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Reproductive strategies in decapod shrim

SudnikDr Svetlana Sudnik (Kaliningrad State Technical University, Kaliningrad, Russia) visited the Institute of Marine Research, Flødevigen, near Arendal in southeastern Norway, 28 April – 25 May 2009. Dr. Sudnik has a long experience from studies on reproductive strategies in decapods shrimps.

The objective of her visit in Arendal was to analyze reproductive characteristics of pelagic decapod shrimps, collected on the MAR-ECO 2004 expedition to the mid-Atlantic Ridge on the RV “G.O. Sars”. Pelagic decapods were sampled from 54 stations along the mid-Atlantic Ridge with four types of gears (three pelagic trawls, and one demersal trawl). The MAR-ECO collection contains a total of 44 species of decapods shrimps. In this study Dr Sudnik focused on three species of Caridean decapods: Parapasiphae sulcatifrons, Acanthephyra pelagica and A. purpurea. A total number of 2571 individuals were analyzed during her visit. This included determination of sex, maturity stage of ovaries, embryonic developmental stage, counting absolute individual fecundity and realized fecundity.  Gonads were dissected out and brought back to Kaliningrad University for later histological analysis of oogenesis.

These data will be used to describe and compare the different reproductive strategies in these three species. All three species have parental care (carry eggs on pleopods), but with different strategies regarding egg size and number of eggs.  Also, it will be possible to study latitudinal and vertical variations reproduction.

ovary Acanthephyra      eggs Parapasiphae
Ovary of Acanthephyra pelagica                         Eggs of Parapasiphae sulcatifrons,late maturity stage

Our knowledge of the life history of pelagic shrimps is scare. In general, there are two types of reproductive strategies in pelagic decapods shrimps, depending on the degree of parental care of their offspring. Species with weak parental care usually shed their eggs into the water and have planctotrophic larvae (feeding larvae), while species with strong parental care carry their eggs on the pleopods, and have lecithotrophic larvae (non-feeding larvae). Species belonging to Penaidea usually belong to the first group, while parental care is more common in Caridean shrimps, especially within the order Oplophoridea.

In general, meso- and bathypelagic species produce larger but fewer eggs and larvae relative to the epipelagic species.  The larvae from large eggs are supplied by the internal yolk, and are not dependent on feeding in the euphotic zone. Probably they can adopt the diet of the adults quickly and there is no seasonal breeding period related to the surface production. Usually spawning takes place during much of the year in these deep living species.

There are a wide range of reproductive strategies employed by different species. Life history theory states that there are trade-offs between an individual's fecundity and its survival. Better knowledge on reproductive strategies in different species and how they are linked to the environment can help us predict the response of species to future environmental change.   

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