The coat protein of <Emphasis Type="Italic">Tomato mosaic virus</Emphasis> L<Subscript>11</Subscript>Y is associated with virus-induced chlorosis on infected tobacco plants

The L₁₁Y strain of Tomato mosaic virus (ToMV) causes severe chlorosis on infected tobacco leaves. Sequencing analysis for the genome showed that L₁₁Y contained multiple nucleotide changes and that some led to amino acid substitutions, when compared with that of the common L strain of ToMV. The chimeric virus, which has the CP of L₁₁Y in the context of the L strain RNA genome, caused severe chlorosis on infected tobacco plants, suggesting that the CP of L₁₁Y containing three amino acid changes (E33S, A86T and E97K) was the determinant of the chlorosis. Two of these amino acid changes (A86T and E97K) were associated with the induction of chlorosis when present together in the CP. Severe destruction and deformation of chloroplasts and the formation of discrete dark-staining materials adjacent to chloroplasts were observed with electron microscopy in L₁₁Y-infected plants. Fewer virus particles accumulated in the cytoplasm of L₁₁Y-infected plant cells. The level of accumulation of CP subgenomic RNA and CP in the infected protoplasts was similar between L and L₁₁Y. Fewer virus particles accumulated in L₁₁Y-infected protoplasts, and many of them were shorter-than-full-length. The nucleotide sequence data reported is available in DDBJ/EMBL/GenBank databases as accession AB355139.     

Effects of co‐supply ratios of swimming crab Portunus trituberculatus zoeae and Artemia on survival and growth of East Asian common octopus Octopus sinensis paralarvae under an upwelling culture system

Despite recent advances in culture technology for East Asian common octopus Octopus sinensis paralarvae using upwelling systems, securing suitable feed for the paralarvae is an unresolved issue. The zoea of the swimming crab Portunus trituberculatus is a good candidate for paralarval feed because of the high fecundity of the adult females. To investigate the effects of supplying P. trituberculatus zoeae and their feeding method on paralarvae, we cultured paralarvae with supplying different combination ratios of zoeae and Artemia (10:0, 7:3, 5:5, 3:7 and 0:10), and with or without supplementing rotifers using small‐scale (3‐L) upwelling systems. Paralarval survival rate and growth were improved when zoeae were supplied as the main feed, but reduced when the proportion of Artemia exceeded half the whole preys. Supplementing rotifers did not affect the paralarval survival and growth. Subsequently, paralarvae were cultured by supplying zoeae (partially augmented by Artemia) using three large (1‐kl) upwelling systems to assess their feeding effectiveness in juvenile octopus production. Paralarvae could be cultured at high survival rates of 77.1 ± 5.1% to reach benthic juveniles at 23 days after hatching. In conclusion, supplying P. trituberculatus zoeae augmented with Artemia under an upwelling culture system has great potential for juvenile octopus production.     

Effects of salinity and dietary n-3 highly unsaturated fatty acids on the survival,development, and morphogenesis of the larvae of laboratory-reared mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Decapoda,Portunidae)

We investigated the effects of feeding rotifers containing various levels of n-3 highly unsaturated fatty acids (n-3HUFA) to Scylla serrata larvae at different developmental stages on their survival, development, and morphogenesis when they were cultured at six salinity levels. The first-, third-, and fifth (last)-stage zoeae and megalopae were reared to first-stage crabs at salinities of 10, 15, 20, 25, 30, and 35‰, with three different feeding regimes of rotifers containing different levels of n-3HUFA. The larvae successfully developed to the subsequent stages at 20–35‰ salinity. The highest survival rates to first-stage crabs were recorded at 20–25‰ salinity. The morphological features of the megalopa observed in the last-stage zoeae, represented by the ratio of the chela length to carapace length, tended to advance with increasing salinity, indicating higher assimilation efficiency at higher salinities. The megalopal features of the last-stage zoeae were enhanced when the larvae were fed rotifers containing higher amounts of docosahexaenoic acid (DHA). As reported previously, final-stage zoeal larvae with advanced megalopal features often experienced moult death syndrome (MDS). These results show that when larvae are fed rotifers with high DHA under high-salinity conditions, morphogenesis is accelerated, resulting in MDS. Therefore, to evaluate the effects of salinity on larval survival, it is necessary to examine larval morphogenesis in terms of MDS. In conclusion, we recommend that not only survival but also larval morphogenesis should be examined when evaluating the results of rearing experiments with S. serrata larvae.     

