Name: observation and quantification of mating behavior in the pinewood nematode, bursaphelenchus xylophilus
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Description: Watch this Scientific Journal Video about Observation and Quantification of Mating Behavior in the Pinewood Nematode, Bursaphelenchus xylophilus at JoVE.com

Najie Zhu and Liqun Bai contributed equally to this work. This work was financially supported by the Special Fund for Forestry Scientific Research in the Public Welfare (201204501) and the National Natural Science Foundation of China (31170604, 31270688, and 31570638). We thank Dr. Holighaus Gerrit and Dr. Danielle Hickford for their helpful suggestions on English writing.

1. Acquisition of Virgin Adult Nematodes
<ol>
	<li>Pinewood nematode isolate and culture conditions 
	NOTE: The B. xylophilus isolate Nxy61 was originally extracted from a diseased Pinus massoniana in the Ningbo area of Zhejiang province in China.
	<ol>
		<li>Prepare Potato Dextrose Agar (PDA, See Table of Materials) plates for growing Botrytis cinerea. </li>
		<li>For inoculation, punch a piece of fungal mat with diameter of 10 mm from a B....

<ol>
	<li>Tokushige, Y., Kiyohara, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bursaphelenchus+sp.+in+the+wood+of+dead+pine+trees.">Bursaphelenchus sp. in the wood of dead pine trees.</a> J. Jap. For. Soc. 51, 193-195 (1969).</li><li>Sun, Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bursaphelenchus+xylophilus+was+discovered+in+Sun+Yet-sen's+mausoleum+in+Nanjing.">Bursaphelenchus xylophilus was discovered in Sun Yet-sen's mausoleum in Nanjing.</a> J. Jiangsu Fore. Sci. Tech. (in Chinese). 4, 47 (1982).</li><li>Mota, M. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+report+of+Bursaphelenchus+xylophilus+in+Portugal+and+in+Europe.">First report of Bursaphelenchus xylophilus in Portugal and in Europe.</a> Nematology. 1, 727-734 (1999).</li><li>Robertson, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incidence+of+the+pine+wood+nematode+Bursaphelenchus+xylophlius+Steiner+&amp;+Buhrer,+1934+(Nickle,+1970)+in+Spain.">Incidence of the pine wood nematode Bursaphelenchus xylophlius Steiner &amp; Buhrer, 1934 (Nickle, 1970) in Spain.</a> Nematology. 13, 755-757 (2011).</li><li>Vicente, C., Espada, M., Vieira, P., Mota, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pine+wilt+disease:+a+threat+to+European+forestry.">Pine wilt disease: a threat to European forestry.</a> Euro. J. Plant Path. 133, 89-99 (2012).</li><li>Jones, J. T., Moens, M., Mota, M., Li, H., Kikuchi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bursaphelenchus+xylophilus:+opportunities+in+comparative+genomics+and+molecular+host-parasite+interactions.">Bursaphelenchus xylophilus: opportunities in comparative genomics and molecular host-parasite interactions.</a> Mol. Plant. Path. 9, 357-368 (2008).</li><li>Mamiya, Y., Furukawa, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fecundity+and+reproduction+of+Bursaphelenchus+lignicolus.">Fecundity and reproduction of Bursaphelenchus lignicolus.</a> Jap. J. Nemat. 7, 6-9 (1977).</li><li>Mamiya, Y., Kiyohara, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Description+of+Bursaphelenchus+lignicolus.+n.+sp.+(Nematoda:+Aphelenchoididae)+from+pine+wood+and+histophathology+of+nematode-infested+trees.">Description of Bursaphelenchus lignicolus. n. sp. (Nematoda: Aphelenchoididae) from pine wood and histophathology of nematode-infested trees.</a> Nematologica. 18, 120-124 (1972).</li><li>Liu, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavioural+features+of+Bursaphelenchus+xylophilus+in+the+mating+process.">Behavioural features of Bursaphelenchus xylophilus in the mating process.</a> Nematology. 16, 895-902 (2014).</li><li>Simon, J. M., Sternberg, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+a+mate+finding+cue+in+the+hermaphrodite+nematode+Caenorhabditis+elegans.">Evidence of a mate finding cue in the hermaphrodite nematode Caenorhabditis elegans.</a> Proc. Natl. Acad. Sci. USA. 99, 1598-1603 (2002).</li><li>Barr, M. M., Garcia, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Male+mating+behaviour.">Male mating behaviour.</a> The C. elegans Research Community Wormbook. , (2006).</li><li>Shinya, R., Chen, A., Sternberg, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sex+attraction+and+mating+in+Bursaphelenchus+okinawaensis+and+B.+xylophilus.">Sex attraction and mating in Bursaphelenchus okinawaensis and B. xylophilus.</a> J. Nematol. 47 (3), 176-183 (2015).</li></ol>

Behavioral tests are a fundamental aspect of chemical ecology, neurobiology, molecular biology, and genetics. Nematodes, and particularly C. elegans, are extensively used for studies in these areas. The mating behavior of C. elegans has been investigated previously10-11. However, B. xylophilus is gonochoristic and different from the hermaphroditic C. elegans, and its mating process has different behavioral features9. Recently, the mating behavior of Bursaphele...

