Exploring the structure of genetic variation and the influences of demography on effective population size in the gag grouper Mycteroperca microlepi (Goode & Bean)

Using 11 microsatellite markers, genetic analyses of three successive year-classes of gag Mycteroperca microlepis juveniles across the north-eastern Gulf of Mexico revealed a lack of spatial structure and very little temporal variation between year-classes. These results are consistent with long-term effective population sizes on the order of 30 000 adults. The importance of reproductive-style and sex-ratio variation is discussed as an important influence on long-term effective sizes.     

Population structure, reproduction and sex-change in a tropical East Atlantic grouper

Spawning time and sizes at first sexual maturity and at sex-reversal are described in the tropical blue-spotted grouper Cephalopholis taeniops . All juvenile fish possess non-functional ovaries. At sexual maturity, most juvenile fish become functional females. Some of these later change sex to become males. The remaining juvenile females change immediately to males, without time as functional females. This is a new scheme for sexual differentiation of groupers.     

Territoriality and associated behaviour in three species of the genus Cephalopholis (Pisces: Serranidae) in the Gulf of Aqaba, Red Sea

Social structure and behavioural mechanisms enabling sympatry in three species of predatory fish in the Gulf of Aqaba ( Cephalopholis miniata (Forsskål), Cephalopholis argus Bloch and Schneider, and Cephalopholis henistiktos (Rüppell)) were examined in this study. C. miniata and C. argus formed compound interspecific territories in which they occurred in haremic groups consisting of a dominant male and two to 12 females. C. miniata and C. argus groups occupied territories of up to 475 m², and 2000 m² respectively, subdivided into secondary territories, each inhabited by an individual female. Observations of tagged fish disclosed behaviour patterns of patrolling by males, visiting the females, and antiparallel swimming of sexes. C. hemistiktos , in contrast, was monogamous and each pair jointly defended a common territory of up to 62 m². Among the three species the dominance hierarchy was C. argus > C. miniata > C. hemistiktos .     

Stock Identification of Gag, Mycteroperca microlepis, Along the Southeast Coast of the United States

The gag grouper Mycteroperca microlepis is an important component of commercial and recreational fisheries along the South Atlantic coast of the United States and in the Gulf of Mexico. Over the past two decades, this species has experienced significant declines in abundance and an increasing skew in sex ratios. Analysis of microsatellite DNA variation in this species shows mosaic patterns of population subdivision and significant departures from Hardy-Weinberg equilibrium in all sampling locations. Given the length of the pelagic stage (egg and larvae), the prevailing current patterns, and the migratory capabilities of the adults, it is unlikely that these observations are the result of restricted gene flow among genetically differentiated populations. The apparent structure of gag populations most likely reflects inbreeding in size-limited populations. Population declines, skewed sex ratios, and perhaps variance in female fecundity appear to have acted in concert to limited the number of individuals that contribute to a given year class. These data are reinforced by studies of other fish stocks that have experienced precipitous declines over the past two decades. Received April 13, 1998; accepted September 30, 1998.     

团头鲂 (♀) × 翘嘴鲌 (♂) 杂交后代的遗传特征及生长差异

以棕点石斑鱼(Epinephelus fuscoguttatus)为母本、清水石斑鱼(E. polyphekadion)为父本, 开展了杂交育种试验, 成功获得杂交子一代。由于棕点石斑鱼与清水石斑鱼外型相似, 其杂交子代也与亲本难以区分, 为探究双亲本与杂交子代表型差异和遗传差异, 研究利用外部形态数据及外型框架参数进行比较分析, 同时使用微卫星标记对双亲本及杂交子代的遗传特征进行分析。在外部形态结构的探究中, 杂交子代可量性状及外形框架更偏向于母本棕点石斑鱼。在遗传特征的分析中, 采用ddRAD-seq技术在棕点石斑鱼上获得6266个微卫星标记, 筛选出7对可以在双亲本及杂交子代中稳定扩增且遗传多样性较高的微卫星引物, 其中, 6对引物可以在部分群体中扩增出特异性条带以区分3个群体。通过分析, 7个微卫星标记位点在杂交子代群体中的平均观测杂合度(H_o)为0.891, 平均期望杂合度(H_e)为0.768, 平均多态信息含量(PIC)为0.717, 三者均高于双亲本, 表明杂交子代在遗传信息的多样性方面有一定的提高。研究结果可为棕点石斑鱼、清水石斑鱼及两者杂交子代的鉴别提供方法, 并为杂交石斑鱼的培育提供一定的理论基础。

     

Detection of species-specific long VNTRs in mitochondrial control region and their application to identifying sympatric Hong Kong grouper (Epinephelus akaara) and yellow grouper (Epinephelus awoara)

Length variation and heteroplasmy were observed in PCR products of the first half of mtDNA control region of both Hong Kong grouper (Epinephelus akaara) and yellow grouper (Epinephelus awoara). DNA sequencing unveiled the phenomena were caused by the presence of species-specific long variable number tandem repeats (VNTRs). This is the first report on the mtDNA VNTRs and their heteroplasmy in groupers. Moreover, these VNTRs are also the longest such structure found in teleost fish. Thereafter, we designed two species-specific PCR reverse primers according to the 3' end sequences of the VNTRs and successfully established assays for the identification of these two sympatric grouper species.     

