Progress 01/01/08 to 12/31/12
Outputs
OUTPUTS: Activities: Time on this project for 2012 was spent completing analysis and publication of data over the span of the project. New experiments that are the logical progression from previous findings were initiated, conducted, and are now under analysis. Manuscripts of these new and exciting findings are currently being prepared for publication in 2013. A new grant proposal was developed to support a workshop/ mini-symposium to present our findings and encourage collaboration with investigators working in this area of research. If funded the workshop will be supported by BARD and occur in conjunction with the annual Tilapia Aquaculture Conference in Jerusalem, Israel in October 2013. Six presentations were made by the PI and eleven by postdocs, students and collaborator were made at scientific symposia over the life of the grant to date, which disseminated the information and new knowledge gained. These presentations were mostly at scientific symposia in the US, Japan and Canada; two were provided in lay terms for the public and one was an invited classroom presentation for a class at the Fisheries School in Hokkaido Japan. In information was conveyed and presented in informal meetings with aquaculture farmers in American Samoa and the Republic of the Marshall Islands during annual visits as part of a leveraged component of the work with the University of Hawaii Sea Grant College Program. PARTICIPANTS: Individuals: Darren Lerner, PI; Andre Seale (collaborator); Lori Davis (Postdoctoral fellow); Jason Breves (PhD student and postdoctoral fellow); Christian Tipsmark (postdoctoral fellow); Ben Moorman, (Masters student and PhD candidate); Jacob Stagg (MS candidate) Partner Organizations: University of Hawaii Sea Grant College Program; University of Tokyo, Ocean Research Institute;University of Hawaii at Hilo, Pacific Aquaculture And Coastal Resources Center and American Samoa Community College Training: Over the life of this project these studies were part of the training and advancement of 2 masters students, two PhD students and 3 postdoctoral fellows. This project has leveraged Sea Grant initiatives and funding to provide annual training programs to aquaculture-farmers in American Samoa and the Republic of the Marshall Islands. TARGET AUDIENCES: Targeted Audiences: Aquaculture farmers in Hawaii, American Samoa and the Republic of the Marshall Islands. Efforts: This project has leveraged extension and outreach efforts of the UH Sea Grant College Program. In addition, new knowledge gained has been incorporated into 2 special topic graduate courses (Special Topics in environmental Physiology and Osmoregulation in Fishes; MBBE-691; ) at the University of Hawaii at Manoa by the PI PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Change in Knowledge: Significant fundamental findings from this project were synthesized into 7 publications over the life of this project to date. At least 3 additional publications will be submitted in 2013 from results of this research . Change in Actions: Based on the fundamental findings of this project two new grants were developed and awarded and are currently in progress. 1. Integrating environmental modulation, osmosensitivity and signaling in a model osmoreceptor (NSF) which will focuses on increasing the fundamental understanding of how osmoreceptor cells work in an economically important food fish (tilapia) grown in fresh water and seawater; and 2. Effect of Dietary Salt on the Growth Performance of Tilapia in Aquaculture (BARD), which focuses on understanding the role and function of the gastrointestinal track in fresh water osmoregulation and to develop dietary means to enhance productivity of tilapia. Also, based on new findings that tidal changes in salinity mimicking changes experienced in the natural environment have been used to develop and submit a new pre-proposal to the National Science Foundation. Change in Conditions: Over the life of this research project 2 masters students, two PhD students and 3 postdoctoral fellows were at least partially supported and all were engaged in some aspects of this project.
Publications
- Seale, A. P.,Yamaguchi, Y.,Johnstone W.M.,Borski R.,Lerner, D. T.,and Grau, E. G. 2013. Endocrine regulation of prolactin release and modulation of osmoreception in prolactin cells of the Mozambique tilapia. Gen. Comp. Endocrinol. In review.
- Seale, A.P., Watanabe, S., Breves, J. P., Lerner, D.T., Kaneko, T., and Grau, E. G. 2012 Differential regulation of TRPV4 mRNA levels by acclimation salinity and extracellular osmolality in euryhaline tilapia. Gen Comp Endocrinol. 178, 123-130.
