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Fish show distinct "personalities" when foraging for food

Recent research has unveiled a fascinating aspect of fish behavior: individuals within the same fish species can develop unique foraging personalities and adapt their sense of smell to thrive in diverse habitats.

This study was conducted by a team at the Paris-Saclay Institute of Neuroscience (NeuroPSI – CNRS, Université Paris-Saclay), France.

Fish personalities and sensory evolution

The researchers focused on the Mexican cavefish larvae, specifically examining spontaneous swimming patterns and variations in their olfactory senses. This study sheds light on the remarkable adaptability of bony fishes, which represent half of all vertebrate species.

“With more than 26,000 species representing half of all vertebrates, bony fishes are extremely diverse and have colonized all possible ecological niches, through their ability to adapt their sensory systems,” explains Maryline Blin, the lead author and a Research Engineer at NeuroPSI.

Despite the rich diversity in fish species, most behavioral studies have been limited to a few models, such as zebrafish. This research breaks new ground by linking the evolution of fish sensory systems to their behavior, a largely unexplored area that has hindered cross-species comparisons.

The team chose two subtypes of the Mexican tetra species for their study: a blind cave-dwelling variant and its sighted surface river-dwelling counterpart. Despite similar genetic makeup related to smell, the cave-dwelling fish have evolved larger olfactory pits and different nerve compositions, possibly as an adaptive trait for survival in dark subterranean habitats.

Behavioral responses to food cues

Intriguingly, the study revealed that cave-dwelling fish showed a pronounced behavioral response to alanine, a common food cue. This response included decreased back-and-forth swimming and a tendency to swim towards the amino acid source.

In contrast, surface-dwelling fish exhibited more subtle and individual-specific responses, indicating a significant evolutionary divergence in sensory perception and behavior between the two subtypes.

Further analysis revealed individual differences in response to various amino acids in both cave and surface-dwelling fish.

Surface fish with slower baseline swimming speeds demonstrated better olfactory abilities for certain odors, a trait not observed in cave-dwelling fish. Instead, a unique swimming pattern in the cavefish was indicative of stronger olfactory capabilities.

The role of ‘personalities’ in fish behavior

Senior author Sylvie Rétaux, Research Director at NeuroPSI – CNRS, Université Paris-Saclay, explains, “We have developed a high-throughput, specific sense-of-smell test to compare the individual behavioral responses of blind and sighted fish to different odors. In doing so, we have ruled out the possibility that, when within a group, one ‘good-smeller’ individual could drive others to respond.”

The team’s high-throughput, specific sense-of-smell test ensured accurate individual responses by eliminating the influence of a single ‘good-smeller’ leading the group.

“Instead, our recordings of several hundred individual fish highlight an often-overlooked aspect of fish behavioral analyses: that fish may have a ‘personality’ or ‘temperament’ that influences their behavior and, consequently, their success at responding to environmental cues,” Rétaux concludes. “Moreover, the good sense of smell in cavefish is a genetically-encoded trait, so we will now actively search for the genetic underpinnings of this sensory specialization.”

In summary, this research paves the way for further exploration into the genetic basis of sensory specialization in fish. It emphasizes the complexity of fish behavior and the importance of considering individual variations in ecological and evolutionary studies.


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