Identification of potential recruitment bottlenecks in larval stages of the giant fan mussel Pinna nobilis using specific quantitative PCR

Pinna nobilis is an endangered species of fan mussel found along coastal Mediterranean waters requiring special attention for conservation. Populations are restricted in number, due to anthropogenic disturbances, disease, and in some areas, low rates of recruitment. To date, the difficulties associated with the identification of planktonic stages have prompted the use of benthic collectors as a proxy for quantifying larval supply, despite important information being lost regarding planktonic processes. We present evidence of spawning utilizing a qPCR assay developed for detecting genomic DNA of P. nobilis to enable specific identification of planktonic stages to augment knowledge of P. nobilis life history. In the Ebro Delta, Spain, it has been used to study what might be limiting their reproduction locally. We demonstrate the ability to differentiate DNA of P. nobilis from other bivalve mollusks and distinguish between fertilized and unfertilized eggs of P. nobilis, which may be a crucial point for understanding the low level of recruitment seen in this natural population. Wealso show evidence of larval presence during the expected spawning period, although abundance in positive samples were so low that they pose new questions about factors controlling the availability of planktonic stages of P. nobilis.