Inference of Potential Genetic Risks Associated with Large-Scale Releases of Red Sea Bream in Kanagawa Prefecture, Japan Based on Nuclear and Mitochondrial DNA Analysis

Since 1978, millions of hatchery-reared red sea bream (Pagrus major) juveniles have been released in Sagami Bay and Tokyo Bay in Kanagawa Prefecture, Japan. The stock enhancement program has contributed to total catch; however, no information regarding the genetic interactions with wild counterparts is available. Here, we combined 15 microsatellite loci and mitochondrial D-loop sequencing to characterize the genetic resources of red sea bream in Sagami Bay and Tokyo Bay and to elucidate the potential harmful genetic effects associated with fish releases. Both types of markers evidenced higher levels of genetic diversity in wild samples (SB and TB) compared with offspring before stocking (H07 and H08) as well as a hatchery-released sample recaptured in Sagami Bay (HR). Microsatellite F _ST estimates and Bayesian clustering analysis found significant genetic differences among samples (F _ST?=?0.013–0.054), except for the two wild samples (F _ST?=?0.002) and HR vs. H07 (F _ST?=?0.007). On the other hand, mitochondrial-based Ф _ST suggested haplotypic similarity between SB, H07, and HR. The low effective number of females contributing to the offspring over multiple generations may be responsible for the lack of haplotypic differentiation. Moreover, the putative hatchery origin to three fish (8 %) without deformity in the inter-nostril epidermis was inferred for the first time. Our results showed the usefulness of combining nuclear and mitochondrial markers to elucidate genetic interactions between hatchery-released and wild red sea bream and warned about potential harmful genetic effects should interbreeding takes place.     

中草药饲料添加剂对真鲷(Pagrosomus major)幼鱼生长和非特异性免疫的影响

设计中草药配方分别以1%、2%、3%剂量分粉剂和汁剂的方式添加到基础饲料中,连续投喂真鲷幼鱼2个月。分三个阶段(每20天一阶段)测定鱼体的增重、饵料系数、血液中的NBT阳性细胞和血清中的溶菌酶的活力。结果表明,中草药添加剂能够极显著地影响真鲷幼鱼的生长、血液中NBT阳性细胞数和血清中的溶菌酶的活力(p＜0．01)。且两种添加方式均在第二、三阶段比对照组出现了极显著的差异,且均以2%的添加剂量效果为最佳。     

条石鲷检出的虹彩病毒特性研究

2009年8月份辽宁地区某网箱养殖场出现条石鲷大量死亡病情,对病鱼组织切片观察,在脾脏和肾脏等器官内发现许多形态异常肿大的嗜碱性粒细胞。病鱼组织匀浆液感染GF细胞出现了明显的细胞病变效应(CPE)。经透射电镜观察发现,脾脏、肾脏、肝脏及肠组织细胞质内存在大量呈六边形的病毒粒子,该病毒由核衣壳(100~110nm)和囊膜构成,直径150~180nm,似虹彩病毒。使用真鲷虹彩病毒(RSIV)959bp PstI片段特异性引物对病鱼各脏器组织进行PCR扩增,在脾脏、肾脏、鳃、肠、心脏和脑扩增出570bp大小的目的片段。同时,针对虹彩病毒主衣壳蛋白序列进行PCR扩增后得到1 400 bp大小的基因片段。病毒主衣壳蛋白序列系统进化分析显示,该病毒与真鲷虹彩病毒(RSIV-U1)等几株病毒位于同一进化分枝内。根据上述实验结果,作者认为引发条石鲷大批死亡的病原为真鲷虹彩病毒(Red sea bream iridovirus,RSIV)。     

Ontogenetic change in the relationship between metabolic rate and body mass in a sea bream Pagrus major (Temminck & Schlegel)

Ontogenetic changes in the relationship between resting rate of oxygen consumption and wet body mass were examined at 20° C with the sea bream Pagrus major ranging from 0.00020 g (weight just after hatching) to 270 g (weight at 530 days old). There was a triphasic relationship between oxygen consumption of an individual fish M (μl min⁻¹) and body mass W (g). During a very early stage (weight 0.00020–0.00025 g), corresponding to the pre-larval stage and with the transitional period to the post-larval stage, there was no substantial change in body mass. The mass–specific metabolic rate M/W (μl g⁻¹ min ¹) showed no clear relationship to body mass as expressed by the equation M/ W =4.86 + 1.47 D , where D is age in days. During the post-larval stage (weight 0.00031–0.005 g), M/W remained almost constant independent of body mass following the expression M = 12.5 W0 .949. During the juvenile and later stages (weight 0.005–270 g), M/ W decreased with increasing body mass following the expression M = 6.3 W ^0.821 which is significantly different from the expression for the post-larval stage ( P < 0.001). Ontogenetic changes in the metabolism-body mass relationship are discussed from the viewpoint of relative growth of organs with different metabolic activities.     

