Synchronized molting behavior with social facilitation of maternal care and mutual aggregation reveals a specialized survival strategy in first instar scorpion larvae

Abstract

Molting is a well-known developmental feature of arthropods. The collective and synchronous molting of first instar scorpions is significantly different from the independent molting behavior common to older scorpions and most arthropods, so knowledge on the biological benefits of the unusual behavior of first instar scorpions is limited. Before the neonate scorpions molted, the mothers showed a remarkable ability to efficiently locate the fallen offspring and help them climb onto their backs. This was supported by their strong maternal behavior, as shown by the fact that they climbed more quickly than scorpions on the 7th day after birth. Most neonate scorpions survived molting on their mothers’ backs, with a survival rate of about 100%. Most neonate scorpions also survived by collective molting on sand without the mother (89.83% ± 1.91%). The important role of the mother was further highlighted in mothers with 1–5 first instar scorpions. All first instar scorpions survived on their mothers’ backs, either individually or mutually molting, but only 52.00% ± 7.14% to 79.20% ± 4.24% of neonates isolated from their mothers were able to survive on the sand, either individually or mutually molting, and the collective condition was enhanced as the number of scorpions on the sand increased before molting. These results highlight that cooperative molting is the driving force in the evolution of neonate scorpions. Taken together, both maternal care and cooperative collective molting behavior enhance the survival of first instar scorpions before and after molting, and these advantages over first instar scorpions play essential and evolutionary roles in scorpion survival.