Effects of water temperature on early development of Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

ABSTRACT:   To determine an optimal temperature range for efficient production of healthy eel larvae Anguilla japonica , the effect of water temperature on hatching, survival, and deformity rates was examined. The early ontogeny of morphological features in this species by incubating eggs at five different temperatures (19, 22, 25, 28 and 31°C) was examined. Hatching occurred at 24, 28, 46 and 58 h after fertilization when incubated at 28, 25, 22 and 19°C, respectively; no eggs hatched at 31°C. The growth rate of prefeeding larvae increased as water temperature was elevated and acquisition of feeding ability was also accelerated at higher temperature. Significantly high hatching rates (76–86%, P  < 0.05) and survival rates (61–86%, P  < 0.05) were observed at relatively high temperatures (22–28°C). The deformities were 'open lower jaw', 'pericardial edema', and 'notochordal bending', in which the mouth was deformed with a downward projecting lower jaw, the pericardial cavity was swollen, and the notochord was bent or twisted to various degrees, respectively. Open lower jaw and pericardial edema were especially predominant at 19°C, with rates of 68 and 92%, respectively, compared with 31 and 10% at 25 and 28°C, respectively. The occurrence of notochordal bending was not affected by temperature. The optimal temperature for incubation and rearing A. japonica eggs and prefeeding larvae is approximately 25–28°C.     

The characterization of low pathogenic avian influenza viruses isolated from wild birds in northern Vietnam from 2006 to 2009

Due to concerns that wild birds could possibly spread H5N1 viruses, surveillance was conducted to monitor the types of avian influenza viruses circulating among the wild birds migrating to or inhabiting in northern Vietnam from 2006 to 2009. An H5N2 virus isolated from a Eurasian woodcock had a close phylogenetic relationship to H5 viruses recently isolated in South Korea and Japan, suggesting that H5N2 has been shared between Vietnam, South Korea, and Japan. An H9N2 virus isolated from a Chinese Hwamei was closely related to two H9N2 viruses that were isolated from humans in Hong Kong in 2009, suggesting that an H9N2 strain relevant to the human isolates had been transmitted to and maintained among the wild bird population in Vietnam and South China. The results support the idea that wild bird species play a significant role in the spread and maintenance of avian influenza and that this also occurs in Vietnam.     

Isolation of Theileria sergenti piroplasms from infected erythrocytes and development of an enzyme-linked immunosorbent assay for serodiagnosis of T sergenti infections

A method of obtaining a pure suspension of Theileria sergenti piroplasms from infected bovine erythrocytes was developed and the resulting parasites used as antigen in an enzyme-linked immunosorbent assay (ELISA). Piroplasms were freed from infected erythrocytes using the nitrogen cavitation technique and then separated from unbroken erythrocytes by centrifugation at 670 gmax. The parasites in the supernatant were then sedimented by centrifugation at 2700 gmax and the purified fraction examined by electron microscopy. This examination showed that the isolated piroplasms were morphologically intact and that there were few contaminants. SDS-PAGE and spectrophotometric analysis showed that this fraction contained little erythrocyte component. The piroplasms thus obtained were sonicated and treated with Triton X-100 then used for ELISA antigen. The ELISA values had a high correlation with titres obtained using the indirect fluorescent antibody test on sera from cattle infected with T sergenti.     

Malfunction of spermatogenesis in experimental ischemic mice

An experimental ischemia (EI)-induced mouse model was used to analyze pathological and biochemical alterations in testes. Initial morphological changes were observed in Sertoli cells of EI testes at the light microscopic level. Examination of the ultrastructure using transmission electron microscopy confirmed that Sertoli cells were partially detached from the basement membrane of the seminiferous epithelium and that the cell membranes of adjacent Sertoli cells were not joined. The functional integrity of the blood-testis barrier (BTB) was assessed using the lanthanum tracer technique. Lanthanum had penetrated into the spaces between adjacent Sertoli cells in the adluminal compartment up to the lumen of the seminiferous epithelium in EI testes. Proteome analysis showed that the expression of heat shock protein (HSP) 70 was significantly upregulated in EI testes. Western blot analysis confirmed that the expression of HSP70 increased in a time-dependent manner after the EI procedure. HSP70 immunostaining was observed in spermatocytes and in round and elongated spermatids in EI testes. Our results suggest that a change in the junctions between adjacent Sertoli cells on the basal compartment is involved in the BTB disruption in EI testes. Therefore, male infertility caused by the BTB disruption could be associated with heat stress induced by ischemia.     

