BUSCADOR RECOLECTA

Marine planktonic copepods frequently exhibit diel feeding cycles coupled with vertical migrations. However, copepod feeding rhythms can be influenced by factors others than different food availability between layers. In this study, we determined the changes in the diel feeding behaviour of two marine copepod species (Centropages typicus and Paracartia grani) through multigenerational laboratory rearing, ontogeny, and upon the exposure to predator chemical cues. The wild females of both C. typicus and P. grani showed marked feeding rhythms with higher ingestion rates at night. The diel rhythms of C. typicus were maintained in the first laboratory-reared generation (F1), suggesting maternal effects, but disappeared in the following generations. The P. grani females of a long-term culture (> 10 years) also showed no differences in their day–night feeding activity. Ontogenetic variations were detected in the F1 generation of C. typicus: feeding rhythms were absent in naupliar stages, but adults fed more intensely at night. In the case of the cultured P. grani, in general none of the stages showed feeding rhythms. Laboratory-reared C. typicus (8–11 generations) did not recover back the natural cyclic feeding when exposed to jellyfish and fish exudates, indicating that either predation risk does not significantly affect their diel feeding activity or predator-induced responses in marine copepods might not involve chemical signalling. Our study confirms that feeding-related functional traits of marine copepods can experience quick multigenerational changes in the laboratory; consequently, cultured copepods might not be good models for studies involving their diel feeding behaviour, This study was framed within the Project FERMI (CGL2014-59227-R, MINECO/AEI/FEDER, UE). Manuel Olivares is supported financially by a FPU Grant (FPU15/01747) from the Spanish Ministry of Education, Culture and Sport, Number of experiment, date of experiment, temperature, bottle volume, prey species, prey species AphiaID, copepod species, copepod species AphiaID, copepod generation, copepod stage, day/night, presence/absence of predator exudates, predator species, predator species AphiaID, prey concentration, prey size, number of copepods per bottle, copepod size, incubation time, clearance rate, ingestion rate, Peer reviewed

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, The research leading to these results received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730984, ASSEMBLE Plus project. The open access publication fee was covered by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). This study was framed within the project FERMI (CGL2014–59227-R, MINECO/AEI/FEDER, UE), and M.O. was supported financially by an FPU grant (FPU15/01747) from the Spanish Ministry of Education, Culture and Sport, Number of experiment, date of experiment, temperature, bottle volume, prey species, prey species AphiaID, copepod species, copepod species AphiaID, predator species, predator species AphiaID, day/night, predator/no predator, prey concentration, prey size, number of copepods per bottle, copepod size, number of predators per bottle, predator size, incubation time, number of copepod faecal pellets, faecal pellet volume, Peer reviewed

Changes in the elemental composition and stoichiometric ratios of the marine calanoid copepod Paracartia grani along development, reared in the laboratory fed the cryptophyte Rhodomonas salina, This study was supported by [CTM2017–84288-R] funded by Fondo Europeo de Desarrollo Regional (FEDER)/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación, Body length; C, N and P contents per individual; C:N molar ratio; C:P molar ratio; N:P molar ratio; Body volume; C, N and P contents per unit body volume, Peer reviewed

Changes in the elemental composition and stoichiometric ratios of the marine cyclopoid copepod Oithona davisae along development, reared in the laboratory fed the heterotrophic dinoflagellate Oxyrrhis marina, This study was supported by [CTM2017-84288-R] funded by Fondo Europeo de Desarrollo Regional (FEDER)/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación, Body length; C, N and P contents per individual; C:N molar ratio; C:P molar ratio; N:P molar ratio; Body volume; C, N and P contents per unit body volume, Peer reviewed

Phagotrophic mixotrophs (mixoplankton) are now widely recognised as important members of food webs, but their role in the functioning of food webs is not yet fully understood. This is because of the lack of a well-established technique to estimate mixotrophy. An immediate step in this direction would be the development of a method that separates mixotrophic from heterotrophic grazing that can be routinely incorporated into the common techniques used to measure microplankton herbivory (e.g., the dilution technique). This idea was explored by the addition of rotenone, an inhibitor of the respiratory electron chain that has been widely used to selectively eliminate metazoans, both in the field and in the laboratory. Accordingly, rotenone was added to auto-, mixo-, and heterotrophic protist cultures in increasing concentrations (ca. 24 h). The results showed that mixotrophs survived better than heterotrophs at low concentrations of rotenone. Nevertheless, their predation was more affected, rendering rotenone unusable as a heterotrophic grazing deterrent. Additionally, it was found that rotenone had a differential effect depending on the growth phase of an autotrophic culture. Altogether, these results suggest that previous uses of rotenone in the field may have disrupted the planktonic food web, Marie Skłodowska-Curie grant agreement No 766327

Feeding rates, fecal production rates, egg production rates and gross-growth efficiencies of the copepod Paracartia grani offered a variety of phytoplankton, protozooplankton and mixoplankton in monodiet. See Excel file for details, This research was supported by EC MSCA-ITN 2019 funding to the project MixITiN (Grant Number 766327), Peer reviewed