Universiteit Leiden

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Corné van der Linden

Students solve spider mystery in Borneo

They sprayed with corn starch and made detailed drawings of the genitalia of spiders. In different ways students studied spiders in the dense tropical rainforest of Borneo. With their work they solved a spider mystery and published about this in Biodiversity Data Journal in April.

Unknown male spider in web of female

Every two years students from Leiden University go to the rainforests of Borneo. The expedition of 2018 resulted in an unexpected spin-off. During a walk through the jungle of Malaysian Borneo, students found a spiderweb with on it the female spider Opadometa sarawakensis. In the same web they discovered a male spider. But the male of that species was not yet described in scientific literature. Would the two found spiders belong to the same species?

Males difficult to match

Unlike the female, the male had no striking colours, the students noticed. It was also a lot smaller. ‘Because of big differences between the sexes, the genus Opadometa is known to be difficult to match with the females’, biologist and course leader Jeremy Miller explains. He thought the finding of the mysterious male spider was a nice opportunity for the students of the course Tropical Biodiversity and Field Methods. ‘I thought it would be informative for the students to see how a scientific publication is formed.’ With the help of researchers and other students in the Danau Girang Field Centre (DGFC), students described the found individuals.

Scary

‘The students were very dedicated, and some performed research day and night to find extra data’, Miller tells enthusiastically. One of these fanatics was masterstudent Biology Lianne Koet. ‘It was interesting and instructive, but most of all fun. In the jungle we searched for spiderwebs by spraying corn starch. This makes the webs more visibile. When we found a web, we studied it and caught the spider for identification. When we found a big spider in a web, we were happy, but secretly also scared to catch it. We found out later that it was even still a young individual!’

Improvise

Next to the fieldwork, a lot of work had to be done inside the field station. The lecturers challenged the students to think of creative solutions, Miller explains, because in the tropics resources are limited. ‘Some students developed their own method to make high quality photos of the tiny male. With the help of a mobile phone and an external lens’, Miller tells proudly. In addition, another student made scientific drawings of the sex organs.

Possibilities for DNA research were not yet available in the field station. ‘DNA analysis is a relatively new development in the more than 250-year history of biodiversity research. At the moment researcher and founder of this course Menno Schilthuizen is exploring the possibilities of the portable and quick DNA sequencing device MinION in the field.’

Research in action

In the end the researchers and students concluded that the female and male belong to the same species. Because the male was found in the web of the female, and because there were no other spiders of the Opadometa genus found during the surveys. They processed this conclusion into an article, which also contains an extensive description of the found specimens. During the closing day they submitted it to Biodiversity Data Journal. A month later the article was published.

Benoît Goossens, director of DGFC is enthusiastic about the publication. ‘I think it is great that students were involved in the description of the spider during the course. This is research in action and shows what we can accomplish with our field station. There is still that we do not know about the tropical rainforests and so there are many wonders that have not been discovered yet.’