- Seale, A. P., Moorman, B.P., Stagg, J.J., Breves, J.P., Lerner, D.T., and Grau, E.G. 2012. Prolactin177, prolactin188 and prolactin receptor 2 in the pituitary of the euryhaline tilapia, Oreochromis mossambicus, are differentially osmosensitive. J. Endocrinol. 213, 89-98.
- Tipsmark, C. K., Breves, J. P., Seale, A. P., Lerner, D. T., Hirano, T. and Grau, E. G. 2011. Switching of Na+, K+-ATPase isoforms by salinity and prolactin in the gill of a cichlid fish. J. Endocrinol. 209(2): 237-244.
- Davis, L. K., Katsu, Y., Iguchi, T., Lerner, D. T., Hirano, T., and Grau, E. G. 2010. Transcriptional activity and biological effects of mammalian estrogen receptor ligands on three hepatic estrogen receptors in Mozambique tilapia. J. Steroid Biochem Mol Biol, 122(4):272-8.
- Breves,J. P., Hasegawa,S., Yoshioka,M., Fox,B. K.,Davis,L. K., Lerner, D. T., Takei, Y., Hirano, T., and Grau, E. G. 2010. Acute salinity challenges in Mozambique and Nile tilapia: Differential responses of plasma prolactin, growth hormone and branchial expression of ion transporters. Gen Comp Endocrinol. 167:135-142.
- Davis, L. K., Fox, B. K., Lim, C., Lerner, D. T., Hirano, T., and Grau, E. G. 2010. Effects of 11-ketotestosterone and fishmeal in the feed on growth of juvenile tilapia (Oreochromis mossambicus) Aquaculture; 305;143-149.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Activities: Time on this project this year was spent on synthesis and analysis of the data collected from 2008 to present and the publication of these findings. In addition two grant proposals, one to the National Science Foundation and one to the Binational Agricultural Research and Development fund were developed based on our findings to date. Two graduate students (one MS and one PhD) and one postdoctoral fellow were partially supported. Events: The following presentations were made at scientific symposia, which disseminated the information and new knowledge gained to date: 1. Jul 2011- Seale, A.P., Breves, J.P., Watanabe, S., Kaneko T., Lerner, D.T., Hirano, T. and Grau, E.G. Invited oral presentation: Osmoreception and endocrine responses in the euryhaline tilapia, Oreochromis mossambicus. North American Society for Comparative Endocrinology. Ann Arbor, MI. 2. Jul 2011- Breves, J.P., Seale, A.P., Tipsmark, C.K., Watanabe, S., Lerner, D.T., Kaneko, T., Hirano, T., Grau, E.G., McCormick, S.D., Karlstrom, R.O. Poster presentation: Regulation of branchial ionoregulatory pathways by prolactin and growth hormone: a comparative approach investigating euryhaline and stenohaline teleosts. North American Society for Comparative Endocrinology. Ann Arbor, MI. 3. In conjuction with the PIs duties serving as the Associate Director for the University of Hawaii Sea Grant College Program, presentations and instruction was provided to tilapia farmers in American Samoa. PARTICIPANTS: Individuals:Darren Lerner, PI; Ben Moorman, PhD candidate; Jason Breves fellow; Jacob , MS candidate Partner Organizations: University of Hawaii Sea Grant College Program; University of Tokyo, Ocean Research Institute;University of Hawaii at Hilo, Pacific Aquaculture And Coastal Resources Center and American Samoa Community College Training: These studies are part of the training and advancement of one masters student, on PhD student and a postdoctoral fellow in our laboratory. This project has leveraged Sea Grant intiatives and funding to provide annual training programs to aqua-farmers in American Samoa. TARGET AUDIENCES: Targeted Audiences: Aquaculture farmers in Hawaii, American Samoa and the Republic of the Marshall Islands. Efforts: This project has leveraged extension and outreach efforts of the UH Sea Grant College Program. In addition, new knowledge gained has been incorporated into special topic graduate courses (Osmoregulation in Fishes; MBBE-691) at the University of Hawaii at Manoa by the PI. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Change in Knowledge: Significant fundamental findings from this project were synthesized into 3 new peer-review publication submitted during 2011 (two are under review at the time of this report). Change in Actions: Based on the fundamental findings of this project two new grants were developed and awarded. 1. Integrating environmental modulation, osmosensitivity and signaling in a model osmoreceptor (NSF) which will focuses on increasing the fundamental understanding of how osmoreceptor cells work in an economically important food fish (tilapia) grown in fresh water and seawater; and 2. Effect of Dietary Salt on the Growth Performance of Tilapia in Aquaculture (BARD), which focuses on understanding the role and function of the gastrointestinal track in fresh water osmoregulation and to develop dietary means to enhance productivity of tilapia. Change in Conditions: One postdoctoral fellow and one PhD student completed their fellowship/degree. The postdoctoral fellow gained an EPA fellowship and the PhD student began an NIH postdoctoral fellowship at the University of Massachusetts.