梭鱼幼鱼选择温度的研究

梭鱼幼鱼选择温度的研究张梅英岳玉环（中国医科大学实验动物部,沈阳１１０００１）（吉林农业大学动物科学系,长春１３０１１８）侯文礼（东北师范大学环境科学系,长春１３００２４）ＴｅｍｐｅｒａｔｕｒｅｓｅｌｅｃｔｉｏｎｆｏｒＬａｒｖａｏｆＬｉｚａｈａｅｍａ...     

Some aspects of the embryonic and postembryonic development of the Japanese anchovy Engraulis japonicus Temminck et Schlegel, 1846 in Vostok Bay, Sea of Japan

This study revealed additional data concerning the spawning period of the Japanese anchovy Engraulis japonicus Temminck et Schlegel, 1846 in Vostok Bay (Peter the Great Bay, Sea of Japan). The spawning of E. japonicus in this area ends in September at a water temperature of 17.5 ± 3°C. Some important peculiarities of the embryonic and postembryonic development of E. japonicus in the natural environment are described. The anchovy larvae have characteristic upper and lower rows of melanophores and subcaudal paired rows of melanophores on the trunk. Regular alternating rows of long and short cones were found in the retina of the early larval stages (TL 5.5 ± 0.1 mm). The planes of the photoreceptive lamellae in the outer segments of the short cones are oriented parallel to the long cell axis, which evidently provides sensitivity to polarized light.     

Phenotypic Diversity of Infectious Red Sea Bream Iridovirus Isolates from Cultured Fish in Japan

Megalocytivirus is causing economically serious mass mortality by infecting fish in and around the Pacific region of Asia. The recent emergence of many new iridoviruses has drawn attention to the marked taxonomic variation within this virus family. Most studies of these viruses have not included extensive study of these emergent species. We explored the emergence of red sea bream iridovirus (RSIV) on a fish farm in Japan, and we specifically endeavored to quantify genetic and phenotypic differences between RSIV isolates using in vitro and in vivo methods. The three isolates had identical major capsid protein sequences, and they were closely related to Korean RSIV isolates. In vitro studies revealed that the isolates differed in replication rate, which was determined by real-time quantitative PCR of viral genomes in infected cells and cell culture supernatant, and in cell viability, estimated by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay for infected cells. In vivo studies showed that the isolates exhibit different virulence characteristics: infected red sea bream showed either acute death or subacute death according to infection with different isolates. Significant differences were seen in the antigenicity of isolates by a formalin-inactivated vaccine test. These results revealed that variant characteristics exist in the same phylogenetic location in emergent iridoviruses. We suggest that this strain variation would expand the host range in iridoviral epidemics.Iridoviruses are designated as icosahedral cytoplasmic DNA viruses; this group of viruses has different hosts, including fish, amphibians, and insects, causing economic and environmental problems. The family Iridoviridae includes five genera: Iridovirus, Chloriridovirus, Ranavirus, Lymphocystivirus, and Megalocytivirus (45). Piscine iridoviruses belong to the genera Ranavirus, Lymphocystivirus, and Megalocytivirus. In recent years, the genotypical variation between newly found iridovirus strains included in the genus Ranavirus has been studied in this viral family (5). However, the properties of and variation between iridovirus species have not been well characterized except for a few iridoviruses isolated from amphibians (11, 46), fish (8, 18, 19), and insects (23, 42, 44). Most studies attempting to differentiate variants have relied on genotypic rather than phenotypic properties.Members of the Megalocytivirus genus produce characteristic basophilic inclusion bodies in the enlarged cells of host fish organs, which have been collected from mass mortalities occurring in wild and cultured fish species (14, 37). Red sea bream (Pagrus major) aquaculture has suffered great losses from the prevalence of red sea bream iridovirus (RSIV) infection in Japan. RSIV has been assigned to the Megalocytivirus genus. The virus was first isolated from cultured red sea bream in western Japan in 1990 (22).Many other piscine iridoviruses have been reported in Asian countries (7, 24, 25) from more than 100 different species (41), including freshwater and marine fish (19). RSIV is closely related genetically to viruses isolated from ornamental fish in Southeast Asia, based on nucleotide sequence studies (21, 39). A formalin-inactivated RSIV vaccine has been used in juvenile marine fish against this disease (31, 32).The incidence of iridovirus infection has been increasing among cultured fish in Japan (29, 30). In addition, genetic and phenotypic iridovirus variants suggest the presence of diverse variants in this virus group (16). In the present study, we examined the detailed properties of three RSIV isolates from two fish species collected from fish farms in western Japan. Using in vitro and in vivo processes, we focused close examination specifically on quantitative genetic and phenotypic differences between the three isolates. The aim of this study was to increase understanding of the epidemiology of RSIV.     

