Differences in fish assemblage structure between vegetated and unvegetated microhabitats in relation to food abundance patterns in a mangrove creek

In order to clarify the mechanisms determining fish distribution patterns in a mangrove system on Iriomote Island, in southern Japan, fish assemblage structures were determined by visual observation, along with food abundance and environmental factors, in an area of mangrove roots on the banks, and a bare sand area at the center, within downstream, midstream and upstream portions of a branch creek from the Urauchi River. The fish assemblage structures differed significantly between the area types, with the mangrove-root area supporting a more diverse and abundant fish fauna. A canonical correspondence analysis revealed that the relationships between fish distribution and their food abundance differed among trophic groups. Benthic crustacean or plant feeders were positively associated with their prey i.e. crabs and macroalgae—in other words, these trophic groups were abundant in downstream and/or midstream mangrove-root areas in which their prey were also particularly abundant. However, zooplankton feeders did not show such relationships, their abundance being positively associated with fine sediment particles (characteristic of areas with weak water movement). These results suggested that food availability is a major factor determining the distribution patterns of benthic crustacean feeders and plant feeders, whereas for zooplankton feeders other factors, such as sheltering effects against water current and/or predators, may be more significant.     

Importance of outer reef slopes for commercially important fishes: implications for designing a marine protected area in the Philippines

A passive acoustic telemetry survey was conducted to determine occurrence patterns of commercially important fishes on a steep reef slope along a marine protected area (MPA) in the southern Philippines, where the outer reef edge is often set as an offshore MPA boundary. Based on 4–61 days of tracking data from 21 detected individuals of five species (Lutjanus argentimaculatus, Lutjanus monostigma, Lethrinus atkinsoni, Lethrinus obsoletus, and Siganus guttatus; 20.7–69.2 cm fork length) caught near the reef slope of the MPA, S. guttatus occurred most frequently on the reef flat of the MPA, whereas all individuals of the four lutjanid and lethrinid species were primarily (99.4–100%) detected near the reef slope, and nine individuals (56.3% of these four species) of three of these species (not L. obsoletus) most likely used the shallow (≤10 m) and deep (≥20 m) layers, and thus, middle layers of the slope. These findings indicate that commercially important lutjanid and lethrinid species predominantly and vertically used the areas near the reef slope, suggesting the importance of fully including reef slopes in MPAs to enhance their effectiveness for the conservation of such fishes.     

Effects of chitin degradation products N-acetylglucosamine and N,Nʹ-diacetylchitobiose on chitinase activity and bacterial community structure in an incubated upland soil

ABSTRACT

Chitin, which is the polymer of N-acetylglucosamine (GlcNAc) linked by β1,4 glycoside bonds, has been reported as a soil amendment to mitigate plant soil diseases, increasing the population of chitin-degrading bacteria, and chitinolytic enzymatic activity in the soil. In some chitin-degrading bacteria, whose chitinolytic systems have been intensively studied, the chitin degradation product N,N?-diacetylchitobiose {(GlcNAc)₂} induces expression of genes for chitinases whereas GlcNAc does not. To evaluate the effects of these mono- and disaccharides on the population and activity of chitinolytic bacteria in soil, we investigated the chitinolytic enzyme activity and bacterial community structure in an incubated upland soil supplemented with GlcNAc or (GlcNAc)₂. The added GlcNAc and (GlcNAc)₂ (2 mg g^?1) were consumed within 1 d when incubated at 25°C. Chitinase activity was induced by (GlcNAc)₂ and chitin after 1-d and 7-d incubation, respectively, but not by GlcNAc. N-acetylglucosaminidase (GlcNAcase) activity was induced by GlcNAc but was lower than those by (GlcNAc)₂ and chitin. Amplicon sequencing analysis targeting 16S rRNA genes demonstrated that both GlcNAc and (GlcNAc)₂ significantly increased the rate of the order Bacillales, but the compositions of Bacillales differed from each other: the family Planococcaceae significantly increased in either GlcNAc- or (GlcNAc)₂-added soil, but the genera Bacillus and Paenibacillus were increased mainly by GlcNAc and (GlcNAc)₂, respectively. The family Streptomycetaceae of the order Actinomycetales was significantly increased by (GlcNAc)₂ and chitin, but GlcNAc did not. Thus, GlcNAc and (GlcNAc)₂, which were promptly consumed in the incubated soil, indicated partly similar but distinctive effects on chitinolytic enzyme activity and bacterial communities. Both aminosugars increased GlcNAcase activity and the population size of Planococcaceae. GlcNAc increased Bacillus. Chitinase activity and the populations of Paenibacillus and Streptomycetaceae, a number of strains of which are known as potent chitin-degraders, were increased by (GlcNAc)₂, but not by GlcNAc.     

Objective evaluation of whiteness of cooked rice and rice cakes using a portable spectrophotometer

The whiteness of cooked rice and rice cakes was evaluated using a portable spectrophotometer with a whiteness index (WI). Also, by using boiled rice for measurement of Mido values by Mido Meter, it was possible to infer the whiteness of cooked rice without rice cooking. In the analysis of varietal differences of cooked rice, ‘Tsuyahime’, ‘Koshihikari’ and ‘Koshinokaori’ showed high whiteness, while ‘Satonoyuki’ had inferior whiteness. The whiteness of rice cakes made from ‘Koyukimochi’ and ‘Dewanomochi’ was higher than the whiteness of those made from ‘Himenomochi’ and ‘Koganemochi’. While there was a significant correlation (r = 0.84) between WI values and whiteness scores of cooked rice by the sensory test, no correlation was detected between the whiteness scores and Mido values, indicating that the values obtained by a spectrophotometer differ from those obtained by a Mido Meter. Thus, a spectrophotometer may be a novel device for measurement of rice eating quality.     

