Analysis of phototaxis in nemato des using directional statistics
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The direction of horizontal movement of 2 nematode species with eyespots was observed both with and without directional sources. The results comprise statistical proof of phototaxis in nematodes and demonstrate the usefulness of directional statistics in evaluating and comparing the responses.
Two directional sources were tried, one including all the visible spectrum but red (“blue source”) and one containing only red. Both species had a significant tendency to move in the direction away from the blue source (0°), whereas the directions taken under control conditions were not significantly different from random (Fig. 2, and Table 2). A tendency to move away from the red source was significant forOncholaimus vesicarius but not forEnoplus anisospiculus.
Bimodal distributions with <90° between the modes occurred in at least 2 cases (Fig. 2, Table 3) and their statistical treatment is illustrated and discussed.
The component of the mean direction along the 0° direction,rc, was significantly greater forO. vesicarius than forE. anisospiculus. However a measure of the tendency to move horizontally indicated no significant difference between species. Therefore the difference inrc is probably not due to a difference in motivation. A difference in steering strategy is suggested by a negative correlation betweenr c and the angle between modes.
The results are interpreted in terms of ocellus morphology and possible steering strategies.
KeywordsNegative Correlation Statistical Treatment Visible Spectrum Bimodal Distribution Horizontal Movement
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- Batschelet, E.: Statistical methods for the analysis of problems in animal orientation and certain biological rhythms. Washington, D.C.: American Institute of Biological Sciences 1965Google Scholar
- Batschelet, E.: Recent statistical methods for directional data. In: Animal orientation and navigation. Galler, S.R., Schmidt-Koenig, K., Jacobs, G.J., Belleville, R.E. (eds.), pp. 61–91. Washington, D.C.: National Aeronautics and Space Admin. 1972Google Scholar
- Bollerup, G., Burr, A.H.: Eyespot and other pigments in nematode esophageal muscle cells. Can. J. Zool.57, 1057–1069 (1979)Google Scholar
- Burr, A.H., Burr, C.: The amphid of the nematodeOncholaimus vesicarius: Ultrastructural evidence for a dual function as chemoreceptor and photoreceptor. J. Ultrastruct. Res.51, 1–15 (1975)Google Scholar
- Burr, A.H., Webster, J.M.: Morphology of the eyespot and description of two pigment granules in the esophageal muscle of a marine nematode,Oncholaimus vesicarius. J. Ultrastruct. Res.36, 621–632 (1971)Google Scholar
- Chitwood, B.G., Murphy, D.G.: Observations on two marine monhysterids — their classification, cultivation and behavior. Trans. Am. Microsc. Soc.83, 311–329 (1964)Google Scholar
- Cochran, W.G.: Some methods for strengthening the common chi2 tests. Biometrics10, 417–451 (1954)Google Scholar
- Croll, N.A.: The phototactic response and spectral sensitivity ofChromadorina viridis (Nematoda, Chromadorida) with a note on the nature of the paired pigment spots. Nematologica12, 610–614 (1966)Google Scholar
- Croll, N.A., Riding, I.L., Smith, J.M.: A nematode photoreceptor. Comp. Biochem. Physiol. (A)42, 999–1009 (1972)Google Scholar
- Croll, N.A., Evans, A.A.F., Smith, J.M.: Comparative nematode photoreceptors. Comp. Biochem. Physiol. (A)51, 139–143 (1975)Google Scholar
- Durand, D., Greenwood, J.A.: Modifications of the Rayleigh test for uniformity in analysis of two-dimensional orientation data. J. Geol.66, 229–238 (1958)Google Scholar
- Epp, R.J., Tukey, J.W., Watson, G.S.: Testing unit vectors for correlation. J. Geophys. Res.76, 8480–8483 (1971)Google Scholar
- Hand, W.G.: Phototactic orientation by the marine dinoflagellateGyrodinium dorsum Kofoid. I. A mechanism model. J. Exp. Zool.174, 33–38 (1970)Google Scholar
- Jones, T.A., James, W.R.: Analysis of bimodal orientation data. Int. Assoc. Math. Geol. J.1, 129–135 (1969)Google Scholar
- Keeton, W.T., Brown, A.I.: Homing behavior of pigeons not disturbed by application of an olfactory stimulus. J. Comp. Physiol.105, 259–266 (1976)Google Scholar
- Mardia, K.V.: Statistics of directional data. London: Academic Press (1972a)Google Scholar
- Mardia, K.V.: A multi-sample uniform scores test on a circle and its parametric competitor. J. R. Stat. Soc. B34, 102–113 (1972b)Google Scholar
- Mardia, K.V., Spurr, B.D.: Multisample tests for multimodal and axial circular populations. J. R. Stat. Soc. (B)35, 442–436 (1973)Google Scholar
- Mardia, K.V., Sutton, T.W.: On the modes of a mixture of two von Mises distributions. Biometrika62, 699–701 (1975)Google Scholar
- Siddiqui, I.A., Viglierchio, D.R.: Ultrastructure of photoreceptors in the marine nematodeDeontostoma californicum. J. Ultrastruct. Res.32, 558–571 (1970)Google Scholar
- Stephens, M.A.: Tests for randomness of directions against two circular alternatives. J. Am. Stat. Assoc.64, 280–289 (1969)Google Scholar
- Stephens, M.A.: Multisample tests for the von Mises distribution. J. Am. Stat. Assoc.67, 456–461 (1972)Google Scholar
- Taliaferro, W.H.: Reactions to light inPlanaria maculata, with special reference to the function and structure of the eyes. J. Exp. Zool.31, 59–116 (1920)Google Scholar
- Watson, G.S.: Goodness of fit tests on a circle. Biometrika48, 109–114 (1961)Google Scholar
- Watson, G.S.: Goodness of fit tests on a circle. II. Biometrika49, 57–63 (1962)Google Scholar
- Watson, G.S.: The statistics of orientation data. J. Geol.74, 786–794 (1966)Google Scholar
- Zar, J.H.: Biostatistical analysis. Englewood Cliffs, N.J.: Prentice-Hall 1974Google Scholar