Vitamin C requirement of kuruma shrimp postlarvae, Marsupenaeus japonicus (Bate), using l-ascorbyl-2-monophosphate-Na/Ca

l ‐ascorbyl‐2‐monophosphate‐Na/Ca (AMP‐Na/Ca) was used as a vitamin C source to investigate the ascorbic acid (AsA) requirements on growth performance and stress resistance of the post‐larval kuruma shrimp, Marsupenaeus japonicus. Purified carrageenan‐microbound diets with six levels of AMP‐Na/Ca, AsA equivalent to 0, 20, 56, 87, 759 and 1697 mg kg^?1 diet were fed to triplicate groups of M. japonicus (mean initial weight 16±0.3 mg) for 30 days. The diets with AsA 0, 20 and 56 mg kg^?1 showed high cumulative mortality after 10 days of feeding. After the 30‐day trial, the shrimp fed these diets had significantly lower survival and weight gain (WG, %) than those fed the 87, 759 and 1697 mg AsA kg^?1 diets. Specific growth rate and individual dry weight showed the same pattern as WG (%). There were no significant differences in growth performance among the groups fed the AsA levels at 87, 759 and 1697 mg kg^?1 at the termination of feeding trial. Broken‐line regression analysis indicated that 91.8 mg AsA kg^?1 in the diet was the optimum for post‐larval shrimp. On the other hand, dietary level of more than 800 mg AsA kg^?1 was needed to ensure high resistance to stressful conditions such as osmotic and formalin stressors.     

Influence of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder, Paralichthys olivaceus

A feeding trial using five semi-purified diets (50% crude protein) was conducted to investigate the effects of different dietary amino acid patterns on growth and body composition of juvenile Japanese flounder. The control diet contained casein and gelatin as intact protein sources and four other diets contained 30% casein–gelatin (2:1, w/w) and 20% crystalline amino acids (CAA). CAA were added to the diets to simulate the amino acid pattern found in red sea bream egg protein (REP), Japanese flounder larvae whole body protein (FLP), Japanese flounder juvenile whole body protein (FJP), and brown fish meal protein (BFP), respectively. The test diets were fed to triplicate groups of juveniles (2.75±0.05 g) twice a day for 40 days to evaluate weight gain, survival, feed conversion efficiency (FCE), protein efficiency ratio (PER), and apparent protein utilization (APU). The apparent retention of total dietary amino acids in the whole body and A/E ratios of the whole body were also evaluated. The highest weight gain was observed in fish fed the diet containing the dietary amino acid pattern of BFP followed by fish fed the control, FJP, FLP and the REP diets. Percent survival, FCE, PER and APU were also significantly (P<0.05) affected by the amino acid pattern in the diets, indicating the highest value in fish fed the BFP diet. Except for a few amino acids, the amino acid composition of the whole body did not show marked differences with different dietary amino acid pattern. Results suggest that BFP could be more suitable as a reference amino acid pattern in the diet of juvenile Japanese flounder compared to the amino acid pattern of FLP, FJP or REP.     

Effects of Dietary Vitamin A on Juvenile Red Sea Bream Chrysophrys major

A 55-d feeding experiment was conducted to evaluate the effects of dietary vitamin A on growth of juvenile red sea bream Chrysophrys major . Nine semi-purified diets with supplemental retinol palmitate at levels of 0, 300, 600, 1,500, 3,000, 4,500, 6,000, 15,000 and 30,000 retinol eq/kg diet, were fed twice daily to triplicate groups of 10 juveniles per tank with an initial weight of 1.178 ± 0.001 g. Weight gain and specific growth rate increased with the increase of supplemental retinol palmitate in the diet up to a level of 6,000 retinol eq/kg diet, beyond which those indices tended to decrease slightly or to plateau. Significantly lower weight gain and specific growth rate were observed in fish fed with 0 and 300 retinol eq/kg diet. No significant differences were found in survival rates among the different levels of supplementation. The crude protein, lipid, moisture and ash contents in the whole body were not affected by the different vitamin A supplemental levels. Besides the reduced growth, fish fed with low levels of vitamin A supplement showed no other signs of deficiency. No hypervitaminosis A symptoms were observed in fish fed on high levels of supplementation. Fish fed on diets with 0 and 300 retinol eq/kg diet showed a significantly lower content of vitamin A (as a total retinol) in the liver than those in groups fed with higher levels of supplementation. Vitamin A was stored in the liver mainly as retinyl esters. Total retinal content of the eye showed no significant differences among the treatments; however, fish fed with 0 and 300 retinol eq/kg of diet had slightly higher concentrations. According to the results of the mean weight gain, specific growth rate and liver retinol content, the requirement of dietary vitamin A for juvenile red sea bream was estimated to be between 1,500 and 6,000 retinol eq/kg.     

