To starve or not to starve: Deprivation of essential fatty acids and change in escape behavior during starvation by nauplii of the tropical calanoid copepod Pseudodiaptomus annandalei

Abstract

In nature, marine organisms often face temporal and spatial patchy food sources and are therefore adapted physiologically and behaviourally to these situations. Tropical open water copepods frequently experience food deprivation, which may constrain their growth. Four distinct size fractions of nauplii of the tropical calanoid copepod Pseudodiaptomus annandalei were tested for their response to food deprivation. A 48-h food deprivation period caused a high mortality of 26–71%, a significant effect on molting and on length increments that were reduced by 27–38% compared to non-starved nauplii. Furthermore, the essential fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were reduced by >65% within the 48 h starvation period, and were most profound for the earliest development stages of nauplii. To examine the effect of starvation on the individual copepod nauplius ability to escape a potential predator, a flow generated hydrodynamic signal was used to stimulate an escape response. Starvation slowed down the average escape velocity of the nauplius by up to 49%, and significantly reduced the initial nauplii development stages ability to escape from the flow-generated suction. Additionally, the initial nauplii stages net to gross displacement ratio (NGDR) were significantly reduced by starvation. Hence, the nauplii response to overcome food deprivation is exhibited by both ‘sit and wait’ while recruiting storage compounds and by minimizing their motile behavior. Since starvation affects the nauplii stages escape performance, it is likely to have a profound effect on their ability to avoid a potential predator.