Nitrogen promotes water consumption in seedlings of Cryptomeria japonica but not in Chamaecyparis obtusa

To evaluate the influence of excessive N deposition on the water consumption of a Japanese plantation forest, 1-year-old seedlings of major plantation trees, Cryptomeria japonica (Japanese cedar) and Chamaecyparis obtusa (Hinoki cypress), were treated with combinations of two N levels (Moderate N and High N) and two soil water conditions (Dry and Moist) for 4 months. The High N treatment received five times as much N as in the Moderate N treatment; the total amount of N added in the High N treatment was roughly 25 times the annual N deposition in precipitation. An increase in soil N availability increased the needle transpiration rate, needle biomass, and needle N content of C. japonica under the Moist treatment, whereas those of C. obtusa were not significantly affected by soil N treatment at either soil water level. Needle N content in C. japonica was positively related to needle photosynthetic rate and transpiration rate. Our results suggested that excessive N deposition has the potential to enhance water consumption in C. japonica stands on moist soils. However, the effects of increased N deposition would be insignificant for C. japonica grown on dry sites. Unlike in C. japonica, water consumption in C. obtusa would be unlikely to respond to excess N deposition, regardless of the soil moisture level. Moreover, the significant reduction in the fine root to needle ratio observed with excessive N application in C. japonica under both Dry and Moist treatments suggests that excessive N deposition is likely to cancel out the tree's morphological adaptation to drought.     

Hyposmoregulatory ability and ion- and water-regulatory mechanisms during the leptocephalus stages of Japanese eel Anguilla japonica

We explored osmoregulatory ability and mechanisms of ion and water regulation in Japanese eel leptocephali. Tissue osmolality of leptocephali ranged from 360 to 540 mOsm/kg·H₂O. Immunocytochemical observations revealed that Na⁺/K⁺-ATPase-immunoreactive mitochondrion-rich (MR) cells were distributed over the entire body surface of leptocephali. Using a fluorescent sodium indicator and the chloride test, we localized Na⁺ and Cl^? secreting sites at the apical region of cutaneous MR cells. To further examine drinking behavior and water absorption in the intestine, leptocephali were exposed to seawater containing dextran labeled with Alexa Fluor. To calculate relative water absorption, fluorescent intensity was measured along the digestive tract. Whereas water was hardly absorbed in the stomach and intestine, water absorption predominantly took place in the rectum. Our findings indicate that Japanese eel exert hyposmoregulatory ability as early as during leptocephalus stages, secreting Na⁺ and Cl^? through cutaneous MR cells and primarily absorbing water from ingested seawater in the rectum.     

Effect of squid meal in dry pellets on the spawning performance of striped jack Pseudocaranx dentex

SUMMARY: This study was carried out to investigate the effects of dietary squid meal or a combination of squid meal and krill meal as part of the protein source in dry pellets on the spawning of striped jack Pseudocaranx dentex . Five months prior to spawning, 7-year-old fish were divided into three groups of 10 fish each (male : female ratio, 5 : 5). The control group was fed a raw fish mix (RF) and the other two groups were fed either steam-dry pellets with squid meal replacing 50% of their fish meal (fs-DP) or steam-dry pellets containing equal proportions of fish, squid and krill meals (fsk-DP). Feeding was carried out once every other day in 5 × 5 × 5 m floating net cages and the fish were transferred to 65 m³ indoor tanks for spawning. Eggs and yolksac larvae produced were evaluated for their quality and those obtained during the first 2 weeks of spawning were sampled for chemical analysis. The fish had an average bodyweight of 3.5 ± 0.4 kg at spawning. Although egg production of the RF group was significantly higher ( P < 0.05) than that of the dry pellet groups, the fs-DP group produced the best quality eggs with higher fertilization and hatching rates. The fsk-DP group had the lowest egg production and quality. Lipid classes and fatty acid compositions of eggs and yolksac larvae were dependent on the broodstock diets. These results show that the combination of fish meal and squid meal in dry pellets for striped jack improved egg quality but not production whereas the combination of fish meal, squid meal and krill meal was not effective.     

Tetrodotoxin accumulation conflicts with low salinity tolerance in juvenile tiger puffer Takifugu rubripes

We evaluated whether bearing tetrodotoxin (TTX) affects salinity stress in the juvenile tiger puffer Takifugu rubripes. Juveniles of hatchery-reared non-toxic T. rubripes [body weight (BW): 1.7?±?0.2 g, n?=?120] were divided into six tanks and acclimatized to salinity (8.5 ppt) that is equivalent to blood osmolality. Fish in three tanks were fed non-toxic diet, and those in the other three tanks were fed a TTX-containing diet (356 ng/g diet) three times a day until satiation. In each diet treatment, salinity of one tank was kept at 8.5 ppt, and the other two tanks were adjusted to either 1.7 or 34.0 ppt, and fish were reared for another 33 days. Then, we compared survival, growth, TTX accumulation, plasma osmolality, plasma cortisol, and glucose levels among treatments. We detected TTX only in the fish in the TTX-diet groups. Survival was highest at 8.5 ppt (70%) and lowest at 1.7 ppt in the TTX-diet group (20%). The BW was greater at 8.5 ppt, and plasma osmolality was significantly higher at 34.0 ppt than at any other salinities. Plasma cortisol level was significantly higher but glucose level was lower at 1.7 ppt. Possessing TTX at a low salinity may be lethal to tiger puffer juveniles.

