September 26, 2013

The sounds emited by microgastrine wasps

From 2002 to 2005 I worked as an entomologist for a natural history museum in Cuba, and as part of that I was lucky to participate in a number of field expeditions to many special places of the island. Among the colleagues I shared time with during those expeditions, a significant number devoted themselves to the study of sounds emitted by all kinds of animals -mostly birds, amphibians, and bats. The use of advanced technology to record those sounds, and the "scientific paraphernalia" (=equipment) surrounding those efforts made those  researchers the absolute mega-stars of the expeditions. Local guides and farmers would die for a chance to try the microphones, listen to the songs recorded, see the sinusoid waves in the computer screens... in comparison, my entomological net was of not interest whatsoever. Who cares about those minuscule parasitoid wasps? They were not only small and of rather dull coloration, but on top of that they could not even emit any interesting sound! 

I confess I was a bit jealous because of this. But there was nothing that could be done, so I continued setting up my (boring) Malaise traps, my (boring) yellow pan traps, and doing my (boring) sweeping to collect those (boring) parasitoid wasps. Oh well...

More than eight years later, I suddenly found myself enjoying those memories while reading an interesting paper published in 2013 in PLOS ONE. The title attracted me from the very beginning: Characterization and generation of male courtship song in Cotesia congregata (Hymenoptera: Braconidae). So, there were actually sounds emitted by small parasitoid wasps! Courtship songs! And I could even find the familiar sound waves in the paper, just like those of a showy bird or a charismatic frog. Wow!

One of the figures of the PLOS ONE paper mentioned. The caption of the original figure actually reads: "Figure 1. Oscillograph of typical male courtship song of Cotesia congregata with a buzz followed by boings.(A) Complete song. (B) Expanded selection of initial buzz. (C) Expanded selection of four boings illustrating the initial high amplitude component followed by a lower amplitude terminal buzz and short gap.doi:10.1371/journal.pone.0062051.g001"

What is more, the paper included among its Supporting Information one audio-recording and two high-speed videos of the courtship song of a male of Cotesia congregata. This was for me mind-boggling, and listening and watching to that small wasp while "singing" was certainly a thing of beauty... But I may be a bit biased here, of course. I only wish my former colleagues were now near me, to be able to tell them: Take THAT! :)

But, beyond funny memories, it made me look for more information. Parasitoid wasps have been long known to produce sounds. The earliest paper in the scientific literature I could find was from 40 years ago, and it dealt with an ichneumonid wasp (Vinson S.B. 1972: Courtship behavior and evidence of a sex pheromone in the parasitoid Campoletis sonorensis (Hymenoptera: Ichneumonidae). Environ Entomol 1: 409–414). 

The earliest paper that specifically referred to sounds emitted by a microgastrine wasp was published 20 years ago (Field S.A. Keller M.A. 1993: Courtship and intersexual signaling in the parasitic wasp Cotesia rubecula (Hymenoptera: Braconidae). J Insect Behav 6: 737–750. doi: 10.1007/BF01201673). After that, there have been a handful of papers (mostly but not exclusively using the genus Cotesia as a model) published. The last one from PLOS ONE is the icing on the cake, but hopefully more studies on the topic will follow. Sounds in these wasps are mainly related to mating. The dynamic of sound transmission, and its effects on the behaviour of both male and female wasps, is nothing short of remarkable.

It is evident that I am way behind in the knowledge of this topic. Sometimes we, taxonomists, focus on some aspects of "our" group/species, and forget to look around and gather tons of useful information and data that are already available in other fields of study (Ecology, Behaviour, Physiology, Chemistry, etc). They are not necessarily published in taxonomic journals, but are nevertheless of capital importance.

If anything, I learned that I should make more efforts to read about those approaches -and hopefully use that information more often. And I confirmed, once again, the sad feeling that I know barely nothing about microgastrine wasps. 

Hopefully now I will pay more attention to the sound of the parasitoid wasps...

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