The rectal gland and euryhalinity in elasmobranch fish

Good, Jonathan (2005). The rectal gland and euryhalinity in elasmobranch fish PhD Thesis, School of Biology, The University of St Andrews.

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TH_151390_Appendix.pdf Appendix application/pdf 105.45KB 359
TH_151390_Refs.pdf References application/pdf 138.75KB 313
TH_151390_ch1.pdf Chapter 1 application/pdf 720.54KB 888
TH_151390_ch2.pdf Chapter 2 application/pdf 242.36KB 195
TH_151390_ch3.pdf Chapter 3 application/pdf 135.52KB 246
TH_151390_ch4.pdf Chapter 4 application/pdf 331.99KB 166
TH_151390_ch5.pdf Chapter 5 application/pdf 233.62KB 278
TH_151390_ch6.pdf Chapter 6 application/pdf 149.61KB 97
TH_151390_ch7.pdf Chapter 7 application/pdf 101.43KB 130
TH_151390_frontmatter.pdf Front matter application/pdf 33.98KB 411
Author Good, Jonathan
Thesis Title The rectal gland and euryhalinity in elasmobranch fish
School, Centre or Institute School of Biology
Institution The University of St Andrews
Publication date 2005-08
Thesis type PhD Thesis
Supervisor Hazon, Neil
Language eng
Subjects 270500 Zoology
Abstract/Summary 1) Both the partially euryhaline Scyliorhinus canicula and the fully euryhaline Carcharhinus leucas significantly modify plasma concentrations of urea and chloride (Cl-) (and sodium (Na+)) in response to changes in environmental salinity, in order to maintain overall plasma osmolality slightly hyper- or isosmotic to the environment. C. leucas has a greater capacity for urea retention in dilute environments. In S. canicula all of these changes occur within 12 hours of transfer, with the notable exception of increasing plasma urea in response to acute transfer to elevated salinity. 2) A new technique, 51Cr-labelled erythrocytes, was developed to assess blood volume in elasmobranch fish. S. canicula displays significant haemodilution and concentration during chronic acclimation to decreased and increased environmental salinity respectively. Significant changes in blood volume were seen within 6 hours of acute salinity transfer. 3) In vivo secretion rates were measured in the rectal gland of S. canicula during both chronic and acute salinity transfer. Significant changes in Cl- clearance occur during acute transfer, as plasma Na+ and Cl- levels are modified, but do not persist in chronically acclimated animals. This is achieved through modifications in the volume and Cl- concentration of the secretory fluid. 4) C. leucas is able to significantly alter the abundance and/or recruitment of Na+, K+-ATPase in both the rectal gland and the kidney during chronic acclimation to salinity transfer. This is presumably in response to increased requirements for NaCl secretion in SW and osmolyte retention in FW respectively. S. canicula do not significantly alter abundance and/or recruitment of Na+, K+-ATPase in the principle osmoregulatory organs following chronic acclimation to salinity transfer. 5) Chronically SW acclimated C. leucas modify the proportion of ouabain-sensitive oxygen consumption in the tissues of the rectal gland in response to the secretory endocrine stimulus C-type natriuretic peptide (CNP). No such modification occurred in the rectal glands of FW acclimated C. leucas. This represents a change in the sensitivity and response to endocrine control factors during chronic acclimation to salinity transfer in this species. No such modification was seen the in the proportion of ouabain-sensitive oxygen consumption in the rectal glands of chronically acclimated S. canicula in response to CNP. These results were discussed in relation to the capacity for modification of osmoregulatory organs in partially and fully euryhaline elasmobranchs.
Keyword rectal gland
euryhalinity
elasmobranch fish
environmental salinity
urea retention
blood volume

Document type: Thesis
Collection: UQ Theses Collection (RHD) - Open Access
 
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Created: Wed, 18 Jun 2008, 12:14:48 EST by Belinda Weaver on behalf of School of Biomedical Sciences