Gonadal morphogenesis and sex differentiation in cultured chub mackerel,Scomber japonicus

The timing of primordial germ‐cell (PGC) migration with regard to the gonadal anlagen, gonad formation and sex differentiation was examined histologically in the chub mackerel (Scomber japonicus) at 5–190 days post hatching (dph). At 5 dph, PGCs appeared on the peritoneal epithelium surface or in the mesentery, on the dorsal side of the abdominal cavity. By 10 dph, stromal cells around the PGCs proliferated. The gonadal primordium was formed by 15 dph. The gonadosomatic index was 0.01% at 30 dph and increased thereafter (0.32% in females and 0.04% in males at 160 dph). Ovarian differentiation occurred at 30–40 dph, indicated by ovarian cavity formation (elongation and fusion of the upper and lower ovarian edges). Meiosis was subsequently initiated. A few meiotic oocytes surrounded the cavity at 50 dph; most were in the perinucleolus stage at 60 dph and attained a diameter of 60–70 μm at 190 dph. Testicular differentiation occurred at 30 dph, indicated by the formation of the sperm duct primordium. Spermatogonia gradually proliferated, developing into spermatocytes at the chromatin–nucleolus stage (after 90 dph) and subsequently into spermatids and spermatozoa (160 dph). These data could aid the development of seeding and cell‐engineering technologies for scombrid fish.     

Effects of high dose of vitamin A on reproduction and egg quality of Japanese flounder Paralichthys olivaceus

ABSTRACT: The present study was conducted to investigate the effects of dietary vitamin A on reproduction and egg quality in Japanese flounder Paralichthys olivaceus . Broodstock were fed experimental pellets containing two levels of vitamin A [11 × 10³ IU/100 g (control diet; CD), 337 × 10³ IU/100 g (experimental diet; ED)] for approximately 2 months before spawning and during the spawning period. Two groups of five females (average weight 1.4 kg) and 10 males (average weight 0.7 kg) were randomly allocated to two 30 m³ indoor tanks. Total egg production of the CD group was slightly higher than the ED group. Percentage of buoyant eggs and hatching rate of the ED group were significantly higher than the CD. In other egg quality parameters, such as percentage abnormal larvae and starvation tolerance of larvae, no notable difference was found between these two groups. At the end of the experiment, the skin color of broodstock in the ED group was darker than that of the CD group. Vitamin A content in eggs of the ED group was significantly higher than that of the CD group. However, the difference in vitamin A content in eggs between the ED and CD groups was much smaller than that in the liver of the females between the two groups. These results indicate that feeding broodstock a higher level of vitamin A increases the vitamin A content in eggs but does not affect egg quality in Japanese flounder because excess dietary vitamin A was stored mainly in the broodstocks' liver.     

Chemical and Thermal Properties of Freshwater Prawn (Macrobrachium rosenbergii) Meat

Chemical compositions and thermal properties of cultured freshwater prawn meat (FPM) were studied. FPM contained 83.2% protein (dry basis), 62.7% of which was myofibrillar protein. Pepsin-soluble collagen (PSC) and insoluble collagen (ISC) contents were 0.63 and 0.32%, respectively. Both collagens were similar to type V collagen from porcine placenta. Glutamic acid/glutamine, arginine, aspartic acid/?asparagine, and lysine were abundant amino acids in FPM. Glycine, proline, hydroxyproline, and aspartic acid/?asparagine were predominant in both collagens. FPM exhibited thermal transition temperatures (T_max) of 48.3 and 64.7°C, whereas T_max of PSC and ISC were 43.0 and 46.0°C, respectively. Textural changes in FPM during post-mortem storage on ice are plausibly dependent upon its compositional and thermal properties.     

Quantitative structure-activity analysis of larvicidal 1-(substituted benzoyl)-2-benzoyl-1-tert-butylhydrazines against Chilo suppressalis

The larvicidal activity of a number of 1-(substituted benzoyl)-2-benzoyl–1 -ten-butylhydrazines against the rice stem borer (Chilo suppressalis Walk.) was measured. Variations in the activity were examined quantitatively using physico-chemical substituent and molecular parameters and regression analysis. The results indicated that the molecular hydrophobicity and the electron-withdrawing inductive/ field effect of ontho substituents are favourable to larvicidal activity. The bulkiness of substituents at the meta and para positions was unfavourable to activity, substitution at the para position being more unfavourable than that at the meta position in terms of van der Waals' volume. The 2,3–, 2,5- and 2,6-disubstitution patterns were also unfavourable to activity. Reductions in larvicidal activity caused by the 2,6-,- 2,3,5- and 2,3,4,5-substitutions were greater than those induced by the 2,3- and 2,5-disubstitutions. When the sum of contributions from favourable effects is greater than that from unfavourable effects, the larvicidal activity is expected to be superior to that of the unsubstituted compound.     