Considerations on Sustainable Agriculture and Rural Development in Dryland Areas

Drylands of the world cover 41%of the Earth＇s land surface and are a direct source of livelihood for 6.5 billion people, especially in developing countries. However, nearly all drylands are at risk of land degradation as a result of human activities. Poverty and desertification in dryland areas are major problems threatening sustainable agriculture and rural development in dryland areas. Several topics that are significant for sustainable agriculture and rural development for food security and environmental rehabilitation in dryland areas were stressed in this paper.     

Differences in fish assemblage structures between fragmented and continuous seagrass beds in Trang,southern Thailand

Fish assemblage structures in fragmented and continuous seagrass habitats in Trang Province, Thailand, were examined in detail to elucidate the effects of habitat fragmentation. The assemblage structures clearly differed: fish species diversity was apparently higher in the fragmented seagrass beds, although total fish numbers did not differ between them. A total of 37 fish species were collected, including 24 and 34 species from the continuous and fragmented beds, respectively. Thirteen species were restricted to the fragmented beds, compared with three restricted to the continuous beds. In addition, eight species were more abundant in the fragmented beds and only two in the continuous beds. Such differences may have arisen, at least in part, from differences in microhabitat diversity and the relative amounts of microhabitats between the two habitat types, as well as specific microhabitat preferences of the resident fishes. Although fragmented beds supported greater fish species diversity at the present study sites, it is axiomatic that habitat fragmentation caused by anthropogenic disturbance is unacceptable, with seagrass-habitat conservation being essential for both the preservation of high overall biodiversity and the successful management of local fisheries.     

Food habits of small fishes in seagrass habitats in Trang,southern Thailand

To clarify the feeding habits of seagrass fishes, we examined the gut contents from 42 fish species collected in seagrass habitats in Trang. Thirteen species showed ontogenetic and/or seasonal changes in food-use patterns. Smaller individuals generally preyed on small planktonic items (e.g., copepod larvae) or small benthic/epiphytic crustaceans (e.g., harpacticoid copepods), with subsequent changes to other prey items (e.g., shrimps, crabs, detritus and filamentous algae) with growth. The most important dietary items for the seagrass fish assemblages comprised benthic/epiphytic crustaceans, detritus, and planktonic copepods. Cluster analysis based on dietary overlaps showed that the seagrass fishes comprised eight feeding guilds (large benthic/epiphytic crustacean, detritus, planktonic animal, small benthic/epiphytic crustacean, mollusc, invertebrate egg, polychaete, and fish feeders). Of these, the first three guilds were the most abundantly represented, whereas the last three were each represented by only a single species.     

Study on the Mechanism of the Blood-Glucose-Lowering Effect of Collagen Peptides from Sturgeon By-Products

In a previous study, we found that the collagen peptides prepared from the by-products of Bester sturgeon had an inhibitory effect on elevated blood glucose levels in a glucose tolerance test with ICR mice. In the present study, we examine the mechanism of the effect of sturgeon collagen peptides (SCPs) in detail. When glucose was orally administered to mice along with the SCPs, it was found that the glucose remained in the stomach for a longer time. In the above tests, the amount of glucose excreted in the feces of mice also increased. On the contrary, it was revealed that the SCPs have a dipeptidyl-peptidase-IV (DPP-IV) inhibitory ability in an in vitro test. In subsequent oral and intravenous glucose administration tests, glucagon-like peptide-1 (GLP-1) and insulin levels in the blood of mice were maintained at high levels. These results suggested the following three mechanisms: SCPs slow the rate of transportation of glucose from the stomach into the small intestine, resulting in delayed glucose absorption; SCPs suppress the absorption of glucose in the small intestine and excrete it from the body; SCPs inhibit DPP-IV in the blood and maintain a high GLP-1 level in blood, which in turn stimulates insulin secretion.     

Age-specific plasma biochemistry reference ranges in <1 year old dogs in Japan

The purpose of this study was to investigate and propose possible reference intervals of plasma biochemical analytes in young dogs (<12 months old) in Japan, using 896 canine plasma samples, collected from an array of veterinary clinics throughout the greater Tokyo metropolis area in Japan. The following biochemical parameters were assessed: albumin (ALB), alanine aminotransferase (ALT), alkaline phosphatase (ALP), amylase, aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine (CRE), glucose, lipase, total cholesterol (T-Cho), and total protein (TP) were evaluated. Multivariate linear regression analysis indicated that partitioning according to age or gender may be necessary for some plasma analytes. Age appeared to significantly affect ALB, ALT, ALP, BUN, Glucose, Lipase, and Total Protein (P=?<0.001, <0.001, <0.001, 0.013, <0.001, 0.025, and <0.001, respectively). On the other hand, gender significantly influenced ALP, Amylase, Lipase, and T-Cho levels (P=0.017, <0.001, <0.001, and <0.001, respectively) whereas it may be borderline significant with ALT (P=0.072).