Intestinal Absorption of Fucoidan Extracted from the Brown Seaweed,Cladosiphon okamuranus

The aim of this study was to examine the absorption of fucoidan through the intestinal tract. Fucoidan (0.1, 0.5, 1.0, 1.5 and 2.0 mg/mL) was added to Transwell inserts containing Caco-2 cells. The transport of fucoidan across Caco-2 cells increased in a dose-dependent manner up to 1.0 mg/mL. It reached a maximum after 1 h and then rapidly decreased. In another experiment, rats were fed standard chow containing 2% fucoidan for one or two weeks. Immunohistochemical staining revealed that fucoidan accumulated in jejunal epithelial cells, mononuclear cells in the jejunal lamina propria and sinusoidal non-parenchymal cells in the liver. Since we previously speculated that nitrosamine may enhance the intestinal absorption of fucoidan, its absorption was estimated in rats administered N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in their drinking water. Rats were fed 0.2% fucoidan chow (BBN + 0.2% fucoidan rats), 2% fucoidan chow (BBN + 2% fucoidan rats) and standard chow for eight weeks. The uptake of fucoidan through the intestinal tract seemed to be low, but was measurable by our ELISA method. Fucoidan-positive cells were abundant in the small intestinal mucosa of BBN + 2% fucoidan rats. Most fucoidan-positive cells also stained positive for ED1, suggesting that fucoidan was incorporated into intestinal macrophages. The uptake of fucoidan by Kupffer cells was observed in the livers of BBN + 2% fucoidan rats. In conclusion, the absorption of fucoidan through the small intestine was demonstrated both in vivo and in vitro.     

Survival,development and growth of larvae of the coconut crab,Birgus latro,cultured under different photoperiod conditions

Populations of the coconut crab, Birgus latro, have been severely depleted on most inhabited islands throughout the Indo‐Pacific regions because of overharvesting and environmental degradation. To assist in the development of artificial propagation technologies for supportive breeding programmes in conserving this species, this study was designed to elucidate the effect of photoperiod on the survival, developmental period of zoeae and body size of megalopae through laboratory experiments. We tested six light (L) and dark (D) photoperiod regimes times of 0–24 h, thus 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Photoperiod conditions significantly affected larval survival. Survival was lower in the 0L:24D condition than in other photoperiod conditions, reflecting higher mortality during the zoeal stage in the 0L:24D condition. On the other hand, survival rates were high during the periods when larvae metamorphosed into megalopae, regardless of photoperiod conditions. In the 24L:0D condition, larval survival rate was slightly lower than in other conditions containing a light phase. Zoeal duration and megalopal body size were not different in light durations ranging from 0 to 18 h, but they were longer and larger, respectively, in the 24L:0D condition. Thus, continuous dark or continuous light conditions impaired the survival and development of larvae, and such photoperiod regimes should be avoided for culturing larvae of the coconut crab.     

The enhancement of abalone stocks: lessons from Japanese case studies

The dramatic declines in abalone Haliotis spp. fishery production have been documented all over the world. Release of hatchery‐reared juveniles into natural habitats has been considered as one measure to sustain and/or augment the current fishery production of abalone, as well as to restore collapsed abalone stocks. However, attempts at abalone release programmes have only been undertaken at experimental scales, except for Japan, where large‐scale stock enhancement programmes for abalone have been undertaken since late 1960s. To evaluate the potential of stock enhancement for abalone, we analysed the release surveys of 13 case studies in Japan in terms of the overall recapture rate (number of recaptures through a lifetime/number of juveniles released), yield per release (YPR, yields from released individuals), the economic efficiency of releases (ratio of income from recaptured abalone to release cost) for each release year, and the contribution of hatchery releases to total catches for each fishing year. The average estimates for overall recapture rates (0.014–0.238) and YPR (3.1–60.3 g/individual) varied between locations and release years. The economic efficiency was estimated at 0.4–6.2. The released abalone contributed 6.9–83.5% to total catches. Hatchery releases could augment total production at some locations, but the success of release programmes would be limited by the carrying capacity at release areas, because density‐dependent mortality occurred following releases in some cases. Throughout Japan, the annual catch of abalone has continuously declined from ～6500 t in 1970 to ～2000 t in the mid‐1990s, despite the increase in the number of hatchery releases. Based on the estimates for YPR, the magnitude of the abalone releases on a national scale has not been sufficiently large to sustain the total production of Japanese abalone, which has primarily fluctuated according to the abundances of wild populations. Our results suggest that releases should be targeted at local populations in regions where stock enhancement is predicted to have the greatest chance of success, and the magnitude of releases should be considered carefully and determined for each region by taking the local carrying capacity into account. We also address the future prospects of abalone stock enhancement.     

