Turbellarian taxonomic database

Abstract / Notes

"Ecdysis or molting evolved [approximately]535 mya in Ecdysozoa, the most diverse and species-rich animal
superphylum.1 A cascade of ecdysis-related neuropeptides (ERNs) controls the innate behavioral programs
required for cuticle shedding in some ecdysozoan lineages (e.g., arthropods)2-12 but is lacking in others
(e.g., nematodes). 13 We recently reported on the surprisingly ancient bilaterian origin of key ERNs, such as
eclosion hormone (EH), crustacean cardioactive neuropeptide (CCAP), myoinhibitory peptide (MIP), bursicon
alpha (Burs[alpha]), and bursicon beta (Burs[beta]).13,14 Thus, ERNs far predate the emergence of ecdysis, but
the question as to their ancestral functions remains unresolved. Here, we compare the ERN toolkits and
temporal expression profiles of six ecdysozoans (tardigrades, crustaceans, and insects), eight
lophotrochozoans (planarians, annelids, and mollusks), and five deuterostomes (crinoids, sea urchins, and
hemichordates). Our results show that the major, coordinated upregulation of ERNs always coincides with a
transition between key life history stages, such as hatching in direct developers and metamorphosis in
indirect developers. This implies that ERNs already played an ancestral role in the switch from embryonic or
larval ontogeny to juvenile maturation in the last common ancestor of Nephrozoa. Consequently, the
transcriptional signature of invertebrate life cycle transitions presented here was already in place in the
Precambrian and was only secondarily co-opted into regulating the molting process at the dawn of Ecdysozoa."

Return to taxon listing