A description of the post-naupliar development of Southern Ocean krill (Thysanoessa macrura)

Abstract

Southern Ocean krill (Thysanoessa macrura) is one of the most abundant euphausiid species in the Southern Ocean. Despite a wide distribution and high abundance this species remains poorly understood. Unique ecological traits of this species, including a late-winter reproductive period, highly omnivorous diet and large lipid deposits within the carapace, suggest T. macrura is attuned to the seasonal patterns of the Southern Ocean. The absence of the descriptions of T. macrura larval stages limits the development of a comprehensive understanding of the early life-history of this species. Here, I provide the first detailed descriptions of the post-naupliar larval developmental stages of T. macrura with accompanying photographic documentation. Three calyptopis and 6 furcilia stages were identified and described for T. macrura, providing an accessible guide for their identification in both historical samples and for future investigations.