Host−parasite relationships between Gyrodactylus stellatus (Monogenea: Gyrodactylidae) and Parophrys vetulus (Pleuronectidae−english scale) from coastal waters of Oregon
Host−parasite relationships between Gyrodactylus stellatus (Monogenea: Gyrodactylidae) and Parophrys vetulus (Pleuronectidae−english scale) from coastal waters of Oregon
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俄勒冈州沿海水域的 Gyrodactylus stellatus（Monogenea：Gyrodactylidae）和 Parophrys vetulus（Pleuronectidae-englishscale）之间的宿主-寄生虫关系
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发表时间：
1986
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影响因子：
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通讯作者：
R. Olson
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文献类型：
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作者：
H. N. Kamiso;R. Olson
Gyrodactylus stellatus Crane and Mizelle，1967年，在俄勒冈州亚奎纳湾的幼鱼(Parophrys Vetulus)、斑点沙丁鱼(Citharichthys Stellmaeus)和星状比目鱼(Platichthys Stellatus)上被发现。幼年英国比目鱼的感染率和感染强度高于斑点沙鱼或星状比目鱼。在1981年7月至1982年6月的12个月期间，幼鱼的平均感染率和感染强度分别为69.2%/尾和5.5尾/尾。6月份患病率最高(98.0%和10.1条/鱼)，10月份最低(37.0%和1.7条/条)。在实验室中，幼体对英国足鲨的摄食强度比在河口观察到的宿主高。强度在9wk内增加，然后在接下来的3wk期间下降。在6~18℃温度范围内，海星天牛种群增长率随温度的升高而增加，不摄食的海星天牛种群增长率高于摄食的海星天牛。盐度和以往高感染水平的经验并不显著影响星虫的增长速度。英国比目鱼(Paroprys vetulus Girard，1854)是在美国太平洋沿岸发现的最常见的脊索鱼种类之一，也是商业渔业的重要组成部分(Hart，1973)。根据Olson(1978)的说法，许多幼年的英国比目鱼在它们生命的第一年就利用亚基那湾作为托儿所(Olson和Pratt，1973)，并且通常被Gyrodactylus stellatus Crane和Mizelle(1967)寄生。在淡水和海洋硬骨鱼中都有由该属几种单发生吸虫引起的回指线虫病的报道(Cone和Oense，1984)。本研究探讨了白纹伊蚊和星纹夜蛾的寄主-寄生关系。材料和方法用5米水母拖网从俄勒冈州亚奎纳湾采集鱼类，并将其运送到俄勒冈州立大学海洋科学中心。将试验用英国比目鱼幼鱼(P.vetulus)置于圆形水箱(直径87 cm，海水125 L)中，加入流经紫外线过滤的海水(3~4 L/分钟)1~2wk，开始投喂。实验鱼大小相似(7.5±3.2厘米长)，无异常。所有的鱼都以商业湿润的三文鱼饲料喂养。用1：4000的福尔马林溶液处理未感染的实验鱼1小时(Putz和Hoffman，1963)。实验室感染是将未感染的鱼与2-3条受感染的鱼放在一个水箱中1-3天产生的。1985年4月16日收到；1985年9月27日修订；1985年9月30日接受。通过检测亚奎纳湾的多种潜在寄主物种，并在实验室中将潜在寄主暴露于该寄生虫，从生态学角度研究了该寄生虫的寄主专一性。从1981年7月至1982年6月每月采集样本，测定不同季节和不同鱼体大小的亚奎纳湾英鱼星形线虫的感染率和感染强度。捕获后不久，随机选择50条鱼，在解剖显微镜下计数每条鱼鳍上的回指线虫数量。如果渔获量少于50条，则全部作为样本。在一个由4个处理组成的实验中，研究了星星虫从一个寄主转移到另一个寄主的方法。在第一和第二个处理中，将感染的英制比目鱼与未感染的宿主分别放在流动和静止的水中。在第三种处理中，被感染和未被感染的鱼被允许在静态水中直接接触。在最后一次处理中，在引入未感染的英式比目鱼之前，先将感染的英式比目鱼从容器中取出。每个集装箱装2只感染的和3只未感染的英式比目鱼。在实验室条件和环境温度条件下，通过跟踪50例自然感染个体的感染过程，测定了在实验室条件和环境温度下，星形吸虫在幼鱼(长8.8±1.08 cm)上的增殖率。每周计数每条鱼的胸鳍、腹鳍和尾鳍上的蠕虫数量，为期一年。为了确定温度对感染强度的影响，将自然感染的英国比目鱼保存在流动海水的圆形水箱中，保持在6℃、12℃或18℃，每个处理重复25条鱼(10.3？1.12 cm长)。实验持续6wk，每周计数一次每条鱼的星形线虫数量。在一项盐度对星虫感染强度影响的实验中，感染的鱼(10.1±0.62厘米长)在静水中分别保持在14、21和28度的盐度下。
Gyrodactylus stellatus Crane and Mizelle, 1967, was found on juvenile English sole (Parophrys vetulus), speckled sanddabs (Citharichthys stigmaeus) and starry flounder (Platichthys stellatus) in Yaquina Bay, Oregon. Prevalence and intensity of infections were higher on juvenile English sole than on speckled sanddabs or starry flounders. Over a 12-mo period from July 1981 to June 1982, prevalence and intensity of infection on juvenile English sole averaged 69.2% per sampling and 5.5 worms per fish, respectively. Prevalence and intensity were maximum in June (98.0% and 10.1 worms/fish) and minimum in October (37.0% and 1.7 worms/ fish). In the laboratory, intensity on juvenile English sole reached higher levels than observed on hosts in the estuary. Intensity increased for 9 wk then decreased over the next 3-wk period. Rate of G. stellatus population growth increased with temperature from 6 to 18 C, and was higher on unfed than on fed English sole. Salinity and previous experience with high infection levels did not significantly influence the rate of G. stellatus increase. English sole (Parophrys vetulus Girard, 1854) is