Publications
- Tipsmark, C. K., Breves, J. P., Seale, A. P., Lerner, D. T., Hirano, T. Grau, E. G. 2011. Switching of Na+, K+-ATPase isoforms by salinity and prolactin in the gill of a cichlid fish. J. Endocrinol.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: 1.We examined the effects of nonylphenol (NP) and estradiol (E2) on the maintenance of osmoregulatory homeostasis and endocrine responses in freshwater (FW) and seawater (SW)-acclimated tilapia. RIAs were conducted for measurement of plasma concentrations of growth hormone (GH), insulin-like growth factor I (IGF-I)and prolactin (PRL). An ELISA was used to determine plasma concentrations of vitellogenin. A biochemical enzymatic assay was used to determine activity potential for branchial sodium-potassium adenosine triphosphotase activity (NKA). Changes in gene expression of GH receptor (GHR) and IGF-I mRNA were measured using quantitative real-time polymerase chain reaction (qrtPCR). 2. We sought to determine whether the contrasting degrees of salinity tolerance between two con-generic tilapiine species (Nile and Mozambique tilapia) is related to dissimilar abilities to modulate hormonal signaling and osmoregulatory machinery in response to salinity challenges. We have partnered with colleagues at the Ocean Research Institute (ORI) of the University of Tokyo. . Plasma osmolality was measured using a vapor pressure osmometer. Plasma levels of cortisol, IGF-I, PRL and GH was measured by radioimmunoassay. Pituitary mRNA expression of GH, PRL, GHR, PRLR and osmotic transcription factor 1 (OSTF), branchial mRNA expression of IGF-I, PRLR, gluccocorticoid receptor (GR), sodium-potassium-2chloride cotransporter (NKCC), sodium-chloride cotransporter (NCC) and sodium-hydrogen exchanger (NHE3), and hepatic mRNA expression of GHR and IGF-I were be determined by qrtPCR. 3.A third experiment was designed to establish a time-course of changes during seawater acclimation in plasma levels of osmoregulatory hormones, branchial gene expression of receptors for hormones of the growth hormone family and for glucocorticoid hormones, as well as of expression of putative osmodetectors. The local expression of IGF-I and -II in the gill was also characterized to provide insight into the possible paracrine action of the GH/IGF axis during SW acclimation. Additionally, the expression patterns of factors proposed to play a role in osmodetection were elucidated and the expressions of ion transporters were measured to clarify the differentiation of specific chloride cell-types. 4.To determine the transcriptional activity and biological effects of mammalian estrogen receptor agonists on three hepatic estrogen receptors in Mozambique tilapia we characterized the roles of estrogen receptors (ERs) in vitellogenin (Vg production) through transactivation assays and an in vivo study utilizing specific agonists for mammalian ERα and ERB, and an antagonist for mammalian ERα propyl pyrazole triol (PPT), diarylpropionitrile (DPN), and Methyl-piperidino-pyrazole (MPP), respectively. Full length sequences of 3 types of ERs were cloned from Mozambique tilapia. To examine these effects we utilized the reporter gene assay using transient transfection. To expand further on the effects of the mammalian ER agonists, PPT and DPN, and antagonist, MPP, in tilapia, an in vivo experiment was conducted. PARTICIPANTS: Individuals: Darren Lerner, PI; Jason Breves, PhD candidate; Lori Davis,Postdoctoral fellow; Anna Koztowny, MS candidate Partner Organizations: University of Tokyo, Ocean Research