Effects of restricted feeding on growth of red sea bream and sedimentation of aquaculture wastes

For improving the economic and environmental sustainability of fish farming, it is necessary to optimize feeding regimes. From this viewpoint, we monitored the growth and mortality of red sea bream (Pagrus major), C and N fluxes and sediment chemistry at 2 commercial fish cages; cage 1 (conventional satiation feeding) and cage 2 (restricted feeding: same feeding frequency but 18% reduction in the feed amount) for 276 days. The similar specific growth rates (0.43% in cage 1 and 0.39% in cage 2) but different feed conversion efficiencies (0.54 in cage 1 and 0.62 in cage 2) and mortality (> 2-times higher in cage 1) between the 2 cages, indicate overfeeding in cage 1 culture. Elemental and stable isotopic analyses of sediment trap materials enabled the quantification of waste feed- and fecal matter-derived organic matter (OM) separately. The results shows that (1) aquaculture-derived OM comprised most of the fish-farm settling OM, excluding the period from January to April, when natural OM often accounted for a half of the bulk OM, (2) there was a difference in the seasonal trend between the fluxes of waste feed and fecal matter, and (3) there were no differences in the percentage compositions and fluxes of waste feed and fecal matter between the 2 cages. The isotopic analysis showed that the waste feed-derived OM in the sediment below cage 2 was 24% less than that below cage 1, suggesting effect of restricted feeding. Determining the relative amount of waste feed and fecal matter in settling and sedimentary OM is an effective method to evaluate the optimum feeding regime.     

Mechanism of visceral fat reduction in Tsumura Suzuki obese, diabetes (TSOD) mice orally administered β-cryptoxanthin from Satsuma mandarin oranges (Citrus unshiu Marc)

The carotenoid β-cryptoxanthin (β-CRX) is abundant in Satsuma mandarins (Citrus unshiu Marc). Several studies have shown a relationship between Satsuma mandarin consumption and a low risk of several diseases, for example, diabetes, gout, and hypertension, suggesting β-CRX involvement in disease prevention. We investigated the effect of β-CRX on mildly obese males. β-CRX administration reduced visceral adipose tissue, body weight, and abdominal circumference. However, the detailed mechanism by which β-CRX mediates these changes remains unknown. To identify this mechanism, we used an obese model mouse (TSOD). Oral β-CRX administration repressed body weight, abdominal adipose tissue weight, and serum lipid concentrations in TSOD; these results are identical to previous human trial results. β-CRX administration significantly repressed adipocyte hypertrophy. Gene expression analysis strongly indicated that β-CRX can alter cytokine secretion and cell proliferation. These results suggest that β-CRX derived from Satsuma mandarins can help prevent obesity by repressing hypertrophy of abdominal adipocytes.     

Alteration of release and role of adenosine diphosphate and thromboxane A2 during collagen-induced aggregation of platelets from cattle with Chediak-Higashi syndrome

OBJECTIVE: To compare the interaction of endogenous ADP with collagen and thromboxane A(2) (TXA(2)) during collagen-induced platelet aggregation between platelets from healthy cattle and those with Chediak-Higashi syndrome (CHS). POPULATION SAMPLE: Platelets harvested from blood samples from healthy Japanese Black cattle and those with CHS. PROCEDURES: Aggregation of gel-filtered platelets; release of ATP-ADP; and generation of thromboxane B(2) (TXB(2)), a metabolite of TXA(2), were measured. RESULTS: The potency of collagen to induce aggregation in platelets of cattle with CHS (ie, CHS platelets) was less than a tenth of that in platelets of healthy cattle (ie, control platelets). Platelet aggregation induced by collagen at an intermediate concentration depended on the coexistence of ADP and TXA(2), suggesting that released ADP cannot cause platelet aggregation by itself. Collagen-induced ADP release was markedly decreased, whereas TXB(2) production was slightly low in CHS platelets, compared with that in control platelets. A combination of subthreshold amounts of ADP and 9,11-dideoxy-9alpha, 11alpha-methano-epoxy-prostaglandin F(2) (U46619), a TXA(2) analogue, caused platelet aggregation. Similarly, a combination of subthreshold amounts of collagen and ADP caused platelet aggregation, whereas collagen and U46619 were not synergistic. CONCLUSIONS AND CLINICAL RELEVANCE: Deficient ADP release ensuing from the delta-storage pool deficiency in platelets from cattle with CHS resulted in reduction of collagen-induced platelet aggregation, through attenuation of synergism between TXA(2) and ADP and between ADP and collagen. Furthermore, results of the study reported here indicated that TXA(2) was important for aggregation of bovine platelets.