Duration and timing of reproduction in decapod crustaceans of the NW Mediterranean continental margin:: is there a general pattern?

To describe how decapod crustaceans are adapted to depth, the duration and timing of the reproductive periods of the 19 most abundant species were compared across the continental margin of the NW Mediterranean Sea. Reproductive activity centered on different seasons, depending on genus, but the deepest-dwelling species of this study, i.e. those living at depths from 600 to >1000 m, showed more seasonal reproductive activity than species dwelling in shallower waters, in which reproductive activity occurred year-round. Thus, in genera where 2 or more species were studied (Pasiphaea, Processa, Plesionika, Munida), the duration of the reproductive periods decreased with increasing depth distribution of congeneric species. This pattern was present in epi-mesopelagic, nektobenthic and benthic species. The only exception was the blind palinuran Polycheles typhlops. Suspended particulate matter concentration in the water column generally decreased from the shelf and upper-slope down to the deep-slope region along the 3 seasonal samplings. Furthermore, vertical fluxes collected near the bottom at similar to1000 m depth showed a clear seasonal trend. We discuss how differential matter sinking to the benthic ecosystems versus species depth distribution may be the proximal cause of decapod crustacean reproductive seasonality, and how phylogenesis and light intensity should also be taken into account when describing how species are adapted to the transitional depths of the continental margin of the NW Mediterranean Sea.