細睪枝單杯吸蟲孵化與幼蟲行為之研究

Abstract

本實驗目的在於研究細睪枝單杯吸蟲蟲卵的孵化條件及環境因子對孵化率之影響，期望能尋找阻斷其生活史的方法，以有效抑制細睪枝單杯吸蟲的感染。本研究從受感染的雪花鴨嘴燕魟(Aetobatus narinari)身上收集細睪枝單杯吸蟲(Dendromonocotyle torosa)，將蟲卵培養於26℃、鹽度35‰的環境下，以12小時光照黑暗交替處理(L：D=12:12)，觀察結果顯示第3天可觀察到幼蟲輪廓及眼點，第5天可觀察到鉤毛蚴孵化。剛孵化的鉤毛蚴活力旺盛，泳動迅速，隨著鉤毛蚴老化，纖毛漸漸脫落，大部分約於孵化後63小時纖毛開始脫落，泳動變為緩慢，經過63 -67小時後纖毛會完全脫落，幼蟲停於底部只能靠蠕動方式移動。幼蟲最短壽命為61小時，最長壽命為74.5小時，平均壽命為64.3小時。 在光照試驗中，結果顯示蟲卵無論培養於正常光照週期( 06:00開燈，18:00關燈)或相反光照週期(06:00關燈，18:00開燈)，蟲卵皆於光照期間孵化，幼蟲大多集中在光照期間的第2小時孵化(光照期間第2h的孵化率：LD為56.2%，DL為48.6%)，得知蟲卵孵化受光照的影響。 溫度和鹽度對蟲卵的胚胎發育及孵化率之影響，發現溫度明顯影響蟲卵胚胎發育時間：於18°C時第15天開始孵化，30°C時第4天開始孵化。於18°C-30°C範圍內孵化率皆高於60%，於18°C時孵化率為68.6%，30°C時孵化率升高為90.3%。當蟲卵培養於鹽度30‰-45‰時，超過50%的蟲卵孵化，鹽度最佳培養條件為35‰，孵化率為71.8%。於20‰、25‰和50‰時孵化率較低，於15‰和10‰時孵化率很低甚至完全沒有孵化。此外，溫度和鹽度的複因子試驗中，將蟲卵培養於18-30°C (以4°C為一間隔)、鹽度10-50 ‰ (以5‰為一間隔)、以12小時光照黑暗交替處理。實驗結果經統計分析顯示兩者有顯著的交感效應，表示溫度和鹽度會互相影響孵化率的結果。

The experiment aims to study the hatching conditions of the eggs and environmental factors on the influence of hatching rate. We hope to able to look for an effective method to inhibit the infection of D. torosa. The eggs were produced by Dendromonocotyle torosa were collected from the skin of Aetobatus narinari, and were incubated in 26℃, 35‰ and alternating 12 h periods of light and dark (L: D=12:12). We can observe the outline and the eyespots of the larvae at 3 days of cultivation, and hatching took play at 5 days of cultivation. The newly hatched oncomiracidia were vigorous and swum quickly. Along with aging of larvae, its ciliary zones began shedding 63h after of hatching and swimming activity become slower. When the larvae ciliary zones were completely shed, the larvae just stayed at the bottom of container and moved just by squirming. These results showed that the longevity of the larvae ranged from 61h to 74.5h with the average of about 64.3h. In the illumination test, the larvae emerge only during daylight incubated in alternating 12 h periods of light and dark (light on 06.00 h, light off 18.00 h). D. torosa larvae emerge with a distinct peak during the first 2 h of light (56.2%). On the other hand, the eggs incubated in a reverse light/dark cycle (light on 18.00 h, light off 06.00 h) hatched only during periods of illumination, again with a peak during the first 2 h of light (48.6%). The results showed that illumination has an effect on the hatching rhythms of eggs. The effects of temperature and salinity on the embryonation period or hatching success of the eggs of D. torosa were also investigated. It was found that temperature strongly influenced embryonation period. At 30 ℃, the eggs began to hatch 4 days after they were laid, and at 18℃, 15 days after they were laid. Hatching success was >60% for the eggs incubated at temperatures ranging from 18℃ to 30℃. hatching success of increases with the increasing temperature with 68.6% hatching rate at 18℃, and 90.3% at 30℃. When incubated at salinities ranging from 30‰ to 45‰ more than 50% of D. torosa eggs hatched. The best condition was found at 35 ‰, with hatching success of 71.8%. Hatching success was lower at 20‰, 25‰ and 50‰ and few or no eggs hatched at 10‰ and 15‰. Besides, in the factorial design of temperature and salinity, eggs were incubated in 18℃-30℃(in 4℃increments), 10‰-50‰ (in 5‰increments) and alternating 12 h periods of light and dark(LD=12:12). The results showed significant statistical difference in the interaction between salinity and temperature, that is, the interaction of temperature and salinity affected hatching rate.