台湾棘带吸虫囊蚴在鳙鳃丝、鳃耙上的分布

通过对鳙为期16个月的定期取样研究发现，1993年8月到1994年3月，台湾棘带吸虫的囊蚴主要分布在鳃耙上，1994年4月至11月，囊蚴则主要分布在鳃丝上；当鳙体长范围为30-90mm时，囊蚴主要分布在鳃耙上，当体长大于90mm时，囊蚴主要分布在鳃丝上，随着鳙的生长，鳃丝囊蚴所占的比例逐渐增大，从0增加到100%，而鳃耙囊蚴所占的比例逐渐减小，从100%下降到0；不同月份、不同体长组鳙其不同组鳃丝囊蚴分布规律相同，第2组鳃丝囊蚴分布较多，第3、第1、第4组鳃丝囊蚴分布依次减少：其不同组鳃耙囊蚴分布规律也相同，总是第1组鳃耙囊蚴分布较多，其余依次为第2、第3、第4组鳃耙；囊蚴在鳙鳃丝和鳃耙上的分布都呈聚集分布，且聚集的强度随囊蚴内种群密度的增高而增高。

DISTRIBUTION OF METACERCARIAL CYSTS OF THE DIGENEAN CENTROCESTUS FORMOSANUS (NISHIGORI,1924)ON THE GILL FILAMENTS AND GILL RAKERS OF BIG-HEAD CARP,ARISTCHTHYS NOBILIS

The present paper deals with distribution of the metacercarial cysts infrapopulation of Centrocestus formosanus(Digenean: Heterophyidae)in the gill filaments and gill rakers of Aristchthys nobilis from August 1993 to November 1994. The results indicated that most of the matercercarial cysts distributed in the gill filaments from August 1993 to March 1994, and distributed in the gill rakers from April to November 1994. When the body length of the host varied form 30 to 90 mm most of the matercarial cysts distributed in the gill rakers, but distributed in the gill filaments when the body length of the host exceeded 90 mm. The metacercarial cysts percentage of the gill filaments and gill rakers changed with the growth of the host, the percentage of the gill filaments increased with the growth and varied from 0 to 100% ,but the gill rakers declined with the growth and varied from 100% to 0. Distribution of the metacercarial cysts in the different groups of gill filaments showed the same regular changes in different months and groups of body length, so did the different groups of the gill rakers. The second groups of gill filament had more matacercarial cysts, then the third, the first and the fourth, but the first groups of gill rakers had more metacercarial cysts and then the second , the third and the fourth. The distribution of the metacercarial cysts in the gill filaments and gill rakers showed aggregated distribution and the degree of aggregation increased with the mean density of the metacercarial cysts infrapopulation.