Polysaccharide-induced protection of carp, Cyprinus carpio L., against bacterial infection

Abstract. The efficacy of 10 polysaccharides (curdlan, inulin, krestin, laminaran, lentinan, levan, schizophylian, selerogiucan, yeast glucan and zymosan) to enhance protection of carp, Cyprinus carpio L., against bacterial infection was investigated. Carp were intraperitoneally injected with the polysaceharides (2–l0 mgkg^-1) on days 1 and 4, and challenged with Edwardsiella tarda on day 7. Among the polysaccharides tested, lentinan, schizophyllan and scleroglucan, which are l,6-branchcd-β-l,3-glucans, significantly increased the survival rate. They also induced a protective effect against Aeromonas hydrophila at a dose of 5 mg kg^-1. The ability of the polysaccharides to activate the alternative complement pathway (ACP) was examined by incubating the polysaccharides with carp serum and measuring the residual ACP activity. At a final concentration of 0.l mgml^-1, l,6-branched-β-1,3-glucans greatly reduced (76–77%) the ACP activity. Therefore, it is suggested that the protective effect of the l,6-branched-β-1,3-glucans may be associated with the activation of ACP.     

A molecular phylogeny of wild and cultivated Echinochloa in East Asia inferred from non-coding region sequences of trnT-L-F

The phylogenetic relationship among 30 accessions belonging to nine species of the genus Echinochloa Beauv. was studied on the basis of the sequence of three non-coding regions ( trn T-L, trn L-F intergenic spacers, and trn L intron) of chloroplast DNA (cpDNA). A strict consensus parsimonious tree of the three most parsimonious trees derived from 25 polymorphic sites (six indels and 19 substitutions) in the total sequences, ranging from 1715–1760 bp, represented five groups: (i) Echinochloa oryzicola Vasing. and Echinochloa stagnina Beauv. from Thailand; (ii) Echinochloa crus-galli Beauv. complex; (iii) Echinochloa crus-pavonis Schult; (iv) Echinochloa colonum Link. and Echinochloa frumentacea Link.; and (v) the African species, Echinochloa obtusiflora Stapf and Echinochloa stagnina . Japanese barnyard millet ( Echinochloa esculenta H. Scholz) and various weedy varieties of E. crus-galli and Echinochloa oryzoides Fritsch had quite similar sequences and formed the E. crus-galli complex, which was characterized by six substitutions. A cultivated form of E. oryzicola (Mosuo barnyard millet) and various morphological and agronomical forms of E. oryzicola were characterized by two indels. Indian barnyard millet ( E. frumentacea ) and its wild counterpart ( E. colonum ) were characterized by five substitutions. Domestication as millets and adaptation to paddy environments as mimic weeds might occur after the divergence of species in the Asian Echinochloa .     

Evaluating the impact of COVID-19 on ex-vessel prices using time-series analysis

The spread of coronavirus disease 2019 (COVID-19) and subsequent lockdown measures have impacted economies and industries worldwide. The fisheries industry witnessed a sharp decline in demand and a slump in fish prices due to its dependence on the food service industry. It is important to quantitatively assess those fish species affected most and the extent of the pandemic’s impact on them, to take specific countermeasures. We propose a time-series analysis as an alternative to the current practice of using ad hoc year-on-year comparisons. Although the pandemic makes it difficult to construct a counterfactual approach due to the lack of an appropriate control group, we use time-series forecasting to simulate normal conditions using pre-pandemic data. In Tokyo, the unit price of fish species that were negatively impacted by the food services industry dropped by 12.65% to 14.64%, and by 26.08% to 28.22% after the declaration of a state of emergency. Seasonality, short weekly cycles, and short-term market trends are factors that affect the price of fish. Species-specific impact estimates related to the COVID-19 pandemic can allow policymakers to implement recovery measures in a more targeted and effective manner. The results of our analysis can increase fishers’ and policymakers’ awareness of the usefulness of economic analyses and incentivize them to release data to establish a system to accumulate and analyze data strategically for urgent and appropriate interventions in the fisheries industry.

     

Fat depot‐specific differences in leptin mRNA expression and its relation to adipocyte size in steers

ABSTRACT This experiment was conducted to investigate leptin mRNA expression, adipocyte size, and their relationship in several adipose tissues of fattening steers. Subcutaneous, perirenal, intermuscular and intramuscular adipose tissues were collected from three crossbred steers (Japanese Black cattle X Holstein) aged 21 months. The mRNA level and adipocyte diameter were determined in these adipose tissues. The intramuscular adipose tissue had a lower leptin mRNA level than the intermuscular and perirenal adipose tissues (P < 0.05). Leptin mRNA level was lower in the subcutaneous depot than in the intermuscular depot (P < 0.05). Adipocyte diameter was larger in the intermuscular adipose tissue than in the subcutaneous and intramuscular adipose tissues (P < 0.05). Leptin mRNA level was positively correlated with adipocyte diameter (r² = 0.81, P < 0.05). These results suggest that the cattle have fat depot‐specific differences in leptin gene expression, which are a result of a difference in adipocyte size.     

