Behavioral and Neuroendocrine Correlates of Sex Change in the Gilthead Seabream (Sparus aurata)

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dc.contributor.advisorZohar, Yonathanen_US
dc.contributor.authorReyes-Tomassini, Jose J.en_US
dc.contributor.departmentMarine-Estuarine-Environmental Sciencesen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2009-11-13T06:30:34Z
dc.date.available2009-11-13T06:30:34Z
dc.date.issued2009en_US
dc.description.abstractSequential hermaphroditism is the most radical form of environmental sex determination observed in fish: functional adult males or females retain their ability to change sex even as adults. Among the factors that affect sex change in these species, the least understood is the social environment. Here, I studied the influences of social context on sex change in the Gilthead Seabream, Sparus aurata, by using the individual‟s dominance rank as an indicator of social status. To understand the role that the brain might play in sex change, I also studied the two main neuroendocrine factors that serve as the sexually differentiated axes of neural plasticity in most teleost species: AVT and GnRH. To do this, I first developed a set of tools designed to address the challenges associated with observing the behavior of aquacultured species. Using these tools, I provide the first in-depth study of seabream captive behavior, including the results of size-matched and sex-matched paired encounters. I found that females are more aggressive than males, but this difference is influenced by gonadal developmental status. I also showed that small but young males are more aggressive than bigger but older females. I cloned the AVT mRNA in seabream, and validated a quantitative assay to measure total brain AVT levels together with GnRH-1, GnRH-2, and GnRH-3 levels. I found that AVT and GnRH-3 levels rise during the onset of the hypothesized sex-change window, and drop to pre-quiescent levels until spawning, when all of these factors seem to increase their expression levels again. I also show for the first time, that GnRH-2 and dominance rank are strongly correlated in seabream during the spawning season but not during quiescence. GnRH-1 was strongly correlated to rank during quiescence but not during spawning. Finally, neither dominance rank nor size were a good predictor of the outcome of sex change, which seems to contradict what has been documented in sequential hermaphrodite reef fishes. I provide a model that accounts for this apparent contradiction and conclude that the Gilthead seabream remains true to the size-advantage hypothesis of sex allocation theory, if size and dominance are seen as proximate, rather than ultimate, factors.en_US
dc.identifier.urihttp://hdl.handle.net/1903/9721
dc.subject.pqcontrolledAgriculture, Fisheries and Aquacultureen_US
dc.subject.pqcontrolledBiology, Animal Physiologyen_US
dc.subject.pqcontrolledBiology, Molecularen_US
dc.subject.pquncontrolledAnimal Behavioren_US
dc.subject.pquncontrolledAVTen_US
dc.subject.pquncontrolledColor Changeen_US
dc.subject.pquncontrolledEndocrinologyen_US
dc.subject.pquncontrolledGnRHen_US
dc.subject.pquncontrolledImage Analysisen_US
dc.titleBehavioral and Neuroendocrine Correlates of Sex Change in the Gilthead Seabream (Sparus aurata)en_US
dc.typeDissertationen_US

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