Data from: Non-lethal imaging and modeling approaches for estimating dry mass in aquatic larvae

Body mass is crucial for scaling and comparing physiological rates. For
example, dry body mass is important in determining an organism’s metabolic
rate since it excludes metabolically inactive water weight. Obtaining
repeated measurements of body mass throughout an individual’s lifetime is
trivial. In contrast, we are normally able to obtain only a single
estimate of dry body mass per individual since classical methods require
end-point euthanasia followed by drying. We present imaging and modeling
techniques for estimating individual dry body mass in African clawed frog
(Xenopus laevis) tadpoles, which allows repeated sampling of the same
individuals. We applied allometric principles and tested whether external
anatomy would yield reliable estimates of dry body mass. Specifically, we
describe a procedure to embed tadpoles in agarose media for obtaining
morphological data in 3-D, and then we evaluate dry mass predictions among
nine cross-validated maximum likelihood and machine learning models. The
best performing and flexible model is an allometric model that uses
estimates of body volume to predict dry body mass (validation r2 = 0.75).
However, other models based only on wet body mass or meant to reduce the
number of necessary input variables may also be logistically tractable. We
discuss the pros, cons, and future directions of all nine models and give
practical advice for users on data collection and analysis. This research
develops a strong foundation for continued research on the biological
importance of dry body mass, particularly in the context of growth and
physiological ecology. Future development of similar approaches is crucial
for understanding the importance of body mass indices for the
standardization and comparison of physiological rates in plants and
animals.