The relationship between sperm morphology and in vitro fertilization ability in mice

In vitro fertilization (IVF) is widely used in reproduction research, but the sperm of some inbred strains of mice yield low fertilization rates in IVF. To determine the cause of this problem, we examined the effect of epididymal sperm morphology, in particular, tail bending and the presence and type of cytoplasmic droplet (CD), on fertilizability in vitro. Sperm suspensions were obtained from the following five strains: C57BL/6J, BALB/cA, C3H/HeN, DBA/2J, and 129 x 1/SvJ. The sperm were fixed in 10% formalin and three parts of the sperm, namely the head, tail, and CD, were examined. We recorded the proportion of abnormal sperm heads and hairpins at the neck; tails were categorized as straight, proximal bent, or distal bent; and the CDs were categorized as none, light-type, and heavy-type. Based on these parameters, we determined the correlations between sperm morphology and fertilizability in vitro, as judged by IVF using ICR oocytes. The proportion of sperm with a hairpin neck was higher in strain C57BL/6J, while abnormal head morphology occurred significantly more often in strain BALB/cA. The percentage of sperm with a proximal bent tail was highest in strain DBA/2J and lowest in strain 129 x 1/SvJ. A heavy-type CD was observed more frequently in the 129 x 1/SvJ and C57BL/6J strains than in the other three strains in which a light-type CD predominated. The rank order of the fertilization rates was 129 x 1/SvJ < C57BL/6J < C3H/HeN < BALB/cA < DBA/2J. In addition, fertilization rate was positively correlated with a proximal bent tail, but negatively correlated with a heavy-type CD and distal bent tail. This new classification system establishes that the morphological characteristics of epididymal sperm differ among inbred strains of mice and that tail and CD morphology are closely related to fertilization ability in IVF. Thus, our results provide a novel method for assessing the quality of mouse sperm used for IVF.     

Characterization of salt tolerance in tomato plant in terms of photosynthesis and water relations

Three commercial tomato cultivars (UC-97, Momotaro, and Edkawi) were subjected to a gradual increase of NaCI concentrations and the effect on biomass production and its parameters was compared. The data indicated that salinity reduced plant growth and the reduction was more pronounced in UC-97 and less in Edkawi. The apparent photosynthetic rate (P _o) was also depressed by the salt treatment and the depression was more remarkable in UC-97 and less in Edkawi. Edkawi shoot showed a much higher concentration of sodium ion and proline compared with the other cultivars, which may result in the maintenance of a higher turgor potential. In all the cultivars examined the stem diameter decreased after the beginning of exposure to light and recovered after the light was turned off. The decrease in the stem diameter during day light was enhanced and the recovery at night decreased after 1 d of salt treatment and the changes in the stem diameter were less conspicuous in Edkawi than in the other cultivars. These results suggest that Edkawi is more tolerant to salinity than the other cultivars due to a higher ability of maintaining the root function for the uptake and supply of water to shoot under salinity conditions but not due to the adjustment of transpiration from stomata.     

Altitudinal life-cycle and body-size variation in ground beetles of the genus Carabus (subgenus Ohomopterus) in relation to the temperature conditions and prey earthworms

The body size of univoltine insect species generally decreases with increasing altitude or latitude. This pattern may have arisen from adaptations to multiple factors that potentially affect body-size variation, such as temperature, food, and interspecific interactions. We examined altitudinal variations in life history and body size, and their relationships to temperature and food resources in two ground beetle species of the genus Carabus (subgenus Ohomopterus; C. tosanus and C. japonicus) in a mountainous area (altitude 860–1730 m) of Shikoku Island, Japan. Larvae of these species are specialist predators of earthworms. The body size of C. tosanus decreased with an increase in altitude. Carabus japonicus, which is much smaller than C. tosanus, exhibited similar sizes across altitudes, although it was not abundant at high altitudes. Available cumulative temperatures for larval development were limited at higher altitudes, and C. tosanus started reproducing 1 month earlier at higher than at lower altitudes. Earthworms (larval food) were less abundant at higher than at lower altitudes. This may imply that food resources also restrict the optimal body size of C. tosanus at higher altitudes.     

Relationships between postnatal plasma oxytocin concentrations and social behaviors in cattle

We examined the associations between natural individual variations in basal oxytocin (OXT) in postnatal cattle and social behavioral traits. At 1, 2 and 6 weeks of age, the basal OXT exhibited individual variability in 20 Holstein heifer calves. Cluster analysis of mean OXT for these time periods obtained two subgroups: high OXT (HOXT; n = 9) and low OXT (LOXT; n = 11). Social behaviors were observed for 2 days at week 6 after introduction into a four‐peer group, and at 10–14 months of age (10 months) immediately and 1 week, 1 month and 5 months after introduction into 11–15 heifers. At week 6, the main effect of the OXT groups was not significant for all social behaviors. At 10 months, there tended to be interactions between the OXT groups and time periods with respect to the frequency of escape behaviors. LOXT heifers exhibited more escape behaviors than HOXT heifers on the first day of the second sociality tests. At 10 months, HOXT heifers exhibited both attacking and affiliative behavior for peers more than LOXT heifers during 5 months after the second social introduction. This suggests that postnatal OXT concentrations may have long‐lasting effects on individual differences among social behavioral traits in cattle.