Trophic habits of the endemic and threatened Lampetra zanandreai (Vladykov, 1955): first insights from the LIFE Minnow project

Small-sized freshwater species with little or no direct economic value are often threatened yet poorly understood from an ecological perspective. Lampetra zanandreai (Vladykov, 1955) is a non-parasitic, strictly freshwater lamprey endemic to the ancient Po basin and threatened with extinction. Apart from some general information on its biology and life cycle, much of its ecology, including its feeding habits, remains unknown. This study aimed to investigate the feeding habits of the Po brook lamprey using a molecular approach. Twenty-seven specimens and sediment samples were collected from two different streams in the upper Po basin (NW Italy) and analysed. The content of the digestive tracts were collected in the laboratory and preserved in absolute ethanol. Species composition of these contents was investigated through DNA metabarcoding using the primer set 1391f/EukBr targeting the V9 hypervariable region of eukaryotic 18S rDNA. Sediment samples were also analysed using the same metabarcoding protocol to identify potential trophic sources. Taxa other than lamprey were found in 15 out of 27 individuals. The most frequently found taxon in the digestive tract contents was Ciliophora (found in 9 individuals), followed by Euglenozoa (5 individuals), Chlorophyta and Nematoda (2 individuals each), Cryptomycota and Mollusca (1 individual each). All the taxa were also found in the sediment with the exception of Mollusca. This is the first molecular assessment of the diet of L. zanandreai and provides new insights into the trophic ecology of this endemic, threatened and neglected species. A more detailed analysis using additional primers is underway. Understanding the ecological requirements and needs of different species is essential for effective conservation strategies, and diet is a key ecological parameter.