Novel polymorphic microsatellite DNA markers from Malaysian giant freshwater prawn, <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

Seven single locus microsatellite markers were characterized in Malaysian giant freshwater prawn, Macrobrachium rosenbergii from an enriched genomic library Primer pairs were designed to flank the repeat sequences and the loci characterized for this species. The bands resulting from the PCR amplifications of these eight microsatellite loci were polymorphic with the number of alleles ranging from 8 to 26 alleles per locus, whereas the observed heterozygosity ranged from 0.0641 to 0.6564. These newly developed microsatellite markers should prove to be useful for population studies and in the management of genetic variations in broodstocks of freshwater prawn, M. rosenbergii.     

Effect of different stock types and dietary protein levels on key enzyme activities of glycolysis‐gluconeogenesis,the pentose phosphate pathway and amino acid metabolism in Macrobrachium rosenbergii

A feeding trial was conducted to study the effect of dietary protein (DP) levels on the enzyme activities of different stocks of Macrobrachium rosenbergii juveniles, fed two diets prawn type diets either at optimum (ODP, 32%) or sub‐optimum (SDP, 27%) dietary protein. The activity of key enzymes: glycolysis, gluconeogenesis, amino acid catabolism, pentose phosphate pathway, and energy metabolism was examined on different stocks of M. rosenbergii juveniles in various tissues (muscle, hepatopancreas, and gill). Wild juveniles of M. rosenbergii were collected from the west coast of India, Gujarat (G), Maharashtra (M) and from the east coast of India, Andhra Pradesh (A), and raised in culture ponds of 200 m² at 1 juvenile m^‐2. The experiment was conducted for a period of 60 days. A Visible Implant Elastomer (VIE) Tag was injected into different prawn juveniles’ stocks A, (3.06–3.10 g), M, (0.80–1.01 g) and G (0.90–1.06 g) for the individual identification of each class. All the animals were acclimatized for 7 days before being released into the pond. Each of the two diets, the first with 27% SDP, termed the sub‐optimum level (S), and the second 32% DP, termed the optimum level (O), was fed in triplicate ponds. The weight gain of stocked prawn was significantly higher for G stock (3.03 ± 0.18 g) compared to M stock (2.53 ± 0.25 g) and A stock (1.33 ± 0.10 g). In addition weight gain in ODP was significantly higher (3.05 ± 0.22 g) compared to SDP (2.11 ± 0.17 g). Furthermore, both protein level and stock type had a significant (p ≤ 0.05) effect on the survival rate, specific growth rate, and feed conversion ratio of the prawn. A significant interaction was recorded between metabolic enzyme activities and the variation of dietary protein levels and differences in M. rosenbergii stocks, in which stock “G” and “M” exhibited healthier enzyme physiological status than stock “A”. The findings presented here may conclude that the enzymes quickly respond to dietary protein manipulations of cultured shrimp. The results can be useful in identifying the optimum stock (genotypes) in a given culture condition and subsequently higher production may be achieved.     

Isolation and characterization of microsatellite loci in giant freshwater prawn, Macrobrachium rosenbergii

This paper reports on isolation and characterization of 8 microsatellite loci from a partial genomic library of Macrobrachium rosenbergii using DIG labeled dinucleotides, (GT)₁₅ and (CT)₁₅ as probes. Primers were designed and PCR conditions optimized for repeat arrays. Polymorphism was studied using 24 individuals collected from the wild. All the loci were polymorphic with number of alleles ranging from 3 to 5 and observed heterozygosity 0.50–0.85. All the loci except one were in agreement with Hardy–Weinberg equilibrium. No significant pair wise linkage disequilibrium was found among the loci. These markers should prove useful for characterization of natural population as well as brood stock management of this species.     

