Abstract
ABSTRACT Since temperature is a key condition in the initiation of cercarial emergence, the objective of the work reported here was to evaluate the effect of that variable on the shedding of two morphologic and taxonomic types of cercariae. Bioassays were accordingly performed with snails naturally infected with either monostome or pleurolophocercous cercariae because those two cercarial types were found to be the most prevalent in the environment under study. The snails were placed in 6-ml circular plastic dishes with soft plastic stoppers containing 3 ml of reconstituted water and then sequentially exposed for 24 h to a 14:10-h light:dark cycle at 20, 25, or 30 °C. The data were analyzed at a significance level of p <0.05 by means of the InfoStat program. The optimum temperature for cercarial emergence was typically in the range of 25 °C and decreased significantly at 30 °C. We observed no significant difference in the number of cercariae emerging between the two morphologic types.
Highlights
Since temperature is a key condition in the initiation of cercarial emergence, the objective of the work reported here was to evaluate the effect of that variable on the shedding of two morphologic and taxonomic types of cercariae
In Argentina the evaluation of freshwater trematodes has focused on morphological descriptions and on the study of the life cycles of different species, whereas considerations of environmental variables affecting cercarial emergence have been restricted principally to the influence of light – for example, the number of cercariae emerging per h after exposure to the light (Martorelli, 1984, 1989, 1990; Ostrowski de Nuñez, 1995; Ostrowski de Nuñez et al, 2003; Davies & Ostrowski de Nuñez, 2012; Fernandez et al, 2013a,b)
The optimum temperature for the shedding of the monostome type appeared to be from 20 °C to 25 °C since the emergence diminished markedly at 30 °C
Summary
Since temperature is a key condition in the initiation of cercarial emergence, the objective of the work reported here was to evaluate the effect of that variable on the shedding of two morphologic and taxonomic types of cercariae.
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