Tantulocarida

Petrunina, Alexandra S., Høeg, Jens T. & Kolbasov, Gregory A., 2018, Anatomy of the Tantulocarida: first results obtained using TEM and CLSM. Part I: tantulus larva, Organisms Diversity & Evolution (New York, N. Y.) 18 (4), pp. 459-477 : 474

Comparison of Tantulocarida and Thecostraca

The present TEM investigations of the Tantulocarida give us for the first time a chance for comparison of their internal structures with other Crustacea in search of possible homologies. It has for a long time been suggested that Tantulocarida could be closely related to the Thecostraca, and recent molecular phylogenetic studies support this hypothesis and even suggest that they could be nested within this taxon (Khodami et al. 2017; Petrunina et al. 2014). The Thecostraca comprise the assumedly parasitic Facetotecta, the parasitic Ascothoracida, and the Cirripedia that comprise both parasitic and filter-feeding forms ( Grygier 1987; Høeg et al. 2009). Although adult thecostracans differ widely in morphology and life style, their monophyly has until now been unchallenged based on very strong evidence from both larval morphology and molecular data (Pérez-Losada et al. 2004; Høeg et al. 2009). Whether or not tantulocarids are nested within Thecostraca, there are numerous spectacular similarities between the two taxa that need to be discussed in order to decide whether or not they represent homologies or convergent evolution: the general life cycle including permanently attached adult stages, the general tagmosis and function of the larval stages, the mode of fixation on a substratum and the sensory structures used in this process, and feeding mechanisms. Finally, the presence of several parasitic groups within Thecostraca obviously raises the question: are Tantulocarids closely related to one of these (Høeg et al. 2009; Pérez-Losada et al. 2009)? Only based on such a comparison together with additional molecular evidence can it be decided if the concept of Thecostraca and its intrinsic phylogeny need to be revised.