[1] In addition to his studies of microscopic life, he did extensive research on invertebrate groups that included echinoderms, hexapods, helminths and cnidarians.

In the Foraminifera, he noticed an apparently formless life substance that he named "sarcode", later renamed protoplasm by Hugo von Mohl (1805–1872).

Dujardin remains famous for the naming, identification and the first description in 1850 of the mushroom bodies (corpora pedunculata)[2] in the hymenopteran brain (bee, bumblebee, sphex, ant, fruitfly Drosophila melanogaster, etc.

This major discovery proved to be significant, as these structures are now considered the place where memory and many other behaviors are formed and processed in invertebrates.

[3] He suggested that one sign of honey bees' intelligence was their communication about flower locations, seventy-seven years before Karl von Frisch's 'waggle dance' theory was published.