Functional Morphology of Branchiae

Project Title: Functional morphology and ultrastructural analysis of branchiae in Annelida

Funding Source: University

Principle Investigator: Günter Purschke with Dirk Weihrauch, University of Manitoba; Heiko Harten and Achim Paululat

Investigations on evolution, systematics, phylogeny and functional morphology are in the focus of interest. Currently these investigations are carried out on annelids, the segmented worms, and those taxa which are presumed to be closely related to them. Special emphasis is laid to the phylogenetic relationships within and validity of Lophotrochozoa.

Although many annelids do not possess respiratory organs, such organs are present in many of the larger and especially in tubiculous forms. Seemingly simple in structure, these organs came again into focus of scientific interest with detection of annelids at hydrothermal vent sites at the ocean floor spreading centers. However, these organs are complex structures being provided with ventilation and sensing and nervous elements, musculature, coelom and blood spaces. A thorough investigation of the branchiae in the fire worm, Eurythoe complanata, revealed their complex structure including very short diffusion distances between the environment and the blood vascular system of much less than 1 µm in thickness and their involvement in ammonia excretion as, for instance, in aquatic arthropods. These results led to expand these investigations into other branchiate annelids; first results show that short diffusion distances are likely a general characteristic of these organs rather than being restricted to hydrothermal vent annelids as previously hypothesized.

Top row: Scanning electron micrographs of regenerating specimen of Eurythoe complanata with parapodia and branchiae; right: close-up of parapodium with branched gill.

Bottom: LM of juvenile Scoloplos armiger with segmentally arranged branchiae.