Identification of Trichoderma SKT-1, a biological control agent against seedborne pathogens of rice

Trichoderma SKT-1 was previously reported as a powerful biological control agent against seedborne pathogens of rice, but the taxonomic disposition of the fungal isolate was not clear. Trichoderma SKT-1 produced irregular pyramidal warts on conidia and had an optimum growth temperature of 30°C. Morphological characteristics and colony growth were identical to those of known species of Trichoderma, including the newly recognized species T. asperellum. The 5.8S rDNA with the internal transcribed spacer (ITS) region (ca. 514 bp) of the fungus was compared with those of known species to determine the phylogenetic placement of the fungus. The length and sequence of the regions from Trichoderma SKT-1 were completely identical to those of an isolate of T. asperellum NRRL 5242 (AJ230669). On the basis of these results, we concluded that Trichoderma SKT-1 was T. asperellum.     

Estimation of daily urinary potassium excretion using urinary creatinine as an index substance in prepartum dairy cows

In the present study, the daily excretion of potassium (K) in urine (urinary K(UK)) was estimated from a 6 h urine sample using urinary creatinine (UC) as the index substance. All urine was collected from six pregnant Holstein cows at 6 h intervals for 24 h on 3 days of the 4th, 2nd and final week before the expected date of parturition. In total, 72 6 h urine samples were obtained. Daily UC excretion (mg/day per kg bodyweight (BW)) was almost the same for the three sampling days. Daily UC excretion varied among cows from 22.1 to 24.3 mg/day per kg BW with a mean of 22.8 mg/day per kg BW with no significant difference. Thus, daily UC excretion was confirmed to be constant throughout the prepartum period with no differences among individuals. The concentration ratios of K to creatinine ((UK mg/dL)/(UC mg/dL) (UK/UC)) correlated strongly to the hourly K excretions (mg/h per kg BW) (r = 0.952, P < 0.01) in the 6 h urine samples. The differences in the UK/UC ratio between sampling periods were not significant within each cow. Therefore, daily UK excretion (mg/day) can be estimated using the equation: daily UK excretion (mg/day) = daily UC excretion (mg/day per kg BW) × BW (kg) × 6 h urine sample UK/UC, where daily UC excretion can be a given value.     

Effects of feeding and animal performance on nitrogen, phosphorus and potassium excretion by Holstein cows

Thirty‐four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume.     

Quantitative structure—activity studies of insect growth regulators. XI. Stimulation and inhibition of N-acetylglucosamine incorporation in a cultured integument system by substituted N-tert-butyl-N,N′-dibenzoylhydrazines

The ability to stimulate N-acetylglucosamine (GluNAc) incorporation in-vitro of a number of N-tert-butyl-N,N′-dibenzoylhydrazines having various substituents on both phenyl rings was measured in cultured integument excised from the rice stem borer (Chilo suppressalis Walker). The relationship between in-vitro and larvicidal potency was approximately linear. The substituent effects on variations in the potency were similar between in-vitro and larvicidal activities. An inhibitor of oxidative detoxication, piperonyl butoxide, had no synergistic effects on the in-vitro potency. The ability of some dibenzoylhydrazines to inhibit GluNAc incorporation at exposure periods longer than the optimum for stimulation was also measured in a similar cultured integument system. The relationship between the inhibitory and stimulatory potency indices was linear, indicating that the larvicidal activity of dibenzoylhydrazines is closely related to its ability to stimulate as well as to inhibit GluNAc incorporation into the larval cuticle.     

Geographical variation of skull morphology and its functional significances in the red-cheeked squirrel

Skulls of the red-cheeked squirrel (Dremomys rufigenis) from various geographical locations: Malaysia (peninsular area), Vietnam (south district)-Laos, and Thailand (north district) were osteometrically examined. The skull size of the squirrels in the southern (Malaysia) population was fundamentally larger than that in the northern (Vietnam, Laos and Thailand) populations. The proportion indices indicated that the splanchnocranium was relatively longer in the Malaysia population, and that the interorbital space was narrower in Vietnam-Laos, and Thailand populations. We suggest that the long nose and laterally-oriented orbits in the skull may be better adapted for terrestrial-insectivorous life in the Malaysia population and the binocular sense facilitated by rostrally-oriented eyes contributes to the arboreal-fruit eating behavior in the two northern populations. The Malaysia population was clearly distinguished from the other populations by the principal component analysis. We suggest that the geographical barrier of the Isthmus of Kra influences the morphological variation of the skull among the squirrel populations.