Gael Dur

Effects of animal density, volume, and the use of 2D/3D recording on behavioral studies of copepods

Studies on the behavior of copepods require both an appropriate experimental design and the means to perform objectively verifiable numerical analysis. Despite the growing number of publications on copepod behavior, it has been difficult to compare these studies. In this study, we studied two species of copepods, Eurytemora affinis and Pseudodiaptomus annandalei, and employed recently developed scaling and non-scaling methodology to investigate the effects of density and volume on the swimming behavior of individual organisms in still water. We also compared the results of two- and three-dimensional projections of the swimming tracks. A combination of scale-dependent and scale-independent analysis was found to characterize a number of behavioral observations very effectively. We discovered that (i) density has no effect except to increase the time spent in the swimming state of “breaking”, (ii) smaller volumes resulted in more complex trajectories, and larger volumes, like density, increased the time spent in the swimming state “breaking”, and (iii) three-dimensional projections gave a more accurate estimation of speed and the time spent cruising. When only a vertical 2D projection was used, “cruising” could be confused with “sinking”. These results indicate that both experimental conditions and the selection of 2D or 3D projection have important implications regarding the study of copepod behavior. The development of standardized procedures with which to compare the observations made in different studies is an issue of particular urgency.

Analysis of high frequency temperature time series in the Seine estuary from the Marel autonomous monitoring buoy

AbstractIn the marine sciences, continuous monitoring systems have been regarded as very useful tools to provide continuous high frequency measurements of many parameters. We analyse here a high frequency time series of temperature measurements recorded every 10 min between 1997 and 2004 in the macro tidal Seine estuary (France) by a Marel buoy, an automatic monitoring network for littoral environment. We have adapted multi-scale data analysis methods to deal with the many missing values present in the time series. A power spectral density analysis is performed over time scales spanning 5 decades, from 20 min to more than 7 years. A scale invariant behaviour of the form

Dormant eggs of a calanoid copepod from tropical brackish aquaculture ponds

{E\left(f \right)\approx f^{-\beta}}

An overview of the influence of hydrodynamics on the spatial and temporal patterns of calanoid copepod communities around Taiwan

with β = 2.2 is revealed for scales below 5 h. Over this scaling range, we have performed structure functions analysis, and shown that the Seine river temperature data exhibit turbulent-like intermittent properties, with multifractal statistics. The multifractal exponents obtained possess some similarities with passive scalar turbulence results.

Differences in behavioral responses of Eurytemora affinis (Copepoda, Calanoida) reproductive stages to salinity variations

Copepods are a class of small crustaceans that are widespread and naturally abundant in all aquatic ecosystems as a key link between primary producers and higher predators. They have 13 distinct life stages (i.e., egg, six naupliar stages, five copepodite stages, adult), making development easy to trace, and many species are sexually dimorphic. These life-history traits and its importance in the aquatic food web make copepods a suitable candidate as reference organisms for ecotoxicology. Copepods are used particularly for full life-cycle toxicity evaluation. This potential is recognized by researchers, government agencies, and international bodies. This chapter provides a summary of the current state of science in copepod toxicity testing, published protocols of copepod tests, and identifies key research area for further development of copepod testing.

The different aspects in motion of the three reproductive stages of Pseudodiaptomus annandalei (Copepoda, Calanoida)

Many Asian aquaculture farms cultivate copepods as live-feed for aquaculture species, as copepod nutritional and behavioural qualities are usually higher than those of traditional live-feeds (i.e., Artemia and rotifers). The most convenient method to use zooplankton in aquaculture as live feed involves dormant eggs. In this study, to establish whether the copepod species of the tropical Taiwanese ponds exhibit quiescence of their eggs, several sediment samples were collected from the ponds and incubated at low temperature. After 3 months of cold incubation, several nauplii of Acartia bilobata Abraham, 1970 hatched from the sediment at high temperature over several days. Further investigations need to be conducted to understand the origin of the dormancy (i.e., induced originally in the field or in the laboratory). Nevertheless, it is the first reported case of dormant eggs in calanoid copepods in tropical regions. The present study will certainly find some interest in tropical aquaculture as our results showed that long-term storage of tropical calanoid copepod eggs is possible, even if collected directly from the sediment without sorting the eggs.

Mating and mate choice in Pseudodiaptomus annandalei (Copepoda: Calanoida)

It was hypothesized that the Malabar grouper Ephinephelus malabaricus larvae have developed search patterns adapted to the distribution of their prey to maximise their net energy intake per unit time. Analysis of the swimming behaviour of E. malabaricus larvae in both the presence and absence of Artemia sp. nauplii is presented to test this hypothesis. A method derived from turbulence studies (the moment function of the displacements) was used to characterize the behaviour. The results revealed that larval swimming pattern was multifractal (intermittent and long-range-correlated) and isotropic (i.e. uniform in all directions) in the presence of prey, but multifractal and anisotropic (i.e. more frequent long displacement on the vertical axis) in the absence of prey. It is suggested that the search behaviour observed in the absence of prey is an adaptive response to prey distribution pattern, which is often characterised by multifractality and anisotropy (i.e. larger patches on the horizontal axes). In the presence of prey, E. malabaricus shifted to intensive search behaviour. Other possible contributors to the observed patterns are discussed. It is concluded that multifractality and anisotropy of swimming patterns observed in the experiment are mainly explained in an optimal foraging theory framework.