Isolation and characterisation of 11 microsatellite loci in the abyssal carapine grenadier Coryphaenoides carapinus (Actinoperygii, Macrouridae) and cross-amplification in two other deep-sea macrourid species

Microsatellites represent an important tool for characterising population structure, for attributing individuals to stocks, and for revealing ecological processes taking place on population and meta-population levels. A sound knowledge of population structure is essential for sustainable management of exploited fish stocks, and helps to understand population connectivity and speciation. We developed for the first time primers for microsatellite loci in the carapine grenadier, Coryphaenoides carapinus, inhabiting the abyssal Atlantic. Eleven microsatellites were obtained from partial genomic DNA libraries enriched for tetranucleotide repeats. The loci were characterised in three unrelated individuals and nine loci were found to be polymorphic. Cross-amplification in two commercially exploited deep-sea macrourid species (Coryphaenoides rupestris and Macrourus berglax) resolved two polymorphic loci in each species.     

Genetic Analysis of Trichocyst Discharge of the Wild Stocks of Paramecium tetraurelia*

SYNOPSIS. Aberrant discharge of trichocysts in response to picric acid occurs in 8 of the 28 wild stocks of Paramecium tetraurelia. There are at least 4 distinguishable phenotypes: nondischarge, stocks 139, 163, 169, and 242; temperature-sensitive nondischarge, stock 126; leaky nondischarge, stock 203; and a clonally unstable phenotype, stocks 146 and 148. From each of these stocks a single recessive gene causing nondischarge has been isolated by backcrosses to stock 51. The original stocks 126, 146, and 148 possess other genes which affect the extracted genes. The copper resistance locus is ～ 10 centiMorgans from nd169 and nd242, but none of the other nondischarge genes are linked to 6 marker loci. The genes nd169 and nd242 are only 0.5 centiMorgans apart making them the closest known pair of loci in P. tetraurelia. The genes nd126 and nd242 are distinguishable alleles at the same locus and the genes nd146 and nd148 are apparently identical alleles. The large number of loci involved in producing a similar phenotype in different stocks supports the idea that mutation is much more important than gene flow in this highly inbreeding species.     

Evaluating the genetic basis of multiple-locule fruit in a broad cross section of tomato cultivars

Lycopersicon esculentum accessions bearing fasciated (multiloculed) fruit were characterized based on their flower organ and locule number phenotypes. Greenhouse and field evaluations indicate that increases in locule number are associated with increases in the number of other floral organs (e.g., sepals, petals, stamens) in all stocks. F₁ complementation, F₂ segregation analysis, and genetic mapping indicate that at least four loci account for increases in the number of carpels/locules in these stocks. The most significant of these map to the bottoms of chromosomes 2 and 11 and correspond to the locule number and fasciated loci. All stocks tested were fixed for mutations at the fasciated locus, which maps to the 0.5-cM interval between the markers T302 and cLET24J2A and occurs in at least three allelic forms (wild type and two mutants). One of the fasciated mutant alleles is associated with nonfused carpels and repressed recombination and may be due to a small inversion or deletion. The other two loci controlling locule number correspond to the lcn1.1 and lcn2.2 loci located on chromosomes 1 and 2, respectively.     

Twelve polymorphic microsatellites in Oriental river prawn, Macrobrachium nipponense

Oriental river prawn, Macrobrachium nipponense, is a commercially important freshwater prawn species in China, Japan, Korea and Vietnam. Due to overfishing for food, the wild stocks M. nipponense are endangered. Twenty microsatellite loci were isolated from the M. nipponense. Twelve of these loci were polymorphic (seven to 16 alleles per locus), with expected heterozygosity ranging from 0.68 to 0.86 (n = 48). These polymorphic loci provide a valuable tool for assessing genetic diversity of wild and cultured populations.     

Genetic linkage relationships of eight enzyme/electromorph loci in Anopheles minimus

Two laboratory stocks of Anopheles minimus, each fixed for variant electromorphs of esterases, aspartate aminotransferase, hydroxyacid dehydrogenase, phosphogluconate dehydrogenase, mannose phosphate isomerase and glycerol dehydrogenase were used to assess linkage relationships between presumed gene loci controlling this variation. The two F₁, which had been obtained from crossing the stocks, were backcrossed to a parental stock. Three loci controlled the esterases and one locus each of the other enzymes. Mpi is sex-linked. The rest are autosomal and suggested relationships are: Pgd 2.3% recombination from Aat and unlinked to any other loci; Est-1-33.8%-Est-3-31.5%-Est-2-21.0%-Had. Gcd is unlinked to any other locus.There was evidence of strong interaction between the X chromosome of one stock and autosomes of the other in which individuals bearing the X chromosome of the one suffered relatively greater mortality and had delayed development with respect to other genotypic classes.     

