Strategies for tube construction in Owenia caissara (Oweniidae, Annelida) from southern Brazil.

In this paper, we have experimentally assessed tube-building strategies of Owenia caissaraSilva & Lana, 2017, including the particle size preferences. After acclimation, individual tubes were broken by their mid-region, and placed in experimental aquaria with four types of homogeneous substrates (from silt-clay to coarse sand) and four types of mixed substrates. Animals completely removed from their tubes were unable to build new tubes. Adults in broken tubes were able to use a wide range of particles, from fine to coarse sand, but not silt-clay. Owenia caissara showed a clear preference for coarse sediment particles. In extreme conditions, individuals were able to rebuild their tubes using only filamentous debris. Owenia caissara may display higher selection ability and preference for larger particles when growing, although adults can also adapt to bottoms with predominantly smaller particles such as fine sand.