Which one of the following animals has two blood types?
A freemartin calf has two blood types.
In older, multiparous cows, chorionic placental blood vessels form a common circulation between twin fetuses prior to sexual differentiation.The interchange of cells between twin fetuses yields heifer calves with two blood types (and also both XX and XY chromosomes).
Refs: Zhang, Diagnosis of freemartinism in cattle: the need for clinical and cytogenic evaluation, J Am Vet Med Association 1994 15;204 (10):1672-5.
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