Biology subjects

Killen, S.

Publications and source records attributed to Killen, S..

4 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↗

bioRxiv2023

Kinematic performance declines as group size increases during escape responses in a schooling coral reef fish

Escaping predation is essential for species survival, but prey must effectively match their response to the perceived threat imposed by a predator. For social animals, one mechanism to reduce risk of predation is living in larger group sizes, which dilutes each individuals risk of capture. When a predator attacks, individuals from a range of taxa (e.g., fishes, sharks, amphibians) perform an escape response, to evade the attack. Here, using the schooling coral reef damselfish Chromis viridis, we assess if there is an optimal group size that maximizes both individual escape response performance as well as group cohesion and coordination following a simulated predator attack, comparing schools composed of four, eight, and sixteen fish. We found that fish in various group sizes exhibited no difference in their reaction timing to a simulated predator attack (i.e., escape latency), but larger groups exhibited slower kinematics (i.e., lower average turning rate and shorter distance covered during the escape response), potentially because larger groups perceived the predator attack as less risky due to safety in numbers. Both school cohesion and coordination (as measured through alignment and nearest neighbor distance, respectively) declined in the 100ms after the predators attack. While there was no impact of group size on alignment, larger group sizes exhibited closer nearest neighbor distances at all times. This study highlights that larger group sizes may allow individuals to save energy on costly behavioral responses to avoid predators, potentially through a greater threshold of the threat necessary to trigger a rapid escape response.

animal behavior and cognition↗

bioRxiv2021

Group size influences individual metabolic traits in a social fish

O_LIGroup living is widespread among animal species and yields both costs and benefits. Presence of conspecifics can restrict or enhance the expression of individual behaviour, and the recent social environment is thought to affect behavioural responses in later contexts, even when individuals are alone. However, little is known about how social dynamics influence the expression of individual physiological traits, including metabolic rates. C_LIO_LIThere is some evidence that shoaling can reduce fish metabolic rates, but habitat conditions such as shelter availability may generate density-dependent influences on individual metabolic rates. C_LIO_LIWe investigated how social group size and availability of shelter influence Eurasian minnow Phoxinus phoxinus metabolic rates estimated by respirometry in the presence or absence of plant shelter. Respirometry trials were conducted before and after we housed fish for three weeks in a social treatment consisting in a specific group size (n= 4 or 8) and shelter availability (presence or absence of plant shelter in the holding tank). C_LIO_LIMinimum day-time and night-time metabolic rates estimated while in presence of plant shelter were lower than when estimated in absence of plant shelter, both before and after individuals were housed in their social group size and shelter availability treatment. Standard metabolic rate was higher for fish held in groups of four as compared to fish held in groups of eight while maximum metabolic rate showed no difference. Shelter availability during the social treatments did not influence standard or maximum metabolic rates. C_LIO_LIOur results suggest that group size may directly influence energy demands of individuals, highlighting the importance of understanding the role of social dynamics on variations in physiological traits associated with energy expenditure. C_LI

physiology↗

bioRxiv2021

Design, construction, and deployment of an affordable and long-lasting moored deep-water fish aggregation device

Fish aggregation devices (FADs) are used worldwide to enhance the efficiency of various fisheries. Devices consist of a floating or subsurface component designed to exploit natural fish behavior, using species attraction to structure (e.g., Sargassum spp.) to aggregate fish and increase capture success in open ocean environments. Concerns have arisen regarding the scale and management of FAD-associated fisheries, however, the efficiency of FADs to aggregate fish also introduces the possibility for FADs to be used as conservation tools to study pelagic species ecology. Building on two successful and several failed deployments of anchored deep-water (>500 m) subsurface (10 m) FADs over three years in The Bahamas, and observations from the subsequent FAD monitoring program, the objectives of the paper are to: 1) provide details and considerations for the design, construction, and deployment of an affordable and durable deep-water subsurface FAD that can be deployed using small boats; and 2) highlight the potential for a long-lasting moored FAD to be used as a sustainable and reliable scientific platform for pelagic species research and conservation, lending specifically to several research applications. This information will be useful for assessing the impacts that FADs and other anthropogenic marine infrastructure have on wild marine species, and their efficacy for conserving pelagic fish through increased encounters for study.

ecology↗