Many macrofaunal burrowers found in muddy sediments exhibit peristaltic behavior and use eversible mouthparts or anterior regions to apply dorso-ventral forces to burrow walls and extend the burrow by fracture (Dorgan et al., 2005). Armandia brevis, however, lacks both circular muscles and an expansible anterior necessary for peristalsis (Dorgan et al., 2013). Instead, A. brevis exhibits undulatory movements; however, unlike other undulatory burrowers that fluidize sediments—such as the sandfish lizard—A. brevis plastically rearranges sediment grains to create a burrow (Dorgan et al., 2013). This mechanism is likely limited to uncompacted, surface sediments, consistent with habitat descriptions for A. brevis.
A. brevis also exhibits swimming behavior, the only member of its own subfamily Ophelininae to exhibit this behavior (Hermans, 1978). Though dispersal is one explanation, most swimming A. brevis are reproductive, and spawning occurs only once before death.