Javier Ortega-Hernández, Assistant Professor in the Department of Organismic and Evolutionary Biology at Harvard University, has been awarded an Early Career Grant from the 2022 Human Frontier Science Program (HFSP).
Ortega-Hernández in collaboration with Dr. Rosa Fernández, Institute of Evolutionary Biology in Barcelona, and Dr. Ana Belén Muñoz-García, University of Naples, Federico II., will address the evolution of aerial breathing in arthropods. The three-year, $1.1 million project titled Reconstructing water to land transitions in arthropod evolution combining atoms, genes and fossils is one of seven awarded grants following a rigorous selection process.
The water-to-land transition is one of the most important events in animal evolution because it was the first step before the main diversification of the modern terrestrial biosphere. The rise of atmospheric oxygen fundamentally changed the chemistry of Earth’s surface, opening ecological opportunities for complex organisms to explore new environments. Arthropods were among the first animals to venture out of the oceans onto dry land. In fact, arthropods transitioned to land more than 100 million years before vertebrate tetrapods, and this terrestrialization process occurred at least three times among the major lineages including the chelicerates (e.g. horseshoe crabs and spiders), myriapods (centipedes and millipedes) and hexapods (e.g. insects).
“We know about the timing of arthropod terrestrialization based on multiple lines of evidence, including the fossil record, but we want to learn more about the key evolutionary steps that were necessary for this process,” said Ortega-Hernández.
One focus of the team will be on arthropod blood, specifically one key protein. Human blood contains hemoglobin that transport oxygens to the lungs for aerobic respiration. By contrast, arthropod blood (known as hemolymph) contains the protein hemocyanin, which transports oxygen throughout their body. By combining tools from genomics and physical chemistry, the team has the goal of understanding the physical properties of the hemocyanin, the genes responsible for coding this protein, and how it might have evolved more than 400 million years ago.
Ortega-Hernández, who is Curator of Invertebrate Paleontology in the Museum of Comparative Zoology at Harvard, will supply a macroevolutionary perspective of how the gill-like structures used for respiration have changed through arthropod history. This effort will require tracking down all instances of soft-tissue preservation in the fossil record spanning from the Cambrian to Carboniferous, covering approximately 200 million years, and investigating changes in the morphology and organization of gill-like structures, and their relationship with changing levels of atmospheric oxygen in deep time.
“We know that there have been important periods of oxygenation of Earth’s atmosphere in the past, but the extent to which these have directly impacted the morphology or physiology of extinct arthropods has not really been examined in detail, or even quantified. Our objective is to better understand how respiratory structures have changed in the transition from water to land, and if the environment might have triggered this evolutionary innovation to begin with” Ortega-Hernández said.
“Our ultimate goal is to test whether there is a correlation between the rise of atmospheric oxygen during the Paleozoic and arthropod terrestrialization. Did the oxygen levels in the atmosphere facilitate the evolution of the first land-dwelling animals?” Ortega-Hernández said. Arthropods are an excellent model of studying this question because they are the first animals to venture onto dry land to explore an entirely new ecosystem.
“This is an exciting opportunity to learn more about an important event in the early evolution of animals, and we are extremely fortunate to have the generous support of HFSP because it will allow us to tackle this complex question from multiple angles. A project of this scope cannot be answered by one line of inquiry alone, so it is a great privilege to be able to work with a fantastic interdisciplinary team of international experts,” said Ortega-Hernández.
The Human Frontier Science Program is an international program funded by 13 countries and the European Union. HFSP was established in 1989 to encourage international collaboration on basic research topics.