| Abstrakt: |
AbstractThis study established ex vivo conditions suitable for studying early trophont development in excised tissues of channel catfish Ictalurus punctatuswithin the first 48 h. Infective theronts of Ichthyophthirius multifiliiswere added to freshly excised channel catfish fin, gill, and skin and established fin cells (BF-2) of bluegill Lepomis macrochirus.The early development of trophonts, including growth, rotation speed, attachment, and survival (%), was studied in different tissues and at different times. In all, 86–92% of the theronts attached to fish tissues in an enter, leave, and reenter pattern within the first 10 min. Theront attachment was more than 88% in fins, gills, and skin 1 h post exposure (PE). Attachment and shape transformation of theronts were not observed on BF-2 cells. Trophonts grew to a size of 30.0 ± 3.1 μm in diameter 4 h PE in the gills, an increase of 9.6%/h. The size increase of trophonts was 1.2%/h in the gill between 4 and 8 h. Trophonts grew slowly and increased in diameter 0.5%/h from 8 to 48 h after addition to the gills. The mean volumes of trophonts at 1, 24, and 48 h PE in gills were 1,072.6 ± 3,131.6, 20,373.6 ± 8,357.4, and 28,102.3 ± 4,740.0 μm3, respectively. No difference in trophont rotation speed was found in different tissues between 1 and 24 h PE. At 48 h, the rotation speed of trophonts was significantly slower (P< 0.01); the average speed was 819.3 ± 195.7 μm/min. Most trophonts were alive 8 h PE; survival was higher than 97%. The mean survival was 67.8% at 24 h and 8.4% at 48 h PE in all tissues. The viability of excised tissues without theronts was considerably higher than that in tissues with theronts after 48–72 h in culture. |
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