetic rates were associated with high rates of dark respiration indicating limited photosynthesis in the young leaves. As leaves matured, dark respiration decreased and assimilation reached maximum values. Photosynthetic efficiency was strongly reduced late in the season due to leaf age and senescence. Fruit load precipitated an early leaf senescence and drop that resulted in a 53% decrease in leaf area in bearing vs. nonbearing shoots, strongly decreasing the seasonal photosynthetic performance of bearing shoots. Bearing shoots produced a 26% lower seasonal carbon gain compared to nonbearing shoots., G. Marino, M. La Mantia, T. Caruso, F. P. Marra., and Obsahuje bibliografii
The proteocephalid tapeworm Proteocephalus torulosus (Batsch, 1786) exhibited a marked seasonality in its occurrence and maturation in barbel (Barbus harhus L.) from the Jihlava River, South Moravia, Czech Republic. Recruitment took place in winter and early spring, growth and maturation in spring and gravid worms left the fish hosts in May; during summer and autumn, the parasite was almost absent from the fish population. Parasite burden was related to fish size, with larger barbel being more heavily infected than smaller ones.
This is the first study detailing the microhabitat specificity of the monogenean parasite, Paradiplozoon ichthyoxanthon Avenant-Oldewage in Avenant-Oldewage et al., 2014. Samples of the monogenean were collected from the gills of the smallmouth yellowfish Labeobarbus aeneus (Burchell) from the Vaal Dam, South Africa, over four seasons with the use of gill nets. Host condition factor fluctuated between the different seasons, with the highest values recorded in summer. Adults and diporpas of P. ichthyoxanthon were found in all four seasons. Adult parasites predominantly infect the first gill arch, whereas diporpas were found on the second and fourth arches. In utero eggs were also found throughout the sampling seasons and their number negatively correlated with the condition factor of the host. The occurrence of adults and diporpas of P. ichthyoxanthon correlated with the size of the host but not the condition factor. Water quality of the study site also had little correlational relationship with the occurrence of the parasites and fluctuations were related to season. The main factor that may drive the microhabitat specificity of P. ichthyoxanthon is the flow of water over the surfaces of the gills and chances of the parasites becoming dislodged. Size of the attachment organs has also been shown to play a role in this specificity, because smaller attachment structures favour stronger holdfast to areas where flow might be stronger compared to larger attachment structures., Beric M. Gilbert, Annemariè Avenant-Oldewage., and Obsahuje bibliografii
Seasonal polyphenism in adults may be a season-specific adaptation of the adult stage and/or a by-product of adaptive plasticity of the juvenile stages. The swallowtail butterfly Papilio xuthus L. exhibits seasonal polyphenism controlled by photoperiod. Adults emerging in spring from pupae that spend winter in diapause have smaller bodies than adults emerging in summer from pupae that do not undergo diapause. Pupal diapause is induced by short-day conditions typical of autumn. To explore the interactive effects of temperature and developmental pathways on the variation in adult body size in P. xuthus, we reared larvae at two temperatures (20°C, 25°C) under two photoperiods (12L : 12D and 16L : 8D). Pupal weight and adult forewing length were greater in the generation that did not undergo diapause and were greater at 25°C than at 20°C. Thus, body size differences were greatest between the individuals that were reared at the longer day length and higher temperature and did not undergo diapause and those that were reared at the shorter day length and lower temperature and did undergo diapause. Unlike in other Lepidoptera, larvae of individuals that undergo diapause had shorter developmental times and higher growth rates than those that did not undergo diapause. This developmental plasticity may enable this butterfly to cope with the unpredictable length of the growing season prior to the onset of winter. Our results indicate that there are unexplored variations in the life history strategy of multivoltine Lepidoptera., Shinya Komata, Teiji Sota., and Obsahuje bibliografii
Eristalis pertinax varies seasonally, with the spring morph more hairy than the summer morph. We measured the size and the venation of the wings of the seasonal morphs. Wings of the spring morph were significantly larger than those of the summer morph and those of females were larger than those of males. There were also significant differences between the morphs in wing venation and their allometric relationship. The differences between sexes were larger than differences between seasonal morphs. The allometry can account for the sexual dimorphism but not seasonal dimorphism. The differences between seasonal morphs in wing shape were relatively large with very few intermediate individuals. The differences were comparable to those between two related species of Syrphidae. Genetic analyses based on markers in nuclear and mitochondrial genomes unequivocally revealed that spring and summer morphs of E. pertinax form a single population and should not be regarded as separate taxa. Thus seasonal variability in this species is a rare example of polyphenism in Diptera., Lukasz E. Mielczarek, Andrzej Oleksa, Katarzyna Meyza, Adam Tofilski., and Obsahuje bibliografii