Exoskeletal deformities in Palaemonidae: are they a threat to survival?

Shrimps of the Palaemon genus have been affected for over 15 years by a problem of exoskeletal deformities, particularly in the Gironde estuary (France). Given the large numbers of individuals affected, this study focus on a better description of the phenomenon to estimate its impact on shrimps. This study, on Palaemon longirostris and Palaemon macrodactylus, is based on samples collected from 1992 to 2007 in the Gironde estuary with particular focus on the year 2007, and on a 4-month rearing of adult shrimps in experimental system. The different approaches reveal the relative persistence of the phenomenon since 1992 (with on average more than 58% of ovigerous females affected) and its persistence during shrimp life cycle, even after several moults. Important consequences associated with deformities at the individual level were demonstrated: a higher mortality, a lighter egg mass and a lower weight for a given size. The presence of exoskeletal deformities is now a major phenomenon, with profound effects on individual shrimps, and which may in turn have an important impact on the survival of the P. longirostris population in particular.