Effect of temperature on development rate and egg production in Caligus elongatus and other sea louse species

The sea louse Caligus elongatus (Siphonostomatoida, Caligidae) is a generalist ectoparasite commonly found on farmed salmonids in the Atlantic Ocean. Together with the salmon louse Lepeophtheirus salmonis and the Chilean sea louse Caligus rogercresseyi , they represent a major challenge to sustainable farming of Atlantic salmon Salmo salar . Here, the development rate, egg production, and copepodid survival time of C . elongatus are described at 6, 9, 12, and 15°C, and compared to available data for L . salmonis and C . rogercresseyi in a seminal attempt to qualitatively compare how these life-history traits and epidemiological factors vary among the 3 caligid sea louse species. A development model for C . elongatus was established by applying a constant scaling factor to the published model for L . salmonis and compared to the data obtained. The model assumes that caligid sea lice with similar zones of temperature tolerance share a common basic physiology, and that their rate of development is equally affected by changing temperatures within the interval where their temperature tolerances overlap. Present data, and data from the literature, suggest that C . elongatus develops to adult at approximately 63% of the time required by L . salmonis females and, compared to L . salmonis , they produce about 1/3 of the eggs per day over the temperature interval studied. This study represents a new experimental approach for establishing caligid development models and demonstrates how important life-history parameters can be scaled by constants and used as temperature-independent measures to characterize and compare the biology and epidemiology of sea lice species.