Friday, 11 September 2015

Turn and face the strange, ch-ch-changes

This time of year is always associated with great change within schools and universities. Many of our students have left the UTC and are set to embark upon an exciting new era in their lives by starting in jobs, apprenticeships or higher education courses. Other students are moving up a year, in some cases making the challenging transition from GCSEs to A Levels. We also welcome a new cohort of Y10 and Y12 students, joining us in the innovation labs at Liverpool Life Sciences for the first time. I have enjoyed meeting you this week and look forward to an exciting year of research in the labs.

The inspiration for my first blog post came to me during my first innovation lab session with Y11 on Friday. During the session the students were making observations about the different stages in the life cycle of our very own model organism – the darkling beetle. It never fails to fascinate the students and indeed myself that an organism can go through such a transition or metamorphosis and emerge as what often looks like a completely different species. So what better topic to begin this time of great change than one of the greatest changes in the animal kingdom; complete metamorphosis. 

It was only after nearly finishing writing this post that I realised that Dave Hornby had already written a little on this topic before the summer, including a title based upon song lyrics. I guess that means I have spent too much time in the labs with him over the last year! Anyway, it is a useful topic to revisit as we continue to develop our use of the darkling beetle as a model organism for genomics and proteomics.

Let us start with the great Charles Darwin. The Voyage Of The Beagle covers Darwin’s part in the second survey expedition of the ship HMS Beagle, which set sail on 27 December 1831. In this book Darwin tells the story of a German Naturalist called Renous, who was arrested for heresy in Chile for claiming that he could turn a caterpillar into a butterfly. Today it is common knowledge that many insects, like the caterpillar go through a process of complete metamorphosis and emerge as a very different looking organism. In fact, people have known since at least as early as Egyptian times that grubs and worm-like 
(they are not really worms) larval stages develop into adult insects. However, there has been much confusion surrounded this incredible process. It is something which has always fascinated me since being a child, collecting caterpillars to look at in an insect viewer, through my final year university project studying the life stages of the swallowtail butterfly (below) and now working on the darkling beetle in the innovation labs at the UTC.

So what is metamorphosis?

According to Thain and Dixon’s - Dictionary of Biology (1992), metamorphosis is a 

“process during, and as a result of, which an animal undergoes a comparatively rapid change from larval to adult form. Under hormonal control, it is most noteable in the life histories of many marine invertebrates, the majority of insects and of Amphibia. Often requires destruction of much larval tissue and changes in gene expression.” 

Basically, what occurs is a reorganisation of the organism’s tissues. Inside the pupae the larvae essentially digests some of its own tissues into their constituent proteins. Some organs stay intact and others are broken down into groups of cells that can be reused. Some groups of highly specialised cells called imaginal discs start the formation of a specific body part of the adult stage, such as an antennae. The obvious physical changes that occur during metamorphosis are accompanied by changes in the biochemistry, physiology and behaviour of the organism.

So the questions which arise are what is the point in going through this complex, potentially costly transformation? How does the organism benefit? 

The most likely explanation comes from a reduction in intraspecific competition for food and space. By having distinct life stages which exploit different resources, these insects avoid direct competition with their young, increasing their survival chances.

The evolution of complete metamorphosis in insects is still considered a great mystery and many theories have been proposed to explain it. An early attempt is the rather entertaining but implausible idea proposed by Donald Williamson that the butterfly metamorphosis is the result of an accidental mating between a ground dwelling species and a flying species. More recent attempts have focused on the more likely idea that complete metamorphosis evolved from incomplete metamorphosis. This theory is supported by evidence from the fossil record as the earliest insects have life cycles which are similar to modern ametabolous insects, like grasshoppers where the young appear more like smaller versions of the adult and there is no pupal stage. It is only later in the fossil record that we find examples with life cycles similar to modern day holometabolous insects, those that undergo complete metamorphosis, like butterflies and our very own darkling beetle. 

To read more about this follow the link below to a good summary by Ferris Jebr in the Scientific American (

Since adopting the darkling beetle as a model organism, our students have had great success and with Professor Hornby’s help, published a paper in the current issue of the Young Scientists Journal ( I am hugely optimistic that our new students will embrace their change in environment and build upon the successes of those who have moved on to the next stage in their lives.

So in the words of the great David Bowie - "Turn and face the strange, ch-ch-changes"

1 comment:

  1. Dr Dyer raises some really important issues about hypothesis and evidence. Why do insects have such life cycles? And how are life cycles accommodated by Darwinian ideas? You should always ask yourself why does this happen or why do insects have six legs and spiders 8? Then when you find an answer ask yourselves how good is the evidence? These are really important aspect of being critical scientists.

    I am about to give a talk in November on the origin of "cycles" in Biology. Was Hans Krebs the first to consider the concept of cycles? Maybe you could discuss (with Dr. Dyer) the cycles found in Nature at the macroscopic, microscopic and nanoscopic (molecular) levels?