How far may life venture? Observations on the harpacticoid copepod Phyllognathopus viguieri under extreme stress conditions

The authors report the first finding of living specimens of the harpacticoid copepod Phyllognathopus viguieri (Maupas, 1892) in the gut content of the teleost fish Merluccius merluccius (Linnaeus, 1758), and their extraordinary viability after the M. merluccius specimens had been stored at − 20 °C for more than 1 month and their stomachs been preserved in 70% ethanol for a further month. After their survival for such a long time in such harsh conditions, P. viguieri, after a few minutes of total immobilization, began to swim actively and fast, and after being reared in freshwater or seawater in Petri dishes under starvation, these animals reproduced, and the presence of nauplii, copepodids and adults which completed the whole life cycle in 3/5 days was observed in freshwater and seawater, respectively. The occurrence of P. viguieri in the stomach of a true marine demersal fish species enlarges the known habitat types the species may stably colonize. The potential for dormancy in fertilized adult females to escape adverse environmental conditions is hypothesized.