Toxoplasma gondii antibody prevalence and isolation in free-ranging cats in Okinawa,Japan

Cats are an important host of Toxoplasma gondii from an epidemiological perspective because they are the only definitive hosts that excrete oocysts in their feces. In this study, 201 free-ranging cats in Okinawa were examined for T. gondii infection. Using the latex agglutination test, we detected antibodies against T. gondii in 26.9% (54/201) of the cats. Oocysts of T. gondii were not detected upon microscopic examination of the feces of 128 cats. T. gondii was isolated from the tissues of 9 out of 24 seropositive or pseudo-seropositive cats with a bioassay using laboratory mice. Genotyping for the GRA6 gene revealed that five and four of the isolates were type I and II, respectively.     

Novel SNP in 5' flanking region of EDG1 associated with marbling in Japanese Black beef cattle

Marbling, defined by the amount and distribution of intramuscular fat, is an economically important trait of beef cattle in Japan. The endothelial differentiation , sphingolipid G-protein-coupled receptor , 1 ( EDG1 ) gene has been considered as a positional functional candidate for the gene responsible for marbling. We have recently reported that 2 single nucleotide polymorphisms (SNPs), c.-312A > G in the 5' untranslated region (UTR) and c.*446G > A in the 3' UTR in EDG1 were associated with marbling in Japanese Black beef cattle, but this was not functional and a causal mutation for marbling. In the present study, we detected 2 novel SNPs, referred to as g.1475435G > A and g.1471620G > T , in the 5' flanking region of the EDG1 between low-marbled and high-marbled steer groups, which were previously shown to have EDG1 expression differences in musculus longissimus muscle. The g.1475435G > A SNP seemed not to segregate in Japanese Black beef cattle. The g.1471620G > T SNP was associated with the predicted breeding value for beef marbling standard number by the analyses using Japanese Black beef cattle population. Based on these findings, we hypothesized that the g.1471620G > T SNP might have an impact on EDG1 expression and also marbling.     

Effect of feeding rotifers enriched with taurine on the growth and survival of larval amberjack Seriola dumerili

The effect of feeding rotifers enriched with taurine on the growth performance and survival of larval amberjack Seriola dumerili was investigated. Rotifers were enriched with a commercial taurine supplement at four levels (0, 200, 400, and 800 mg/l). The larvae were fed the enriched rotifers in triplicate from 3 days post-hatch for 7 days under static conditions. The average taurine contents of the rotifers were 1.5, 2.7, 4.2, and 7.2 mg/g dry matter, respectively. The growth of the fish fed rotifers enriched with the taurine supplement at 800 mg/l was significantly (P < 0.05) improved compared with that of the fish fed the rotifers without taurine enrichment. The survival rate improved proportionally up to a taurine supplement level of 400 mg/l, but no significant differences in survival were observed among treatments. The fraction of the larvae with inflated swim bladders did not vary significantly between treatments. Taurine content in the whole fish body increased with the taurine level in the rotifers. These results suggest that taurine enrichment of rotifers is an effective method of enhancing the growth of amberjack larvae.     

Timing and frequency of egg-collar production of the moonsnail Euspira fortunei

Predation on the Manila clam Ruditapes philippinarum by the non-indigenous moonsnail, Euspira fortunei, has had severe impacts on clam fisheries in some localities in Japan. This paper aims to reveal when and how many egg collars E. fortunei produce during the egg-laying season. To investigate the frequency of egg-collar production, 13 pairs of E. fortunei were reared in aquaria with natural seawater flowing from July to December 2009. Each pair produced only one or two egg collars during 1 day in October; thereafter, no egg collars were produced. The timing of egg collar production, estimated from observational information by fishermen in the field from 2004 to 2010, varied among years. The period between September 1 and the day of the initial observation of egg collars was positively correlated with the average water temperature in August, suggesting that water temperature can be used to predict the timing of egg collar occurrence.     

Partial characterization and ontogenetic development of pancreatic digestive enzymes in Japanese eel Anguilla japonica larvae

The pancreatic digestive enzymes, trypsin, chymotrypsin, lipase and amylase were partially characterized, and changes in their activities were examined during the initial ontogeny of Japanese eel Anguilla japonica larvae from 5 to 34 days post-hatching (dph). The pH optima of the eel larval enzymes were narrower than those other fish species; trypsin activity was highest at pH 9, chymotrypsin and amylase activities were highest at pH 7 and 8, and lipase activity was highest at pH 8 and 9. In an analysis of thermal profiles, the larval pancreatic enzymes had a high optimal temperature and high thermal stability, which are typical of fish from the tropics. At 12 and 13 dph, lipase activity and gene expression levels of trypsin (-a and -b), lipase and amylase decreased markedly, suggesting a marked change in larval metabolism at that time. These data could be useful in the development of artificial larval diets in Japanese eel.     