Relationship of glomerular filtration rate based on serum iodixanol clearance to IRIS staging in cats with chronic kidney disease

We examined the correlation between the glomerular filtration rate (GFR) estimated from an equation based on the serum iodixanol clearance technique and International Renal Interest Society (IRIS) stages of chronic kidney disease (CKD) in cats. The equation included the injection dose, sampling time, serum concentration and estimated volume of distribution (Vd) of the isotonic, nonionic, contrast medium iodixanol as a test tracer. The percent changes in the median basal GFR values calculated from the equation in CKD cats resembled those of IRIS stages 1–3. These data validate the association between the GFR derived from the simplified equation and IRIS stages based on the serum creatinine concentration in cats with CKD. They describe the GFR ranges determined using single-sample iodixanol clearance for healthy cats and cats with various IRIS stages of CKD.     

Differences in lamina joint anatomy cause cultivar differences in leaf inclination angle of rice

ABSTRACT

Leaf erectness is an important agronomic trait for improving canopy photosynthesis in rice. It is well known that leaf inclination angle (LIA) decreases after expansion during ripening. However, the high-yielding indica cultivar ‘Takanari’ retains a greater LIA during ripening than the high-quality japonica cultivar ‘Koshihikari’. To clarify the cause of the cultivar difference in LIA, we investigated anatomical characteristics of the lamina joint of a flag leaf. We found a close linear correlation between LIA at the centre and at the base of the leaf blade in both cultivars during ripening. The length of the lamina joint increased significantly more on the adaxial side of a leaf (the margin of the collar) than on the abaxial side (the abaxial side of the central part of the collar) in ‘Koshihikari’ after leaf expansion, but there was no clear difference in ‘Takanari’. We found a close linear correlation between the ratio of lamina joint length on the adaxial to abaxial sides and LIA in ‘Koshihikari’ and ‘Takanari’ during ripening. In ‘Koshihikari’, the average length of cells on the adaxial side increased significantly after leaf expansion, with no significant increase in that on the abaxial side and no significant change in cell number on either side. In ‘Takanari’, cell length and cell number showed no significant changes on either side of the lamina joint. We conclude that the cultivar difference in LIA during ripening is caused mainly by cell elongation on the adaxial side of the lamina joint.

List of Abbreviations: k: light extinction coefficient; LIA: leaf inclination angle; QTL: quantitative trait locus     

Glycoprotein hormone in the pituitary of hagfish and its evolutionary implications

The pituitary gland is present in all vertebrates, from agnathans (jawless vertebrates) to mammals, but not in invertebrates. Reproduction in gnathostomes (jawed vertebrates) is controlled by two pituitary gonadotropins (GTHs), luteinizing hormone and follicle-stimulating hormone, which are part of the pituitary glycoprotein hormone (GPH) family. Hagfishes, which lack both jaws and vertebrae, are considered the most primitive vertebrate known, living or extinct. Accordingly, they are of particular importance in understanding the evolution of the pituitary GPHs and their functions related to vertebrate reproduction. Nevertheless, key elements of the reproductive endocrine system in hagfish have yet to be elucidated. Our current report has revealed the first identification of a functional GPH composed of two subunits that possess gonadotropic action at the pituitary of brown hagfish. It seems most likely that an ancestral GPH gave rise to only one GTH in hagfish pituitary and that multiplicity of GPHs arose later during the early evolution of gnathostomes. This paper briefly summarizes the latest findings on the hagfish GPH from an evolutionary point of view.     

