Transmission of white spot syndrome virus (WSSV) from Dendronereis spp. (Peters) (Nereididae) to penaeid shrimp.

Dendronereis spp. (Peters) (Nereididae) is a common polychaete in shrimp ponds built on intertidal land and is natural food for shrimp in traditionally managed ponds in Indonesia. White spot syndrome virus (WSSV), an important viral pathogen of the shrimp, can replicate in this polychaete (Desrina et al. 2013); therefore, it is a potential propagative vector for virus transmission. The major aim of this study was to determine whether WSSV can be transmitted from naturally infected Dendronereis spp. to specific pathogen-free (SPF) Pacific white shrimp Litopenaeus vannamei (Boone) through feeding. WSSV was detected in naturally infected Dendronereis spp. and Penaeus monodon Fabricius from a traditional shrimp pond, and the positive animals were used in the current experiment. WSSV-infected Dendronereis spp. and P. monodon in a pond had a point prevalence of 90% and 80%, respectively, as measured by PCR. WSSV was detected in the head, gills, blood and mid-body of Dendronereis spp. WSSV from naturally infected Dendronereis spp was transmitted to SPF L. vannamei and subsequently from this shrimp to new naïve-SPF L. vannamei to cause transient infection. Our findings support the contention that Dendronereis spp, upon feeding, can be a source of WSSV infection of shrimp in ponds.

Replication of white spot syndrome virus (WSSV) in the polychaete Dendronereis spp.

This study investigated whether WSSV replicates in naturally infected Dendronereis spp., a common polychaete (Nereididae) species in shrimp ponds in Indonesia. To detect WSSV replication, (i) immunohistochemistry (IHC) using a monoclonal antibody against WSSV VP28 protein and (ii) nested RT-PCR using specific primers set for the vp28 gene to detect WSSV-specific mRNA were applied. WSSV immunoreactive-nuclei were detected in the gut epithelium of the polychaete and WSSV mRNA was detected with nested RT-PCR. This, together with the IHC results, confirmed that WSSV could replicate in Dendronereis spp. This is the first report showing that WSSV replicated in a naturally infected non-crustacean host.

Seasonal variation in mineralization rates (C-N-P-Si) of mussel Mytilus edulis biodeposits.

To determine seasonal variability in mineralization dynamics of mussel biodeposits, we applied a multiple-element approach measuring mineralization rates of carbon (C), nitrogen (N), phosphorus (P) and silicate (Si) during three periods (March, August and November). The results of this study showed that mineralization rates vary between seasons and between elements and that mineralization dynamics were influenced by both temperature and biodeposit nutrient composition. Mineralization rates were 3.2 ± 0.4 mmol C, 0.17 ± 0.04 mmol N, 0.06 ± 0.02 mmol P and 3.91 ± 3.75 mmol Si per gram biodeposit (DW) per day, which represented 24 % of the particulate organic C and 17 % of the particulate organic N in mussel biodeposits. Seasonal variability was largest for Si mineralization with 60-80-fold higher rates measured in March compared to August and November. This difference is most likely related to the difference in biodeposit nutrient composition. It was furthermore shown that the labile fraction of biodeposits became mineralized after, respectively, 18, 9 and 13 days during the experimental periods in March, August and November. This indicates that temperature enhances biodeposit decomposition with approximately 2-3 times faster turnover at a 10 °C temperature interval (Q10 ).