The importance of mother–infant communication for social bond formation in mammals

Mother–infant bonding is a universal relationship of all mammalian species. Here, we describe the role of reciprocal communication between mother and infant in the formation of bonding for several mammalian species. Mother–infant bond formation is reinforced by various social cues or stimuli, including communicative signals, such as odor and vocalizations, or tactile stimuli. The mother also develops cross‐modal sensory recognition of the infant, during bond formation. Many studies have indicated that the oxytocin neural system plays a pivotal role in bond formation by the mother; however, the underlying neural mechanisms for infants have not yet been clarified. The comparative understanding of cognitive functions of mother and infants may help us understand the biological significance of mother–infant communication in mammalian species.     

Habitat modification by invasive crayfish can facilitate its growth through enhanced food accessibility

Background

Invasive ecosystem engineers can facilitate their invasions by modifying the physical environment to improve their own performance, but this positive feedback process has rarely been tested empirically except in sessile organisms. The invasive crayfish Procambarus clarkii is an ecosystem engineer that destroys aquatic macrophytes, which provide a physical refuge for animal prey, and this destruction is likely to enhance vulnerability to predators. Using two series of mesocosm experiments, we tested the hypothesis that the invasive crayfish increases its feeding efficiency on animal prey by reducing submerged macrophytes, thus increasing its individual growth rate in a positive density-dependent manner.

Results

In the first experiment, increasing crayfish density reduced both macrophytes and animal prey (dragonfly and chironomid larvae) and, importantly, increased the growth rate of individual crayfish, in accordance with our expectation. In the second experiment, we used artificial macrophytes to clarify whether the physical architecture of macrophytes itself protects animal prey and limits crayfish growth rate. Increasing the artificial macrophyte quantity not only increased the survival of animal prey, but also retarded the crayfish growth rate.

Conclusions

We conclude that macrophytes strengthen bottom-up control of crayfish, but this effect can be relaxed by increasing the density of crayfish via reduction in macrophytes. This positive feedback process may explain the crayfish outbreaks and regime shifts occasionally observed in invaded freshwater ecosystems.

     

Reproductive traits and diel activity of adultMonochamus saltuarius (Coleoptera: Cerambycidae) at two different temperatures

To investigate the reproductive traits and diel activity ofMonochamus saltuarius, 14 pairs of the adults were reared and observed at each of 20°C and 25°C. Both sexes were more active at 25°C than at 20°C irrespective of the presence or absence of light. A diel change in behavior during 24 h was found on 33% of a total of 48 observations of three age classes of both sexes. No significant difference was found in the mean longevity between sexes or between the two temperature conditions. The time required for reproductive maturation showed no significant difference within the same sex when reared at 20°C and 25°C. The mean oviposition period was significantly longer at 25°C (28.8 days) than at 20°C (12.2 days). The mean lifetime fecundity was significantly greater at 25°C than at 20°C. There was no significant difference in the oviposition ratio (number of eggs deposited/number of oviposition wounds excavated), oviposition rate or hatchability for females between the two temperature conditions.     

Nitrogen uptake by sago palm (Metroxylon sagu Rottb.) in the early growth stages

Previous trials have revealed variable responses of sago palm ( Metroxylon sagu Rottb.) to fertilizer application, particularly nitrogen (N). In the present study, we quantified the fertilizer use efficiency (FUE) of sago palm for the first time using ¹⁵N-labeled fertilizer in pot and field experiments. The pot experiment was conducted in Japan using a 2:1 mixture of sand to Philippine soil. The field experiment was conducted in Leyte in the Philippines. Both experiments consisted of three replicates in each of three treatments: control, ¹⁵N urea at 50 kg N ha⁻¹ and ¹⁵N urea at 100 kg N ha⁻¹. The N uptake of sago palm increased significantly, but inconsistently with increasing N application. The few instances of a significant increase in N uptake did not translate into significant improvements in growth parameters, except for the number of leaflets in the pot experiment. The FUE values for sago seedlings (< 6 months) in the pot experiment treated with 50 and 100 kg N ha⁻¹ were 10.5 and 13.2%, respectively, whereas for the 2-year-old sago palms in the field, the corresponding FUE values were 14.8 and 12.0%. The FUE values were similar at the two levels of N application in both experiments. Sago growth parameters appeared to be insensitive to N application, suggesting that the form of N and the timing of N fertilization are important factors for sago palms. Therefore, the use of N fertilizer in sago production can only be justified after determining and fully understanding the response of sago palm to N application.