Biophysical and biochemical changes occur in Nephrops norvegicus during starvation

Abstract

The nutritional status of an animal is maintained through a balance between energy intake and energy expenditure, and in the natural environment can fluctuate due to limited food availability and behavioural changes that remove the animal from its food. The integrated physiological processes that underlie an animal's nutritional status can be measured biophysically or biochemically. The Norway lobster Nephrops norvegicus has been shown to survive long periods of time without food, which is advantageous when food availability is low, such as during the winter months or when access to food is reduced due to risks associated with predation. In this study N. norvegicus was subjected to nutritional stress (starvation) for a period of 20 weeks and various biophysical measures (hepatosomatic index [HSI], length: weight ratio, tissue water content, carbon: nitrogen ratio) and biochemical measures (copper, carbohydrate, lipids, protein, stable isotopes δ15N δ13C) were used to determine how these animals maintain themselves over this period of forced starvation. Results indicate that while there was no variation in the whole weight of each individual, the organ-specific weight of the hepatopancreas (HSI) decreased and there was a corresponding increase in the water content of the hepatopancreas (and tail muscle). In contrast to the findings of previous studies, reserves of lipids decreased within the hepatopancreas. Fuel resources of protein from the tail muscle were not utilised, but reciprocal change in the copper content of the haemolymph to the hepatopancreas is suggestive of a breakdown of haemocyanin. The results provide an initial indication of how N. norvegicus can survive for long periods of time without food, and identify some potential biomarkers for starvation that can be applied to animals caught from the field.