A group of UB researchers participate in centipede genome sequencing

An atypical species used as study model

The first myriapod genome sequence belongs to the species S. maritima. It is included in one of the five subphyla of the phylum Arthropoda, together with hexapods (insects), crustaceans, chelicerates and trilobites (extinct). To be exact, S. maritima is atypical in not having eyes and springing from its egg with the full adult complement of segments.

According to Julio Rozas, professor in the Department of Genetics of the UB and ICREA researcher, “S. maritima is the myriapod species used as model in studies of ecology and development biology because its genome is small (290 megabases), and individuals are easily caught and kept at the laboratory”.

The international group of experts has identified around 15,000 genes, an amount similar to that found in the genome analysis of many insects. However, 30% of S. maritima genes can be traced back to duplications specific to this myriapod lineage since its divergence from other arthropod groups with sequenced genome.

Arthropods: different strategies throughout evolution

Within the international study, the UB research group has studied several gene families of myriapod chemosensory system (which includes taste and smell. “It has been proved ―points out Professor Julio Rozas― that there are not members of families of olfactory receptors or odorant binding proteins (OBP), which are gene families involved in insectsʼ olfactory function”.

“In fact, we know that myriapods and insects colonized the Earth in an independent way. By comparing genome new data with those obtained from previous projects, it was observed that myriapods have found different molecular strategies to detect odorant molecules”, says Julio Rozas.

No genetic sign of light receptors

The 15,000 identified genes ―the human being has around 20,000― are distributed in one long pair of chromosomes, together with seven pairs of much shorter chromosomes (including sex chromosomes, X and Y). According to results, gene disposition is partly conserved as it is quite similar to the genome of other animal phyla, and less altered than the arthropod ground pattern found, for instance, in flies.

Surprisingly, the authors also find no evidence in S. maritima genome for any recognised way of sensing light, no obvious photoreceptors, and no components of the circadian clock.

Researchers from the Centre for Genomic Regulation and the University Pompeu Fabra have also participated in the centipede genome sequencing developed by the international consortium of researchers from 52 different institutions, led by experts Ariel D. Chipman, David E. K. Ferrier and Michael Akam.

Article reference:

Akam, M.; Almeida, F. C.; Chipman, A. D.; Ferrier, D. E. K.; Rozas, J.; Sánchez Gracia, A., et al. "The first myriapod genome sequence reveals conservative arthropod gene content and genome organisation in the centipede Strigamia maritima". PLOS Biology, November 2014. DOI: 10.1371/journal.pbio.1002005