Growth performance and physiological condition of F1 amago salmon Oncorhynchus masou ishikawae juveniles obtained from broodstock with selective breeding for growth on a low fish-meal diet

A 10-week feeding trial was conducted to evaluate the growth and physiological condition of F1 amago salmon Oncorhynchus masou ishikawae juveniles obtained from broodstock that had been selected for growth on a low fish-meal (LFM) diet. F1 juveniles from broodstock showing superior or inferior growth on a LFM diet (LFM-S, LFM-I), and those from broodstock showing intermediate growth on a fish meal-based (FM) diet (FM-M), were fed a LFM diet and a FM diet. In fish fed the LFM diet, growth of LFM-S was significantly better than FM-M at 3 weeks; however, this superiority in growth disappeared at the end of the 10-week trial. Growth of LFM-I was significantly lower than LFM-S throughout the feeding trial. Growth of fish fed the FM diet was not significantly different among groups, and higher than fish fed the LFM diet. Improvements in the blood hemoglobin concentration and morphological conditions of the distal intestine and liver were observed in LFM-S fed the LFM diet. Although the effect of selective breeding was limited in F1 amago salmon, the present results suggest that continuous selection for growth with a LFM diet has potential as a method to adapt to the limited supply of fish meal.     

Disparities in activity levels and learning ability between Djungarian hamster (Phodopus sungorus) and Roborovskii hamster (Phodopus roborovskii)

The Djungarian hamster and the Roborovskii hamster belong to the same genus of Phodopus. However, the Djungarian hamster is tame and shows sedative behavior, while Roborovskii hamster is not tame and shows high levels of locomotor activity. Hyperactivity occurs in animals with tameless behavior. Tameness or tamelessness behavior is very important because tameness helps for breeding and controlling as well as it enables a strong human‐animal bond. In the present study, we examined the relationships between activity levels and cognitive function in Djungarian and Roborovskii hamsters. Three types of behavioral tests were performed to analyze their activity levels, memory and leaning ability. The levels of L‐ and D‐amino acids and monoamines in the brain were then determined. Roborovskii hamsters showed significantly higher locomotor activity than Djungarian hamsters. Memory ability was not significantly different between the two hamsters, but Roborovskii hamsters showed lower learning ability. Brain levels of D‐serine which is related to enhancement in memory and learning ability, were significantly higher in Djungarian hamsters, but the reverse was true for brain dopamine and serotonin levels. These results suggest that these differences in brain metabolism may be related to the behavioral differences between the two hamsters.     

Comparing the carbon sequestration capacity of temperate deciduous forests between urban and rural landscapes in central Japan

Urbanisation is increasing tremendously in some parts of the world. Consequently, many rural forests may become depleted, although many opportunities exist for urban forests to increase. However, few studies have quantified the carbon (C) sequestration capacities of urban and rural forests in specific climatic zones. The present study compared carbon sequestration in two temperate deciduous forests located in Nagoya and Toyota, central Japan. The Nagoya University forest represented an urban forest, and a site in Toyota represented a rural forest. The urban forest at Nagoya University had comparatively smaller areas of green space and larger areas of buildings and roads. Land uses for building and road, which are typical of urban areas, result in smaller diurnal temperature ranges but higher air temperature, vapour pressure deficit, and atmospheric carbon dioxide (CO₂) concentration. The urban forest in this study exhibited higher gross ecosystem exchange (GEE), especially in the active growing season from May to September, suggesting the possible effect of CO₂ fertilisation. However, higher air temperatures caused comparatively smaller net ecosystem exchange (NEE) because of higher ecosystem respiration (RE). Although both forests functioned as CO₂ sinks at annual time scales, the rural Toyota forest site (5.43 t C ha^–1 yr^–1) had 36% higher net ecosystem production (NEP=–NEE; the negative sign indicates uptake by the forest ecosystem from the atmosphere) than that at the urban forest. The higher normalised respiration (i.e., RE/GPP ratio; GPP=–GEE where GPP represents gross primary production) at the Nagoya University forest might be attributable to factors associated with the degree of urbanisation. Thus, in temperate forests, factors associated with urbanisation may reduce the atmospheric carbon sink function by accelerating respiration. This is an issue of global interest, as many countries are experiencing rapid urbanisation.     

An avirulence gene homologue in the tomato wilt fungus Fusarium oxysporum f. sp. lycopersici race 1 functions as a virulence gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans

Six4, a small protein secreted by Fusarium oxysporum f. sp. lycopersici (Fol) in tomato xylem sap during infection, triggers Fol race 1-specific resistance (I) in tomato. SIX4 is regarded as an avirulence gene. Although SIX4 is considered unique to Fol race 1, we detected this gene in the cabbage yellows fungus F. oxysporum f. sp. conglutinans (Foc) by PCR. Because the genes from Foc and SIX4 in Fol were >99 % identical at the nucleotide level, the Foc gene was designated FocSIX4. The expression of FocSIX4 was detected by RT-PCR in stems and roots of cabbage 8 days after infection with Foc. In contrast with Fol, disruption of FocSIX4 in Foc did not increase virulence to Foc-resistant cabbage cvs. Shutoku-SP and Koikaze. On the contrary, the disruptants had reduced virulence not only on Foc-resistant cultivars but also on Foc-susceptible cv. Shikidori. These results suggested that FocSIX4 is involved in virulence, but not in avirulence, in the cabbage yellows fungus.