The spatial distribution, seasonal abundance, life history pattern, and production of the mysid Mesopodopsis slabberi are described from a warm-temperate estuary on the western coast of Portugal. Mysids were sampled from June 1996 to July 1997, using zooplankton and suprabenthic nets. The higher densities and biomass of M. slabberi were found in upstream areas from the south arm of the estuary. These areas consist of shallow waters with low circulation rates and high residence times, richer in phytoplankton than the rest of the estuary. Mesoopodopsis slabberi was abundant in October, November, and December and again in May, June, and July. No mysids were found in January and February, when salinity decreased to values below 5� and water temperature was below 10°C, and also in August, when oxygen levels declined and the water temperature reached values above 24°C. Morphometric relationships in M. slabberi were determined from freshly caught specimens. Significant positive correlations between total length (TL) and cephalic length (CL) (TL = 2.5 CL + 0.012) and between dry weight (DW) and total length (LnDW = 3.0298 LnTL -6.0229) were found. All size classes, from 0.95-11.36 mm, were equally represented throughout the year. Moreover, juveniles, immature females, mature ovigerous females carrying eggs or embryos, and mature resting females were found throughout the sampling period. As a whole, this pattern suggests that reproduction is continuous rather than seasonal. This, together with migrations, made identification and tracking of population groups impossible from the analysis of sizefrequency diagrams. The secondary annual production of M. slabberi was therefore estimated by the Hynes average cohort method. The annual production was 16.02 mg· m�3year 1, and the P/B ratio was 2.57.

Anti-predator mechanisms are essential for species survival and the description of defensive behaviour may improve our understanding about the ecology, biology and evolution of species. Herein, we describe new anti-predator behaviour for the False Coral Snake Oxyrhopus rhombifer in south-eastern Brazil, through direct observation of a juvenile specimen under laboratory settings. We recorded 10 types of defensive behaviour, seven of which are new records for this species and one of them (body vibration) is the first report for Brazilian snakes. Such behaviour may be explained by ontogeny or physical constraints. We highlight that O. rhombifer may be capable of recognising different threat levels imposed by predators and, accordingly, adjusting its defensive behaviour.

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