Biology subjects

Levet, M.

Publications and source records attributed to Levet, M..

3 recordsLinked to original sources

bioRxiv2024

Acclimation temperature and parasite infection drive metabolic changes in a freshwater fish at different biological scales

O_LIEnvironmental stressors such as elevated temperature and parasite infection can impact individual energy metabolism. However, organismal responses to co-occurring stressors and their effects across biological scales remain unexplored despite the importance of integrative studies for accurately predicting the resilience of natural populations in changing environments. C_LIO_LIUsing wild-caught, naturally parasitized pumpkinseed sunfish, Lepomis gibbosus, we quantified changes in cellular and whole-organism metabolism in response to temperature and parasite infection. We acclimated pumpkinseeds for three weeks at 20{degrees}C, 25{degrees}C, or 30{degrees}C before measuring whole-organism oxygen uptake ([M]O2) using intermittent flow-respirometry to quantify maximal and standard metabolic rates (MMR and SMR, respectively) and aerobic scope (AS). We also measured the maximal activity of enzymes (citrate synthase (CS), respiratory complexes I + III and IV of the electron transport system, and lactate dehydrogenase (LDH)) linked with cellular bioenergetics in fish heart, brain, spleen and gills using spectrophotometry. C_LIO_LIWe found no interactions between acclimation temperatures and parasite intensity on cellular or whole-organism metabolism. However, both stressors were independently related to fish metabolism, with differing impacts across biological scales. C_LIO_LIWhereas MMR increased with acclimation temperature, this was not mirrored by increasing SMR or decreasing AS, suggesting thermal compensation across acclimation temperatures at the whole-organism level. C_LIO_LIOn a cellular level, acclimation responses were similar across organs, with maximal activity of all enzymes decreasing with increasing acclimation temperature. However, LDH activity remained higher than aerobic enzyme activities (CS, ETS complexes I + III and IV) across acclimation temperatures and organs, especially in gills, where LDH activity drastically increased at 30{degrees}C. This may indicate a stronger reliance on anaerobic metabolism to sustain whole-organism metabolic performance. C_LIO_LIFish with greater trematode infection had lower MMR and AS. There were no relationships between parasite intensity and SMR nor maximal enzyme activity. C_LIO_LIOur work shows that co-occurring stressors have distinct impacts on fish metabolism: parasites are primarily related to whole-organism metabolism while temperature impacts metabolism across biological scales. This highlights that interactions among co-occurring stressors are important for ecological realism and accurate predictions regarding population resilience to environmental changes. C_LI

physiology↗

bioRxiv2022

Mitochondrial metabolism and body condition of naturally infected sunfish (Lepomis gibbosus)

Parasites can affect host behavior, cognition, locomotion, body condition and many other physiological traits. Changes to host aerobic metabolism are likely responsible for these parasite-induced performance alterations. Whole-organism metabolic rate is underpinned by cellular energy metabolism driven most prominently by the mitochondria. However, few studies have explored how mitochondrial enzymatic activity relates to body condition and parasite infection despite being a putative site for metabolic disruptions related to health status. We studied correlations among natural parasite infection, host body condition and the activity of key mitochondrial enzymes in target organs from wild-caught pumpkinseed sunfish (Lepomis gibbosus) to better understand the cellular responses of fish hosts to endoparasite infection. Enzymatic activities in the gills, spleen, and brain of infected fish were not significantly related to parasite infection or host body condition. However, the activity of cytochrome C oxidase, an enzyme involved in oxidative phosphorylation, in fish hearts was higher in individuals with lower body condition. Activities of citrate synthase, complexes I and III and carnitine palmitoyltransferase were also significantly different among organ types. These results provide preliminary information regarding the likely mitochondrial pathways affecting host body condition, the maintenance energetic requirements of different organs and their specific dependency on particular mitochondrial pathways. These results help pave the way for future studies on the effects of parasite infection on mitochondrial metabolism.

ecology↗

bioRxiv2021

Escaping from multiple visual threats: Modulation of escape responses in Pacific staghorn sculpin (Leptocottus armatus).

Fish perform rapid escape responses to avoid sudden predatory attacks. During escape responses, fish bend their bodies into a C-shape and quickly turn away from the predator and accelerate. The escape trajectory is determined by the initial turn (Stage 1) and a contralateral bend (Stage 2). Previous studies have used a single threat or model predator as a stimulus. In nature, however, multiple predators may attack from different directions simultaneously or in close succession. It is unknown whether fish are able to change the course of their escape response when startled by multiple stimuli at various time intervals. Pacific staghorn sculpin (Leptocottus armatus) were startled with a left and right visual stimulus in close succession. By varying the timing of the second stimulus, we were able to determine when and how a second stimulus could affect the escape response direction. Four treatments were used: a single visual stimulus (control); or two stimuli coming from opposite sides separated by a 0 ms (simultaneous treatment); a 33 ms; or a 83 ms time interval. The 33 ms and 83 ms time intervals were chosen to occur shortly before and after a predicted 60 ms visual escape latency (i.e. during Stage 1). The 0 ms and 33 ms treatments influenced both the escape trajectory and the Stage 1 turning angle, compared to a single stimulation, whereas the 83 ms treatment had no effect on the escape response. We conclude that Pacific staghorn sculpin can modulate their escape response only between stimulation and the onset of the response, but that escape responses are ballistic after the body motion has started. SUMMARY STATEMENTUsing double stimulation from opposite sides at different time intervals to simulate coordinated predatory attacks, Pacific staghorn sculpin escape away from the first stimulus, but were unable to turn away from the second stimulus while the escape response was in progress.

animal behavior and cognition↗