Dyopedos bispinis occasionally shows a more complex social structure than other corophiids: masts are occasionally not individual but collective dwellings. The prerequisites for the appearance of this trait might be (1) the possibility of several individuals successfully coexisting and (2) the possibility of continuous reinforcement of the dwelling.
Mast-building dulichiids are involved in multiple interactions with fouling organisms, so in Dyopedos bispinis, most masts are attached to other animals, which can be partly or fully immured.
Masts occasionally have a complex structure. One mast can have several central cylinders covered by a common cortex, and several supports or, in contrast, can branch (following hydroid immuration).
We did not detect any crucial differences in the glandular complex structure of tube-building species and the mast-builder Dyopedos bispinis. The variability in the dwellings most likely reflects behavioural adaptations; large masts are potentially supported by continuous growth and collective building.
Amphipod silk glands of Dyopedos bispinis and many other amphipods have an unusual structure in comparison with other crustacean glands, so we refer to them as “pseudotubular” glands. They are multicellular, strongly elongated type-3 glands (according to Noirot and Quennedey, 1974) that comprise optionally binuclear secretory cells, a duct cell and a lining of uncertain origin.