Reconstruction of the extinct Ezo wolf's diet

On Hokkaido, Japan, the Ezo wolf (Canis lupus hattai), an apex predator, became extinct at the end of the 19th century owing to human activities. Top predators often have an important role in their ecosystems, yet we have no scientific information on the feeding habits of the Ezo wolf. We performed carbon and nitrogen stable isotope analysis and radiocarbon dating of specimens of the wolf (n = 7) and its prey species and estimated the components of the wolves' diet using an isotope mixing model. Radiocarbon dating suggested that most of the wolves examined came from different populations or generations. The mean stable isotope ratios of the wolves were −19.5 ‰ (± 1.9 ‰ SD) for δ13C and 8.7 ‰ (± 2.6 ‰ SD) for δ15N. The discrimination-corrected isotopic ratios of five of the seven wolves were almost the same as those of Sika deer at the same sites. In contrast, those of two wolves had clearly higher isotopic values than those of deer, suggesting that these wolves depended partly on marine prey such as salmon and marine mammals. Thus, Ezo wolves had similar ecological roles to Canadian grey wolves, and were a second subspecies shown to have fed on a marine diet, in addition to the "coastal wolves" of British Columbia

Seasonal shifts in the contributions of the Changjiang River and the Kuroshio Current to nitrate dynamics in the continental shelf of the northern East China Sea based on a nitrate dual isotopic composition approach

The northern East China Sea (ECS) serves as a spawning and nursery ground for many species of fish and squid. To clarify the basis of the food web in the northern ECS, we examined the nitrate (NO3) dynamics along four latitudinal transects based on stable nitrogen and oxygen isotopes of NO 3 (δ15NNO3 and δ18ONO3) and temperature-salinity dynamics in both winter (February 2009) and summer (July 2009 and July 2011). The δ15NNO3 and δ18ONO3, which were distinctly different among the potential NO3 sources, were useful for clarifying NO3 sources and its actual usage by phytoplankton. In winter, Kuroshio Subsurface Water (KSSW) and the Yellow Sea Mixed Water (YSMW) predominantly contributed to NO3 distributed in the shelf water. In the surface water of the Okinawa Trough, NO3 from the KSSW, along with a temperature increase caused by an intrusion of Kuroshio Surface Water (KSW), seemed to stimulate phytoplankton growth. In summer, Changjiang Diluted Water (CDW), Yellow Sea Cold Water Mass (YSCWM), and KSSW affected the distribution and abundance of NO 3 in the northern ECS, depending on precipitation in the Changjiang drainage basin and the development of the YSCWM in the shelf bottom water. Although isotopic fractionation during NO3 uptake by phytoplankton seemed to drastically increase δ15NNO3 and δ18ONO3 in summer, relatively light nitrate with δ15NNO3 lower than expected from this fractionation effect might be explained by contribution of atmospheric nitrogen and/or nitrification to NO3 dynamics in the surface and subsurface layers. If the latter were a dominant process, this would imply a tightly coupled nitrogen cycle in the shelf water of the northern ECS

Do Termites Avoid Carcasses? Behavioral Responses Depend on the Nature of the Carcasses

BACKGROUND: Undertaking behavior is a significant adaptation to social life in enclosed nests. Workers are known to remove dead colony members from the nest. Such behavior prevents the spread of pathogens that may be detrimental to a colony. To date, little is known about the ethological aspects of how termites deal with carcasses. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, we tested the responses to carcasses of four species from different subterranean termite taxa: Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe) (lower termites) and Microcerotermes crassus Snyder and Globitermes sulphureus Haviland (higher termites). We also used different types of carcasses (freshly killed, 1-, 3-, and 7-day-old, and oven-killed carcasses) and mutilated nestmates to investigate whether the termites exhibited any behavioral responses that were specific to carcasses in certain conditions. Some behavioral responses were performed specifically on certain types of carcasses or mutilated termites. C. formosanus and R. speratus exhibited the following behaviors: (1) the frequency and time spent in antennating, grooming, and carcass removal of freshly killed, 1-day-old, and oven-killed carcasses were high, but these behaviors decreased as the carcasses aged; (2) the termites repeatedly crawled under the aging carcass piles; and (3) only newly dead termites were consumed as a food source. In contrast, M. crassus and G. sulphureus workers performed relatively few behavioral acts. Our results cast a new light on the previous notion that termites are necrophobic in nature. CONCLUSION: We conclude that the behavioral response towards carcasses depends largely on the nature of the carcasses and termite species, and the response is more complex than was previously thought. Such behavioral responses likely are associated with the threat posed to the colony by the carcasses and the feeding habits and nesting ecology of a given species

