This clearly was a goat-glanded production; Criterion gives its original date as 1927, while the IMDb gives it as 1929. The copy I saw had a score of Chopin music, title cards and a voice-over commentary. Clearly it was issued in some form as a silent and then, equipped with a sound track, re-issued by Gaumont a couple of years later.
The two types of crustaceans are small critters of two related genuses that resemble small crabs. Individual species are sometimes called crabs. They have the peculiarity of using bibs and bobs from their localities to adorn themselves for camouflage, resulting in what might appear to be a walking mass of seaweed.
Painlevé uses only about seven of the ten minutes of this short subject on these animals. The rest is devoted to the spirograph worm, a sessile creture that puts out fronds to breathe and gather in food in what the narrator calls "a Loie Fuller ballet". It is here that Painlevé uses his most extreme microphotography; ten micrometers take up the entire screen.
Like the director's other science films of the era, it uses marvelous camerawork to produce amazing results. We could do better today, but that's only after ninety years of technological advances.