Adaptations to Hypoxia in Freshwater Triclads, With Particular Reference to Dendrocoelum lacteum (Mueller)

Zoology

Brough, Stuart

University:University of Glasgow

关键词: Zoology;   

Others  :  http://theses.gla.ac.uk/77480/1/10995528.pdf

来源: University of Glasgow

【 摘 要 】

Preliminary observations on triclads in rivers, suggested that individuals in some populations were more tolerant to low PO2 than others. In particular, those from organically enriched sites were best at tolerating these conditions. This study attempted to describe these environmental differences in more detail and tried to relate them to any possible physiological, biochemical or genetic differences between different populations. This work has concentrated mainly on Dendrocoelum Iacteum (Muller) and to a lesser extent Polycelis tenuis Ijima. All populations in this study were from the River Kelvin System situated on the west coast of Scotland, near Glasgow. Two sites were chosen with apparently large differences in organic input, and hence PO2; the Allander Water, (N.G.R.NS 539769) situated downstream from a sewage effluent input and the River Kelvin (NS 568664), downstream from a weir. Diurnal and seasonal measurements of PO2 were estimated and this showed that there were considerable differences in PO2 between sites i.e. the Allander Water site was hypoxic more frequently and for longer periods of time than the River Kelvin site. The tolerance of triclads to low PO2 was measured in open and closed systems. These results indicated that Polycelis tenuis and Dendrocoelun lacteun were capable of surviving prolonged exposure to hypoxia and anoxia and that LT50 values were affected by temperature, time of year, number of animals present, and nutritional state. Intraspecific differences were only considered for D. lacteum and here individuals from the Allander Water had significantly higher LT50 values than those from the River Kelvin (P<0.05). In general, animals lived longer at a low PO2 after acclimation to hypoxia, but the intraspecific differences that persisted between populations before acclimation were also observed after acclimation. It should also be noted that these intraspecific differences also persisted in the F1 generations. Hence, there may be both environmental and genetic components in these differences. Oxygen consumption was measured in closed and open respirometers for D. lacteum at various temperatures and PO2. Intraspecific differences in oxygen consumption were observed at two experimental temperatures (10 and 20