Why the scaly cricket should have its DNA sequenced

Here, he explains why it should be done.

What are scaly crickets?

The scaly cricket, or Atlantic beach cricket (Fig 1), is one of the rarest and least well-known of our Orthoptera (grasshoppers and crickets). It is the only member of the family Mogoplistidae to be found in the UK.

Members of this family are known as scaly crickets, quite simply, because their bodies are clothed in tiny scales (Fig 2).

The species is very unusual in that it lives on pebbly and stony beaches, apparently feeding on debris washed up by the sea. In the UK, it is known from only four small populations, two in Pembrokeshire and one each in Devon and Dorset, and is classified as “vulnerable” globally. Until recently, very little was known about the ecology of this secretive species.

Scaly cricket research at the University of Derby

Over the last few years, I have been researching the life cycle and ecology of the scaly cricket. This has involved sampling populations with baited pitfall traps (plastic pint cups sunk into the pebbles) at different times of the year to find out what developmental stages were present. I also managed to rear scaly crickets from egg to adulthood in the labs here at the University of Derby (Fig 3).

The results revealed that the scaly cricket has an unusually long life cycle: the eggs, which are laid over the summer, take a whole year to hatch. The resulting nymphs take a further year to become adult (and pass the winter when only half grown) and the adults sometimes live for up to a year. This means that the scaly cricket somehow survives up to three winters, in which fierce winter storm waves frequently inundate its shingle habitat.

A particularly ferocious series of storms occurred in the winters of 2013/14 and caused much damage to scaly cricket habitat in the UK. Last year, Rose Poston-Saynor, one of my MSc Conservation Biology project students, and I conducted surveys of the three main populations of scaly crickets in the UK. We set pitfall traps positioned at the same localities used in surveys that pre-dated the storms. These were baited with fish flavoured cat biscuits (since these were found to attract most crickets in trials using different baits). We found that while populations of scaly crickets were still present at all three sites, the numbers caught per trap were much lower than in previous surveys and there was evident loss of much of the shingle habitat at the sites in Pembrokeshire and Devon. This led me to seek permission from Natural England to release some of my captive-bred scaly crickets originating from the Devon colony to a new suitable site close to the original population (Fig 4).

Why sequence the scaly cricket’s genome?

One thing that unravelling the genetic code of an organism allows us to do is to look at similarities and differences between populations of the same species. This can give us an insight into the history of the populations and where they originally came from. In the case of the scaly cricket, my research on the life cycle revealed that eggs are often laid in driftwood. This raises the intriguing possibility that the eggs, which take a year to hatch, might actually survive winter storms by “rafting” in chunks of driftwood and, importantly, might be able to colonise new areas by this method. If so, it is possible that our populations of scaly crickets (some of which were discovered as recently as 1999) might not have colonised the UK when we were still joined to the continent at the end of the last ice age (like most other British insects), but might instead have “rafted” over much more recently from populations on the French coast.

Revealing the genetic code of the scaly cricket will provide the basis to test this idea, and allow us determine if individuals from French populations are able to come over to Britain. This will also be an important step in examining whether population crashes, such as those caused by recent storms, have had impacts on the genetic diversity of our scaly cricket populations.

Sequencing the genome of a species can also tell us a lot about evolutionary relationships between different species and between higher taxonomic levels such as families; it can tell us where they fit in the tree of life. By comparing the genomes of different species, we can also learn how the genome itself evolves. So far only a few insects have had their entire genomes sequenced, and this list is also dominated by the so called “advanced” insects such as flies, bees and wasps, moths and beetles, which have a complete metamorphosis (including a grub or caterpillar-like larval stage and a resting pupal stage). Crickets, on the other hand, belong to a much more ancient branch of insects, which do not have a pupal stage, but instead hatch out of the egg looking like miniature adults. Looking at more “primitive” insects will help us understand the origin of the adaptations that make insects so successful.

Vote for the scaly cricket!

To celebrate its 25th birthday, the Wellcome Sanger Institute (one of the world’s leading genomics research centres and home to the Human Genome Project) is going to unravel the entire genetic code of 25 British species. It has already selected 20 of these, but the remaining five are to be put to public vote (votes will come primarily from school children).

Over the summer, the Institute requested researchers and wildlife specialists to put forward species to take part in this competition. My suggestion of the scaly cricket was accepted. This means that I will now act as the champion for the species. I have populated an profile page for the scaly cricket on the 25 Genomes website and, for the next five weeks, will be engaging in online chats and answering questions from school children, in order to persuade them to vote for the scaly cricket.

Voting is also available to the public via social media. I will be joined in my mission to advocate the scaly cricket by Dr Darren Parker, a University of Derby Zoology graduate, who now conducts research on insect genetics and genomics at the University of Lausanne, Switzerland, and by my colleague Graham Rowe. The scaly cricket needs all the help it can get – it is up against charismatic species such as the Scottish Wild Cat.

The Wellcome Sanger Institute’s Genome competition runs from November 6, with the final vote taking place on December 8 2017.