This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Amphibian larvae—often known as tadpoles—exhibit a behavior known as "social aggregation," in which they gather together to avoid predators. These interactions are evidence of their "association preferences," or their tendency to recognize members of their own species.
Some varieties of tadpoles have even shown a preference for their siblings. These association preferences and kin recognition in tadpoles have become a key topic in understanding the evolution of social behavior. Recent studies have suggested that microorganisms may influence communication through animal body odors, indicating that pond water rich in microbes may also affect social behavior.
Yet whether this sociality is innate, shaped by early-life experiences or influenced by the aquatic environment has remained unclear. This uncertainty motivated Kazuko Hase at Kyoto University to investigate how early-life social experiences and the aquatic environment influence the development of sociality. The research is published in the journal Animal Cognition.
Hase collected tadpoles of the species Bufo formosus, the Japanese common toad, from four different egg masses found around the University of Tokyo's Botanical Gardens, treating the egg masses as sibling groups. After hatching, she raised the tadpoles using an experimental design combining two different water environments—tap water and pond water—with two different rearing conditions: group rearing with 20 siblings and solitary rearing. After two weeks, Hase conducted choice experiments that involved simultaneously presenting the tadpoles with both sibling and nonsibling individuals to assess their social preferences.
She established sibling, nonsibling and neutral zones within the experimental tanks and tracked the tadpoles' movements for 60 minutes, analyzing the amount of time spent in each zone. The analysis revealed that the tadpoles did not exhibit any preference for siblings, regardless of rearing conditions, indicating lower kin recognition than tadpoles of other species. Hase observed that tadpoles reared in isolation showed a reduced tendency to approach other individuals, whether siblings or nonsiblings, and spent more time in the neutral zones, suggesting that the effects of social isolation remain robust across aquatic environments.
She did not observe any significant effects resulting from the water environment. "Unlike closely related species in which kin recognition has been confirmed during social aggregation, I was surprised to find that it is not essential for social aggregation in the Japanese common toad," says Hase, the corresponding author. This study indicates that the social behavior of this tadpole is shaped more by experiences with peers than by kinship or the water environment, contributing to a better understanding of how some amphibians develop sociality.
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