Institute;University of Hawaii at Hilo, Pacific Aquaculture And Coastal Resources Center Training: These studies are part of the training o=and advancement of one masters student, on PhD student and a postdoctoral fellow in our laboratory. TARGET AUDIENCES: Knowledge gained through this research will be utilized in developing education and outreach activities and leveraged with the PI as a the Associate Director of the University of Hawaii Sea Grant College Program to serve aquaculture farmers in Hawaii, American Samoa and the Republic of the Marshall Islands. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The following are a summary of the results/outcomes of the experiments described in the outputs section: 1. Injection of E2 or NP elicited a classic estrogenic response (increased vitellogenin production) in male Mozambique tilapia regardless of environmental salinity. There was no evidence for an effect of E2 or NP on steady state osmoregulation of fish acclimated to either salinity. NP differentially affected plasma hormones known to affect seawater osmoregulatory ability (GH, IGF-I), but only in freshwater acclimated animals. E2 and NP reduced liver GHR mRNA, which could contribute to the observed decreases in liver IGF-I mRNA. NP increased gill GHR mRNA and IGF-I mRNA. Seawater acclimation may alter the effects of exposure to estrogenic compounds like NP. 2. Results indicated that there was no essential difference in most of the osmotic and endocrine responses between Nile and Mozambiques tilapia despite their contrasting osmoregulatory capacities. The difference in their euryhalinity may be due, at least in part, to the limitation in branchial capacity to excrete excess ions in a hyperosmotic environment, likely due to a limited capacity to produce a sufficient amount of NKCC for the development of SW-type chloride cells. The manuscript resulting from this study was accepted by General and Comparative Endocrinology and is currently in press. 3. Results suggest that expression of GHR, OSTF1 and AQP3 is modulated prior to the systemic hormonal response, suggesting direct effects of salinity on the gill to regulate gene expression. Systemic PRL and GH appear to feedback upon PRLR and GHR expression. In addition, there is no evidence for an increase in local production of IGF-I or -II in the gill during SW acclimation. The rapid changes in gene expression of NKCC and NCC towards the differentiation of chloride cells are in accord with the excellent adaptability of Mozambique tilapia to varying osmotic conditions. Taken together, these results provide the impetus to experimentally link the systemic hormonal response with differentiation of chloride cells during acclimation to FW and SW. A manuscript of this research is under consideration for publication in the Journal of Experimental Biology. 4. This study has demonstrated that, in particular, the mammalian ERβ agonist DPN has the ability to act as a selective ER agonist, likely for ERα, in tilapia. Additionally, PPT does not appear to be a specific agonist for tilapia ERs, while MPP has antagonistic effects on all three ER forms. Given these differences, it is apparent that further characterization of these synthetic compounds is necessary in non-mammalian vertebrates. Nonetheless, the unique effects of PPT, DPN, and MPP on ERs and Vg production in tilapia show promise that these tools, traditionally used in mammalian research, may also help in understanding the important actions of ERs in fishes. A draft manuscript for this study has recently been completed.
