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Abstract:
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Daphnia exilis is a halophylic species that was recently found in Chile, distant from
its natural range. In this study, we analyze the osmoregulatory and life-history
responses to salinity exhibited by Daphnia exilis, as a first step towards understanding
the ecology of this exotic species whose invasion potential has been related to
its ability to tolerate saline environments. A set of laboratory experiments were
carried out, in which we exposed organisms to a salinity gradient, and measured
internal and environmental osmolality, assessed the effect of acclimation time and
measured life-history traits that were used to perform a demographic retrospective
analysis. Our results showed that (i) D. exilis exhibited a hyper-osmoconformer
response, (ii) acclimation time did not exert effects on the osmoregulatory
response, (iii) salinity up to 6 g L21 did not alter the population growth rate, (iv) at
8 g L21 population growth rate declined, mainly due to a delayed age at maturity
and reduced fertility. Based on this information, we suggest that the responses to
salinity exhibited by the exotic D. exilis confer an advantage over its natural
enemies and may facilitate colonization through exploiting disturbed places as
chemical refuges. |