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The Journal of Experimental Biology 205, 1019-1029 (2002)
© 2002 The Company of Biologists Limited

Discontinuous gas-exchange in centipedes and its convergent evolution in tracheated arthropods

C. Jaco Klok^1,*, Richard D. Mercer² and Steven L. Chown¹

¹ Department of Zoology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
² Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa

^* e-mail: cjklok{at}sun.ac.za

Accepted 7 January 2002

We have examined the gas-exchange characteristics of five southern African centipede species from three orders. Two scolopendromorph species exhibit discontinuous gas-exchange cycles (DGCs) identical to those recorded for several insect and chelicerate species. Another scolopendromorph and a lithobiomorph species exhibit weak periodic patterns, and a scutigermorph species shows continuous gas exchange. A crucial component for DGCs in tracheated arthropods is the presence of occludible spiracles. However, on the basis of studies of temperate centipedes, most recent invertebrate biology texts hold the view that centipedes, as a group, cannot close their spiracles. Using flow-through normoxic and normoxic—anoxic—normoxic respirometry and electron microscopy, we conclusively demonstrate that at least one of the scolopendromorph species, Cormocephalus morsitans L., can close its spiracles fully, thus accounting for its DGCs. Homologies in spiracular structure and DGCs suggest that several other tracheated arthropod taxa probably have this ability too and that DGCs have evolved convergently at least four times in the Arthropoda. Spiracular closure and discontinuous gas-exchange cycles are probably more widespread in arthropods than has previously been suspected.

Key words: Chilopoda, Scolopendromorpha, centipede, Cormocephalus morsitans, spiracle, NAN respirometry, metabolic rate

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