Assessing and interpreting lateralised behaviours in anuran larvae.

Area of Science:

• Ethology
• Neuroscience
• Developmental Biology

Background:

• Lateralized behaviors, specifically turning biases, are observed in tadpoles, influencing their motor control.
• These biases are not universal across all tadpole species and can vary in manifestation and timing.
• Existing research suggests a potential link between these biases and Mauthner cell-mediated responses.

Purpose of the Study:

• To review and synthesize current knowledge on tadpole lateralized behaviors, focusing on turning biases.
• To examine various testing methods used to assess these biases, distinguishing between explosive and slower turns.
• To explore the ontogenetic and potential phylogenetic aspects of tadpole turning biases.

Main Methods:

• Review of studies employing specific testing protocols for explosive turns (e.g., air-breathing descents, mechanical startles).
• Analysis of methods assessing slower turns (e.g., T-mazes, tube exits, barrier avoidance).
• Consideration of morphological asymmetries (e.g., spiracle) and their relation to behavioral lateralization.

Main Results:

• Turning biases are observed in some tadpole species, often left-sided, with magnitudes typically between 60-90%.
• Explosive turns show biases likely mediated by Mauthner cells, while slower turns may involve different pathways.
• Biases usually appear post-hatching and disappear before metamorphosis, though exceptions exist during metamorphosis.

Conclusions:

• Tadpole turning biases are a significant aspect of their early motor development, with potential links to Mauthner neuron asymmetry.
• Further research is needed to understand phylogenetic patterns and the relationship between early and later lateralized behaviors.
• A model is proposed suggesting that biases arise from 'hardwired' neuromotor programs prioritizing speed.