Cavanilles Institute of Biodiversity and Evolutionary Biology, Science Park, University of Valencia, PO Box 22085, Valencia, Spain.
Vet Parasitol. 2013 Mar 31;193(1-3):163-71. doi: 10.1016/j.vetpar.2012.12.013. Epub 2012 Dec 20.
We examined the seasonal and yearly population dynamics of the monogenean pathogen Zeuxapta seriolae on juvenile fish from wild populations of Seriola dumerili. The study is based on bimonthly monitoring between April, 2005 and April, 2007 off Majorca, and newly obtained monogenean population data for juvenile fish from three additional localities in the Western Mediterranean (off Alicante, Corsica and Sardinia). We documented the highest intensities and abundances of Z. seriolae, with mean abundance values similar to or higher than those reported in the single case of wild fish mortalities reported to date. There was a recurrent pattern of seasonal change in infection with Z. seriolae in the populations of S. dumerili off Majorca, with substantially higher parasite loads during the warm season (April to June). Mean parasite abundance was significantly correlated with seawater temperature and associated with higher proportions of juvenile worms in the parasite populations, thus suggesting increased transmission rates at higher temperatures. There was a significant negative association between abundance of Z. seriolae and fish length. Comparisons with the samples of younger and older fish off Majorca indicated that whereas infection parameters gradually increased in the first year of juvenile fish life, larger/older fish (>43 cm; 1+) were much lightly infected than the smaller/younger (<30 cm; 0+) juvenile fish examined in the same season. The observed increases in abundance during the warm weather months were invariably associated with sharp increases in monogenean aggregation levels and this was in contrast with the markedly low levels for both parameters during the cold season months. These data, coupled with the strong negative correlation between the levels of aggregation of Z. seriolae and mean fish total length, indicate that heavily infected individuals are being rapidly removed (i.e. within 2-3 months) from the host population thus reducing the heterogeneity of parasite distribution as fish grow. We discuss parasite-induced host mortality and other mechanisms that may account for observed recurrent patterns in monogenean abundance and spatial aggregation and review the data available on the spread of Z. seriolae infections in the Mediterranean.
我们研究了野生杜氏棱鳀幼鱼中单殖吸虫病原体 Zeuxapta seriolae 的季节性和年度种群动态。该研究基于 2005 年 4 月至 2007 年 4 月在马略卡岛的每两个月监测一次，并获得了来自西地中海其他三个地方（阿利坎特、科西嘉岛和撒丁岛）的幼鱼新的单殖吸虫种群数据。我们记录了 Z. seriolae 的最高感染强度和丰度，其平均丰度值与迄今为止报告的野生鱼类死亡的单一病例相似或更高。马略卡岛附近的杜氏棱鳀种群中存在季节性变化的感染模式，在温暖季节（4 月至 6 月）寄生虫负荷明显较高。平均寄生虫丰度与海水温度显著相关，与寄生虫种群中幼体蠕虫的比例较高有关，因此表明在较高温度下传播速度增加。Z. seriolae 的丰度与鱼的长度呈显著负相关。与马略卡岛的年轻和年老鱼类样本的比较表明，感染参数在幼鱼生命的第一年逐渐增加，而较大/年老的鱼（>43 厘米；1+）的感染程度明显低于同一季节检查的较小/年轻的鱼（<30 厘米；0+）。在温暖月份观察到的丰度增加总是与单殖吸虫聚集水平的急剧增加有关，这与寒冷月份这两个参数的明显低水平形成对比。这些数据，加上 Z. seriolae 的聚集水平与鱼总长度之间的强烈负相关，表明感染严重的个体正在迅速从宿主种群中被清除（即在 2-3 个月内），从而随着鱼的生长减少寄生虫分布的异质性。我们讨论了寄生虫引起的宿主死亡和其他可能解释单殖吸虫丰度和空间聚集的周期性模式的机制，并回顾了地中海地区 Z. seriolae 感染传播的数据。