Effect of Translocations on the Genetic Structure in Populations of the Red Deer (Cervus elaphus) in Poland

Russian Journal of Genetics - The red deer (Cervus elaphus) has been translocated across Europe, including Poland in order to improve the quality of local populations of the animal. The aim of the...     

Isolation and characterization of 30 novel polymorphic microsatellite loci from Japanese halfbeak, Hyporhamphus sajori (Temminck et Schlegel, 1846)

The construction of genetic linkage map and evaluation of population genetic diversity both require large numbers of polymorphic molecular markers. In the study, 60 microsatellite loci were isolated from a dinucleotide-enriched genomic library of Japanese halfbeak (Hyporhamphus sajori). And 30 polymorphic microsatellite loci were found to be polymorphic between 2 and 11 alleles. The number of observed, expected heterozygosity and polymorphism information content per locus in 24 individuals ranged from 0.1667 to 1.000, 0.1828 to 0.9220, 0.1828 to 0.8945, respectively. Three loci significantly deviated from Hardy–Weinberg equilibrium after Bonferroni correction analysis and there was no significant linkage disequilibrium found between pairs of loci. As a result, 30 microsatellite loci probably should provide sufficient level of genetic diversity to investigate the fine-scale population structure, stock management and enhancement, genetic linkage map construction and molecular marker-assisted breeding in H. sajori.     

Cannibalism on eggs by dark chub, Zacco temmincki (Temminck & Schlegel) (Cyprinidae)

During spawning male dark chub, Zacco temmincki (Temminck & Schlegel), buried eggs by stirring up the river bed with their anal fins. No parental care was shown for eggs after spawning. Many satellites (both males and females) preyed upon eggs at the instant of spawning. The number of eggs produced is a function of body length [log₁₀ E =−0.273+3.519log₁₀ S , where E is the number of eggs and S is standard length (cm)]. From the size distribution of females that spawned during a reproductive season, the total number of spawning sites used and mean number of eggs per spawning site, at least 97.1% eggs were estimated to be consumed by cannibalism. This marked cannibalism resulted from a lack of parental care and the presence of many satellites produced by the polygynous mating system.     

A new species of Benedenia Diesing, 1858 (Monogenea: Capsalidae) parasitic on Lethrinus haematopterus Temminck & Schlegel (Perciformes: Lethrinidae) from Japan

Systematic Parasitology - A new species of capsalid monogenean, Benedenia armata n. sp., is described from Lethrinus haematopterus Temminck &amp; Schlegel (Perciformes: Lethrinidae) from off...     

Identification of Quantitative Trait Loci for Resistance to RSIVD in Red Sea Bream (<Emphasis Type="Italic">Pagrus major</Emphasis>)

