Feeding selectivity and egg production of Calanus helgolandicus in the English Channel

Abstract

Copepods are able to discriminate between different foods on the basis of particle size and nutritional quality. However, the extent of selective feeding behavior and the mechanisms controlling it in the field are still poorly understood. In this study, we investigated selective feeding behavior and egg production for Calanus helgolandicus feeding on natural phytoplankton (using high-performance liquid chromatography techniques), and egg production, at a coastal station off Plymouth with the annual phytoplankton cycle from July 1996 to June 1997. The phytoplankton succession included biomass peaks of dinoflagellates, prymnesiophytes, and diatoms. C. helgolandicus showed little selective feeding behavior throughout the study with a slight preference for diatoms. The influence of the diet composition on egg production was analyzed using forward stepwise regression methods. Prymnesiophytes and diatoms were shown to have positive effects whereas the effect of dinoflagellates was negative. The effect of the different phytoplankton peaks is analyzed and discussed in relation to the phytoplankton taxonomic composition and dietary diversity.Since the initial controversies (see Harvey 1937) the ability of calanoid copepods to discriminate between different particles, either as a function of size (Frost 1972) or of food quality (Huntley et al. 1983;Cowles et al. 1988) has been clearly demonstrated in laboratory experiments using phytoplankton cultures. Video techniques have also helped us to understand the mechanisms used by copepods to detect, capture, and manipulate different particles as a function of their characteristics, their concentration, or the physical environment (Paffenhöfer 1988;Price 1988;Kiørboe and Saiz 1995).However, field studies are less conclusive (Poulet 1978;Huntley 1981) and the factors, other than the size (Cowles 1979), governing selective feeding from natural particulate assemblages are still doubtful. Optimal foraging theory has been advanced as an explanation of selectivity in the field (DeMott and Moxter 1991;DeMott 1993DeMott , 1995a, hypothesizing that the intensity of selection should depend on the concentration of high-quality food. This has been demonstrated in the laboratory with pairs of particles (DeMott 1993) and in the field with the same food (DeMott 1995a,b). However, other studies provide evidence for nonselective feeding by copepods on natural particle mixtures (Huntley 1981;Turner and Tester 1989).On the other hand, the fact that different phytoplankton Acknowledgments This research was supported by funding from the European Commission through the TASC project, Contract MAS3-CT95-0039. B. Meyer-Harms was supported by a EU grant (TMR, MAS3-CT96-5032). Thanks are due to the captains and crew of the RV Squilla and RV Sepia for collecting the samples. We also would like to thank W. DeMott and an anonymous reviewer for their helpful comments and suggestions.

FEEDING AND REPRODUCTIVE ACTIVITY OF THE COPEPODS Drepanopus forcipatus AND Calanus australis DURING LATE SUMMER ON THE SOUTHERN PATAGONIAN SHELF (ARGENTINA, 47°-55°S)

“…Some experimental studies have shown that cell size seems to be the main selection factor for C. finmarchicus and C. helgolandicus when feeding on algal cells with no clear distinction in external morphology (MEYER et al, 2002). However, a slight preference particularly for diatoms has been observed in the field for both species, although there has been little evidence developed for selective feeding on different phytoplankton (MEYER-HARMS et al, 1999;IRIGOIEN et al, 2000). In our study, C. australis exhibited a more carnivorous diet than D. forcipatus.…”

Effect of food concentration and type of diet on Acartia survival and naupliar development

“…A recent study assessing the impacts of P. minimum on A. tonsa stated the insufficiency of this species as a food source, but did not report toxic effects (Dam and Colin 2005). An adverse effect of dinoflagellates on copepod egg production has been reported for Calanus helgolandicus in the field (Irigoien et al 2000).…”

“…Studies from the Mediterranean Sea illustrate deleterious effects of diatoms on copepod reproduction (Miralto et al 1999) and depression of reproductive success at high Thalassiosira abundance has been reported for Calanus pacificus from Dabob Bay, Washington (Pierson et al 2005). Yet, other work provides evidence for the importance of diatoms as copepod food (Irigoien et al 2002), and grazing selectivity in favour of diatoms has been demonstrated in copepods under natural conditions (Meyer-Harms et al 1999;Irigoien et al 2000). The diatom Thalassiosira weissflogii has been proved to constitute a high-quality food source for copepod development (Klein Breteler et al 2005), including Acartia tonsa (Støttrup and Jensen 1990;Jónasdottir and Kiørboe 1996).…”

Testing of the CHEMTAX program in contrasting Neotropical lakes, lagoons, and swamps

“…The application of the CHEMTAX program to pigment data from phytoplankton samples has been shown to be a useful tool in marine environments for several purposes, including medium-large scale analysis of phytoplankton class distribution in the open ocean (Schlüter et al 2000;Wright and Van der Enden 2000;Vidussi et al 2000;Higgins and Mackey 2000;Gibb et al 2001;Latasa et al 2005) and zooplankton feeding studies (Irigoien et al 2000;Guisande et al 2002). However, the application of CHEMTAX in freshwater environments has received little attention (Buchaca et al 2004;Fietz and Nicklisch 2004;Descy et al 2005;Schlüter et al 2006).…”