Thursday, 4 December 2014

Talk : Reproduction in Bedbugs

Interesting Cafe Sci talk recently by Professor Michael T Siva-Jothy from the Dept of Animal and Plant Sciences at the University of Sheffield. Prof Siva-Jothy talked on the topic of bedbugs!

This post covers some of what was covered in the talk (and the fascinating Q&A afterwards), together with a little extra linkage thrown in..

Prof Siva-Jothy began by explaining many of the extreme body forms found in nature were due to sexual selection, for example, the tail of the male Peacock, or the remarkable Peacock Spider.

It turns out that Bedbugs are another example of this type of selection.

In the case of Bedbugs, the male penis has evolved to have a shape similar to that of a hypodermic needle. This is because the male impregnates the female not via the usual route but instead by stabbing her in the abdomen. The sexual anatomy of Bedbugs is described (and illustrated) more fully in this article and also here. Incidentally, this type of sex is know as "Traumatic Insemination".

Quality reposte from Prof Michael Siva-Jothy

Prof Siva-Jothy described how on the one hand this form of insemination resulted in a shorter lifespan for the female; whilst on the other hand it was accompanied by a "donation" of Vitamin B from the male (something Bedbugs cannot make themselves) and that the male sperm delayed the onset of female menopause and allowed the females to lay more eggs overall.

The Prof went on to describe how he had been part of a team that had undertaken fieldwork in Kenya where they had looked for species of African "Batbug". This was based on research in the 1930s that had identified a number of caves in the area that contained species similar to Bedbugs. Unfortunately, the team discovered that in the intervening decades the local population had DDT'ed the insect population of most of these caves so that they (the people, not the bugs) could extract the bat guano that was there. Populations of Batbugs remained in only the most remote caves, such as those at Mount Elgon. The research is summarised in this National Geographic article.

The Q&A
As is often the case at Cafe Sci, the Q&A was just as fascinating as the main talk....

Prof Siva-Jothy commented that, before WW2, bedbugs were a fact of life in many countries, including the UK and that management of bedbugs, rather than their elimination, was usually the approach that was taken. Crevices in wooden furniture and beds was a particularly popular home for bedbugs. It was to combat this that the metal hospital beds were introduced; they provided few hiding places for bedbugs and could easily be treated with boiling water as a further precaution. Similarly, many hospitals and hotels built in the 1930s used metal framed windows and mimimalist features to reduce the number of possible bedbug hiding places. This all changed at the end of WW2 when DDT was introduced - it was a devastatingly effective insecticide and bedbugs were soon virtually eliminated from homes, hotels and hospitals through its use.

Indeed, the Prof described how some of his team had gone to the centre of Sheffield and asked people if they recognised a particular smell (which was the characteristics coriander-like smell of of bedbugs) and found that those who had been aged 10 or more at the end of WW2 recognised it immediately while those who were younger had no idea what it was.

But, in more recent times, bedbugs have started to build up immunity to insecticide effects, and infestations have again become a serious problem in many countries, especially the US. The whole story of the battle against bedbugs is told in this fascinating article by AE Potter.

A bedbug

The Prof explained how, for most insects, developing resistance to insecticides imposes a biological cost and colonies kept in a lab lose their immunity over a few generations because of this. In contrast, bedbug populations that have been kept in labs for 60 years still retain their insecticide resistance, suggesting that, for bedbugs, the immunity has a very low biological cost.

Perhaps the most practical place to end this post is with this NHS advice on bedbugs.

Related Links
Dr Sara Goodacre on Spiders
Dr Duncan Cameron on Soil Science
Dr Helen West on Dung Beatles

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