Different ideas of the relationship between the crustacea (crabs, barnacles, copepods and others) and insects have been discussed at length over the past century. The emergence of more and better DNA information is allowing the evolutionary relationships to be explored and clarified.
Ronald Jenner (Zoology) co-authored a first phylogenomic test of the recent hypothesis of a sister group relationship between hexapods (insects) and remipede crustaceans. Numerous data and testing of different interpretations led the authors to robustly find hexapods and remipedes as sister groups.
Remipede crustaceans were first described as Carboniferous fossils in the 1950s (around 310 million years old). However, living species have been discovered since 1979, living only in underground aquifers connected to the sea. They are slow-moving with relatively basic segmented body plans, but can have specialised characteristics such as poison fangs and advanced sense of scent, important for securing prey in their unusual habitat.
A Remipede from Mexico
The paper looks at the idea of the Pancrustacea - a large group containing both crustaceans and insects. The data support the idea that the Pancrustacea can be divided into two major groups. In the first are the marine decapods (crabs, prawns and lobsters), barnacles and copepods. In the second group are found the freshwater Branchiopoda (such as the familar waterflea Daphnia), the Remipedes and the insects. This supports the insects as a part of the Pancrustacea, possibly as part of a subgroup that moved from shallow marine environments to specialist freshwater, groundwater and terrestrial habitats.
von Reumont, B. M., Jenner, R. A., Wills, M. A., Dell’Ampio, E., Pass, G., Ebersberger, I., Meyer, B., Koenemann, S., Iliffe, T. M., Stamatakis, A., Niehuis, O., Meusemann, K. and Misof, B. Early online. Pancrustacean phylogeny in the light of new phylogenomic data: support for Remipedia as the sister group of Hexapoda. Molecular Biology and Evolution (doi:10.1093/molbev/msr270) Abstract