Aloo P A, Dezfuli B S
Department of Zoology, Kenyatta University, Nairobi, Kenya.
Folia Parasitol (Praha). 1997;44(3):233-8.
From January 1992 to December 1993, a total of 2158 fish, namely Oreochromis leucostictus (Trewavas, 1983), Micropterus salmoides (Lacépède, 1802), Tilapia zillii (Gervais, 1848) and Barbus amphigrama (Boulenger, 1902) were sampled from thirteen stations on Lake Naivasha, Kenya, using a fleet of gill nets and examined for helminth parasites. The prevalence of infection due to cystacanths of an acanthocephalan, Polyacanthorhynchus kenyensis Schmidt et Canaris, 1967 among parasitized O. leucostictus ranged from 30.4 to 86.9%; among T. zillii from 4.1 to 77.7%; in M. salmoides from 20 to 50%; and in B. amphigrama from 5.8 to 100%. In 735 hosts belonging to the above four species, a total of 4198 immature specimens of P. kenyensis were recovered. All cystacanths were found in extraintestinal sites, either free within the fish body cavity or encysted within the host visceral organs. There was no significant variation in the prevalence of the parasite within months (P > 0.001). Host sex ratio was significant (P < 0.001) in favour of male T. zillii, and also highly significant (P < 0.001) in favour of male O. leucostictus. Moreover, in this fish, prevalence of infection was observed to increase with the increase in the size of the fish. Among infected M. salmoides, there was no significant departure from a 1:1 sex ratio.
1992年1月至1993年12月期间，从肯尼亚奈瓦沙湖的13个站点，使用刺网捕捞了总共2158条鱼，即白纹罗非鱼（Trewavas，1983年）、大口黑鲈（Lacépède，1802年）、吉利罗非鱼（Gervais，1848年）和双纹魮（Boulenger，1902年），并对其进行了蠕虫寄生虫检查。在被寄生的白纹罗非鱼中，1967年的一种棘头虫——肯尼亚多棘吻虫（Schmidt et Canaris）的棘头体感染率在30.4%至86.9%之间；在吉利罗非鱼中为4.1%至77.7%；在大口黑鲈中为20%至50%；在双纹魮中为5.8%至100%。在属于上述四个物种的735个宿主中，总共回收了4198个肯尼亚多棘吻虫的未成熟标本。所有棘头体均发现于肠外部位，要么游离于鱼体腔内，要么包囊于宿主体内脏器内。寄生虫感染率在各月份之间无显著差异（P>0.001）。宿主性别比例在吉利罗非鱼中对雄性显著有利（P<0.001），在白纹罗非鱼中对雄性也极为显著有利（P<0.001）。此外，在这种鱼中，观察到感染率随鱼体大小的增加而升高。在被感染的大口黑鲈中，性别比例没有显著偏离1:1。