Publications
- Davis, L. K., Katsu, Y., Iguchi, T., Lerner, D. T., Hirano, T., Grau, E. G. 2010. Transcriptional activity and biological effects of mammalian estrogen receptor ligands on three hepatic estrogen receptors in Mozambique tilapia. J. Steroid Biochem Mol Biol, 122(4):272-8
- Breves, J. P., Hasegawa, S., Yoshioka, M., Fox, B. K., Davis, L. K., Lerner, D. T. Takei, Y., Hirano, T., and Grau, E. G. 2010. Acute salinity challenges in Mozambique and Nile tilapia: Differential responses of plasma prolactin, growth hormone and branchial expression of ion transporters. Gen Comp Endocrinol. 167:135-142
- Davis, L. K., Fox, B. K., Lim, C., Lerner, D. T., Hirano, T., and Grau, E. G. 2010. Effects of 11-ketotestosterone and fishmeal in the feed on growth of juvenile tilapia (Oreochromis mossambicus) Aquaculture; 305: 143-149
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: To date project funds have been used in partial support for training of a graduate student and postdoctoral student involved with carrying forward experimental design and conducting assays resulting in the first and second years accomplishments and outcomes for this project. We presented a portion of our findings, at the 16th International Congress of Comparative Endocrinology in Hong Kong, held during 22-26 June and the Society for Integrated and Comparative Biology Annual meetings in January 2009 and 2010 in Boston and Seattle, respectively. 1. See previous progress report. 2. See previous progress report and outcomes section this report 3. We have established a time-course of changes during seawater acclimation in plasma levels of osmoregulatory hormones, branchial gene expression of receptors for hormones of the growth hormone family and for glucocorticoid hormones, as well as of expression of putative osmodetectors. The primary goal was to characterize the time-course of changes in both systemic hormones and branchial expression of their cognate receptors during the course of SW acclimation. The local expression of IGF-I and -II in the gill was also characterized to provide insight into the possible paracrine action of the GH/IGF axis during SW acclimation. Additionally, the expression patterns of factors proposed to play a role in osmodetection were elucidated in parallel with these endocrine responses. Lastly, the expressions of ion transporters were measured to clarify the differentiation of specific chloride cell-types during the course of SW acclimation alongside with the systemic hormonal response. 4. We have determined the transcriptional activity and biological effects of mammalian estrogen receptor agonists on three hepatic estrogen receptors in Mozambique tilapia. The aims of this study were to characterize the roles of estrogen receptors (ERs) in vitellogenin (Vg production) through transactivation assays and an in vivo study carried out utilizing specific agonists for mammalian ER alpha and ER beta, and an antagonist for mammalian ER alpha propyl pyrazole triol (PPT), diarylpropionitrile (DPN), and Methyl-piperidino-pyrazole (MPP), respectively. The results describe their effects on gene expression of three ERs and Vgs and on plasma Vg levels after intraperitoneal injection. Full length sequences of 3 types of ERs were cloned from Mozambique tilapia. We utilized the reporter gene assay using transient transfection. To expand further on the effects of the mammalian ER agonists, PPT and DPN, and antagonist, MPP, in tilapia, an in vivo experiment was conducted. PARTICIPANTS: Dr. Darren T. Lerner has supervised a graduate and 2 postdoctoral fellows in conducting the research described in this report. This research has been conducted in collaboration with Drs. Tetsuya Hirano and E. Gordon Grau of the Hawaii Institute of Marine Biology. Drs. Hirano and Grau have provided in kind support including use of laboratory space and equipment as well as intellectual contributions. To date funds for this research have provided partial funding to Jason Breves, and the results will be utilized in partial fulfillment of his Ph.D. dissertation. Funding has also contributed partial support for postdoctoral training for Dr. Lori Davis and Dr Christian Tipsmark. A portion of this research has been conducted in partnership with the Ocean Research Institute, Universty of Tokyo, Tokyo Japan. Both Mr. Breves and Dr. Davis were provided additional educational and career development opportunities through working with our partners in their laboratory at ORI. TARGET AUDIENCES: Information will assist persons engaged in aquaculture. Presentations of findings have been made at two national meetings and one international meeting to disseminate new knowledge in basic biology as well as knowledge that will support the aquaculture industry. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