Genetic changes in Atlantic salmon stocks since historical times and the effective population size of a long-term captive breeding programme

Human-caused genetic changes in two Atlanticsalmon (Salmo salar L.) stocks, from therivers Iijoki and Oulujoki in Finland, wereassessed by comparing the genetic parameters ofthese stocks before and after the hatcherybreeding of several successive generations,corresponding to 40 and 33 years since the wildstate. The changes were also compared withthose observed in a large wild salmon stock inthe River Teno during 56 years. In all, thevariation at seven microsatellite DNA loci wasexamined in 11 Atlantic salmon samplesoriginating from these three rivers. Theeffective population size, N_e, duringbreeding of the Iijoki broodstock and for theTeno salmon was also estimated by the temporalmethod based on allele frequency changes. Forthe Iijoki broodstock, the changes could betracked generation by generation from thefounding of the stock. Statisticallysignificant changes in allele frequencies werecommon in the hatchery stocks (F = 0.029, forIijoki), but not in the wild Teno stock, whichwas temporally very stable (F = 0.007). Allelicrichness decreased statistically significantly(24.8%) in the Oulujoki broodstock, from 62.1to 46.7 alleles at nine loci. On average, therewere 9.7 fewer alleles (15.7%) in thecontemporary broodstocks than in thecorresponding historical stocks. The meanheterozygosity was 6.6% lower in thecontemporary Oulujoki broodstock, but remainedunchanged in the Iijoki broodstock. Theestimated N_e for the Iijoki broodstock wasunder 80 for 4.5 generations from 1962 to 1995and for the wild Teno salmon over 900 for 56years from 1939 to 1995.     

Linkage Disequilibrium in Natural Populations of Trypanosoma cruzi (Flagellate), the Agent of Chagas’ Disease1

ABSTRACT. We have studied linkage disequilibrium in natural populations of Trypanosoma cruzi, the agent of Chagas’ disease, by analyzing (i) a set of 524 stocks from the whole geographical range of the parasite, characterized at four gene loci coding for enzymes; (ii) a subsample of 121 stocks characterized at 12 enzyme loci; and (iii) a subset of 386 stocks from six locations in Bolivia, characterized by four enzyme loci. Our results show that the linkage disequilibrium reaches the maximum possible value, given the observed allelic frequencies, for almost all the locus pairs. This result is most consistent with the hypothesis that genetic recombination is absent or very rare in T. cruzi natural populations. Partition of the linkage disequilibrium variance for the six Bolivian populations shows that both inter- and intrapopulation components are substantial and that the relationships among the components are D_IS² < D_ST², and D'_IS² < D'_ST². These inequalities are interpreted as the result of an interplay between genetic drift, rare or absent mating, and clonal selection in generating linkage disequilibrium in T. cruzi populations.     

Isolation of polymorphic microsatellite markers for the demersal fish Helicolenus dactylopterus (Dela Roche 1809)

Six microsatellite loci were identified for the demersal deep‐sea fish Helicolenus dactylopterus. All loci were highly polymorphic (5–21 alleles per locus). Observed heterozygosities were from 0.378 to 0.868, while the expected heterozygosities ranged from 0.529 to 0.925. Multiplex PCR reactions were optimized. Microsatellite markers were developed for analysis of genetic structure including identification of stocks and migration patterns. The resulting data will be used to help in the establishment of scientifically based fisheries management for this species. Departures from the expected Hardy–Weinberg equilibrium were observed in three loci, and are likely to be a consequence of population structuring across the Azorean islands.     

