Diatoms Versus Copepods: Could Frustule Traits Have a Role in Avoiding Predation?

Abstract

Predation is one of the strongest selection pressures phytoplankton has evolved strategies to cope with. Concurrently, phytoplankton growth must deal with resource acquisition. Experiments on mono- and mixed cultures of morphologically different diatoms exposed to copepods were performed to assess if size and shape were primary drivers in avoiding predation. Additionally, frustule silicification was investigated as a potential factor affecting prey selection by copepods. Thalassiosira pseudonana, Conticribra weissflogii, Cylindrotheca closterium, and Phaeodactylum tricornutum were exposed to the presence of Temora longicornis, a calanoid copepod. The physiological response in terms of growth, elemental composition and morphology was determined. The power of Image Flow Cytometry allowed functional single-cell analyses of mixed cultures in the presence and absence of copepods. Results highlighted that T. pseudonana although the most eaten by copepods in monospecific cultures, was not the preferred prey when the bigger C. weissflogii was added to the culture. When pennates were co-cultured with centric diatoms, their growth was unaffected by predators. Our data suggested that the frustule morphology contributes to long-term prey-predator interaction since the elongated thinner frustule, which evolved more recently, benefited cells in escaping from predators also when facing competition for resources.

Si decline and diatom evolution: Insights from physiological experiments

“…predation pressure, may have influenced both observed paleontological patterns and inferred temporal variation in seawater composition (Falkowski et al, 2004;Zachos et al, 2008;Ratti et al, 2013;Lazarus et al, 2014;Conley et al, 2017;Giordano et al, 2018;Petrucciani et al, 2022). The experiments reported here confirm that whatever other factors inform our understanding of Mesozoic-Cenozoic diatom evolution, declining DSi could have had a direct influence on diatom growth, physiology, and morphogenesis.…”

“…Data suggest that over geologic time, DSi availability has affected the overall C allocation pattern of diatoms (in particular pennates) and, therefore, predation pressure via its influence on palatability for predators. Thus, DSi decline has favored the evolution of energysaving, less palatable cells, which are more competitive in intraspecific and interspecific interactions (Petrucciani et al, 2022).…”

Integrative effects of morphology, silicification, and light on diatom vertical movements

“…Details and settings for the IFC data acquisition were as follows: 10 µm core size diameter, 132 mm/s speed, and 20× magnification; bright field data were collected in channel 1 (LED intensity 35.46 mW), and chloroplast autofluorescence data were collected in channel 5 (642 nm, laser 2 mW). Post-acquisition data analysis was performed using the IDEAS software package following the procedure illustrated in Petrucciani et al. (2022a) .…”

“…Moreover, frustule traits indirectly control sinking capacity by changing cell density. In particular, Si deposition shows a phenotypical response to different external environmental factors (i.e., predators, nutrient availability, pH, temperature, salinity, and light intensity) affecting cell density ( Durbin, 1977 ; Brzezinski et al., 1990 ; Flynn and Martin-Jezequel, 2000 ; Pondaven et al., 2007 ; Vrieling et al., 2007 ; Hervé et al., 2012 ; Shrestha et al., 2012 ; Su et al., 2018 ; Xu et al., 2021 ; Petrucciani et al., 2022a ). Among them, light is a crucial driver in the distribution of phytoplankton through the water column, not only affecting their photosynthetic performance, but also influencing cell density.…”

Fermentation of Microalgal Biomass for Innovative Food Production

“…Akin to nutrient starvation or limitation, many other abiotic factors contribute to the biochemistry of microalgae ( Figure 2 ). Additionally, biotic factors such as competition for resources, predation, and symbiosis can drastically affect the behavior and composition of microalgae [ 18 , 20 , 21 ]. The presence of predators affects algal palatability, modulating their organic composition, and activating their chemical defenses [ 20 ].…”