The taxonomy and functional anatomy of Southern African Echiurans

Doctoral Thesis


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University of Cape Town

The southern African echiuran fauna currently comprises two families, four genera and eighteen species. The taxonomic positions of three other species, one of Ochetostoma and two of Thalassema, remain to be resolved. Of the recorded species, three are new to science and a further five are new records for the southern African region. This survey reveals that there are ten species of Ochetostoma, four of Thalassema and three of Anelassorhynchus. The family Echiuridae contains a single genus, Echiurus and in southern Africa, E. antarcticus is the only species recorded to date. Full descriptions of the new species and those formerly inadequately described are given. The diagnoses of some others are modified and, where necessary, additional notes added. Keys for the identification of families, genera and species are provided and the taxonomic characters are evaluated and discussed. The zoogeographic distribution of the southern African species is mapped and an attempt has been made to analyse the recorded species on the basis of faunistic provinces. The phylogenetic position of the Echiura in the system of the animal kingdom is discussed. The lack of any form of segmentation of the mesodermal bands during embryonic developnent seems to justify their status as a separate phylum. The biomechanics of burrowing, locomotion and trunk irrigatory movements of Ochetostoma caudex are described and compared with the activities of some other animals with unsegmented coelomic cavities. Pressure changes within the coelom have been measured with the use of electronic recording techniques and the results interpreted in relation to direct visual observation. The anatomy of the reproductive system and the process of gametogenesis in O. caudex have been investigated with light and electron microscopes. Some observations on aspects of breeding behaviour and spawning are also included.