The largest RBC have been seen in?

The largest red blood cells (RBCs) have been observed in certain species of fish, particularly in the giant species like the elephant fish (Callorhinchus milii). These RBCs can be significantly larger than those found in mammals, often due to adaptations to their aquatic environments. Additionally, some amphibians and reptiles also exhibit larger RBCs compared to mammals. The size variation is generally related to the organism's metabolic needs and habitat.