Levet, M. | bioRxiv Science

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↗