A set of 16 consensus primer pairs amplifying the complete mitochondrial genomes of orange-spotted grouper (Epinephelus coioides) and Hong Kong grouper (Epinephelus akaara)

Groupers are of considerable economic value; however, their classification and evolutionary relationships have long been hindered by the overwhelming number of species and lack of morphological specializations. Mitochondrial genome is a source of original markers that are potentially useful in the study of phylogeny and population genetics of groupers. We describe a set of 16 new primer pairs that allow PCR amplification of the entire mitochondrial genomes of orange-spotted grouper and Hong Kong grouper. This primer set has been defined for consensus over eight other grouper species, facilitating further studies on the molecular evolution and population genetics of groupers.     

Sexual development and sexuality in the Nassau grouper

Hermaphroditic sexual patterns are widespread among teleosts and are especially characteristic of certain perciform families. Among the most diverse groups of hermaphroditic species are the groupers, hamlets and sea basses of the family Serranidae. Like other groupers, the epinepheline serranid, Epinephelus striatus , the Nassau grouper, has long been assumed to exhibit monandric protogyny (a form of hermaphroditism in which all males derive from adult females by sex change). Histological and demographic data, however, indicate that the sexual pattern of this species is not monandric, and that, unlike other group species, the juveniles pass through a bisexual stage of gonadal development. Sexuality in the Nassau grouper is essentially gonochoristic, with potential for sex change. The combination of bisexuality and gonochorism is previously undescribed in the serranids.     

动物的生境选择

动物的生境选择颜忠诚陈永林（中国科学院动物研究所,北京１０００８０）ＨａｂｉｔａｔＳｅｌｅｃｔｉｏｎｉｎＡｎｉｍａｌｓ．ＹａｎＺｈｏｎｇｃｈｅｎｇ,ＣｈｅｎＹｏｎｇｌｉｎ（ＩｎｓｔｉｔｕｔｅｏｆＺｏｏｌｏｇｙ,ＡｃａｄｅｍｉａＳｉｎｉｃａ,Ｂｅｉｊｉ...     

珍珠龙胆石斑鱼对7种蛋白源的表观消化率

研究测定了珍珠龙胆石斑鱼(Epinephelus fuscoguttatus♀×Epinephelus lanceolatu♂)对黄粉虫粉(TMM)、黑水虻虫粉(HIM)、乙醇梭菌蛋白(CAP)、荚膜甲基球菌蛋白(MCM)、小球藻粉(CVM)、棉籽浓缩蛋白(CPC)和秘鲁鱼粉(PFM)共7种蛋白源的表观消化率(ADCs)。试验配制1组含50%鱼粉的基础饲料, 而7组试验饲料按70%的基础饲料和30%的蛋白源配制而成, 8组饲料都加入0.1%氧化钇(Y₂O₃)作为外源标志物。将初始平均体重为(9.95±0.50) g的杂交石斑鱼幼鱼随机分配到0.3 m³的玻璃钢桶中, 每个处理组设置3个重复(桶), 每桶30尾鱼。经过5d的试验饲料饲喂驯化后, 每天两次用虹吸法收集粪便样本。结果表明, 7种蛋白源的干物质ADCs从高至低依次为: CVM>TMM=CAP=CPC>HIM=MCM=PFM。CVM的干物质、粗蛋白和大多数氨基酸(包括蛋氨酸和苏氨酸)的ADCs最高。而HIM的干物质、粗蛋白和大多数氨基酸的ADCs低于其他组。CAP的赖氨酸ADCs高于其他6种蛋白原料, 粗蛋白ADCs仅次于CVM。PFM的干物质ADCs明显低于CVM, 但与CAP没有显著差异。此外, PFM的粗蛋白ADCs低于CVM、CAP和MCM三种蛋白原料, 并且其赖氨酸ADCs低于CAP, 苏氨酸ADCs也低于CAP和CVM。研究表明, 这7种蛋白源中小球藻粉(CVM)和乙醇梭菌蛋白(CAP)在珍珠龙胆石斑鱼中显示出较高的表观消化率。