Fatty acid composition in sea cucumber Apostichopus japonicus fed with microbially degraded dietary sources

Fatty acids (FAs) in the body walls of sea cucumber, Apostichopus japonicus, reared under diet‐administered conditions were analysed to determine the accumulative status of dietary FAs. Four test diets different in diet source and microbial degradation, that is, a diet composed of powdered pennate diatoms (diet PD), one microbially degraded of diet PD (diet PDM), one composed of brown algae [tangle weed, Saccharina (Laminaria) longissima (Miyabe); diet BA], and one microbially degraded of diet BA (diet BAM), were fed to juvenile A. japonicus, respectively, for 2 months and the FA composition of the juvenile body wall was determined. FAs in body wall were influenced and changed by diet source and microbial degradation of diet. Degradation significantly promoted juvenile's growth and increased iso‐15:0 in the body wall; however, iso‐15:0 was not a growth factor. FA 20:4n6 and 20:5n3 were dominant in all groups despite being a minor dietary constituent, suggesting that these FAs can be readily accumulated or synthesized in the animal.     

Isolation and characterization of bacteria causing mortality in early stage larvae of captive‐bred Japanese eels (Anguilla japonica Temminck & Schlegel)

Bacteria with lethal effect on eel larvae were isolated from moribund captive‐bred eel larvae and their 16S rRNA gene sequences were analysed. Nucleotide sequence of 10 isolates showed highest similarity with Lacinutrix algicola, Crocinitomix catalasitica and Pseudoalteromonas rubra. Age‐dependent changes in the susceptibility of eel larvae were observed in response to challenge by a highly lethal isolate. Compared with 10 and 11 days after hatching (DAH), larval susceptibility to the highly lethal isolate was lower at 18 DAH. We found that the bacterial isolates have lethal effect on the captive‐bred eel larvae, especially at the early developmental stage. These results will be useful to establish appropriate culture practices for eel larvae that will improve the success of mass production of glass eels for aquaculture.     

Distribution of immunoglobulin-positive cells in the spleen and kidney of Japanese flounder Paralichthys olivaceus

SUMMARY: The distribution of surface immunoglobulin-positive (sIg⁺) cells in the spleen, the head-kidney, and the trunk-kidney of adult Japanese flounder Paralichthys olivaceus was investigated by a flow cytometric analysis using a monoclonal antibody FB17 against flounder immunoglobulin M. Although the percentage of sIg⁺ cells varied among organs, a good correlation was revealed between the percentage in the head-kidney and that in the trunk-kidney ( r = 0.996, P < 0.001). In contrast, no correlation was obtained between the percentage of sIg⁺ cells in the spleen and the head-kidney or trunk-kidney. The head-kidney and the trunk-kidney contained cells bearing fewer sIg that were stained dimly by FB17 in addition to brightly stained sIg⁺ cells regarded as mature B cells, while the spleen contained only sIg⁺ cells stained brightly. Moreover, the immunocytochemical analyses showed that the head-kidney contains plasma cells with strongly stained cytoplasm in addition to B cells with stained cell surface, which suggests that the cells with fewer sIg detected by flow cytometric analysis are presumed to be at a stage during the processes of differentiation to plasma cells. These results suggest that there are some differences between the spleen and kidney in the role of the immune system and it is considered that differentiation of B cells to plasma cells occurs in the kidney.     

Photosynthesis and growth of Thujopsis dolabrata var. hondai seedlings in the understory of trees with various phenologies

We have studied the photosynthetic production and growth of Thujopsis dolabrata var. hondai (hiba) seedlings under typical light conditions found in mixed forests, including constant shade, phenological gaps under broad-leaved trees with different lengths of foliation period, and in an open plot. Leaves sampled from the open plot had significantly higher rates of light-saturated gross photosynthesis and dark respiration, and a significantly lower specific leaf area than leaves from the other plots. The relative growth rate of whole plant biomass was significantly higher in plots that received larger amounts of light. The variations in these properties under the various light conditions are considered to reflect the ability of hiba seedlings to adapt to available light. In the late autumn, leaves sampled from the open and from the gap under deciduous trees indicated photoinhibition. However, the estimated value of monthly net photosynthesis of hiba seedlings was greater in these plots, indicating that the benefit of a greater light intensity for photosynthesis seems to be larger than the detriment of photoinhibition. The seasonal pattern of photosynthesis by understory hiba seedlings was affected by the phenology of canopy trees. Light availability under the canopy of deciduous trees associated with phenological gaps helped hiba seedlings to tolerate the relatively dark conditions during the subsequent foliation period. These results for reaction to the light regime and for the phenology of hiba seedlings are practicable for hiba forest management.     

