Aggregation patterns in juvenile southern king crab <i>Lithodes santolla</i> (Molina, 1782). Are the aggregations related to moulting activity?

The early life history of decapod species involves several stages and ontogeny-related shifts in habitat requirements and behaviour. Early publications have reported that, in the San Jorge Gulf (45–47°S), Argentina, juvenile southern king crab <i>Lithodes</i> <i>santolla</i> (Molina, 1782) (SKC) remain in rocky coastal habitats for at least three years, prior to their migration to soft bottoms. In this study, we analysed the gregarious behaviour of juvenile SKCs and its relation with moulting activity through the early ontogeny of the species. Different aggregation patterns were observed in SKC juveniles during sampling. These aggregation patterns were related to an increase in moulting activity. SKC 1+ and 2+ formed small groups of 7–31 juveniles in holes or cracks at shallower depths. A large aggregation was recorded in November 2014 associated with <i>Macrocystis pyrifera</i> forests. This aggregation involved advanced juveniles 3+, probably at the end of their stay in the coastal environment. Our results suggest that the aggregation of juvenile SKCs is related to high moulting activity and that differences in the aggregation patterns are related to ontogeny. The aggregation of advanced juveniles may reflect a (re)synchronous moult prior to a coordinated abandonment of the coastal environment. The aggregation behaviour of SKC juveniles is related to an increase in moulting activity.The aggregation pattern exhibits differences related to the size/age of SKC juveniles.SKCs form large aggregations at the end of their stay in coastal environments. The aggregation behaviour of SKC juveniles is related to an increase in moulting activity. The aggregation pattern exhibits differences related to the size/age of SKC juveniles. SKCs form large aggregations at the end of their stay in coastal environments.十足目（Decapoda）物种的早期生活史包含多个发育阶段，其栖息地需求与行为会随个体发育（ontogeny）发生适应性改变。早期研究报道称，在阿根廷圣豪尔赫湾（45°S~47°S），幼年南方帝王蟹（*Lithodes santolla*，Molina, 1782，简称SKC）会在岩质近岸栖息地停留至少三年，随后才会迁移至软底质生境。本研究针对该物种早期个体发育阶段中的幼年SKC集群行为及其与蜕皮活动的关联展开分析。采样过程中，研究者观察到幼年SKC存在多种集群模式，且这些模式与蜕皮活动的增强存在显著关联。1+龄与2+龄幼年SKC会在较浅水域的洞穴或缝隙中，形成由7~31只个体组成的小型集群。2014年11月，研究者在巨藻（*Macrocystis pyrifera*）林生境中记录到一处大型集群，该集群由3+龄的晚期幼年个体组成，此时它们大概率已临近结束近岸栖息地的停留阶段。本研究结果表明，幼年SKC的集群行为与高蜕皮活动密切相关，且集群模式的差异与个体发育进程紧密关联。晚期幼年个体的集群行为，可能反映了它们在协同离开近岸生境前，正处于（再次）同步蜕皮的阶段。幼年SKC的集群行为与蜕皮活动增强相关，集群模式的差异与个体体型/年龄相关，SKC会在结束近岸栖息地停留时形成大型集群。幼年SKC的集群行为与蜕皮活动增强相关，集群模式的差异与个体体型/年龄相关，SKC会在结束近岸栖息地停留时形成大型集群。