Date of Award

2011

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

First Advisor

Zielinski, Barbara (Biological Sciences)

Keywords

Biology, Animal Physiology.

Rights

CC BY-NC-ND 4.0

Abstract

Fishes widely employ the olfactory sense for communication in most aspects of their life. The olfactory system of fishes contains olfactory sensory neurons (OSNs) of three polymorphisms – ciliated, microvillous and crypt. This thesis describes various studies of the properties of OSNs, from the expression of polymorphisms to odour responses, receptor specificity and second messengers, in two species of invasive fish: the sea lamprey (Petromyzon marinus) and the round goby (Neogobius melanostomus). I describe, for the first time, the expression of ciliated OSNs displaying polymorphisms in the sea lamprey, an ancient jawless fish. In the round goby, I investigate the olfactory properties of several steroids that have been identified as released by the reproductive male (RM) round goby and are putative pheromones. Female gobies detect the novel steroids 11-oxo-etiocholanolone (11-O-ETIO) and 11-O-ETIO-3-sulfate, but not 11-O-ETIO-17-sulfate or 11-O-ETIO-3-glucuronide. In addition, these steroids act upon separate olfactory receptor mechanisms and are transduced via both cAMP and IP3. Female electro-olfactogram resposnes to methanol-extracted steroids from RM conditioned water increased following treatment of the RM with gonadotropin releasing hormone, but not saline. In addition, there was a correlation between female reproductive status (as measured by gonadosomatic index) and response to NRM (but not RM) urine. We tested the possible modulation of olfactory responses by prostaglandin F2α (PGF2α). Perfusing PGF2α directly over the olfactory epithelium had no effect on olfactory responses. Olfactory responses had a tendency to increase 40 minutes following injection with PGF2α, although this was not a significant change. To investigate the possibility that RMs release pheromones with endocrinological effects, we measured female testosterone release following exposure to RM or NRM conditioned water and found that testosterone was unaffected by exposure to male odours. This thesis describes olfactory properties for two fish species of ecological and taxonomic importance. We conclude that these studies of wild fish make important contributions to the field of fish olfactory biology, which is lacking in studies investigating core olfactory biological properties in fish of diverse taxonomic groups or in wild-caught populations.

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