Author Interview: Hammerhead flatworms: mitochondrial genomes and description of two new species

Jean-Lou Justine: I am basically a parasitologist with a long career, beginning in 1978, and I mainly specialize in the parasites of fish. I am a member of the National Museum of Natural History in Paris since 1985 and a Professor since 1995. In 2013, a colleague forwarded to me a photograph of a strange animal found in a garden, and I realized that there was an invasion progressing in France and Europe and that nobody was working on this. Although that was not my field, I decided to dedicate some of my available time to the subject; looked for international collaborations; and ended up making astonishing discoveries on these land flatworms. So far, we have published 6 long papers about land flatworms, all in PeerJ.

Leigh Winsor: I am an adjunct zoologist in the College of Science and Engineering at James Cook University, in Queensland, Australia. For the past 48 years I have specialized in the taxonomy and systematics of land flatworms, especially those of Australia and New Zealand, and also flatworm species that are alien or invasive in other countries. I use traditional morphological techniques including histology to identify and classify species. A total evidence approach to taxonomy and systematics of land flatworms is when these traditional methods are combined with the molecular analyses undertaken by my colleagues in Europe, with whom I have collaborated on this research for the past 8 years.

Romain Gastineau: I am a French assistant professor in the Institute of Marine and Environmental Sciences, in the University of Szczecin, Poland. My main topic of research are genomic investigations of microalgae, but I also apply my skills to the sequencing of the mitochondrial genomes of invertebrates, at the top of which are of course the terrestrial invasive flatworms. The data I processed in the current study allowed for an accurate phylogeny of these organisms, and suggested the presence of an unknown, new genus of land flatworms.

Enrico Ruzzier: Before being a scientist, I am a lover of nature and biodiversity in general. I consider myself a lucky person since I have been able to make my passion my job (I am currently a research fellow at the Department of Agronomy, Food, Natural Resources, Animals, and the Environment (DAFNAE), Padua University, Padua, Italy). I define myself as an entomologist despite my interests range in many different research fields. My principal research is focused on Coleoptera morphology, taxonomy, and systematics, despite in the last few years I started cultivating a certain curiosity for exotic and invasive species, early detection, and introduction pathways.

Laurent Charles: I am the manager of the recent and fossil molluscs collections in the Natural History Museum of Bordeaux, France. As a generalist malacologist, I have a particular interest in the terrestrial mollusc faunas of France, French West Indies, and Mayotte. During my fieldtrips, I observed several flatworms species in the same habitats as molluscs. They aroused my curiosity which led me to observe and collect them for my colleagues.

Delphine Gey: I am a technician at National Museum of Natural History in Paris and I am mainly involved in molecular analyzes, in collaboration with researchers. I was especially happy to participate in this project on tapeworms, which are absolutely fascinating creatures. For this project, I have been producing new sequences since 2013!

Diversibipalium Mayottensis

Can you briefly explain the research you published in PeerJ?

Jean-Lou Justine: In this paper, we formally describe two species of hammerhead flatworms, which mean that we gave Latin names to species that we previously collected. One species was collected from France and Italy, and the other is from the French island of Mayotte, in the Indian Ocean.

What specific methods have you used in this article?

Jean-Lou Justine: There are two main parts in this research:

First, a traditional part of taxonomy and description of new species. This was made on specimens we collected since 2013, and most of the work was done by Leigh Winsor in Australia. He is one of the few scientists in the world who can describe the internal anatomy of these animals. Secondly, there is a very modern part about mitochondrial genomes. This was done by Romain Gastineau in Poland.

What I like in this research is that we combined the results of field expeditions (by Laurent Charles and Enrico Ruzzier), traditional techniques (Leigh Winsor), and molecular techniques (Delphine Gey  and Romain Gastineau). Real team work!

Leigh Winsor: Land planarians have few external morphological features that can be reliably used to positively identify them, unless of course they are an already well described species. Ideally in studies such as ours, sexually mature flatworms are examined anatomically to confirm whether or not they are a known or a new species.

Unfortunately, the organs of land planarians are embedded in parenchymatous tissue and cannot be readily dissected. In order to study their anatomy the flatworms are examined using histological methods.

This entails the examination of stained thin sections of the flatworm under the light microscope. From this the internal anatomy is revealed and described, and the anatomy of the copulatory organs is reconstructed from serial drawings made using a camera lucida.

If specimens are non-sexual, as can often be the case with alien species, then histological investigations are of limited use as the characters required for validating a species are not present. This is where molecular methods have proved so valuable in characterizing such species through its DNA bar-code or mitogenome.

Humbertium Covidum

The names of the species

Jean-Lou Justine:  When scientists describe a new species, they have to give a name, which is, since Linnaeus, in Latin. For the blue species from Mayotte, we chose “mayottensis” which simply means “from Mayotte”. For the black species from France and Italy, we wanted to do something in relation with the current Covid-19 pandemic. First, most of our research was done when our laboratories were in lockdown. And finally, we were all affected by the pandemic, and we wanted to pay homage to the victims, so we chose “covidum”.

What kinds of lessons do you hope your readers take away from the research?

Jean-Lou Justine:  The fact that we describe a new species (Diversibipalium mayottensis) from a remote island in the Indian Ocean will surprise nobody. In contrast, describing a new species in Europe is more exceptional. In addition, this species, Humbertium covidum, is an alien species. It is not the first time that an alien hammerhead flatworm is described from specimens in the country they invaded. This was the case for Bipalium kewense, named after the Kew Botanical Gardens, or Bipalium pennsylvanicum, named for Pennsylvania in the USA. In both cases, we know that these species originate from Asia. Even worse, there are no confirmed records of Bipalium pennsylvanicum in Asia, meaning that the species has spread over several states in the USA but has not been collected from its land of origin. The same is true for Humbertium covidum. We have tried to find mention of this very characteristic black species in the literature: to date we have only found a few possible records in far-east Asia, but no definitive proof that it is the same species. This illustrates the main problem with invasive species: they proliferate in the country they invade, because they find abundant food and have no enemies, even when they are rare and discreet in their land of origin.

How did you first hear about PeerJ, and what persuaded you to submit to us?

Jean-Lou Justine: I published my fist paper in PeerJ in 2013 and paid my personal subscription then… since 2013 I never had to pay again, except when we published very long papers.

How would you describe your experience with us and our submission/review process?

Jean-Lou Justine: Submitting a paper with PeerJ is great, and at the end you have this nice message “now it’s time to have a well-deserved coffee” and the system churns out your PDF.

Would you submit again, and would you recommend that your colleagues submit?

Jean-Lou Justine: Yes, of course, I believe I convinced many of my colleagues. In addition, I am also an Academic Editor for PeerJ, because I am a full partisan of open access in science, as long as it is not scandalously expensive.