one of the most common pleuronectid species found along the Pacific Coast of the United States and an important component of the commercial fishery (Hart, 1973). Large numbers of juvenile English sole utilize Yaquina Bay as a nursery ground during their first year of life (Olson and Pratt, 1973) and according to Olson (1978) are commonly parasitized by Gyrodactylus stellatus Crane and Mizelle, 1967. Gyrodactyliasis caused by several species of monogenetic trematodes in this genus has been reported in both freshwater and marine teleosts (Cone and Odense, 1984). This study examines the host-parasite relationship between English sole and G. stellatus. MATERIALS AND METHODS Fishes from Yaquina Bay, Oregon were collected with a 5-m otter trawl and transported to the Oregon State University Marine Science Center. Juvenile English sole (P. vetulus) to be used in experiments were held in circular tanks (87 cm in diameter with 125 L of seawater) supplied with running ultraviolet light filtered seawater (3-4 L/min) for 1-2 wk to allow feeding to begin. Experimental fish were of similar size (7.5 + 3.2 cm long) and free of abnormalities. All fish were maintained on a diet of commercial moist salmon feed. Uninfected experimental fish were obtained by treating with a 1:4,000 formalin solution for 1 hr (Putz and Hoffman, 1963). Laboratory infections were produced by placing uninfected fish in a tank with 2-3 infected fish for 1-3 days. Received 16 April 1985; revised 27 September 1985; accepted 30 September 1985. Host specificity of G. stellatus was studied ecologically by examining a variety of potential host species from Yaquina Bay and experimentally by exposing potential hosts to the parasite in the laboratory. Prevalence and intensity of infection of G. stellatus on English sole from Yaquina Bay by season and by size of fish were determined from samples taken monthly from July 1981 to June 1982. Shortly after capture, 50 fish were selected randomly and the number of Gyrodactylus present on the fins of each fish was counted under a dissecting microscope. If the catch was less than 50 fish, all were used as samples. The method by which G. stellatus transfers from one host to another was examined in an experiment that consisted of 4 treatments. In the first and second treatments infected English sole were kept separate from uninfected hosts in flowing and static water. In the third treatment, infected and uninfected fish were allowed direct contact in static water. In the last treatment infected English sole were removed from the container before introduction of uninfected sole. Each container contained 2 infected and 3 uninfected English sole. The rate at which G. stellatus increased in number on juvenile English sole (8.8 ? 1.08 cm long) under laboratory conditions and ambient temperature was determined by following the course of infection on 50 naturally infected individuals. The number of worms on pectoral, ventral and caudal fins on each fish was counted weekly for 1 yr. To determine the effect of temperature on intensity of infection, naturally infected English sole were held in circular tanks of running seawater maintained at 6, 12, or 18 C. Each treatment was replicated with 25 fish (10.3 ? 1.12 cm long) per replicate. The experiment extended for 6 wk and the number of G. stellatus per fish was counted weekly. In an experiment to determine the effect of salinity on intensity of G. stellatus infections, infected fish (10.1 + 0.62 cm long) were maintained at salinities of 14, 21 and 28%o in static water.