Mud skipper4/12/2023 This hypothesis is supported by paleontological data showing that the Tetrapodomorpha came onto land during the Middle Devonian (∼350 mya) (although potential terrestrial trackways have been found as early as 395 mya) ( Niedźwiedzki et al. ![]() (1995) also proposed that increased availability of oxygen may have fueled the diversification and ecological radiation of early tetrapods by allowing for elevated aerobic capacity and the concomitant increase in terrestrial performance. These proposed implications are supported by the fossil record showing gigantism in a diverse lineage of insects, with prehistoric dragonflies having wingspans extending up to 70 cm during the late Carboniferous and Permian (320–250 mya) ( May 1982 Shear and Kukalová-Peck 1990 Carpenter 1992). (1995) hypothesized that the late Paleozoic oxygen pulse (likely caused by the appearance of vascular land plants) may have released the constraints of diffusion for some organisms and allowed for the evolution of insect gigantism and the emergence of costly aerobic processes, such as insect flight. Nevertheless, there is general consensus among historic models of the Earth’s atmospheric composition that oxygen concentration increase during the middle and late Paleozoic Era (400–250 mya), reaching 30–35% during the late Paleozoic oxygen pulse (∼320–260 mya), a period linked to several transformative evolutionary events. Although many researchers have correlated a number of biological phenomena with changes in the Earth’s atmosphere throughout the Phanerozoic Eon (from 550 million years ago to the present), modeled oxygen levels as well as paleontological data generally lack the temporal resolution required to provide direct association (i.e., cause and effect) between atmospheric changes and a biological response ( Powell 2010 Graham et al. The appearance of cyanobacteria and algae in the fossil record correlates with rises in atmospheric oxygen 2.7 and 1 billion years ago, respectively (reviewed by Xiong and Bauer 2002), while relatively sharp drops in oxygen have been suggested as a factor in large losses of biodiversity (extinction events) ( Berner et al. The timing and magnitude of fluctuations in atmospheric oxygen have not only been heavily shaped by biological processes but have also likely impacted the evolutionary history of life on this planet. The composition of the Earth’s atmosphere has fluctuated throughout history, being molded by the forces of climate, tectonics, asteroid impacts, and the appearance and abundance of life ( Knoll 2003). modestus and early tetrapods suggest that increasing atmospheric oxygen levels during the middle and late Paleozoic allowed for elevated aerobic capacity and improved terrestrial performance, and likely led to an accelerated diversification and expansion of vertebrate life into the terrestrial biosphere. modestus can exercise longer and recover quicker under higher oxygen concentrations. Taken together, the results of this study show that P. Finally, following exercise, ventilatory movements associated with buccopharyngeal aerial respiration returned to their rest-like pattern more quickly at higher concentrations of oxygen. ![]() However, in normoxia, oxygen consumption increased above hyperoxic values 13–20 h post-exercise suggesting a delayed repayment of the incurred oxygen debt. The time required post-exercise for mudskippers to return to a resting metabolic rate did not differ between treatments. modestus can increase oxygen utilization both during and following exercise. ![]() Endurance and elevated post-exercise oxygen consumption (EPOC the immediate O 2 debt repaid post-exercise) correlated with atmospheric oxygen concentration indicating that when additional oxygen is available P. The effects of different atmospheric oxygen concentrations (hyperoxia = 35%, normoxia = 21%, and hypoxia = 7% O 2) on terrestrial performance were tested during exercise on a terrestrial treadmill and during recovery from exhaustive exercise. The Japanese mudskipper ( Periophthalmus modestus), an amphibious fish that possesses many respiratory and locomotive specializations for sojourns onto land, was used as a model to study how changing atmospheric oxygen concentrations during the middle and late Paleozoic Era (400–250 million years ago) may have influenced the emergence and subsequent radiation of the first tetrapods.
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