At a concentration of approximately 8 ppm, naphthalene inhibited circadian black pigment dispersion in the integumentary chromatophores of the fiddler crab no matter what the initial state of the black pigment. The inhibition was concentration dependent. Naphthalene was not toxic to fiddler crabs under these conditions at any concentration up to 16.69 ppm. Naphthalene has no effect on the black chromatophores themselves. The black chromatophores in naphthalene exposed crabs disperse to a point equal to controls when injected with an eyestalk extract. Naphthalene, then must act somewhere in the central nervous system. Eyestalk extracts made from naphthalene exposed crabs show that these crabs have functional black pigment dispersing hormone (BPDH), but more of it is stored in the eyestalk neurosecretory apparatus than in the control crabs. It appears that naphthalene acts to decrease black pigment dispersion during the dark phase of the Circadian rhythmn by inhibiting the release of BPDH. This hypothesis is strengthened by the finding that BPDH activity stored in the eystalks of naphthalene exposed crabs can be released by exogenous norepinephrine (NE) No chemically induced phase shift in the circadian rhythm of naphthalene exposed crabs occurs. In addition there is no difference in the mean black chromatophore index at midnight between control and naphthalene exposed crabs, indicating that the release of black pigment concentrating hormone (BPCH) is not being influenced by naphthalene. The only possibility remaining is that naphthalene must interfere with some aspect of the control of BPDH release by NE. Exposure to naphthalene does not inhibit black pigment dispersion when crabs are placed on a black background or kept on a black background throughout the experiment. This argues against naphthalene acting to inhibit the synthesis of NE, or to promote its metabolism, since NE is involved in adaptation to a black background. Naphthalene, therefore, must act to prevent the release of BPDH by interfering with some aspect of the presynaptic control of BPDH release by NE / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_25329 |
| Date | January 1983 |
| Contributors | Staub, Gregory Cyril (Author) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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