Born in London, he studied natural history in Paris. From 1837 to 1841 he led a scientific expedition to Canada where he studied the fauna of the Canadian lakes and the political systems of Upper and Lower Canada (roughly corresponding to the modern provinces of Ontario and Quebec) and of the United States.
The genus Laportea of tropical stinging trees is named after him.
Hoax Australian fish
Through no fault of his own, Castelnau's name is attached to an Australian hoax. "Ompax spatuloides", a supposed ganoid fish said to have been discovered in 1872 and named by Castelnau, was a joke originally directed at Carl Staiger, the director of the Brisbane Museum. Staiger forwarded a sketch and description of the made-up fish to Castelnau, who duly described it.
Works
Histoire naturelle, 1837.
Vues et souvenirs de l'Amérique du Nord
Expédition dans les parties centrales de l'Amérique: histoire naturelle des insectes coléoptères, 1840.
Mémoires sur les poissons de l'Afrique australe, 1843.
