Quantitative Evaluation of the Larval Density of Sea Potato Acaudina spp.with Mitochondrial Molecular Marker

The sea potato Acaudina spp.is a species of sea cucumber,belonging to the class Holothuroidea under Phylum Echino-dermata.It becomes blooming recently in the East Sea of China,causing serious ecological problems.However,until now there are no molecular data for its larval identification and population genetic analysis.In this study,we firstly screened a mtDNA fragment and demonstrated that it was the species-specific molecular marker for the identification of Acaudina spp.We then developed a quantitative polymerase chain reaction(PCR)method to evaluate the larval density of Acaudina spp.based on this molecular probe.Utilizing this method,we examined 116 plankton samples collected in four seasons from 13 stations along the coastal region in Fu-jian province,China.The results showed that the high larval density was presented at stations 1,2,and 3,which were near a quay in the coast.The larval density increased from April and reached the highest value in June and July,suggesting temperature might be the main environmental factor on the effects of its population distribution and density.Our work provides an important molecular tool for species identification and risk evaluation of a potentially invasive species.

Environmental Factors and Seasonal Variation in Density of Mussel Larvae(Mytilus edulis) in Danish Waters

Mussel larval densities may fluctuate considerably on both small spatial and short temporal scales. So far, only few and scattered data on the occurrence of mussel larvae have been reported from Danish waters. However, seasonal variation in density of blue mussel (Mytilus edulis) larvae as related to environmental factors (temperature, salinity, phytoplankton biomass) is basic information of relevance for future line-mussel farming in Danish waters. Here we report on the density of mussel larvae in a number of potential farming sites in the inner Danish waters. The mussel larval density measured in Skive Fjord, an eutrophicated inner branch of Limfjorden, during a period of 20 years, from 1989 to 2009, along with corresponding temperatures and chlorophylla, makes up the most important series of data reported here. In most years, a pronounced spring density peak and a subsequently lower autumn peak could be seen in Skive Fjord, but most conspicuous in the period 1993 to 2002 where the mean maximum spring larval density was 319 ± 260 ind·l-1. Further, data on mussel larval densities have been recorded on 4 locations in the Great Belt region: Kerteminde Bay in 2008 to 2011, and in 2008 at 3 other locations: Musholm Bay, Svendborg Sund, and Horsens Fjord. The maximum spring densities in the studied waters were observed in Skive Fjord, typically in May, whereas 10 to 100 times lower peak densities were found at the other locations studied. The reported observations show that mussel larvae are omnipresent in the studied areas and it is suggested that the larval density is sufficient forrecruitment to future line-mussel farms.