The top ocean predators during the Cretaceous were primarily giant marine reptiles and sharks, or so researchers have thought. Now, a new study suggests colossal “kraken-like” octopuses once hunted Late Cretaceous seas, growing as large as 19 meters in length and competing with – and perhaps even preying upon – large ocean apex predators like mosasaurs. For hundreds of millions of years, marine ecosystems were thought to be dominated by large vertebrate apex predators. Invertebrates served as smaller prey. However, unlike shelled invertebrates, octopuses followed a unique evolutionary trajectory. Instead of protective shells, these creatures evolved soft-bodies, which gave them unprecedented mobility, vision, and intelligence. Some of these species grew to enormous sizes, too, and have functioned as top-tier predators, yet their precise ecological role has remained uncertain due to limited fossil evidence.

To aim to fill this gap, Shin Ikegami and colleagues evaluated the patterns of wear on fossilized jaws of ancient octopus relatives. Wear on the jaw – produced when biting into hard, skeletal prey – leaves characteristic damage similar to the damage seen in modern shell-crushing cephalopods. Measurements of an octopus jaw can also be used to estimate their overall body size. Ikegami et al. reexamined 15 large fossil jaws from ancient octopus relatives and identified clear signs of wear on particularly well-preserved specimens. Using advanced digital fossil-mining techniques, they uncovered 12 additional jaws of finned octopuses from Late Cretaceous sediments (~100 to 72 million years ago). In analyzing them, they identified two main species – Nanaimoteuthis jeletzkyi and N. haggarti. These finned octopuses, N. haggarti in particular, grew to exceptional sizes, say the authors, ranging from ~7 to 19 meters, rivaling the size of contemporaneous giant marine reptiles and potentially representing the largest invertebrates currently described. Moreover, in the largest individuals, the jaws showed extensive wear, with once-sharp features in small juveniles becoming blunted and rounded over time. The wear patterns suggest that these creatures were active carnivores that routinely crushed hard shells and bones with powerful bites, and used their long, flexible arms to seize sizable prey while dismantling it with their strong beaks, a behavior that has been linked to advanced intelligence. According to Ikegami et al., the findings indicate that N. jeletzkyi and N. haggarti were not merely prey but highly active participants in shaping marine ecosystems while occupying roles previously attributed only to large vertebrates.

Large, warm-bodied fish, like sharks and tuna, may owe their dominance to being able to retain their own body heat, but that advantage comes at a cost. According to a new study, these mesothermic species require nearly four times more energy than other fish, and as oceans warm, their tendency to generate heat faster than they can lose it may push these already vulnerable species closer to the brink of extinction. A small fraction of fish species, like tuna and some sharks, have evolved the ability to retain metabolic heat within the body – a strategy known as mesothermy – which can enhance their physiological capabilities. However, while the advantages allow such species to dominate as top ocean predators, they also come with elevated energetic costs, as maintaining elevated body temperatures and high activity levels demands substantial energy. However, the energetics of warm-bodied mesotherms, which can heavily influence marine food webs, are poorly understood, particularly in rapidly warming ocean environments.

To address this gap, Nicholas Payne and colleagues developed a method to estimate routine metabolic rate (RMR) in fish by analyzing heat exchange in tagged individuals and combining the results with published respiratory data for the species. This allowed Payne et al. to assemble a comprehensive dataset spanning nearly the full spectrum of fish sizes – from microscopic larvae to massive 3-ton sharks – from a wide range of ocean temperatures for both ectotherms and mesotherms. Then, using this framework, the authors evaluated how body size, environmental temperature, and heat-retaining physiological adaptations shape energy demands. The findings show that mesothermic fish require nearly four times more energy than their cold-bodied counterparts, high energy costs that likely constrained body size and contributed to extinction risk in both living and extinct species. Moreover, the analysis revealed a scaling mismatch between heat production and heat loss, in which rates of heat production increase faster than heat loss as fish species grow larger, meaning larger mesothermic fish become increasingly warm-bodied. According to the authors, this creates an “overheating predicament,” which may explain why such species are more commonly found in cooler, deeper, or higher-latitude waters. However, as these cooler waters warm under climate change, large mesothermic fishes – many already vulnerable and under severe pressure from overfishing – face increasing energy demands and substantial overheating risk, elevating their threat of extinction.

University of Missouri researchers are using metal-organic frameworks (MOFs) to protect fragile enzymes so they can function in harsh industrial conditions. These porous, customizable “exoskeletons” shield enzymes while still allowing them to speed up chemical reactions, much like a shark cage protects a deep-sea diver. By creating the MOFs using water instead of toxic chemicals, the team’s approach is more sustainable and could improve efficiency and reduce waste in industries such as pharmaceuticals, renewable energy, food and agriculture.