環境因子及次氯酸鈉對短莖枝單杯吸蟲孵化成功之效應

Abstract

從野外所捕獲健康之邁氏條尾魟身上僅有少量單殖吸蟲寄生，而在水族館飼養一段時間後，魟魚體表的單殖吸蟲強度會越來越高，可在眼睛、入水孔和肩部附近區域，觀察到黏液顏色呈現灰濁狀，感染魚隻游泳時會呈現不安的狀態。利用虹吸原理，使用水管從感染嚴重魚隻背面體表輕輕刮下單殖吸蟲，經固定壓片染色等步驟製成永久標本，根據其型態特徵，鑑定此單殖吸蟲為短莖枝單杯吸蟲(Dendromonocotyle pipinna)。組織切片顯示，魟魚遭吸蟲附著之皮膚表皮層出現空泡、孔洞及單細胞腺體減少等組織病變。 收集短莖枝單杯吸蟲成蟲所產之卵進行人工孵化，發現最適條件為溫度26 ℃，鹽度35 ‰，並紀錄蟲卵內胚胎發育情形。在探討溫度對蟲卵孵化率與孵化期之影響時，發現蟲卵在30 ℃時第4天即會孵化，而在16 ℃時孵化時間會延遲到第16天才開始孵化。其餘孵化時間與溫度的關係為，在18℃時蟲卵會在第12天開始孵化，在20 ℃時蟲卵會在第9天開始孵化，在22 ℃時蟲卵會在第7天開始孵化，在24-28 ℃時，蟲卵在第5天開始孵化。 分析鹽度對蟲卵孵化率之影響實驗中，最佳孵化鹽度為30- 40 ‰之間，蟲卵孵化率可高於80 %；鹽度為25和 45 ‰之孵化率較差，分別為77.19 %與58.65 %；而鹽度為10和 15 ‰時蟲卵完全不孵化。 利用乾燥處理實驗中，蟲卵乾燥時間1和2分鐘，其孵化率為72.62和73.74 %，乾燥3分鐘其孵化率為10.56 %，乾燥5分鐘其孵化率為1.54 %，而乾燥10分鐘後蟲卵之孵化率為0，顯示乾燥蟲卵10分鐘即可有效抑制蟲卵的孵化。 次氯酸鈉實驗中，次氯酸鈉濃度為5 ppm時，四個處理時間對蟲卵孵化率之影響無差異，孵化率皆高於80 %。次氯酸鈉濃度為10 ppm時，處理時間分別為6小時和12小時，其孵化率為46.99和29.45 %。次氯酸鈉濃度為15 ppm時，處理時間分別為6小時和12小時，其孵化率為10.65和1.17%。20 ppm濃度處理6小時即可有效抑制蟲卵孵化，濃度為10 ppm處理18小時也同樣可完全抑制蟲卵的孵化。

Monogenean intensities are usually low on wild blotched fantail ray (Taeniura meyeni) and that fish, when infected, appear to be healthy. But the rays kept in the aquarium during a period of time, the rays displayed skittish swimming behaviors and cloudiness on the dorsal surface around the eyes, spiracles and shoulder region. These symptoms and behaviors were attributed to high parasite loads. Monogeneans were removed directly by gently scraping and sucking a water conduit along the dorsal surface of a heavily infected specimen of T. meyeni. Specimens were stained with Semichon’s carmine or left unstained, dehydrated in an ethanol series, cleared in creosote and mounted in Permount. The parasite was identified as Dendromonocotyle pipinna according to published paper. Histological studies of infected Taeniura meyeni showed that there had holes and vacuoles between epidermal cells, and unicellular gland cell became less. Eggs were collected for the following experiments after laying by adult D. pipinna directly. Conditions of incubation at 26 ℃ and 35‰ salinity fitted for hatching and the embryonation of D. pipinna was recorded. The effects of temperature and salinity on the embryonation period and hatching success of eggs of D. pipinna were investigated. Temperature influenced embryonation period strongly; eggs first hatched 4 days after laying at 30 ℃, 16 days after laying at 16 ℃, 12 days after laying at 18 ℃, 9 days after laying at 20 ℃, 7 days after laying at 22 ℃and 5 days after laying at 24-28 ℃. Hatching percentages of D. pipinna eggs were similar for eggs incubated at 30, 35 and 40 ‰ salinity, but increased for eggs incubated at higher or lower salinities. More than 80 % of D. pipinna eggs hatched when they were incubated at salinities ranging from 30 to 40 ‰. Hatching success was lower at 25 and 45 ‰ salinity, and few or no eggs hatched at 10 and 15 ‰. Hatching success of D. pipinna eggs that were rehydrated and incubated after periods of desiccation from 1 min to 10 min, the percentage of eggs hatched were 1 min-72.67 %, 2 min-73.73 %, 3 min-10.56 % and 5 min-1.54 %. Hatching of D. pipinna eggs can be prevented by desiccation for 10 min. Sodium hypochlorite treatment tested for its ability to prevent hatching of D. pipina eggs. The percentage of control was 96.01 %. Hatching of D. pipinna eggs was similar for eggs by treatment with 5 ppm sodium hypochlorite for 6 to 24 hr,more than 80 %. Treatment with 10 ppm sodium hypochlorite for 6 and 12 hr, the percentage of eggs hatched were 46.99 and 29.45 %. Treatment with 15 ppm sodium hypochlorite for 6 and 12 hr, the percentage of eggs hatched were 10.65 and 1.17 %. Hatching of D. pipinna eggs can be prevented by treatment with 20 ppm sodium hypochlorite for 6 hr or by treatment with 10 ppm sodium hypochlorite for 18 hr.