ErythroCite: a database on red blood cell size of fishes

Size is a fundamental trait in biology, and cell size plays a key role in cellular functions, influencing physiological adaptations and evolutionary processes in living organisms. For decades, scientists have been fascinated by the considerable variation in cell sizes among animals, yet systematic efforts to compile such data have been scarce. To address this gap, we employed a systematic map approach to create ErythroCite, an open-source database of fish erythrocyte sizes. This comprehensive resource encompasses 1,764 records from 660 species among four major lineages: Actinopterygii, Chondrichthyes, Dipnoi, and Cyclostomata. Our findings reveal a remarkable 414-fold range in cell volume, with most studies on bony fishes and limited data on juveniles and earlier life stages. Life stage and sex were infrequently reported, but available data showed equal representation of adult of females and males. ErythroCite offers valuable insights for studies in macroecology, macrophysiology, comparative physiology, evolutionary biology and cell biology. We anticipate this resource will facilitate comparative approaches and meta-analyses, globally driving further exploration of erythrocyte diversity and function in fish.