Behaviour of immature yellowtails (Seriola quinqueradiata) observed by electronic data-recording tags

The long-term behaviour of immature yellowtails, Seriola quinqueradiata , was studied using electronic data-recording tags in Sagami Bay, Japan, during the autumn and early winter. Temperature or depth data were continuously recorded for 5–69 days on six yellowtails. The temperature recorded from the 0-year-old yellowtails showed only small variations (<0.5°C day⁻¹) around the SST on the coast, indicating the 0-years stayed in the immediate coastal area with little horizontal movement. The 1-year-old yellowtail showed larger temperature variations that reached 3°C day⁻¹, which implies distinctly larger horizontal movements than the 0-year-olds. Depth records showed the 0-years stayed around 10 m while the 1-year yellowtail swam in deeper water (mainly 10–30 m) with large variations. The latter often dived to 40 m in the daytime, but shallower than the depth of the thermocline. Both temperature and depth records showed apparent diurnal patterns. Comparing the fish data with environmental conditions, it is suggested that 1-year yellowtails stay close to the coast during the night, move at dawn to feed in the daytime and return at dusk via a frontal zone. In addition, wind stress could change yellowtails' behaviour.     

Freshwater migration and feeding habits of juvenile temperate seabass <Emphasis Type="Italic">Lateolabrax japonicus</Emphasis> in the stratified Yura River estuary,the Sea of Japan

Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were particularly abundant in areas with aquatic vegetation in the freshwater zone. This distribution pattern suggests that the early life history of the temperate seabass depends more intensively on the river (freshwater) than previously considered. Small juveniles in the freshwater zone fed on copepods and chironomid larvae and upon reaching a standard length (SL) of approximately 20 mm did they fed on mysids. In contrast, juveniles (approx. 17–80 mm SL) in the surf zone fed mainly on mysids.     

Effect of light irradiation on the antibacterial activity of compounded papers containing wasted tea leaves

The endurance of the antibacterial properties of compounded papers containing wasted green tea leaves needs to be examined before considering these papers for long-term use. Hence, compounded papers containing 60 wt% wasted green tea leaves were irradiated for 1–200 h using a xenon lamp to examine the effect of irradiation on antibacterial properties of the paper. Irradiation for 20 h (cumulative ultraviolet dose at 365 nm, 6.67 × 10⁶ J/m²) or longer was found to greatly increase the antibacterial activity of the paper to a level at which no bacterial cell was confirmed to be viable. The paper was also covered with various glass filters and irradiated for 1 h. Irradiation exclusively with visible rays did not significantly affect the antibacterial activity of the paper, whereas irradiation exclusively with ultraviolet rays, even for a short time, greatly increased the antibacterial activity.     

Circadian locomotor activity in Japanese sea catfish <Emphasis Type="Italic">Plotosus lineatus</Emphasis>

To find out whether or not the locomotor activity of the Japanese sea catfish, Plotosus lineatus, shows a circadian rhythmicity, the locomotor activity of this catfish was recorded in a laboratory. All of the catfish recorded (n = 20) showed a nocturnal locomotor activity rhythm under a light–dark (LD) cycle (LD 12:12). The locomotor activity started after the light was turned off, and declined during the period of darkness. In five of the six catfish we examined, locomotor activity shifted gradually over the course of 3–4 days in order to synchronize to the LD cycle after it was advanced by 6 h. Locomotor activity persisted within a constant darkness (DD) in all eight of the catfish. The average free-running period of locomotor activity under DD lasted for 24.2 ± 0.4 h (mean ± SD). Thus, the present results demonstrate that the Japanese sea catfish has an endogenous circadian oscillator entrained by an LD cycle.     

Inactivation of koi‐herpesvirus in water using bacteria isolated from carp intestines and carp habitats

Since its first outbreak in Japan in 2003, koi‐herpesvirus (KHV) remains a challenge to the carp Cyprinus carpio L. breeding industry. In this study, inactivation of KHV in water from carp habitats (carp habitat water) was investigated with the aim of developing a model for rapidly inactivating the pathogen in aquaculture effluent. Experiments with live fish showed that, in carp habitat water, KHV lost its infectivity within 3 days. Indications were that inactivation of KHV was caused by the antagonistic activity of bacteria (anti‐KHV bacteria) in the water from carp habitats. Carp habitat water and the intestinal contents of carp were therefore screened for anti‐KHV bacteria. Of 581 bacterial isolates, 23 showed anti‐KHV activity. An effluent treatment model for the disinfection of KHV in aquaculture effluent water using anti‐KHV bacteria was developed and evaluated. The model showed a decrease in cumulative mortality and in the number of KHV genome copies in kidney tissue of fish injected with treated effluent compared with a positive control. It is thought that anti‐KHV bacteria isolated from the intestinal contents of carp and from carp habitat water can be used to control KHV outbreaks.     

The effect of temperature on environmental DNA degradation of Japanese eel

Fisheries Science - The environmental DNA (eDNA) technique is a convenient and powerful tool to detect rare species. Knowledge of the degradation rate of eDNA in water is important for...     