1. See previous progress report 2. Update: The manuscript resulting from this study was accepted by General and Comparative Endocrinology and is currently in press. 3. The results of this study suggest that expression of GHR, OSTF1 and AQP3 is modulated prior to the systemic hormonal response, suggesting direct effects of salinity on the gill to regulate gene expression. Systemic PRL and GH appear to feedback upon PRLR and GHR expression. In addition, there is no evidence for an increase in local production of IGF-I or -II in the gill during SW acclimation. The rapid changes in gene expression of NKCC and NCC towards the differentiation of chloride cells are in accord with the excellent adaptability of Mozambique tilapia to varying osmotic conditions. Taken together, these results provide the impetus to experimentally link the systemic hormonal response with differentiation of chloride cells during acclimation to FW and SW. A manuscript of this reserach is under consideration for publication in the Journal of Experimental Biology. 4. This study has demonstrated that, in particular, the mammalian ER beta agonist DPN has the ability to act as a selective ER agonist, likely for ER alpha, in tilapia. Additionally, PPT does not appear to be a specific agonist for tilapia ERs, while MPP has antagonistic effects on all three ER forms. Given these differences, it is apparent that further characterization of these synthetic compounds is necessary in non-mammalian vertebrates. Nonetheless, the unique effects of PPT, DPN, and MPP on ERs and Vg production in tilapia show promise that these tools, traditionally used in mammalian research, may also help in understanding the important actions of ERs in fishes. A draft manuscript for this study has recently been completed. Participants: Dr. Darren T. Lerner has supervised a graduate and postdoctoral student in conducting the research described in this report. This research has been conducted in collaboration with Drs. Tetsuya Hirano and E. Gordon Grau of the Hawaii Institute of Marine Biology. Drs. Hirano and Grau have provided in kind support including use of laboratory space and equipment as well as intellectual contributions. To date funds for this research have provided partial funding to Jason Breves, and the results will be utilized in partial fulfillment of his Ph.D. dissertation. Funding has also contributed partial support for postdoctoral training for Dr. Lori Davis and Dr Christian Tipsmark. A portion of this research has been conducted in partnership with the Ocean Research Institute, Universty of Tokyo, Tokyo Japan. Both Mr. Breves and Dr. Davis were provided additional educational and career development opportunities through working with our partners in their laboratory at ORI.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: To date project funds have been used in partial support for training of a graduate student and postdoctoral student involved with carrying forward experimental design and conducting assays resulting in the first years accomplishments and outcomes for this project. The following are the experiments conducted thus far: 1. We examined the effects of nonylphenol (NP) (a xenoestrogen) and estradiol (E2) on the maintenance of osmoregulatory homeostasis and endocrine responses in freshwater (FW) and seawater (SW)-acclimated tilapia. Male fish (~100 g) were acclimated to either FW or 100% SW (35 ppt) for 2 weeks. They were injected with either E2 (5 mg/kg), NP (150 mg/kg), or vehicle (vegetable oil). A second injection was given on day 3, and blood, gill and liver were sampled from all fish on day 6. Radioimmunoassays were conducted for measurement of plasma concentrations of growth hormone (GH), insulin-like growth factor I (IGF-I)and prolactin (PRL). An enzyme-linked immunosorbent assay was conducted to determine plasma concentrations of vitellogenin. A biochemical enzymatic assay was used to determine activity potential for branchial sodium-potassium adenosine triphosphotase activity (NKA). Changes in gene expression of hepatic and branchial GH receptor (GHR) and IGF-I mRNA were measured using quantitative real-time polymerase chain reaction (qrtPCR). 2. In a second experiment we sought to determine whether the contrasting degrees of salinity tolerance between two con-generic tilapiine species (Nile and Mozambique tilapia; NT and MT, respectively) is related to dissimilar abilities to modulate hormonal signaling and osmoregulatory machinery in response to salinity challenges. For this project we have partnered with colleagues at the Ocean Research Institute (ORI) of the University of Tokyo. The graduate and postdoctoral students working on this project were provided an opportunity to travel to ORI to conduct the following experiments on the Nile tilapia, while parallel experiments were conducted on Mozambique tilapia at our laboratory at the Hawaii Institute of Marine Biology. To induce acute salinity challenges, fish were netted from either FW or SW control tanks and transferred to either 50%, 100%, or 200% SW for 1, 2 or 6 hours. Plasma osmolality was measured using a vapor pressure osmometer. Plasma levels of cortisol, IGF-I, PRL and GH was measured by radioimmunoassay. Pituitary mRNA expression of GH, PRL, GHR, PRLR and osmotic transcription factor 1 (OSTF), branchial mRNA expression of IGF-I, PRLR, gluccocorticoid receptor (GR), sodium-potassium-2chloride cotransporter (NKCC), sodium-chloride cotransporter (NCC) and sodium-hydrogen exchanger (NHE3), and hepatic mRNA expression of GHR and IGF-I were be determined by qrtPCR. 