1. To monitor the diversity and distribution patterns of large branchiopods and the effects of local and regional processes, 30 temporary wetlands in a nature reserve in the Camargue (southern France) were sampled and characterised during three consecutive inundations . Additional species were added to the list for each wetland by hatching animals from the resting egg bank, after determining the optimal hatching conditions. 2. A total of five species were found, representing 28% of the species known in France and 56% of the known Camargue species. Tanymastix stagnalis, Branchipus schaefferi, Chirocephalus diaphanus (Anostraca), Triops cancriformis (Notostraca) and Imnadia yeyetta (Spinicaudata) were distributed over a total of 19 wetlands. 3. More than one species was present in 79% of the wetlands containing large branchiopods. Individual wetlands harboured on average 2.8 species, with a maximum of five coexisting species. Large branchiopod assemblages were temporally variable, differing among the three inundations with different climatological conditions. 4. The most important habitat factor influencing the distribution of large branchiopods was salinity, adversely affecting the density and survival of hatchlings. The persistence of large branchiopods in these temporary waters may be threatened by increasing salinisation driven by intensive water management and climate change.

We assessed the predatory impact of Mesostoma sp. (Rhabditophora) on hatching and survival of Branchipodopsis wolfi (Anostraca) under laboratory conditions. The hatching percentages of resting eggs of B. wolfi were negatively influenced to a significant degree by the presence of Mesostoma sp. or the medium in which the worms were kept before, but only when prey and predator originated from the same pool. This relationship was also not observed when eggs of the American anostracan Thamnocephalus platyurus were exposed to the Turbellaria from Botswana. There was, however, no indication of predation of B. wolfi eggs by Mesostoma sp., either by eating them totally or by sucking them out. When the same number of anostracans of different ages was offered simultaneously to Mesostoma sp., the 1-and 3-day-old specimens were eaten significantly faster than the 5-day-old juveniles and the adult B. wolfi. We conclude that Mesostoma sp. has a potentially strong influence on the population dynamics and life history characteristics of B. wolfi in temporary aquatic systems. Additionally, the feeding behaviour of Mesostoma sp. was described and the ultra structure of its rostral area was investigated.

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