The pinewood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, is one of the most destructive invasive species, causing the wilting and eventual death of pine trees. This pathogenic nematode is believed to be native to the USA, but it was transported to several countries, including China, Japan, South Korea, and Portugal. Recently, it has also been reported in Spain, killing millions of pine trees at huge economic losses and threatening forest production and ecological stability1-5.
Once a host pine tree is infected by pinewood nematodes, thousands of millions of offspring are propagated rapidly within the trunk. This causes xylem dysfunction, resulting in wilting and eventually in the death of the host tree6. However, there is currently no efficient way to control this disease. Mating behavior might play an important role in the high fecundity of this nematode7. We therefore investigated the mating behavior of B. xylophilus in the laboratory, trying to find an effective way of disturbing its mating and decreasing its fecundity. 
This protocol is intended to introduce the detailed methods of how to obtain the virgin adults of B. xylophilus and how to observe and analyze the mating behavior using a video recorder and a stereomicroscope. This protocol can also be used as a reference for behavioral studies of other nematodes.

<table border="0" cellpadding="0" cellspacing="0" width="944">
	<tbody>
		<tr height="18">
			<td height="18" style="height:18px;width:233px;">B. xylophilus isolate Nxy61</td>
			<td style="width:123px;"></td>
			<td style="width:125px;"></td>
			<td style="width:463px;">Extracted from Pinus massoniana in Ningbo area of China</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Grey mold strain</td>
			<td></td>
			<td></td>
			<td>Obtained from Forestry Academy of China</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Baermann funnels</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">falcon tubes</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">centrifuge</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">pipette</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">sterile dd H2O</td>
			<td></td>
			<td></td>
			<td>Sterilized by high pressure of steam at 121&#176;C for 30 min.</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Petri dishes</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PDA medium</td>
			<td>Huankai Bio.</td>
			<td>021050</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">incubator</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Laminar flow</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">glass capillary</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Stereoscope</td>
			<td>Leica</td>
			<td>LED5000 RL</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">inverted stereo microscope</td>
			<td>Zeiss</td>
			<td>A1</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">concave slides</td>
			<td>Sengong</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

observation and quantification of mating behavior in the pinewood nematode, bursaphelenchus xylophilus

A method for observing and quantifying the mating behavior of the pinewood nematode, Bursaphelenchus xylophilus, was established under a stereomicroscope. To improve the mating efficiency of B. Xylophilus and to increase the chances of mating observation, virgin adults were cultured and used for the investigation. Eggs were obtained by keeping the nematodes in water and allowing the females to lay eggs for 10 min. The second-stage juveniles (J2) were synchronized by incubating the eggs for 24 h at 25 &#176;C in the dark, and the early J4 were obtained by culturing the J2 with grey mold, Botrytis cinerea, for another 52 h. At this time point, most J4 nematodes could be clearly distinguished as being male or female using their genital morphology. The male and female J4 were collected and cultured separately in two different Petri dishes for 24 h to get virgin adult nematodes. A virgin male and a virgin female were paired in a drop of water in the well of a concave slide. The mating behavior was filmed with a video recorder under a stereomicroscope. The whole period of the mating process was 82.8 &#177;3.91 min (mean &#177;SE) and could be divided into 4 different phases: searching, contacting, copulating, and lingering. The mean minutes of duration were 21.8 &#177; 2.0, 28.0 &#177; 1.9, 25.8 &#177; 0.7 and 7.2 &#177; 0.5, respectively. Eleven sub-behaviors were described: cruising, approaching, encountering, touching, hooping, locating, attaching, ejaculating, separating, quiescence, and roaming. Interestingly, obvious intra-sexual competition was observed when one female was grouped with 3 males or one male with 3 females. This protocol is useful and valuable, not only in investigating the mating behavior of B. xylophilus, but also in acting as a reference for ethological studies of other nematodes.

The mating success rate (R) of virgin adults was 86.67% on average, which was significantly higher than that of the randomly selected adults: 13.33&#160;&#177; 4.65% (F = 1301.71, df = 1, P = 0.0001) (Figure&#160;2). This finding suggests that it is easier to observe the mating behavior of B. xylophilus with virgin adults than with randomly selected adults.
When one male was paired wit...

Watch this Scientific Journal Video about Observation and Quantification of Mating Behavior in the Pinewood Nematode, Bursaphelenchus xylophilus at JoVE.com

Observation and Quantification of Mating Behavior in the Pinewood Nematode, Bursaphelenchus xylophilus

A protocol for investigating the mating behavior of the pinewood nematode, Bursaphelenchus xylophilus, is presented. Behavioral features of B. xylophilus are described in the mating process.

Observation and Quantification of Mating Behavior in the Pinewood Nematode, Bursaphelenchus xylophilus

A method for observing and quantifying the mating behavior of the pinewood nematode, Bursaphelenchus xylophilus, was established under a stereomicroscope. ...

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