3. We have conducted a third experiment designed to establish a time-course of changes during seawater acclimation in plasma levels of osmoregulatory hormones, branchial gene expression of receptors for hormones of the growth hormone family and for glucocorticoid hormones, as well as of expression of putative osmodetectors. Samples for this experiment are currently being assayed. PARTICIPANTS: Dr. Darren T. Lerner has supervised a graduate and postdoctoral student in conducting the research described in this report. This research has been conducted in collaboration with Drs. Tetsuya Hirano and E. Gordon Grau of the Hawaii Institute of Marine Biology, University of Hawaii. Drs. Hirano and Grau have provided in kind support including use of laboratory space and equipment as well as intellectual contributions. To date funds for this research have provided partial funding to Jason Breves, and the results will be utilized in partial fulfillment of his Ph.D. dissertation. Funding has also contributed partial support for postdoctoral training for Dr. Lori Davis. A portion of this research has been conducted in partnership with the Ocean Research Institute, University of Tokyo, Tokyo Japan. Both Mr. Breves and Dr. Davis were provided additional educational and career development opportunities through working with our partners in their laboratory at the Ocean Research Institute. TARGET AUDIENCES: Portions of the data developed thus far have been presented in oral and poster formats at the annual meeting for the Society of Integrative and Comparative Biology in Boston, January 2009 and is scheduled to be presented at the 16th International Congress of Comparative Endocrinology at the University of Hong Kong, Hong Kong, China in June 2009. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The following are the results/outcomes of the experiments described in the outputs section: 1. Treatment with E2 increased plasma vitellogenin 10-fold, while NP-treated fish exhibited a 2-fold increase. Plasma prolactin, GH, IGF-I, chloride, and NKA were not affected at either salinity. E2 treatment reduced liver GH receptor (GHR) and IGF-I mRNA by approximately 50% in FW and SW. NP increased gill GHR 2.5-fold in FW only. Both E2 and NP increased gill IGF-I mRNA 100% over controls in FW. In summary, Injection of E2 or NP elicited a classic estrogenic response (increased vitellogenin production) in male Mozambique tilapia regardless of environmental salinity. There was no evidence for an effect of E2 or NP on steady state osmoregulation of fish acclimated to either salinity. NP differentially affected plasma hormones known to affect seawater osmoregulatory ability (GH, IGF-I), but only in freshwater acclimated animals. E2 and NP reduced liver GHR mRNA, which could contribute to the observed decreases in liver IGF-I mRNA. NP increased gill GHR mRNA and IGF-I mRNA. Seawater acclimation may alter the effects of exposure to estrogenic compounds like NP. 2. Marked increases in plasma osmolality were observed 1 or 2 h after transfer from FW to 200% SW (MT) or from FW to SW (NT). Plasma levels of PRL were significantly higher in FW-acclimated fish than in fish acclimated to SW (MT) or 50% SW (NT); nearly identical patterns were obtained regarding pituitary expression of PRL. Surprisingly, marked increases in plasma PRL were observed 1 h after exposure to 200% SW in MT and 2 h after exposure to SW in NT. There was a significant increase in branchial PRLR mRNA in NT, whereas no change was seen in MT. There was no change in plasma GH levels in MT, whereas significant increases were observed following salinity challenges in NT. No were no significant differences observed in plasma cortisol, pituitary expression of GH or branchial expression of GH and glucocorticoid receptors between the species. Marked increases in branchial expression of OSTF1 were observed in both species following salinity challenges. Branchial expression of NKCC was significantly higher in SW-acclimated MT or 50% SW-acclimated NT compared with FW-acclimated fish. In MT, NKCC mRNA increased dramatically 6 h after transfer from SW to 200% SW. In contrast with this response, NKCC expression in NT was reduced significantly 6 h after transfer from 50% SW to SW. NCC transcripts were significantly lower in SW- or 50% SW-acclimated fish than in FW-acclimated fish in both species. No clear response was observed with respect to NHE3 expression in either species. These results indicate there was no essential difference in most of the osmotic and endocrine responses between the two species despite their contrasting osmoregulatory capacities. The difference in their euryhalinity may be due, at least in part, to the limitation in branchial capacity to excrete excess ions in a hyperosmotic environment, likely due to a limited capacity to produce a sufficient amount of NKCC for the development of SW-type chloride cells.
Publications
- No publications reported this period
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