engleski

Bacterial load in different tissues of signal crayfish Pacifastacus leniusculus (Dana, 1852) and its potential role as fitness indicator

Background: Invasive non-indigenous crayfish species (NICS) negatively impact ecosystems and native crayfish populations by, among others, introducing pathogens into the new environment. Literature suggests that hemolymph of apparently healthy crayfish is unsterile and can, in stressful conditions, contain a higher bacterial load which may be correlated with higher bacterial load in hepatopancreas. Understanding how bacterial load affects crayfish immunity and fitness would help us assess whether the healthiest individuals are the first to disperse to new environment. Objectives: To determine whether bacterial load in hemolymph could be used as crayfish fitness proxy and to establish whether there is a link between bacterial load in hemolymph and hepatopancreas of the most successful crayfish invader in Europe – the signal crayfish (Pacifastacus leniusuclus), in the Korana River, Croatia. Methods: We collected over 110 individuals along the Korana River and sampled cuticule swabs, and hepatopancreas, gut and hemolymph tissues and recorded any visible signs of decreased fitness, such as injuries, potential diseases (melanisations) or presence of parasites in examined tissues. We compared bacterial presence, load and diversity in hemolymph and hepatopancreas of 48 individuals by using 16S ribosomal DNA PCR. Results: Our results show that 18.75% of individuals had bacteria present in the hepatopancreas, and 10.42% individuals in the hemolymph. Out of them, only 2 (4.2 %) individuals had bacteria present in both tissues. Individuals with bacteria recorded in the examined tissues had higher occurence of morphological signs of decreased fitness (75%) than individuals with no bacterial load in the tissues (55%).

signal crayfish ; hemolymph ; hepatopancreas ; bacteria

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