Isolation and characterization of microsatellite DNA loci in sea bass,Lates calcarifer Bloch

Polymerase chain reaction (PCR)‐based isolation of microsatellite arrays (PIMA) technique was used to isolate seven polymorphic microsatellite loci in sea bass, Lates calcarifer Bloch. A total of 62 samples of wild and cultivated sea bass collected from a few populations within Peninsular Malaysia were used in the study. For seven polymorphic loci, the number of alleles ranged from four to nine and locus heterozygosities ranged from 0.710 to 1.000. The loci will be useful for studying population structure, genetic variability of wild and hatchery stocks of L. calcarifer and broodstock management purposes.     

Minimal gene flow from introduced brown trout (Salmo trutta L.) after 30 years of stocking

Lake Tinnsjø, Norway, has been heavily stocked over three decades with two different brown trout stocks. A population genetic survey based on 13 allozyme coding loci was conducted to investigate the genetic composition of the present trout population and the genetic impact of the two donors. Contrary to expectations, highly significant differences in allelic frequencies between Lake Tinnsjø trout and the two donor stocks were found at several loci, suggesting minimal gene flow from stocked trout to the wild populations. Pairwise genetic distance values were several times higher between donor stocks and Lake Tinnsjø samples than between the various spawning inlets to Lake Tinnsjø. F_st increased from 0.024 to 0.090, when samples from the donor stocks were included in the material. There were no deviations from expected Hardy–Weinberg distribution of genotypes in the spawning inlets. It was concluded that the donor stocks contributed little to the trout gene pool in the lake. A possible exception is the trout population below the lake outlet.     

Identification of a genetic network for an ecologically relevant behavioural phenotype in Drosophila melanogaster

Pupation site choice of Drosophila third‐instar larvae is critical for the survival of individuals, as pupae are exposed to various biotic and abiotic dangers while immobilized during the 3–4 days of metamorphosis. This singular behavioural choice is sensitive to both environmental and genetic factors. Here, we developed a high‐throughput phenotyping approach to assay the variation in pupation height in Drosophila melanogaster, while controlling for possibly confounding factors. We find substantial variation of mean pupation height among sampled natural stocks and we show that the Drosophila Genetic Reference Panel (DGRP) reflects this variation. Using the DGRP stocks for genome‐wide association (GWA) mapping, 16 loci involved in determining pupation height could be resolved. The candidate genes in these loci are enriched for high expression in the larval central nervous system. A genetic network could be constructed from the candidate loci, which places scribble (scrib) at the centre, plus other genes known to be involved in nervous system development, such as Epidermal growth factor receptor (Egfr) and p53. Using gene disruption lines, we could functionally validate several of the initially identified loci, as well as additional loci predicted from network analysis. Our study shows that the combination of high‐throughput phenotyping with a genetic analysis of variation captured from the wild can be used to approach the genetic dissection of an environmentally relevant behavioural phenotype.     

A series of mutable alleles of the white locus in Drosophila melanogaster

Summary The origin and phenotypes of a number of zeste mutant stocks with mutable white loci are described. Each newly arising form was lighter in eye color than the mutant it originated from. In each case the lighter pigmentation is believed to be due to an increase in genetic material in the proximal region of the white locus, the increase supposedly being the result of unequal crossing over. Some of the mutations which arose in the mutable stocks are reversions. They occurred in males as well as in homo- and heterozygous females. The reversions are believed to be due to a decrease in genetic material in the proximal region of the white locus. The decrease is assumed to be the result of intrachromosomal recombination. At least some of these events took place premeiotically. New mutants which originate frequently from mutable stocks are stable. In addition to the structure of the mutable white locus there is probably at least one still unknown factor which affects its mutability since the frequency of mutations arising in the mutable stocks decreases over the years.     

Isolation and characterization of microsatellites in the Southeast Asian river catfish Mystus nemurus

A total of 26 simple sequence repeats were identified using a random amplified polymorphic DNA (RAPD) based technique in the Southeast Asian river catfish Mystus nemurus. We report on the characterization of five polymorphic microsatellite loci in M. nemurus. The average number of alleles per locus was 3.2. These are the first microsatellite loci that have been developed for this species. These markers should prove useful as tools for managing the brood stocks and for future aquacultural development of this species.     