Sticky plant captures prey for symbiotic bug: is this digestive mutualism?

NatuurwetenskappePlant- en DierkundePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Strain-specific incorporation of methanotrophic biomass into eukaryotic grazers in a rice field soil revealed by SIP-PLFA

In wetland ecosystems, methane is actively utilized by methanotrophs. The immobilized methane carbon is then passed on to other organisms such as grazers. Here, we traced the incorporation of methanotrophic biomass into eukaryotes in a rice field soil using phospholipid fatty acid stable-isotope probing (PLFA-SIP). Addition of 13C-labeled cells of five methanotrophs to soil (5 × 107 cells g−1 soil) did not affect the CO2 release rate, but significantly increased the carbon isotopic ratio within 24 h. In 48 h, 2–7% of the added bacterial biomass carbon was detected as 13CO2. The soil with Methylobacter luteus released the highest amount of 13CO2, comparable to that with Escherichia coli. The amount of polyunsaturated PLFAs (C18:3ω6c and C20:4ω6c) was not affected by the addition of bacterial cells to soil, but their carbon isotopic ratio increased significantly within 24–48 h. The extent of 13C-enrichment in PLFAs differed between the added methanotrophs, with the highest labeling upon addition of M. luteus. The relative abundance of 13C-labeled C18:3ω6c to C20:4ω6C also differed between the strains. The results indicated that the eukaryotes in soil, probably protozoa, preferentially graze on specific methanotrophs and immediately incorporate their biomass

Studying the Effect of Elevated pCO2 on the Nitrogen Cycle Within the Coral Holobiont Using Stable Isotopes

The efficient recycling of nitrogen plays an integral role in the health of the coral holobiont, it is therefore essential to understand how elevated pCO2 may affect this biogeochemical cycle under ocean acidification scenarios. We investigated how elevated pCO2 (~950 ppm pCO2) affects the nitrogen cycle in corals by making use of a natural CO2 seep on Shikine-jima, Japan. Colonies of two species of corals (Acropora solitaryensis and Porites heronensis) were sampled from a nearby reference site (~300 ppm pCO2), and fragmented into smaller pieces. After recovery, some fragments (n = 8) were individually incubated in chambers for three hours (incubation A) in order to determine changes in nitrate, nitrite, ammonium, total and organic dissolved nitrogen concentration and their respective nitrogen and oxygen isotopic composition. Following the initial incubation, half of the fragments were transplanted from the reference pCO2 site into the elevated pCO2 site for two weeks, and then a second incubation (n = 8, from each site) was carried out on the acclimatised fragments (incubation B). During incubation A, dissolved inorganic nitrogen decreased after three hours, as well as dissolved organic nitrogen (DON) for both species. Moreover, the nitrogen isotopic composition of total dissolved nitrogen (15NTDN) decreased over this period for both species. At the two-week point, there was a decrease in nitrate and nitrite concentrations for both species and treatments, with a concurrent increase in ammonium. For both species in the elevated pCO2 treatment there was a slight decrease in DON after three hours, however, there was an increase in DON after three hours in the reference pCO2 treatment. In the elevated pCO2 treatment there was an increase in 15NTDN after three hours for both species, conversely, there was a decrease after three hours for the reference pCO2 treatment. These preliminary results suggest elevated pCO2 may have an effect on the nitrogen cycle within the coral holobiont, specifically on the (re)cycling of DON