Open AccessA hemocyanin from the Onychophora and the emergence of respiratory proteins
Author(s) -
Kristina Kusche,
Hilke Ruhberg,
Thorsten Burmester
Publication year - 2002
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.152241199
Subject(s) - biology , hemocyanin , hemolymph , arthropod , zoology , ecology , genetics , antigen
The velvet worms (Onychophora) are considered living fossils and are closely related to the Euarthropoda. Onychophora possess a tracheal system for respiratory function, but oxygen-transport proteins have been considered unnecessary. Here, we show that the hemolymph of the Epiperipatus sp. (Onychophora: Peripatidae) contains an arthropod-type hemocyanin, demonstrating that such protein exists outside the Euarthropoda. Thus, the evolution of oxygen carriers preceded the divergence of the Onychophora and Euarthropoda and was most likely linked to the evolution of an efficient circulatory system in a low-oxygen environment. The cDNA of the Epiperipatus hemocyanin subunit comprises 2,287 bp and encodes for a protein of 641 aa (73.6 kDa). Phylogenetic analyses of the arthropod hemocyanin sequences show that the Onychophora form a robust sister-group of the Euarthropoda, whereas the monophyly of the Tracheata is not supported.