PhD candidate Gabrielle Genty from the College of Science and Engineering at Flinders University noted, "We actually know very little about the genetic diversity of modern whales, compared to terrestrial animals, so these insights give fresh information about their radiation and changes over the past 50 million years."
The study delves into the genetic traits that have shaped the evolution of various whale species, ranging from the enormous blue and fin whales to other baleen species like humpbacks, minkes, and gray whales. Researchers identified genes linked to survival, aging, movement, immunity, and reproduction, emphasizing the importance of future adaptations in response to climate change, marine pollution, and diseases.
Ms. Genty, representing the Flinders Cetacean Ecology, Behaviour and Evolution Lab (CEBEL) and the Molecular Ecology Lab at Flinders University (MELFU), highlighted a key finding: "For example, we found genes that improve immunity have been important for the largest species, fin whales and the world's largest animal, the blue whale."
These immune-related adaptations are thought to help these species achieve their large sizes without experiencing significant health issues, such as tumors and cancer, which are generally linked to rapid cell growth in large-bodied animals.
The research involved analyzing a dataset of 10,159 genes from 15 cetacean species and two terrestrial species, hippos and cows (Hippopotamus amphibius and Bos taurus), considered the closest land relatives of whales. The highly mobile and pelagic nature of baleen whales makes them challenging subjects for study.
Associate Professor Luciana Moller, a senior co-author from Flinders University, explained that cetaceans (whales, dolphins, and porpoises) have diversified into numerous groups since their ancestors transitioned from land to water. This diversification resulted in a minimum of 89 main species, divided into two suborders: Odontoceti (toothed whales, dolphins, and porpoises) with 74 species, and Mysticeti (baleen whales) with 15 species that use baleen plates for filter-feeding.
The focus of the latest study was on the Balaenopteridae family within Mysticeti, represented by nine recognized species known for their throat and chest grooves, extensive migrations, and rapid calf growth.
Ms. Genty emphasized, "By identifying positively selected genes and enriched mammalian phenotypic terms, this research highlights the genetic and physiological adaptations that underpin the diversification and specialization of balaenopterids."
Associate Professor Moller added that the study provides substantial evidence of the successful adaptive evolution of baleen whales. "This allowed them to thrive in their aquatic habitat and diversify into distinct species with variations in size, morphology, mating systems, feeding strategies, and diving abilities," she said. "The work advances our understanding of the genetic mechanisms behind the evolution of baleen whales, offering new insights into their evolutionary triumph."
Recent studies indicate that a significant increase in body size was likely the last step in the evolution of present-day whales, driven by improved thermal isolation in larger bodies. Additionally, baleen whales exhibit a variety of feeding mechanisms suited to different energetic strategies and ecological niches.
Despite their similar body shapes, balaenopterids vary significantly in size, from the smaller common minke whale (Balaenoptera acutorostrata), approximately 7-8 meters long, to the blue whale (Balaenoptera musculus), the largest mammal on Earth, exceeding 30 meters in length.
Research Report:Into the Blue: Exploring genetic mechanisms behind the evolution of baleen whales
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Cetacean Ecology, Behaviour and Evolution Lab
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