Experimental H-type bovine spongiform encephalopathy characterized by plaques and glial- and stellate-type prion protein deposits

ABSTRACT: Atypical bovine spongiform encephalopathy (BSE) has recently been identified in Europe, North America, and Japan. It is classified as H-type and L-type BSE according to the molecular mass of the disease-associated prion protein (PrPSc). To investigate the topographical distribution and deposition patterns of immunolabeled PrPSc, H-type BSE isolate was inoculated intracerebrally into cattle. H-type BSE was successfully transmitted to 3 calves, with incubation periods between 500 and 600 days. Moderate to severe spongiform changes were detected in the cerebral and cerebellar cortices, basal ganglia, thalamus, and brainstem. H-type BSE was characterized by the presence of PrP-immunopositive amyloid plaques in the white matter of the cerebrum, basal ganglia, and thalamus. Moreover, intraglial-type immunolabeled PrPSc was prominent throughout the brain. Stellate-type immunolabeled PrPSc was conspicuous in the gray matter of the cerebral cortex, basal ganglia, and thalamus, but not in the brainstem. In addition, PrPSc accumulation was detected in the peripheral nervous tissues, such as trigeminal ganglia, dorsal root ganglia, optic nerve, retina, and neurohypophysis. Cattle are susceptible to H-type BSE with a shorter incubation period, showing distinct and distinguishable phenotypes of PrPSc accumulation.     

Comparison of the variability in the levels of pesticide residue observed in Japanese cabbage and grape units

To estimate variations in pesticide residue levels in crops, the variability factors (VFs, the 97.5th percentile of the residue levels in the sample divided by the average residue levels in the lot) in residue levels of acetamiprid and cypermethrin applied to cabbage and grapes were investigated, respectively. The VFs in the residue levels of both pesticides in cabbage (2.00 and 2.39, respectively) were clearly higher than those in grapes (1.82 and 1.63, respectively). Although the residue levels of both pesticides in grapes showed a normal distribution, those values in cabbage were slightly skewed at lower residue levels. Individual residue levels in grapes had a good agreement between acetamiprid and cypermethrin. In contrast, the distribution of cypermethrin residue levels in cabbage was slightly skewed at higher residue levels as compared to that of acetamiprid. These results indicate that the difference in the relative distribution of the two pesticides between cabbage and grapes might be due to the influence of various factors such as differences in crop species, plant cultivation methods, and physicochemical properties of the pesticides.     

Availability of a Microglia and Macrophage Marker,Iba-1, for Differential Diagnosis of Spontaneous Malignant Reticuloses from Astrocytomas in Rats

In rats, it is sometimes difficult to distinguish malignant reticuloses from astrocytomas in routine histopathological assessment. In the present study, four spontaneous brain neoplasms developing in the cerebrum of one Wistar Hannover rat and three Sprague-Dawley rats were immunohistochemically examined using microglia and macrophage markers. Histopathologically, these neoplasms were localized mainly in the cerebral cortex, hypothalamus or piriform lobe, and the portions showing solid growth did not show characteristic cellular arrangement but had an indistinct boundary with the surrounding brain parenchyma. Neoplastic cells had oval or pleomorphic small nuclei with abundant eosinophilic cytoplasm. Two cases showed neoplastic cell infiltration into the meninges and perivascular spaces. Silver staining showed lack of reticulin fiber production in the stroma of the neoplasms. Immunohistochemically, the neoplastic cells were strongly positive for Iba-1 and sporadically positive for CD68 in all four cases. On the basis of these results, all the neoplasms examined here could be distinguished from astrocytomas and diagnosed as malignant reticuloses. Thus, immunohistochemical demonstration of microglia/macrophage characters, such as using Iba-1, is considered to be helpful for differential diagnosis of malignant reticuloses from astrocytomas among spontaneously occurring primary brain neoplasms in rats.     

Long-Time Exposure of Mouse Embryos to the Sperm Produces High Levels of Reactive Oxygen Species in Culture Medium and Relates to Poor Embryo Development

Small amounts of reactive oxygen species (ROS), metabolites of oxygen, are necessary for sperm-fertilizing capability. However, in excessive levels, their role in infertility has been extensively studied. The conventional in vitro fertilization (IVF) method employs a prolonged co-incubation of gametes for 16–18 h to reach fertilization. However, it has been shown that this long period might create high levels of ROS. We aimed at finding out whether ROS increases in vitro during prolonged incubation with fertilized oocytes and whether high level of ROS relates to poor embryo development. To confirm if levels of ROS relate to length of time, we measured the ROS levels in fertilization medium (FM), which contained mouse embryos exposed to spermatozoa. To evaluate the contribution of sperm in production of ROS, we measured the ROS in the medium with only sperm. The measurements were performed by chemiluminescence assay using luminol as a probe after 4 and 18 h of incubation separately. The ROS levels were significantly increased after 18 h as compared with 4 h (p < 0.0001). Moreover, ROS in the medium with only sperm was also increased after 18 h (p < 0.0001), demonstrating that they were generated either by spermatozoa or as a result of possible reaction of sperm with medium during prolonged incubation. In addition, we compared embryo development after 2, 4, 6, 8, 10, 12 and 18 h of incubation. The number of degenerated embryos exposed to sperm for 12 and 18 h was significantly higher than those exposed for 4 or 6 h (p < 0.01). These results demonstrate that ROS concentrations appear to be related to the length of incubation time, and their excessive levels have a negative effect on embryo development. We suggest reducing incubation time to at least 4 h.