Abstract
The infection dynamics and distribution of the ectoparasitic fish monogenean Neobenedenia sp. (Monogenea: Capsalidae) throughout its development was examined on barramundi, Lates calcarifer (Bloch) (Latidae), by labelling transparent, ciliated larvae (oncomiracidia) with a fluorescent dye. Replicate fish were each exposed to approximately 50 fluorescent oncomiracidia and then examined for parasites using an epifluorescence stereomicroscope at 10 time intervals post-exposure (15, 30, 60, 120 min, 24, 48 h, four, eight, 12, and 16 days). Fluorescent labelling revealed that parasites attached underneath and on the surface of the scales of host fish. Parasite infection success was 20% within 15 min, and peaked at 93% two days post-exposure, before gradually declining between four and sixteen days. Differences in parasite distribution on L. calcarifer over time provided strong evidence that Neobenedenia sp. larvae settled opportunistically and then migrated to specific microhabitats. Parasites initially attached (<24 h) in greater mean numbers on the body surface (13 ± 1.5) compared to the fins (4 ± 0.42) and head region (2 ± 0.41). Once larvae recruitment had ceased (48 h), there were significantly higher mean post-larvae counts on the head (5 ± 3.4) and fins (12 ± 3) compared to previous time intervals. Neobenedenia sp. aggregated on the eyes, fins, and dorsal and ventral extremities on the main body. As parasites neared sexual maturity, there was a marked aggregation on the fins (22 ± 2.35) compared to the head (4 ± 0.97) and body (9 ± 1.33), indicating that Neobenedenia sp. may form mating aggregations.
Highlights
The distribution of ectoparasites on their hosts is linked to adaptive strategies and life traits inherent to their evolution (Rohde, 2005)
The carboxyfluorescein diacetate N-succinimidyl ester (CFSE) fluorescent signal emitted by the parasite was maintained throughout development, the signal became weaker over time (Fig. 3)
Neobenedenia sp. oncomiracidia used in this study live for an average of 37 ± 3 h in the absence of a host
Summary
The distribution of ectoparasites on their hosts is linked to adaptive strategies and life traits inherent to their evolution (Rohde, 2005). The invasion route and site-selection of Neobenedenia girellae (Hargis) (see Whittington and Horton (1996) for an account of its likely synonymy with Neobenedenia melleni) has been previously described on Japanese flounder, Paralichthys olivaceus (Temminck and Schlegel) (see Bondad-Reantaso et al, 1995) and quantified on amberjack, Seriola dumerili (Risso) (see Hirayama et al, 2009). In both studies, postlarvae were found attached to the fins, while older parasites were found on the dorsal and ventral body surfaces. These studies used skin scrapings (Bondad-Reantaso et al, 1995) and stereomicroscopy (Hirayama et al, 2009) to detect live parasites
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