寄生于大鳍鳠的鳠鱼鳋的生态研究

鱯鱼鳋能在16℃以上的适宜水温中繁殖,在25℃左右,繁殖快,感染力强;鱯鱼鳋的感染有明显的季节变化,这是由外界因素(如水温、水质和水体流速等)的变化以及它的繁殖和感染力的变化所引起的;鱯鱼鳋的频数在宿主种群中呈负二项分布;鱯鱼鳋的感染可能引起大鳍鱯产生抵抗力,抵抗力的强度随感染次数和感染强度增加而增强;在天然条件下,影响鱯鱼鳋种群消长的主要因素是非密度制约因素和大鳍鱯的免疫反应。     

Ultraviolet reflectance mediates pollinator visitation in Mimulus guttatus

Floral colors are widely believed to be an adaptation to attract pollinators. Recently, our understanding of floral reflectance has broadened to include colors that are beyond the spectrum that human eyes can perceive (such as ultraviolet (UV) reflectance), yet we still know relatively little about which plant species reflect UV light or its effectiveness in attracting pollinators. We investigated the effect of UV reflectance in Mimulus guttatus in a number of different populations in British Columbia, Canada. We found that M. guttatus had distinct regions of the corolla where UV light was reflected and absorbed. When we manipulated the degree of contrast between the reflection and absorption area, we found that pollinator visitation was severely disrupted, in terms of frequency and foraging patterns observed. Despite the bright yellow (bee‐green) coloration and visible nectar guides in M. guttatus, we conclude that UV reflectance is critical in pollinator attraction.     

Predicting evolution of floral traits associated with mating system in a natural plant population

Evolution of floral traits requires that they are heritable, that they affect fitness, and that they are not constrained by genetic correlations. These prerequisites have only rarely been examined in natural populations. For Mimulus guttatus, we found by using the Riska-method that corolla width, anther length, ovary length and number of red dots on the corolla were heritable in a natural population. Seed production (maternal fitness) was directly positively affected by corolla width and anther size, and indirectly so by ovary length and number of red dots on the corolla. The siring success (paternal fitness), as estimated from allozyme data, was directly negatively affected by anther-stigma separation, and indirectly so by the corolla length-width ratio. Genetic correlations, estimated with the Lynch-method, were positive between floral size measures. We predict that larger flowers with larger reproductive organs, which generally favour outcrossing, will evolve in this natural population of M. guttatus.     

注射促黄体素释放激素类似物和地欧酮诱导大鳍■和长吻■排卵的研究

对于性成熟的大鳍Ｍｙｓｔｕｓｍａｃｒｏｐｔｅｒｕｓ（Ｂｌｅｅｋｅｒ）野生鱼,单独注射多巴胺的抑制剂地欧酮（ＤＯＭ）不能影响血清促性腺激素（ＧＴＨ）水平,也不能诱导排卵;单独注射类似物ＬＨＲＨ－Ａ,虽能使血清ＧＴＨ水平显著升高,但仅产生较低的排卵率;而当ＤＯＭ与ＬＨＲＨ－Ａ结合注射却显著增强ＬＨＲＨ－Ａ促进血清ＧＴＨ水平升高的作用,并诱导出较高的排卵率。对性成熟的长吻ＬｅｉｏｃａｓｉｓｌｏｎｇｉｒｏｓｔｒｉｓＧｕｎｔｈｅｒ野生鱼,使用ＬＨＲＨ－Ａ＋ＤＯＭ作２次注射诱导排卵的效果也与注射ＬＨＲＨ－Ａ加脑垂体这一传统诱导排卵方法相似。Ｌｉｎｐｅ方法（ＬＨＲＨ－Ａ＋ＤＯＭ,作１次或２次注射）避免了采集、保存脑垂体不便给生产带来的麻烦,在科鱼类的人工繁殖中,具有较高的推广价值。     

The potential for adaptive evolution of pollen grain size in Mimulus guttatus

We tested whether pollen grain size (PGS) shows heritable variation in three independent populations of Mimulus guttatus by imposing artificial selection for this character. In addition, we looked for correlated responses to selection in a range of 15 other floral characters. Heritable variation in PGS was found in all three populations, with heritabilities of between 19 and 40% (average 30%). After three generations, upward and downward lines differed on average by 30% in pollen volume. No consistent patterns of correlated response were found in other characters, indicating that PGS can respond to selective forces acting on PGS alone. Possible selection mechanisms on PGS in this species could include intermale selection, if large pollen grains produce more competitive gametophytes; or optimization of patterns of resource allocation, if local mate competition varies.     

