LAUSR

Abstract The Tantulocarida is a small taxon of microscopic parasitic crustaceans that has a sophisticated life-cycle. The unique larval stage is called a tantulus, which is adapted to both free-swimming in sediments and attached parasitic mode of life. The anatomy of free-swimming tantulus larvae was studied using confocal laser scanning microscopy (CLSM) for the first time. This revealed previously undocumented details of the internal organisation of the Tantulocarida. Structures known to degrade after larval settlement were observed intact for the first time. The cement glands appeared to consist of six large, spherical cells with relatively large nuclei. The body muscles, proboscis and stylet retractors and protractors were able to be described in detail, whilst the central nervous system, including the compact brain and ventral nerve cord, were observed for the first time. This study has revealed the changes that occur in the internal organisation of the larvae after settlement, and provides a new understanding of certain general aspects of tantulocarid anatomy. The morphological adaptations to parasitism and the relatively minute size of these crustaceans are elucidated. Several aspects of arthropod miniaturisation are illustrated, using tantulocarids as examples. The potential for CLSM in studies of rare, microscopic arthropods is discussed.