Red sea bream iridoviral disease (RSIVD) is a major viral disease in red sea bream farming in Japan. Previously, we identified one candidate male individual of red sea bream that was significantly associated with convalescent individuals after RSIVD. The purpose of this study is to identify the quantitative trait loci (QTL) linked to the RSIVD-resistant trait for future marker-assisted selection (MAS). Two test families were developed using the candidate male in 2014 (Fam-2014) and 2015 (Fam-2015). These test families were challenged with RSIV, and phenotypes were evaluated. Then, de novo genome sequences of red sea bream were obtained through next-generation sequencing, and microsatellite markers were searched and selected for linkage map construction. One immune-related gene, MHC class IIβ, was also used for linkage map construction. Of the microsatellite markers searched, 148 and 197 were mapped on 23 and 27 linkage groups in the female and male linkage maps, respectively, covering approximately 65% of genomes in both sexes. One QTL linked to an RSIVD-resistant trait was found in linkage group 2 of the candidate male in Fam-2014, and the phenotypic variance of the QTL was 31.1%. The QTL was closely linked to MHC class IIβ. Moreover, the QTL observed in Fam-2014 was also significantly linked to an RSIVD-resistant trait in the candidate male of Fam-2015. Our results suggest that the RSIVD-resistant trait in the candidate male was controlled by one major QTL closely linked to the MHC class IIβ gene and could be useful for MAS of red sea bream.     

Influence of oral administration of 3,5,3'-triiodo-thyronine on growth, digestion, food conversion and metabolism in the underyearling red sea bream, Chrysophrys major (Temminck & Schlegel)

The effect of inclusion of 3,5,3'-triiodo-∼-thyronine (T₃) in the diet was examined in underyearling red sea bream Chrysophrys major (Temminck & Schlegel). The treatment brought about increases in growth rate, appetite, food conversion efficiency and activities of intestinal enzymes including leucine nitroanilidase, alkaline phosphatase, α-glutamyltransferas, α-amylase and disaccharidase. There were no changes in the muscle content of water, protein, lipid and glycogen. Liver glycogen content was elevated, as well as activities of the hepatic enzymes glycogen phosphory-lase, glycogen synthetase, glutamate-pyruvate transaminase, fructose- 1, 6-diphosphatase and glucose-6-phosphatase. The serum concentrations of total protein, albumin, globulin, α-amino acids. glucose, ammonia and calcium were increased by the treatment whereas the serum concentrations of free fatty acids, cholesterol and triglyceride remained unaltered. The results suggest that in the red sea bream T, stimulated protein and carbohydrate but not lipid metabolism and that the hormone promoted growth by improving appetite, digestion and absorption.     

Reproductive parameters of invasive topmouth gudgeon Pseudorasbora parva (Temminck and Schlegel, 1846) from Slovakia

Females of an invasive population of topmouth gudgeon Pseudorasbora parva (Temmick and Schlegel, 1846) from the Šúr pond (Bratislava, Slovakia) were examined to analyze their fecundity and other life history traits. Samples were collected during both pre-spawning (n = 137) and post-spawning (n = 89) periods. Standard length of the females from the pre-spawning period ranged from 23.42 to 59.71 mm (mean 32.80 mm), body weight from 0.260 to 5.442 g (mean 0.965 g), and eviscerated body weight from 0.207 to 4.882 g (mean 0.748 g). Absolute fecundity varied between 121 and 7124 oocytes (mean 1106 oocytes). In 75.22% of the females, two or three size groups of oocytes were clearly distinguished. Overall, the life history traits observed in invasive topmouth gudgeon from the Šúr pond demonstrated a high flexibility in their reproductive strategy. This, together with previously described great morphological variability, is likely to make this species such a successful invader.     

Variation in mitochondrial DNA in Far Eastern mullet pilengas, Liza haematocheilus Temminck and Schlegel, acclimatized in the Azov-Black Sea basin

This study continues the investigation of genetic variation in the populations of native and acclimatized in the Azov-Black Sea basin pilengas from the Sea of Japan. The previous comparison based on allozyme analysis was supplemented by analysis of restriction polymorphism of a mitochondrial DNA fragment containing the cytochrome b gene and the D-loop. Five out of fifteen endonucleases tested detected polymorphic sites. In the samples of native and acclimatized pilengas, five common haplotypes were found; ten and three "population-specific" haplotypes were detected in the Far Eastern and the Azov populations, respectively. The differences in haplotype distributions between these populations were highly significant (P < 0.001). The mtDNA variation was lower in the Azov than in the Far Eastern population (haplotype diversity mu respectively 6.35 +/- 0.27 and 9.14 +/- 0.55), which is in good agreement with the decrease in the number of polymorphic loci and the mean number of alleles per locus, found earlier for allozyme markers in this population. The reasons for these differences in the acclimatized population are discussed.