Extended Mother–Offspring Relationships in Crayfish: The Return Behaviour of Juvenile Procambarus Clarkii

Crayfish shows a relatively complex parental behaviour compared with other invertebrates, but the literature provides only anecdotal accounts of this phenomenon. In Procambarus clarkii , we described the ‘return’ behaviour of third‐stage juveniles when offered four types of adults: biological mothers, foster mothers, non‐brooding females and males. Then, we analysed the posture and behaviour of the adults to understand the role played by the putative mother in attracting the juveniles. Contrary to non‐brooding individuals, both biological and foster mothers displayed a relatively rare locomotion, executed few cleaning and feeding acts, and never attempted to prey on juveniles. They often assumed a ‘spoon‐like telson posture’ that seemed to facilitate offspring’s approaches. Juveniles increased the frequency of tail‐flips away in the presence of non‐brooding adults; conversely, they accepted foster mothers, along with biological mothers, but not as fast as the latter. Taken together, these results suggest that mother–offspring relationships in P. clarkii are more refined than previously thought, being possibly a key factor enabling this species to thrive in harsh environmental conditions.