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Title: Growth, larval ecology and taxonomy of spirorbids
Author: Goff, M. C.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1983
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Laboratory feeding experiments reveal that spirorbids are catholic in their feeding habits; Spirorbis spirorbis, S. tridentatus and Janua agenstecheri thrive equally on flagellates and diatoms. Cell size of the food organisms did not influence their favourability as food in the range of 1.5-10p. Phaeodactylum tricornutum and Isochrysis galbana were the most nutritious foods. Growth rates and coil morphogenesis of laboratory-reared animals were very similar to those of wild populations, in which coil morphogenesis is found to be affected by genetic factors, food availability and available space on the substratum. Settlement experiments show that SS spirorbis larvae prefer to settle adjacent to conspecifics. Surprisingly, space-competitive epiphytes of Fucus serratus, such as colonial bryozoans, also promote settlement. Rare Fucus is the least favourable substratum choice. Settlement experiments using light-and dark-adapted F. serratus and the photosynthesis inhibitor 2-4 dinitrophenol demonstrate that a chemical product of photosynthesis must be present before Spirorbis larvae will settle. The ultrastructure of the photoreceptors of S. spirorbis larvae consists of a "rhabdomere" of sensory microvilli underlaid by extensive arrays of submicrovillar cisternae and endoplasmic reticulum. The photoreceptors may be termed "parenchymatous - diverticular" (Salvini-Plawen & Mayr, 1977). There may be one sensory cell or two, surrounded by (usually) one pigment cell. Cross-breeding experiments and starch gel electrophoresis tend to confirm that the species Spirorbis inornatus consists of at least three distinct ecological races - formae reptans and himanthaliae Knight-Jones & Knight-Jones (1977) besides the type which attaches to Laminaria pileolaria (Jugaria) quadrangularis (Stimpson, 1854) is reported from British shores for the first time. It may be distinguished from P. Iranulata by possession of a lobed opercular talon, which is incorporated into the brood-chamber wall. This probably represents an efficient means of strengthening the brood-chamber wall in cold latitudes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available