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Q1.
| Q1. | Please tell us about the chironomids. |
| A. | The chironomids or midges belong to the insect order Diptera and are thus closely related to flies and mosquitoes. They look like mosquitoes, but do not suck blood. Adult males are known for making characteristic swarms in summer. The larvae of these midges are used as bait for fishing or as food for the tropical fishes in aquariums. In Japan, about 1000 species of chironomids, such as Chironomus yoshimatsui or Polypedilum nubifer, were described. |
| Q2. | Does the sleeping chironomid suck blood? |
| A. | Like other members of the chironomid family, the sleeping chironomid does not suck blood. Adults do not feed actively, but it seems that they need some water uptake. |
| Q3. | Is the sleeping chironomid living in Japan? |
| A. | No, the sleeping chironomid does not range in Japan. At present, it has been only recorded in the semi-arid regions of Africa. |
| Q4. | Please tell us about the habitat of the sleeping chironomid. |
| A. | The sleeping chironomids are found mainly in the semi-arid regions of central Africa. In these regions, situated near the equator, temperatures are relatively high all around the year and the length of the day does not vary a lot. Distinct rainy season and dry season exist, and the dry season may last for several months without any drop of rain. Rocky places are found throughout these semi-arid regions. The sleeping chironomid lives in small puddles on these rocks. The water of such puddles is subject to rapid evaporation and in order to survive in such an instable environment, sleeping chironomids are thought to have acquired this surprising resistance to desiccation. |
| Q5. | How long does it take for a sleeping chironomid to develop from the egg to the adult? |
| A. | The ecology of the sleeping chironomid in the field is not clearly understood. The development speed is influenced by many factors, such as the size of the puddle, crowding, desiccation status or temperature. In laboratory conditions, eggs hatch after about one day, larvae develop fully in 3 weeks to 2 months and a half, the pupa period lasts one day and adults may live for 1 day to 1 week (but it depends on if they are mated or not). Thus, the development time and the life span of the sleeping chironomid are quite variable. |
| Q6. | Are there other insects with this capacity of resistance to desiccation, or anhydrobiosis? |
| A. | At present, the sleeping chironomid is the only insect known to perform anhydrobiosis. Among the organisms resistant to desiccation, the sleeping chironomid is the highest animal and the biggest one. |
| Q7. | There are little shrimps that are able to hatch from desiccated eggs. How do they differ from the sleeping chironomid? |
| A. | In the case of brine shrimps or sea monkeys (Artemia), the eggs are able to resist to desiccation because the precedent generation had anticipated drought conditions and thus laid eggs that were prepared for these extreme conditions. In comparison, the larvae of the sleeping chironomid are able to anticipate the loss of moisture by themselves, without any help from the precedent generation and this is the big difference. In such a system, larvae prepare their body for surviving to desiccation and can thus endure several periods of drought successively. |
| Q8. | Is the phenomenon of cryptobiosis observed also in mammals? |
| A. | As far as we know, cryptobiosis does not exist in mammals. For example, human body contains 60% of water and a loss of only 3% of this water content leads to a deterioration of the motor capacity and the regulatory functions responsible for the regulation of body temperature. A loss of 8% of the body water content generates troubles of consciousness and a state of shock due to the lowering of blood pressure. Finally, a loss of about 14% of the body water content leads to death. After such a water loss, humans cannot revive from a state with stopped metabolism. In such a context, the capacity of the sleeping chironomid to revive after passing through a state with less than 3% of body water content is really an extraordinary phenomenon. |
| Q9. | Please tell us about trehalose. |
| A. | Trehalose is a disaccharid made of two glucose molecules bound together and it is found abundantly in the nature. Fungi, algae and yeasts contain trehalose and trehalose is also the main sugar in the blood of insects. Since 1994, when the trading company HAYASHIBARA Inc. succeeded for the first time in the world to synthesize massively trehalose, this sugar is now incorporated in many processed foods and cosmetics. At present, trehalose is the focus of many studies and its applications spread over various fields. |
| Q10. | There was an experiment, where the head and the abdomen were ligated and cut. If you cut the larvae between the head and the abdomen, they won’t be able to breathe any more, right? |
| A. | In insects, respiratory openings called spiracles are present on the thorax and the abdomen. The air is transported from the spiracles through thin tubes called trachea, directly to the tissues and cells throughout the body. However, in aquatic insects such as the sleeping chironomid, spiracles are not present, but are replaced by gills on the tip of the abdomen. |
| Q11. | What kind of phenomenon is vitrification? |
| A. | Vitrification is the process by which a liquid turns into a liquid state with the same hardness as a solid, without taking a crystal structure (structure where molecules are regularly aligned). Since a vitrified substance is in a metastable state, temperature or moisture content can break this vitrified state, that will turn into a crystal or a rubber. A vitrified substance presents high viscosity and disorder at the molecular level, but as molecular movement is almost completely stopped, degradation is contained and that’s why this phenomenon is widely used in the field of food conservation.
The trehalose accumulated in the body of the larvae of the sleeping chironomid has a very high glass transition point (temperature to which molecules begin to move) at 115ºC, and that explains why those larvae can stand the very hot climate of Africa in a glassy state.
Incidentally, the glass of windows presents also molecules in such a metastable state.
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| Q12. | You said that the sleeping chironomids would be used as learning material, but it may pose problem if they flee outside in other countries? |
| A. | This point was carefully considered when we imagined the use of the sleeping chironomid as a learning material. Experiments showed that it was possible to sterilize those insects by exposing desiccated larvae to a given dose of irradiation. Of course, those sterilized larvae do not have any harmful effect on human body. By using sleeping chironomids sterilized by this way for experiments in schools, we can prevent their reproduction, even if they escaped in the nature. |
| Q13. | What will be the future applications of the research on the sleeping chironomid? |
| A. | By studying the resistance to desiccation at ambient temperature, we can expect the development of new methods of conservation for foods at room temperature, keeping a fresher aspect. Applications in the medical field are also possible. In the US, the research group of Dr Crowe succeeded to preserve human blood platelets at ambient temperature. This was possible because trehalose uptake into the blood platelet cells was improved. Along with new advances in our studies on trehalose transporter, the best way to incorporate trehalose into cells will be discovered and this will hopefully contribute to the development of new methods for the conservation of human cells or tissues at room temperature. |