Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.     

Larval and juvenile Australian smelt Retropinna semoni somatic and otolith growth parameters – implications for growth interpretation of wild fish

Abstract –  Relationships between fish length, otolith size, age and weight were assessed for a population of wild Australian smelt ( Retropinna semoni ) larvae and juveniles captured over a 4-year period to aid further interpretation of growth and condition during the early life history of the species. Nonlinear smoothed generalized additive models best described the fish–otolith size relationship during the larval and juvenile period, indicating that the proportionality between fish length and otolith size varies in relation to size. It is proposed that back-calculated predictions of fish size at a previous age or otolith size, accounting for individual variation is possible by assuming a body proportional hypothesis. Growth rate of larval and juvenile Australian smelt was best described using the Gompertz model that indicated a steady decline in growth rate after around 30 days of age. The allometric growth of larval and juvenile Australian smelt established from the length/weight relationship can subsequently be used to assess the condition of fish within this population using a relative condition or relative weight condition index. The results of the study have provided significant information to enable more precise growth reconstruction and condition assessment for the species in Australian lowland rivers.     

Explaining urban governance in the midst of political transformation: The city of Macao

This paper takes a close look at the urban governance and political culture of Macao, the world largest casino city. Macao has experienced spectacular economic growth since gaming liberalisation in 2002 and China's Free Individual Travel scheme launched in 2003. However, the booming gaming sector has crowded out other sectors of Macao. It has not only made the city's economy mono‐structured and consequently extremely vulnerable to external shocks and fluctuations but also induced serious social divisions and political controversies within the local community. By tracing the root cause of the ongoing dilemma and crisis in the mode of governance, the dynamic relationships between formal and informal institutions, consensus politics and the social group culture are intensively discussed in a historical context. In fact, the sustainable development of the former Portuguese colony has largely been hindered by its residents' passive attitudes toward political communication, non‐transparent urban governance, the absence of a middle class and the dominance of pro‐establishment social groups.     

Embryonic development in the blue fox

Embryos from vixens at different stages of gestation were measured and photographed. Implantation was observed 16-18 days after breeding. Differentiation and the development of characteristic features were described and embryonic loss was studied in relation to number of corpora lutea.     

Evaluation of maternal parent and puroindoline allele on kernel texture in a reciprocal cross between two hard spring wheat cultivars

Kernel texture is an important characteristic for both the milling and the end-use quality of wheat (Triticum aestivum L.). Gene sequence variation and mutations to the two puroindoline genes (Pina and Pinb), located at the Ha locus on chromosome 5DS, account for the majority of variation in wheat kernel texture. Other factors also influence kernel texture, including effects associated with different maternal parent backgrounds. To investigate the effect of two hard puroindoline alleles in different maternal backgrounds, a population of 228 recombinant inbred lines (RILs) derived from a reciprocal cross between two wheat cultivars ID377s (Pina-D1b/Pinb-D1a) and Klasic (Pina-D1a/Pinb-D1b) were examined in two succeeding generations (F₇ & F₈). Kernel texture was determined using the Single Kernel Characterization System (SKCS) and the RIL puroindoline haplotype was identified by the sequence-specific PCR amplification of each gene. Analysis of variance identified a significant (P 0.001) effect of the maternal parent and puroindoline mutation on kernel texture. RILs containing the Pina-D1b mutation were significantly harder than lines containing the Pinb-D1b mutation. RILs which had Klasic as the maternal parent were significantly harder than those which had ID377s as the maternal parent. When the maternal parent and puroindoline allele were analyzed in combination, RILs derived from Klasic as the maternal parent and the Pina-D1b allele were significantly harder (P 0.001) than those containing the same allele but ID377s as the maternal parent. The same occurred for RILs containing the Pinb-D1b allele, lines with Klasic as the maternal parent were harder than lines with ID377s as the maternal parent. These results corroborate the harder phenotype of the Pina-D1b allele and indicate a significant maternally-inherited contribution to kernel texture variation.     

Identification of triploid Citrus by isozyme analysis

Summary Seedlessness is a desirable horticultural attribute in Citrus and is positively associated with triploidy. The conventional cytological method for triploid identification is a laborious technique involving the preparation of root tips for chromosomal analysis. Digital densitometry of isozymes, however, offers the possibility of distinguishing triploid Citrus from large populations of seedlings both quickly and cheaply. Where there are no gene dosage regulation effects, greater band density should be evident in the allozyme contributed by the diploid gamete for a heterozygous locus. The isozymes of 4 enzymes; malate dehydrogenase, 6-phosphogluconate dehydrogenase, shikimate dehydrogenase, and phosphoglucose isomerase, were investigated with polyacrylamide gel electrophoresis. Band densities of these isozymes for triploid Citrus, their diploid siblings and diploid progenitors were measured using a digital densitometer. Of the 4 enzymes investigated only allozymes for shikimate dehydrogenase exhibited consistent differences over a wide range of Citrus cultivars. Greater band density was evident in the allozyme contributed by the diploid gamete. The band density ratio between allozymes for triploid Citrus was close to 0.5, while for diploid Citrus band density ratios were close to 1.0. This effect is due to the extra protein coded by the additional gene dose and was not observed in diploids. Shikimate dehydrogenase proved to be an accurate molecular marker for distinguishing between diploid and triploid Citrus for heterozygous progeny.Abbreviations PAGE Polyacrylamide gel electrophoresis - MDH malate dehydrogenase - 6PGD 6-phosphogluconate dehydrogenase - SkDH shikimate dehydrogenase - PGI phosphoglucose isomerase     

Fluorescent in situ hybridization as an aid to introducing alien genetic variation into wheat

Summary Fluorescent in situ hybridization (FISH) has been used to assess the occurrence and frequency of wheat-alien chromosome pairing in a wheat/Thinopyrum bessarabicum hybrid and in wheat/rye hybrids with different levels of chromosome pairing by examining pollen mother cells at metaphase I of meiosis. The use of FISH to identify the presence and size of alien chromatin in a wheat background is also demonstrated.The value of FISH as an aid to the introgression of alien genetic variation into wheat is discussed.Abbreviations FISH fluorescent in situ hybridization - GISH genomic in situ hybridization - PRINS primer-induced in situ hybridization     

Reselection of a Pearl Millet Cultivar Utilizing Residual Variability for Downy Mildew Reaction*

‘BJ 104’ was the most widely grown pearl millet hybrid in India until it became susceptible to downy mildew (DM) in 1984—85. Residual variability for resistance was found in both parental lines, 5141 B (maintainer of 5141 A) and J 104, and through four generations of pedigree selection under intense disease pressure in the DM nursery, two lines, IC-MA841 (from 5141 B) and ICMP 84814 (from J 104), were selected resulting in a reconstituted DM resistant hybrid (‘ICMH 84814’) which was equal in yield to the original ‘BJ 104’. The reconstituted hybrid, though phenotypically similar, can be distinguished from “BJ 104” being slightly taller, flowers later, has heavier heads, and 1000-seed weight, but tillers less. A similar exercise was attempted on Tifton 23 B, the female parent of the first widely grown hybrid (‘HB 3’— the male parent was also J 104), but no variability for resistance to DM was found.