August 8th, 2006

[ waldo ]


I missed several seminars hosted by the departments of entomology and evolutionary biology last semester due to an increasingly busy schedule, and just last week I was lamenting how there were no guest presentations at the university to coincide with my freedom from regular classes. Imagine my surprise then when an email arrived over the weekend announcing an entomology seminar on the subject of "Heterochrony and Modularity of Caste Polyphenisms in Termites" presented by Dr. Toru Miura of Hokkaido University. Despite the complexity of its title the seminar wasn't too extraordinarily hard to follow. Plus, unlike the aging professor I had envisioned, the afternoon's speaker looked to be in his mid-20s with dyed hair, a piercing or two, and clothes that looked more appropriate on a skateboarder than an assistant professor heading his own research team.

Miura's research focuses on the environment's role in influencing developmental plasticity (the flexibility of an organism's growth and maturation) within termite species and the genetics regulating how castes are formed within colonies. All larva initially develop as pseudergates (workers) and may eventually become soldiers or alates (winged, reproductive individuals) if the right conditions exist. The key chemical that activates this process is JH (Juvenile Hormone) and its synthetic equivalent, JHA (Juvenile Hormone Analogue) or pyriproxyfen - oddly named considering it spurs growth from a nymph form.

An interesting study conducted at Hokkaido University observed that trophallaxis (mouth-to-mouth food transfer) led to pseudergates acquiring soldier termite traits as the two groups interacted more often. Presumably termite queens produce a pheromone to arrest this behavior in natural settings, otherwise all the workers in a colony would change into soldiers - which doesn't do the queen much good if she starves to death as a result. This does present an intriguing area of research for pest control chemists though, as an easily produced version of JHA might remove an infestation by forcing morphological changes in the pseudergate population. No more workers, no more wood digestion, no more problem.

For anyone still reading, genetic evidence suggests that termites are essentially "highly modified, social, wood-eating cockroaches". One species of cockroach looks after its young and carries the endosymbiotic bacteria necessary to digest wood in its gut, while a primitive termite still living in Australia is believed to be the missing link between the two groups. Next closest on the cladogram are mantids, even if the three don't look all that similar to one another. Finally, in addition to all of that, do you know how hard it was not to include a picture with this entry?

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