The comparative energetics of the turtles and crocodiles

Physiological variables in machine learning QSARs allow for both cross-chemical and cross-species predictions

A major challenge in ecological risk assessment is estimating chemical-induced effects across taxa without species-specific testing. Where ecotoxicological data may be more challenging to gather, information on species physiology is more available for a broad range of taxa. Physiology is known to drive species sensitivity but understanding about the relative contribution of specific underlying processes is still elusive. Consequently, there remains a need to understand which physiological processes lead to differences in species sensitivity. The objective of our study was to utilize existing knowledge about organismal physiology to both understand and predict differences in species sensitivity. Machine learning models were trained to predict chemical- and species-specific endpoints as a function of both chemical fingerprints/descriptors and physiological properties represented by dynamic energy budget (DEB) parameters. We found that random forest models were able to predict chemical- and species-specific endpoints, and that DEB parameters were relatively important in the models, particularly for invertebrates. Our approach illuminates how physiological properties may drive species sensitivity, which will allow more realistic predictions of effects across species without the need for additional animal testing.

The comparative energetics of the carnivorans and pangolins

Patterns in eco-physiological traits of pangolins and carnivorans are studied, which are functions of underlying Dynamic Energy Budget parameters. The data, parameter values and traits are accessible in the open access Add-my-Pet collection, which currently contains 7 out of 8 species of pangolins and 131 of the extant 276 species of carnivorans and 653 of the extant 6400 species of mammals. Paucity of data and species not included reflect the actual state of knowledge: many species are endangered and/or little measured data is readily available. Although musteloids and pinnipeds form the clade Mustelida, they appear at opposite ends of the classical multidimensional scaling diagram, using 14 traits on all mammals. Yet, in general, the energetic parameters bear a strong taxonomic signal. The weight at birth is proportional to ultimate weight: small for carnivorans and pangolins; extra small for bears; and much larger, but typical for mammals, for the pinnipeds and sea otters. How respiration scales with size is taxon-specific, and we discuss how the body-size scaling of reserve capacity interferes with the waste-to-hurry pattern. Despite their high allocation to soma, the life time cumulated mass of neonates of pangolins and carnivorans equals their own ultimate weight; pinnipeds allocate more to maturation and reproduction. Applying models to support conservation efforts entails needing realistic parameter values. This study contributes to the emerging field of assessing the realism of parameters in biological and evolutionary context.

The comparative energetics of the ray-finned fish in an evolutionary context

To address challenges in management and conservation of fishes and fisheries it is essential to understand their life histories and energetics. The Add-my-Pet (AmP) collection of data on energetics and Dynamic Energy Budget (DEB) parameters currently contains 1150 of the 40000 extant species of fish. It gives 250-280 traits per species, depending on the model type that was applied, such as maximum reserve capacity, lifespan, specific respiration and precociality index, based on which the ray-finned fish (Actinopterygii) was compared with the four other fish classes (Cyclostomata, Chondrichthyes, Actinistia, Dipnoi) and the Tetrapoda. The Actinopterygii are the only vertebrate class that shows metabolic acceleration, and clearly so in only three sub-clades. Different from chondrichthyans, quite a few species follow the waste-to-hurry strategy, especially small bodied freshwater fish such as tropical annual killifish, but also in small minnows and darters in continental climates. We briefly discuss links between waste-to-hurry, which is associated with a large specific somatic maintenance, and sensitivity for pesticides. We discuss why this interferes with the physical co-variation between maximum reserve capacity and ultimate structural length or weight and explains why maximum reserve capacity increases with body length in chondrichthyans, but not in actinopterygians. Reserve capacity has relevance, e.g. mass-specific maintenance, starvation and the kinetics of lipophyllic compounds (such as pesticides), since reserve is relatively rich in lipids in fish. Also, unlike chondrichthyans, the size at birth is very small and not linked to ultimate size; we discuss the implications. Actinopterygians allocate more to soma, compared with chondrichthyans; the latter allocate more to maturity or reproduction. Actinopterygians, Actinistia and Dipnoi are near the supply-end of the supply-demand spectrum, while chondrichthyans clearly show demand properties.