Alteration of burrow-related behaviour of the Norway lobster, Nephrops norvegicus during infection by the parasitic dinoflagellate Hematodinium

This study has used time-lapse video recordings to analyze the burrow-relat ed behaviour of N. norvegicus under a 12 h light: dark regime in aquarium c onditions, and compared this with the behaviour of lobsters infected by the parasitic dinoflagellate Hematodinium. Uninfected lobsters performed a hig her number of burrow departures, of longer duration, during the hours of da rkness than during the light. Infected lobsters performed a relatively cons tant number of departures of similar-duration in the light and the dark per iods. However, the mean number of departures per day performed by infected lobsters (70 day(-1)) was more than double that of uninfected lobsters (30. 1 day(-1)), while the mean duration of burrow departures performed by infec ted lobsters (258.5 s (.) departure(-1)) was more than six times greater th an in uninfected lobsters (38.7 s (.) departure(-1)). This led to a more th an ten-times increase (from 1.7 to 19.4%) in the percentage of the day spen t out of the burrow by infected lobsters. This altered burrow-related behav iour could be due to the nutritional demands of the parasites on infected l obsters, causing an increased requirement to forage, or alternatively to a 'functional hypoxia', due to the additional respiratory demands of the para site, causing the host to emerge from the burrow onto the sediment surface to seek oxygen. Implications for the increased time spent out of the burrow are discussed in relation to availability of infected lobsters by trawlers and predators, and to the use of infection prevalence data from trawl-caug ht samples in stock assessment models for N. norvegicus.