Whole document restricted, see Access Instructions file below for details of how to access the print copy. / The fatty acid content of 30 species of Porifera, including samples of Hexactinellida and Lithistida for which no fatty acid data previously existed, have been examined. Sponges are unique among animal phyla in diversity of fatty acids with generally high levels of LCFAs (C24-30), high unsaturation (mainly polyunsaturation), and high incidence of branched and odd chain fatty acids. Further, peculiarities in the proportions of individual acids of particular chain lengths distinguish the phylum. Hexactinellid fatty acid traits corresponded closely to those of Demospongiae while the calcareous species was atypical in exhibiting comparatively low levels of LCFAs and unsaturation. Seasonal and geographical influences on components of the fatty acid profile limit the extent to which this information can be utilised in a chemotaxonomic sense. The major trends in seasonal variation of fatty acid content were in an increase in the levels of unsaturated fatty acids and a decrease in the levels of LCFAs during winter. The effects were less pronounced in a subtidal than intertidal species and are considered to be related to environmental temperature. LCFAs predominated in the phospholipids but also were present in high amounts in neutral lipids. The major changes in fatty acid content of the total lipid with season were reflected in the fatty acids of the phospholipids. Also, LCFAs were concentrated in cellular membranes of the sponge. Temperature-induced seasonal changes in LCFA and UFA composition could be explained as an attempt to maintain .the membranes from which these acids originate, in an optimal state of physico-chemical function across the environmental temperature range. This interpretation is supported by observation of an increased content of higher melting point lipids in the sponge in summer. The sensitivity of sponge membranes to temperature was demonstrated by thermal-induction of phase separations in membrane lipids. A major phase separation in both isolated lipids and membranes occurred within a ca. 8 °C of the normal growth temperature range of the sponge. It indicated that membrane lipids exist in a fluid state in the living sponge so that any variation in environmental temperature would affect the lipid fluidity of the membrane and hence physiological membrane processes. This also lends support for some control being exerted on the lipid fluidity of sponge membranes. Any such control must be non-behavioural since sponges are poikilotherms. Minor changes in the proportions of different phospholipids with season were indicated and are also likely to affect the physical properties of membranes which contain them. In general, the lipid yield from sponges as a proportion of the total dry weight is highly dependent on the skeletal composition, specifically the ratio of the structural to living tissue. Therefore lipid yield is not a reliable parameter for classifying sponges. The occurrence of terpenoid metabolites has proved more informative taxonomically and characterised those groups with a low sterol content, e.g. Dictyoceratida. A coincidence of occurrence of terpenoids and high levels of C25 of fatty acids was noted.
| Identifer | oai:union.ndltd.org:ADTP/276714 |
| Date | January 1984 |
| Creators | Lawson, Mishelle Patrice |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Whole document restricted. Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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