Phototactic Behavior Of Three Different Nematode Species,and The Reproduction & Development Of Caenorhabditis Elegans Under Light Stress

Bursaphelenchus xylophilus is a type of pathogenic nematode that causes pine wilt disease(PWD).So far,very few researches have been done on its basic biology.We investigated the selectivity and phototaxis of three nematode species which were B.xylophilus,Caenorhabditis elegans and Aphelenchoides besseyi.The phototaxis of three nematode species were examined at different developmental stages by using lights of different wavelengths such as red,orange,yellow,green,white and blue with intensity of 1000 lx,and violet with intensity of 40 lx.We also evaluated the transfer rate of B.xylophilus dauer larvae under the lights of different wavelengths.In addition,the body length,body width and vulva development of C.elegans in response to different lights were also investigated.The results were as follows: 1.At different developmental stages,C.elegans had a strong negative phototaxis response to blueand violet light,but it was rather insensitive to all other lights.2.A.besseyi was insensitive to violet light at all developmental stages,while it had positivephototaxis responses to all other lights.The phototaxis radio of A.besseyi gradually increased withaging.More interesting,the second and third juveniles of A.besseyi had a remarkable phototaxistowards blue light.3.B.xylophilus exhibited a strong negative phototaxis to the violet light,but had obvious positivephototaxis responses to all other lights including the blue light.Moreover,B.xylophilus dauerlarvae had strong negative phototaxis to red,green,yellow,blue,orange,violet and white lights.4.Illumination could inhibit B.xylophilus dauer larvae transfer from Monochamus alternatus to freshpine trees or branches.The transfer rate of B.xylophilus dauer larvae from M.alternatus inillumination condition was much lesser than in dark condition.In dark condition,the transfer ratewas about 39.75% ± 1.44%.While the transfer rate dropped to5.93%± 0.10%,4.23 ± 0.12%and1.68%±0.17% under the green,white and blue light respectively.5.Illumination could inhibit C.elegans development.In illumination,the body length and width of C.elegans were significantly shorter when compared with the C.elegans cultured in the dark.Thevulva development was at a significantly slower rate in C.elegans that were cultured inillumination.The strongest inhibitions of C.elegans development were observed under the violetand blue lights,followed by the green light.The inhibition was much weaker under the red,orange,green,yellow and white lights.Violet light could induce malformation in C.elegans.In addition,prolong exposure under the blue and violet lights could kill the C.elegans.6.Illumination could reduce the reproductive ability of C.elegans.The fecundity rate of C.eleganswas significantly lower in illumination condition than in dark.The number of egg laying in darkcondition was 41±8.50,while the number dropped to 9.50±1.66,10.75±1.80,9.00±1.08,12.75±1.70 and 10.00±2.08 under the stress of red,orange,yellow,green and white light respectively.