Zoological Studies

Vol. 53, 2014

Pseudodiaptomus marinus Sato, 1913, a new invasive copepod in Lake Faro (Sicily): observations on the swimming behaviour and the sex-dependent responses to food

Luciana Sabia1,2,4*, Marco Uttieri2, François G Schmitt3, Giacomo Zagami1, Enrico Zambianchi2 and Sami Souissi3

1Department of Biological and Environmental Sciences, University of Messina, V.le F. Stagno d’Alcontres,31, S. Agata-Messina 98166, Italy
2Department of Science and Technologies, University of Naples ‘Parthenope’, Centro Direzionale di Napoli, Isola C4, Napoli 80143, Italy
3Laboratoire d’Océanologie et de Géosciences UMR CNRS 8187 LOG, Université Lille 1, Station Marine 28 avenue Foch, Wimereux 62930, France
4Present address: Department of Sciences and Technologies, University of Naples ‘Parthenope’, Centro Direzionale di Napoli – Isola C4, Napoli 80143, Italy

Background: The calanoid copepod Pseudodiaptomus marinus Sato, 1913 is an estuarine-coastal species, living in shallow eutrophic inshore waters. It is native of the Indo-Pacific region, but in the last 50 years, it has successfully colonized new areas worldwide. P. marinus, first recorded in Lake Faro (Messina, Italy) in October 2008, is now a stable component of the zooplankton assemblage of the lake. By means of video recordings, for the first time, the swimming behaviour of males and non-ovigerous and ovigerous females of P. marinus has been studied. The individuals were filmed in the presence and absence of food to evaluate how the presence of prey might affect the swimming behaviour.
The swimming motion showed marked sex-dependent features and responses to the presence of food. Mechanisms through which behaviour might influence the outcome of a new colonization were analysed. The behaviour of P. marinus was then compared with that of the congeneric Pseudodiaptomus annandalei showing the typical behaviour displayed by the representatives of the genus Pseudodiaptomus of living in proximity of the bottom.
Conclusions: Environmental and hydrological conditions in Lake Faro have likely provided the newly introduced P. marinus a suitable environment for settling, although normally the presence of an anoxic deep layer would be detrimental for a demersal species. In this case, the plasticity in the behaviour of P. marinus enhanced its capacity for colonising new environments. Switching from demersal to pelagic habitat or being fully planktonic allowed it to express its large individual variability in motion strategies and thus to successfully colonize the lake.

Key words: Pseudodiaptomus marinus; Swimming behaviour; Invasive species; Sex-dependent behaviour.

*Correspondence: E-mail: luciana.sabia@uniparthenope.it