Spatio-temporal stable isotope variation of a benthic primary consumer in a simple food web in a strongly acidic lake.

Analysis of aquatic food webs is typically undertaken using carbon and nitrogen stable isotope composition of consumer and producer species. However, the trophic consequences of spatio-temporal variation in the isotope composition of consumers have not been well evaluated. Lake Katanuma, Japan, is highly acidic and has only one dominant species of benthic alga and one planktonic microalga, making it a prime system for studying trophic relationships between primary consumers and producers.

Isotopic evidence for the spatial heterogeneity of the planktonic food webs in the transition zone between river and lake ecosystems.

Resources and organisms in food webs are distributed patchily. The spatial structure of food webs is important and critical to understanding their overall structure. However, there is little available information about the small-scale spatial structure of food webs.

Responses of the bacterial community to chronic gamma radiation in a rice paddy ecosystem.

Purpose: Public concern about radiation protection of the environment and non-human species is increasing. The potential impact of chronic gamma radiation on the bacterial community in a rice paddy ecosystem was investigated.

Materials And Methods: Paddy field microcosm samples were continuously exposed at a dose rate of 1 Gy day(-1) for five days after which the bacterial community structures in them were compared with those of unirradiated control samples by denaturing gradient gel electrophoresis (DGGE) of the 16S ribosomal ribonucleic acid (rRNA) gene.

Effects of acute gamma-irradiation on community structure of the aquatic microbial microcosm.

To characterise indirect effects of ionising radiation on aquatic microbial communities, effects of acute gamma-irradiation were investigated in a microcosm consisting of populations of green algae (Chlorella sp. and Scenedesmus sp.) and a blue-green alga (Tolypothrix sp.

Estimating isotope fractionation between cercariae and host snail with the use of isotope measurement designed for very small organisms.

Most studies have reported negative carbon and nitrogen isotope fractionations between hosts and parasites, but isotope values have not yet been determined for many parasite species, such as trematodes, due to their relatively small body sizes. We investigated the carbon and nitrogen isotope values of freshwater snails and trematode parasites by using a method for organisms with very small body sizes. We found negative isotope fractionation values between host snails and trematode parasites, similar to published values for other parasite groups with larger body sizes, which suggest that the mechanisms for determining isotope fractionations between hosts and parasites provide similar results.

Female scent mobilizes leukocytes to airways in BALB/c male mice.

The scent of receptive females as a signal to reproduction stimulates male mice to olfactory search of a potential breeding partner. This searching behavior is coupled with infection risk due to bacterial contamination of the fecal and urine scent marks. We hypothesized that sniffing of female soiled bedding induced the migration of immuno-competent cells into airways as a possible adaptation to breeding-related infection.

Parasite-induced changes in nitrogen isotope signatures of host tissues.

To estimate isotopic changes caused by trematode parasites within a host, we investigated changes in the carbon and nitrogen isotope ratios of the freshwater snail Lymnaea stagnalis infected by trematode larvae. We measured carbon and nitrogen stable isotopes within the foot, gonad, and hepatopancreas of both infected and uninfected snails. There was no significant difference in the delta13C and delta15N values of foot and gonad between infected and uninfected snails; thus, trematode parasite infections may not cause changes in snail diets.

Changes in carbon and nitrogen stable isotopes of chironomid larvae during growth, starvation and metamorphosis.

We conducted experiments to determine isotope changes in the deposit-feeding chironomid larvae Chironomus acerbiphilus during feeding, starvation and metamorphosis. Isotope changes in chironomid larvae occurred mainly during growth and rarely afterward. This finding indicates that chironomid isotope turnover mainly occurs in conjunction with growth and suggests that chironomid larvae only break down newly assimilated food for energy during periods of no growth.

The influence of paddy soil drying on Tc insolubilization by bacteria.

Tc insolubilization in four soils samples was compared by pre-incubating them in both dry and wet states, then measuring Tc concentrations in solution when the samples were saturated with an excess of water spiked with 99Tc. Soils pre-incubated in a dry state showed higher Tc insolubilization than soils incubated in a wet state. To clarify the difference in Tc insolubilization, Eh, bacterial abundances, and bacterial species compositions in the dry and wet ponding water samples were determined.