Biology subjects

Otjacques, E.

Publications and source records attributed to Otjacques, E..

5 recordsLinked to original sources

bioRxiv2025

Climate-driven warming disrupts the symbiosis of bobtail squid Euprymna scolopes and the luminous bacterium Vibrio fischeri

Under the current climate crisis, marine heatwaves (MHW) are expected to intensify and become more frequent in the future, leading to adverse effects on marine life. Here, we aimed to investigate the impact of environmental warming on the symbiotic relationship between the Hawaiian bobtail squid (Euprymna scolopes) and the bioluminescent bacterium Vibrio fischeri. We exposed eggs of E. scolopes to three different temperatures during the embryogenesis, namely: i) 25 {degrees}C (yearly average), ii) 27 {degrees}C (average summer), or iii) 30 {degrees}C (category IV MHW), followed by a colonisation assay under the same conditions. Decreased hatching success and reduced developmental time were observed across warmer conditions compared to 25 {degrees}C. Moreover, exposure to the category IV MHW led to a significant decrease in survival after 48 hours. With increasing temperature, bobtail squids required more bacteria in the surrounding seawater for successful colonisation. When colonised, the regression of the light organs appendages was not dependent on temperature, but the opposite was found in non-colonised bobtail squids. Furthermore, the capacity to maintain the symbiosis diminished significantly with temperature. Finally, the capacity for crypt 3 formation in the squids light organ, which is crucial for enhancing resilience under stress, also declined with warming conditions. This study emphasises the critical need to study the dynamics of microbial symbiosis under the projected conditions for the ocean of tomorrow.

ecology↗

bioRxiv2024

Developmental and transcriptomic responses of Hawaiian bobtail squid early stages to ocean warming and acidification

1Cephalopods play a central ecological role across all oceans and realms. However, under the current climate crisis, their physiology and behaviour are impacted, and we are beginning to comprehend the effects of environmental stressors at a molecular level. Here, we study the Hawaiian bobtail squid (Euprymna scolopes), known for its specific binary symbiosis with the bioluminescent bacterium Vibrio fischeri acquired post-hatching. We aim to understand the response (i.e., developmental and molecular) of E. scolopes after the embryogenetic exposure to different conditions: i) standard conditions (control), ii) increased CO2 ({Delta}pH 0.4 units), iii) warming (+3{o}C), or iv) a combination of the two treatments. We observed a decrease in hatching success across all treatments relative to the control. Using transcriptomics, we identified a potential trade-off in favour of metabolism and energy production, at the expense of development under increased CO2. In contrast, elevated temperature shortened the developmental time and, at a molecular level, showed signs of alternative splicing and the potential for RNA editing. The data also suggest that the initiation of the symbiosis may be negatively affected by these environmental drivers of change in the biosphere, although coping mechanisms by the animal may occur.

ecology↗

bioRxiv2023

Neuromolecular responses in disrupted mutualistic cleaning interactions under future environmental conditions

Mutualistic interactions, which constitute some of the most advantageous interactions among fish species, are highly vulnerable to environmental changes. A key mutualistic interaction is the cleaning service rendered by the cleaner wrasse, Labroides dimidiatus, which involves intricate processes of social behaviour to remove ectoparasites from client fish and can be altered in near-future environmental conditions. Here, we evaluated the neuromolecular mechanisms behind the behavioural disruption of cleaning interactions in response to future environments. We subjected cleaner wrasses and surgeonfish (Acanthurus leucosternon, serving as clients) to elevated temperature (Warming, 32{degrees}C), increased levels of CO2 (High CO2, 1000 ppm), and a combined condition of elevated CO2 and temperature (Warming & High CO2, 32{degrees}C & 1000 ppm) for 28 days. Each of these conditions resulted in behavioural disruptions concerning the motivation to interact and the quality of interaction (High CO2 -80.7%, Warming - 92.6%, Warming & High CO2 -79.5%, p<0.001). Using transcriptomic of the fore-, mid-, and hindbrain, we discovered that most transcriptional reprogramming in both species under warming conditions occurred primarily in the hind- and forebrain. The associated functions under warming were linked to stress, heat shock proteins, hypoxia, and behaviour. In contrast, elevated CO2 exposure affected a range of functions associated with GABA, behaviour, visual perception, and circadian rhythm. Interestingly, in the combined Warming & High CO2 condition, we did not observe any expression changes of behaviour. However, we did find signs of endoplasmic reticulum stress and apoptosis, suggesting not only an additive effect of the environmental conditions but also a trade-off between physiological performance and behaviour in the cleaner wrasse. We suggest that impending environmental shifts can affect the behaviour and molecular processes that sustain mutualistic interactions between L. dimidiatus and its clients, which could have a cascading effect on their adaptation potential and possibly cause large-scale impacts on coral reef ecosystems.

animal behavior and cognition↗

bioRxiv2023

Transgenerational exposure to deoxygenation and warming disrupts mate-detection in Gammarus locusta

Ocean deoxygenation and warming have been shown to pose a growing threat to the health of marine organisms and ecosystems. Yet, the potential for acclimation and adaptation to these threats remains poorly understood. The aim of this study was to evaluate the effects of transgenerational exposure to reduced oxygen availability and elevated seawater temperature on the chemosensory-dependent mating mechanisms of male amphipods Gammarus locusta. After exposure, the number of individuals that reached adulthood (in F0 and F2) was gauged, and adult males from F0 and F1 were subjected to behavioral trials to assess their capacity of long-distance female cue detection through quantification of (i) response time; (ii) first direction of movement; (iii) activity rate and (iv) proportion of time spent in female scent cues. Ocean warming induced mortality (especially in F2), and reduced oxygen availability had adverse effects on each of the investigated behavioral traits, which were amplified when combined with elevated temperature. Still, when compared to F0, the F1 generation demonstrated more adaptability (i.e., higher activity rate and preference for female odors) to the combination of the two stressors, suggesting positive carry-over effects. Nevertheless, full recovery to control levels was not observed. Altogether, this study indicates that future scenarios of ocean deoxygenation and warming have the potential to disrupt chemosensory-dependent mate-detection in amphipods, but also suggests possible behavioral adaptations. We call for greater research efforts on long-term impacts of ocean change on the behavioral and physiological processes of benthic coastal communities.

ecology↗

bioRxiv2021

Neuro-molecular characterization of fish cleaning interactions

Coral reef fish exhibit a large variety of behaviours crucial for fitness and survival. The cleaner wrasse Labroides dimidiatus displays cognitive abilities during interspecific interactions by providing services of ectoparasite cleaning, thus serving as a good example to understand the processes of complex social behaviour. However, little is known about the molecular underpinnings of cooperative behaviour between L. dimidiatus and a potential client fish (Acanthurus leucosternon). Therefore, we investigated the molecular mechanisms in three regions of the brain (fore-, mid-, and hindbrain) during the interaction of these fishes. Here we show, using transcriptomics, that most of the transcriptional response in both species was regulated in the hindbrain and forebrain regions and that the interacting behaviour responses of L. dimidiatus involved immediate early gene alteration, dopaminergic and glutamatergic pathways, the expression of neurohormones (such as isotocin) and steroids (e.g. progesterone and estrogen). In contrast, in the client, fewer molecular alterations were found, mostly involving pituitary hormone responses. The particular pathways found suggested learning and memory processes in the cleaner wrasse, while the client indicated stress relief.

animal behavior and cognition↗