The Devil Lies in Details: New Insights Into the Behavioural Ecology of Intertidal Foraminifera

Abstract

The motion behaviour of three species of intertidal foraminifera, Ammonia tepida, Cribroelphidium excavatum and Haynesina germanica, was investigated continuously in the laboratory. We first infer the presence of geotactic and phototactic responses. Significant geotactic responses were observed for all three species; A. tepida was found to be negatively geotactic while C. excavatum and H. germanica showed positive geotaxis. In contrast, no response to light was ever observed. The detailed nature of motility, investigated in terms of both geometric and stochastic complexity of their motion behaviour, was consistently characterised by a strong inter-specific, inter-individual and intra-individual variability. Specifically, A. tepida and H. germanica were characterised by an intensive search behaviour (they explore their environment slowly with straighter trajectories), while C. excavatum adopted an extensive search strategy (it moves more rapidly with more convoluted trajectories). These observations are discussed in the specific context of the ecology of these species. We see their responses as adaptive advantages in spatially and temporally complex environments prone to a range of both predictable and unpredictable rapid stressors. From a methodological point of view, we showed that previous methods used to infer foraminiferal motion behaviour are likely to have systematically underestimated their speed and distance travelled by a factor ranging from 2 to 80.

Motion behavior and metabolic response to microplastic leachates in the benthic foraminifera Haynesina germanica

“…Specifically, locomotion speed was nearly 2-fold lower than those reported previously on the same species (here ~2 mm h -1 vs. ~4 mm h -1 in Seuront and Bouchet, 2015) probably due to the lower experimental temperature (12°C here vs. 22°C in Seuront and Bouchet, 2015) since decreasing temperature is known to reduce foraminiferal activity (Bradshaw, 1961). Our results nevertheless clearly indicated that PP leachates did not affect foraminiferal behavior (Figure 2A, B).…”

Functional xanthophyll cycle and pigment content of a kleptoplastic benthic foraminifer: Haynesina germanica

“…Furthermore, as H . germanica behaviour does not seem to be light driven [ 39 ] their photo-regulation capacity is likely to depend mainly on their kleptoplast physiological capabilities as for other kleptoplastic organisms [ 23 , 41 , 46 ]. We addressed this gap in current knowledge by investigating how H .…”

“…Thus, if H . germanica is not sensitive to light [ 39 ] then we can hypothesise that the xanthophyll cycle might be an important short-term photoprotective mechanism for the diatom kleptoplasts incorporated in the foraminifera cytosol. This was supported by our experiments, i.e.…”

“…However, H . germanica behaviour does not seem to be light driven [ 39 ] and therefore, H . germanica kleptoplast photo-regulation might be more dependent on other physiological photo-regulation mechanisms.…”

Variability of foraminifera associations in seagrass ecosystems in shallow water during winter (Kerkennah – Southern Tunisian coasts)

“…Murray (2006) considered Ammonia species as strictly infaunal which is not the case in this study; as Ammonia beccarii seems to be an epifaunal species for the three biotopes (Seuront & Bouchet, 2015).…”