Oocyte maturation and active motility of spermatozoa are triggered by retinoic acid in pen shell <Emphasis Type="Italic">Atrina pectinata</Emphasis>

For recovery of the declining population of pen shells in the wild, the production of pen shell juveniles for transplantation or aquaculture is underway in Japan. For more stable juvenile production, artificial fertilization methods for pen shells are needed, but methods to induce oocyte maturation (meiosis resumption) used in other bivalves, which make oocytes fertilizable, were ineffective for pen shells. Here, we report evidence showing that retinoic acid (RA) has strong activity in inducing oocyte maturation and activating sperm motility in pen shells. Treatment of fully developed oocytes with 1.0 μM all-trans-RA (at-RA) induced germinal vesicle breakdown, a typical morphological sign of oocyte maturation, but 1.0 μM at-retinol and at-retinal, 2 mM ammonia, and 1.0 μM serotonin were ineffective. Treatment with at-RA for 30 min was sufficient for oocyte maturation and was more potent than its isomers, 9-cis- and 13-cis-RA. Parallel results were obtained for sperm motility activation. Oocyte responsiveness to at-RA increased during the final stage of ovary development. Artificial fertilization was successful only with the oocytes treated with at-RA, and fertilized eggs developed to D-shaped (veliger) larvae without apparent morphological abnormalities. These results indicate the possible application of RA for the artificial fertilization of pen shells.     

A hydro-environmental watershed model improved in canal-aquifer water exchange process

Long-term simulation using the distributed hydro-environmental watershed model is efficacious for assessing irrigation impacts on hydrological cycle in detail and for implementing watershed management successfully. In this article, the previously developed hydro-environmental watershed model (HEWM-1) is improved in the water exchange process caused by surface water-groundwater interaction via drainage canals and/or underdrains. The time-varying stream flow in canals is described by the complete one-dimensional shallow water equations in a newly introduced submodel, the open channel flow submodel. This submodel coordinates with the other submodels: the tank, soil moisture and groundwater flow submodels which are interlinked in a cascade manner. The improved model (HEWM-2) is applied to an agricultural watershed covering an area from an alluvial fan onto a nearly level alluvial plain, to be validated. The simulation by HEWM-2 is informative for identifying whether any drainage canal is gaining or losing water in relation to groundwater level. It could thus provide useful information for conserving a complex network of drainage canals which also functions as a passage for aquatic animals like fishes.     

Growth performance of juvenile kuruma shrimp,Marsupenaeus japonicus (Bate) fed diets replacing fishmeal with soybean meal

A feeding trail was conducted to evaluate the effect of lowering dietary fishmeal (FM) levels while increasing levels of dehulled soybean meal (SBM) on growth, nutrient utilization and body composition of juvenile kuruma shrimp, Marsupenaeus japonicas. Five experimental diets were formulated to be isoenergetic, isolipidic and isonitrogenous with decreasing FM levels from 40 to 16% while increasing SBM from 0 to 33% respectively. Quadruplicate groups of shrimp (initial wt = 1.5 g) were fed the test diets for 56 days under the flow‐through system. There were no significant differences in final weight (g) and specific growth rate (SGR, % day) among shrimp fed FM40, FM34, FM28 and FM22 diets respectively. Growth parameters significantly decreased in shrimp when fed FM16 diet, which was the lowest level of FM. Feed intake was positively correlated with the SGR of shrimp, and the lowest one was found in shrimp fed FM16 diet. Protein gain and retention, whole body lipid, arginine and methionine significantly decreased in FM16 fed group. Thus, it is concluded that dietary FM could be reduced down to 22% with SBM without compromising growth, nutrient utilization and retention, and whole body composition of kuruma shrimp.