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Title: Studies on Sabellida
Author: Knight-Jones, P. K.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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Setae and uncini of Spirorbidae were examined by scanning electron microscopy. Most thoracic 'blades' are rounded in cross-section, whilst others (abdominal setae and sickle-setae, in part) are indeed blade-like. Both types however show some bilateral asymmetry and are orientated so that their more ridged or striated surfaces can grip the tube wall. Setae thus help in anchorage and locomotion, but above all act as distance pieces flanking the faecal groove, pushing the body towards the opposite wall, against which the toothed uncini are engaged as anchors. Within the coiled tube the ventral side must be peripheral since the mouth must face outwards for feeding. Uncini are ventral in most Sedentaria, but those on the abdomen of spirorbids develop dorsally, because of the setal inversion characteristic of Sabellida. They can thus grip the tube wall on the inside of the bend, whilst the faecal groove runs ventrally along the convex surface of the coiled abdomen, where there is most room for the passage of faeces. Ultimate discharge is dorsal, to avoid the mouth, and is attained by the groove running round the body peripherally, i.e. round to the right side in species with sinistral coiling. Setal inversion therefore seems to be an adaptation for life in a coiled tube, and unnecessary in Sabellidae. The second part of this thesis reviews adaptations for tube dwelling in spirorbids, serpulids, sabellids and caobangiids, reaching the conclusion that spirorbids are probably the most primitive family of the order, the limited fossil evidence supporting this idea. Sabellidae were especially sought for these studies, because they seemed to show more diversity than the other families, suggesting that they are phylogenetically advanced. The third part of this thesis describes some of the species found. With related museum material, this comprises a review of the British Sabellinae.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available