Diversity and population density of methanogens in the large intestine of pigs fed diets of different energy levels

Marker gene analysis was performed to assess the effect of energy level on the diversity and population density of methanogens in pig fecal material. Crossbred pigs were fed high or low energy level diets, a high‐energy (HE) diet that satisfied daily gain at 1.2 kg, and a low‐energy (LE) diet with amount of 0.6 times of the HE diet. Growth performance and short‐chain fatty acid in feces were examined. Diversity of methanogen was analyzed by the α‐subunit of methyl coenzyme‐M reductase gene (mcrA) clone library from fecal DNA. The DNA copy numbers of mcrA were quantified by real‐time PCR. There was no difference in the concentration and composition of short‐chain fatty acid between treatments. Differences in the mcrA clone library were observed between HE and LE treatments (p < 0.05). Ninety‐five percent of cloned sequence affiliated genus Methanobrevibacter in the feces of the pig regardless of treatments. During the experimental period, no significant difference in the proportion of copy numbers of mcrA against that of 16S rRNA gene of total bacteria was observed between treatments. In conclusion, feeding energy level affected composition of methanogens in the large intestine of the pig, while population density of methanogen was not affected.     

First report of anthracnose on tillandsia caused by Colletotrichum sp. in Japan

Journal of General Plant Pathology - In July 2018, tillandsia (Tillandsia sp.) plants with brown to dark brown lesions on the leaves and pseudobulbs were found in Japan. Based on morphological and...     

Soil microbial biomass and fluorescein diacetate hydrolytic activity in Japanese acidic tea field soils

The soil microbial biomass (SME) content and fluorescein diacetate (FDA) hydrolytic activity in 21 acidic tea field soils in Japan were determined. SM 3 content in the tea field soils was quantitatively similar to that in 13 arable soils with neutral soil pH previously reported. However, the ratio of the SMB content to organic matter content in the tea field soils classified as red-yellow soil, brown forest soil, and lithosol was clearly lower than that in the neutral arable soils classified as non-volcanic ash soil. FDA hydrolytic activity in the tea field soils was higher than the activity in various soils with neutral soil pH and showed a negative relationship with the soil pH.     

Diversity and fluctuation in ciliate protozoan population in the rumen of cattle

The purpose of this study was to investigate the diversity and fluctuation in the ciliate protozoan population in the rumen of cattle. DNA was extracted from the rumen of three ruminally cannulated, crossbred cattle and a polymerase chain reaction (PCR)‐derived clone library was constructed, using a specific primer set targeting 18S ribosomal RNA genes of ciliate protozoa. DNA fragments of seven selected clones were validated for standard DNA of the protozoa‐specific real‐time PCR assay. Furthermore, population fluctuation of ciliate protozoa and methanogens in the cattle rumen was determined by real‐time PCR. A total of 60 clones were sequenced, phylogenetically analyzed, and classified into 24 operational taxonomic units (OTUs) based on a 99% similarity criterion. More than 80% sequences were phylogenetically placed in the genus Entodinium. The rest of the sequences were placed in the genus Diploplastron (5%), Dasytricha (8.3%) and Isotricha (3.3%). The results suggest that Entodinium was the dominant group in the rumen of cattle used in this study. The ciliate protozoan population showed no significant change in numbers during the monitoring period and reached a peak at 3 h after feeding. Changes in the protozoa population were lower than those of the methanogens.     

The role of IFN-gamma in cattle infected with Theirelia sergenti

The spleen plays an important role in cellular immunity leading to parasite elimination, especially in hemo-protozoan parasite infection. In the present study, we quantified the serum IFN-gamma in splenectomized (SP) and non-splenectomized (NSP) cows infected with Theirelia sergenti (TS) to investigate whether the spleen plays a role in the Th1-type cytokine responses in cows following parasite infection. A transient increase in IFN-gamma was observed in the early stages of infection in the NSP cows, and the cows did not develop parasitemia. In contrast, the SP cows showed no IFN-gamma response at the early stage of infection, and the cows developed parasitemia following anemia. The NSP cows produced IgG1 and IgG2 antibodies to TS-specific, whereas the SP cows showed increases only in IgG1. Increased PBMC proliferation by cocanavalin A stimulation was observed concomitant with the IFN-gamma response. Pretreatment with IFN-gamma suppressed the propagation of TS in the SP cattle. These results suggest that the spleen plays an important role in the resistance to TS infection, leading to a Th1-type immune response. IFN-gamma might contribute to the activation of immunocytes and play an important role in the immune response to resist TS proliferation.