对虾白斑综合征病毒新株型WSSV-CN-Pc的毒力研究

对虾白斑综合征病毒(white spot syndrome virus,WSSV)是一种能够感染虾类并且造成其大面积死亡的环状双链DNA病毒。WSSV有多种分离株,其毒力有所差异。从克氏原螯虾(Procambarus clarkii)中分离得到1株WSSV新分离株WSSV-CN-Pc,其毒力尚不清楚。本研究采用肌肉注射和经口注射的方法,以WSSVTW型作为阳性对照,分别对克氏原螯虾(P.clarkii)和罗氏沼虾(Macrobrachium rosenbergii)进行活体实验。实验结果显示:肌肉注射WSSV-CN-Pc和WSSV-TW的克氏原螯虾均在第6天出现100%的死亡;罗氏沼虾在肌肉注射WSSV-TW后未出现死亡,但在注射WSSV-CN-Pc后的第9天死亡率达100%。经口注射WSSV-CN-Pc和WSSV-TW的克氏原螯虾均在第16天出现100%的死亡;罗氏沼虾经口注射WSSV-CN-Pc后的第19天死亡率为100%,但注射WSSV-TW的实验组并未出现死亡。结果表明,对于克氏原螯虾,WSSV-CN-Pc具有和WSSV-TW相似的毒力,而对罗氏沼虾存在明显的毒力差异。提示克氏原螯虾是WSSV传播途径中的重要因素。     

Polysaccharide-specific probes inhibit adhesion of Hyphomonas rosenbergii strain VP-6 to hydrophilic surfaces

Biofilm formation commences with the adhesion of microorganisms to surfaces. Information regarding the initial bond between a bacterium and a solid surface is essential for devising methods to inhibit the onset of biofilm formation. Three different types of polysaccharide-specific probes, cationic metals, dyes, and lectins, were used to bind the exopolysaccharide of Hyphomonas rosenbergii, a budding, prosthecate marine bacterium. Probes, which specifically bind complex carbohydrates, inhibit the adhesion of H. rosenbergii to hydrophilic surfaces. These results suggest that the polysaccharide portion of H. rosenbergii capsular, extracellular polymeric-substance is involved in the primary adhesion process. Journal of Industrial Microbiology & Biotechnology (2000) 25, 81–85. Received 01 February 2000/ Accepted in revised form 03 June 2000     

Detection and phylogenetic profiling of nodavirus associated with white tail disease in Malaysian <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> de Man

White tail disease (WTD) is a serious viral disease in the hatcheries and nursery ponds of Macrobrachium rosenbergii in many parts of the world. A new disease similar to WTD was observed in larvae and post larvae of M. rosenbergii cultured in Malaysia. In the present study, RT-PCR assay was used to detect the causative agents of WTD, M. rosenbergii nodavirus (MrNV) and extra small virus (XSV) using specific primers for MrNV RNA2 and XSV. The results showed the presence of MrNV in the samples with or without signs of WTD. However, XSV was only detected in some of the MrNV-positive samples. Phylogenetic analysis showed that the RNA2 of our Malaysian isolates were significantly different from the other isolates. Histopathological studies revealed myofiber degeneration of the tail muscles and liquefactive myopathy in the infected prawns. This was the first report on the occurrence of MrNV in the Malaysian freshwater prawn.     

Effect of exposure to cadmium on the tropical freshwater prawn Macrobrachium rosenbergii

The effect of cadmium (Cd) on mortality, resistance and bioaccumulation in the tropical freshwater prawn Macrobrachium rosenbergii from Egypt were studied. Survival of prawns exposed to Cd doses over 60 μg l^?1 were significantly lower than that of prawns exposed to lower doses. After 96 h prawns exposed to >40 μg l^?1 of Cd had a greater reduction in total haemocyte count and phagocytic activity than those exposed to lower concentrations. Bioaccumulation of Cd in the gills, hepatopancreas and muscles was variable. Cadmium accumulated significantly in the gills and hepatopancreas, but Cd accumulation in the muscles increased only marginally. Macrobrachium rosenbergii manifested histopathological alterations in the gills, hepatopancreas and muscles when exposed to various concentrations of cadmium.