These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: A latitudinal cline in the efficacy of endogenous signals: evidence derived from retinal cone contraction in fish.
    Author: Yammouni R, Bozzano A, Douglas RH.
    Journal: J Exp Biol; 2011 Feb 01; 214(Pt 3):501-8. PubMed ID: 21228209.
    Abstract:
    Like many physiological systems synchronised to the light:dark cycle, retinomotor movements in 'lower' vertebrates are controlled by both the ambient illumination and input from endogenous circadian oscillators. In the present study, we examine the relative influence of these two signals in various species of teleost fish with different latitudes of origin. We find equatorial species show very strong endogenous control. The cones of the glowlight tetra, for example, continue to go through undiminished cycles of contraction and relaxation that mirror the previous light:dark cycle for at least two weeks in continual darkness. To quantify the relative effectiveness of the ambient light compared with endogenous signals in causing cone contraction, the degree to which seven teleost species responded to light during the dark phase of their light:dark cycle was examined. In this situation the retina receives conflicting instructions; while the light is acting directly to cause light adaptation, any endogenous signal tends to keep the retinal elements dark adapted. The further from the equator a species originated, the more its cones contracted in response to such illumination, suggesting animals from higher latitudes make little use of endogenous oscillators and rely more on ambient illumination to control behaviours. Equatorial species, however, rely on internal pacemakers to a much greater degree and are relatively insensitive to exogenous light signals. Because these data are consistent with published observations in systems as diverse as melatonin synthesis in Arctic reindeer and the behaviour of regional populations of Drosophila, latitudinal clines in the efficacy of circadian oscillators may be a common feature among animals.
    [Abstract] [Full Text] [Related] [New Search]