     

Properties of Cross‐Linked Starch from Waxy Mutant Wheat Tanikei A6599‐4

Native starch from waxy mutant wheat Tanikei A6599‐4 is known to exhibit more stable hot paste viscosity than a typical waxy wheat (Tanikei H1881) and waxy corn. The objective of this study was to investigate the starch paste properties of Tanikei A6599‐4 after cross‐linking and compare with Tanikei H1881 and waxy corn. As an example of cross‐linking, the reaction (at 30, 60, 120, and 360 min) with sodium trimetaphosphate was used. In Rapid Visco Analyser (RVA) measurement, the unique characteristic was maintained in Tanikei A6599‐4 starch cross‐linked at low reaction time (<120 min) levels. Cross‐linking at a high reaction time (360 min) level suppressed the swelling of both Tanikei A6599‐4 and Tanikei H1881 starches but not waxy corn starch. Although unmodified Tanikei A6599‐4 starch showed the lowest paste clarity among unmodified waxy starches, this defect became unremarkable when starch was cross‐linked for ≥120 min. In gel‐dispersed dynamic viscoelasticity measurement, the order of G′ and G″ values was always Tanikei A6599‐4 > Tanikei H1881 > waxy corn. This indicates that cross‐linked Tanikei A6599‐4 and Tanikei H1881 starches have different starch properties and that swollen Tanikei A6599‐4 starch granules are more rigid than swollen Tanikei H1881 starch granules.     

Polyclonal and monoclonal antibodies specific to the chrysanthemic acid moiety of pyrethroid insecticides

Two polyclonal and two monoclonal antibodies raised against chrysanthemic acid (CAA) were prepared for ELISA of pyrethroid insecticides with the common CAA moiety. The monoclonal antibody KCA226 showed the highest reactivity towards allethrin among the antibodies in C-ELISA, although KCA226 was more sensitive to higher concentrations of methanol than the polyclonal antibodies in ELISA. KCA226 was reacted linearly with allethrin at concentrations ranging from 1 to 10 μg litre^-1 in 0·5% methanol and from 300 to 10000 μg litre^-1 in 30% methanol. KCA226 reacted specifically with the pyrethroid insecticides with the CAA moiety but was much less reactive with CAA itself. These results suggest that C-ELISA based on KCA226 is useful for the assay of pyrethroid residues with the common CAA moiety. © 1998 Society of Chemical Industry     

Nutrient dynamics in decomposing forest leaf litter: A comparison of field and laboratory microcosm approach

The effect of incubation setting (greenhouse: GM and field: FM microcosms) on nutrient element dynamics during decomposition of Japanese Konara Oak (Quercus serrata Murray) and Japanese Red Pine (Pinus densiflora Sieb et. Zucc.) litter was studied. Results show a disparity in relative concentrations and amounts of the same type of litter when incubated in different settings. The nutrient mobility, however, showed similar trend. The order of elemental mobility after 12 months forQuercus in FM was: P>K>Mg>C>Mn>Ca>N>Al>Cu>Zn>Fe; for GM it was: P>K>Mn>Mg>C>Ca>N>Al>Cu>Zn>Fe. ForPinus, elemental mobility in FM was: K>Mg>C>Mn>N>P>Cu>Zn>Al>Fe; while for GM was: K>C>Mn>N>Ca>Mg>Cu>Al>P>Zn>Fe. The elements inQuercus that lost their mass were P, K, Mg, Ca, Mn and C while those that increased were N, Cu, Al, Fe and Zn. ForPinus, K and Mg lost their nutrient mass while the other elements had increased or fluctuated but tended to increase. Three patterns of nutrient mobility were observed: first, the concentration increased while the nutrient mass (absolute amount) decreased; second, both concentration and nutrient mass increased; third, the concentration and nutrient mass decreased. On tracing nutrient mobility over time, the linear regression of nutrient element mass and litter element mass was preferred over the carbon to element ratios because the former gave a clearer picture of the relationship. On the over-all, the pattern of nutrient changes in greenhouse microcosms were different from those observed in the field, hence nutrient cycling studies using greenhouse-microcosm approach alone may give inaccurate results. This study was conducted while the senior author holds a Japanese government scholarship (MONBUSHO Grant No. 920205).     

Comparison of predation risks for small fishes in salt marsh microhabitats in Lake Hinuma,eastern Japan,using tethering experiments

Fisheries Science - To clarify the role of salt marsh creeks as fish refuges, predation risks for two small species (the nektonic Oryzias latipes and benthic Acanthogobius lactipes) were compared...     

Fasting in freshwater severely affects growth of juvenile chum salmon when entering cold seawater

Fisheries Science - We conducted rearing experiments to examine the cumulative effects of fasting in freshwater and transfer to cold seawater on the growth of juvenile chum salmon. In the first...