Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus.

Manuel Olivares,Enric Saiz,Peter Tiselius,Albert Calbet,Xabier Irigoien

doi:10.1093/plankt/fbaa051

Manuel Olivares, Enric Saiz + Show 3 more

Open Access

https://doi.org/10.1093/plankt/fbaa051

Copy DOI

Abstract

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.

Highlights

Predation threat can trigger a wide variety of responses in animals, such as changes in morphology, physiology and/or behaviour (Lima, 1998; Agrawal, 2001)
The krill Meganyctiphanes norvegica was actively feeding on copepods in our experiments
The presence of predator did not have any significant effect on pellet production rates in any of the experiments at high food (summer: RBD ANOVA, F(1,50) = 3.15, P > 0.05; autumn: RBD ANOVA, F(1,27) = 0.04, P > 0.05; Fig. 2), but had a significant effect in the experiment on 25 October at low food (two-way ANOVA, F(1,13) = 13.63, P < 0.01; Fig. 2). In this last case krill caused a decrease of only 12% in the daily production of faecal pellets by copepods

Summary

Introduction

Predation threat can trigger a wide variety of responses in animals, such as changes in morphology, physiology and/or behaviour (Lima, 1998; Agrawal, 2001). These predator-induced phenotypic changes have evolved to increase the animal’s survival chances, and bring certain fitness costs in terms of energy acquisition and resource allocation (Sih, 1980; Lima and Dill, 1990; Preisser et al, 2005). Non-lethal effects of predators on copepod populations can translate into important cascading effects in marine food webs (van Someren Gréve et al, 2019). Migrant copepods typically stay in food-enriched upper waters at night, and move to deeper, darker layers during the daytime to avoid visual predation

Objectives

Methods

Results

Discussion

Conclusion