“Crustacea”: Comparative Aspects of Early Development

Abstract

“Crustacea” – like Hexapoda, Chelicerata, and Myriapoda – are Arthropoda, but as we have seen in the previous chapter, they are not recognized as monophyletic in most recent phylogenetic analyses (Fig. 2.1; see Chap. XX and Dunn et al. 2008). Instead, “Crustacea” is a paraphyletic group and part of Pancrustacea/Tetraconata that include “Crustacea” as well as Hexapoda. Although this means that the model organism Drosophila is more closely related to the “Crustacea” than to the Chelicerata and Myriapoda, EvoDevo studies traditionally treat insect and crustacean development as independent and unrelated. Depending on the observer and the criteria used, the diversity and specialization of forms in adult as well as embryonic crustaceans is considered at least as high as in Hexapoda, Chelicerata, and Myriapoda (cf. Chaps. XX, YY, and ZZ). The diversity of a group can be explored without searching for general evolutionary forces that generate diversity, as it is fascinating in itself, and can be appreciated without further research program. Darwin changed the way diversity is understood when he convincingly argued that diversity of adults and embryos is the product of evolution. He introduced the idea of “nested relatedness” of taxa and used comparison as method to detect homologies and to prove shared evolutionary history. The research program of EvoDevo is to delineate the evolutionary processes of the past and the present that generate the diversity among the developmental modes found today.

Chapter vignette artwork by Brigitte Baldrian. © Brigitte Baldrian and Andreas Wanninger.