Modified mouthparts in hydrophilous cave millipedes (Diplopoda)

In several unrelated cave-dwelling millipedes from southern Europe and the Caucasus, the mouthparts are convergently modified: The biting/masticating parts of the mandibles are reduced, whereas the pectinate lamellae are hypertrophied; the medial labral teeth are often reduced, and the gnathochilarium often broader than usual. Species with modified mouthparts are known in the families Julidae (genera Trogloiulus, Typhloiulus), Leucogeorgia, Blaniulidae (genus Vascoblaniulus), and Polydesmidae (genus Serradium). Julid and blaniulid species with modified mouthparts tend to have fewer segments than related species. Available evidence suggests that species with modified mouthparts live in, or at the edge of, subterranean water bodies. It is suggested that the modified mandibles with their enlarged pectinate lamellae function as a kind of filter, screening suspended organic material from the water. The shortened body may be a consequence of a lessened need for pushing power, and perhaps endows the species with a higher speed of locomotion.