Nickel tolerance and copper - nickel co - tolerance in Mimulus guttatus from copper mine and serpentine habitats

Previous work on M. guttatus suggested that nickel tolerance in copper mine populations may also be given by the genes for copper tolerance. It has been shown that copper tolerance in M. guttatus is controlled by a single major gene, plus a number of minor genes (or modifiers) which elevate copper tolerance. Crosses between nickel tolerant individuals from three families and non - tolerants showed that nickel tolerance in M. guttatus is heritable. In order to study the effects of the major copper tolerance gene on copper - nickel co - tolerance in M. guttatus, homozygous copper tolerant and non - tolerant lines were screened against nickel. Significant differences occur between these lines for copper, but were not found when analysed for nickel, indicating that copper - nickel tolerance is not governed by the major gene for copper tolerance. To test whether the minor genes for copper have a pleiotropic effect on nickel tolerance, five selection lines derived from three copper mines (Copperopolis, Penn and Quail) in Calaveras county, California, which vary in degree of tolerance to copper, by the presence or absence of minor copper genes, were also screened against nickel. Two out of three of the lines from Copperopolis showed elevated tolerance to nickel, but two further selection lines derived from Penn and Quail copper mines gave no indication of increased nickel tolerance. These results suggest that the minor genes for copper do not give tolerance to nickel. This was confirmed by the screening of modifier lines, in which modifiers for differing degrees of copper tolerance were inserted into a non - tolerant background. Genotypes possessing fewer copper modifiers yielded higher nickel tolerance than those genotypes which have a greater number of modifiers. Thus nickel tolerance in this species is heritable and under the control of different genes to those producing copper tolerance.     

Vibrios of the spotted rose snapper Lutjanus guttatus Steindachner, 1869 from northwestern Mexico

AIM: To characterize and identify vibrios present in wild and cultured juvenile snappers (Lutjanus guttatus) in northwestern Mexico. METHODS AND RESULTS: Spotted rose snapper juveniles were collected at four localities in northwestern Mexico. Bacteria were isolated from external lesions, kidney, liver, and spleen from cultured and wild caught organisms. In total, 280 isolates were obtained and fingerprinted with rep-PCR (GTG5). Nearly 93.2% of the strains belonged to the Vibrionaceae family. Species and genera identified were Photobacterium damselae subsp. damselae (76 strains), Photobacterium leiognathi (13), Vibrio sp. (24), Vibrio alginolyticus (12), Vibrio campbellii (19), Vibrio fortis (9), Vibrio harveyi (49), Vibrio ichthyoenteri (4), Vibrio mediterranei (4), Vibrio parahaemolyticus (1), Vibrio ponticus (2), Vibrio rotiferianus (22), and four potential new species. Conclusions: A wide diversity of vibrios was found in the external lesions and internal organs of both wild and cultured spotted rose snapper juveniles. In total, 12 species of vibrios and four potential new species were identified. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on the vibrios present in the spotted rose snapper and therefore might serve as a basis for future studies and diagnosis.     

Reproductive biology of Mystus vittatus (Bloch) (Bagridae: Siluriformes) from Guntur,Andhra Pradesh

Maturation, minimum length at first maturity, spawning season, spawning periodicity, sex-ratio and absolute fecundity of Mystus vittatus, a common bagrid catfish, have been investigated. The observations show that spawning takes place during September and October. Each individual spawns only once in the season as evidenced by the study of the intraovarian ova. Females dominate the catches, and absolute fecundity (F) can be expressed by% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOabaeqabaGaciiBai% aac+gacaGGNbGaaeiiaiaabAeacaqGGaGaaeypaiaabccacaqGTaGa% ae4maiaab6cacaqGYaGaaeyoaiaabkdacaqGGaGaae4kaiaabccaca% qG0aGaaeOlaiaabgdacaqG3aGaaeymaiaabgdacaqGGaGaaeiBaiaa% b+gacaqGNbGaaeiiaiaabYeaaeaacaqGHbGaaeOBaiaabsgacaqGGa% GaaeOraiaabccacaqG9aGaaeiiaiaab2cacaqGXaGaaeOlaiaabwda% caqG0aGaaeinaiaabwdacaqGGaGaae4kaiaabccacaqGWaGaaeOlai% aabMdacaqG0aGaae4naiaabkdacaqGGaGaae4vaaaaaa!5FCC!\[\begin{gathered} \log {\text{ F = - 3}}{\text{.292 + 4}}{\text{.1711 log L}} \hfill \\ {\text{and F = - 1}}{\text{.5445 + 0}}{\text{.9472 W}} \hfill \\ \end{gathered} \]     

Spatially and temporally varying selection on intrapopulation quantitative trait loci for a life history trade-off in Mimulus guttatus

Why do populations remain genetically variable despite strong continuous natural selection? Mutation reconstitutes variation eliminated by selection and genetic drift, but theoretical and experimental studies each suggest that mutation‐selection balance insufficient to explain extant genetic variation in most complex traits. The alternative hypothesis of balancing selection, wherein selection maintains genetic variation, is an aggregate of multiple mechanisms (spatial and temporal heterogeneity in selection, frequency‐dependent selection, antagonistic pleiotropy, etc.). Most of these mechanisms have been demonstrated for Mendelian traits, but there is little comparable data for loci affecting quantitative characters. Here, we report a 3‐year field study of selection on intrapopulation quantitative trait loci (QTL) of flower size, a highly polygenic trait in Mimulus guttatus. The QTL exhibit antagonistic pleiotropy: alleles that increase flower size, reduce viability, but increase fecundity. The magnitude and direction of selection fluctuates yearly and on a spatial scale of metres. This study provides direct evidence of balancing selection mechanisms on QTL of an ecologically relevant trait.