[3] They may share areas with mussel beds and are found in any place that provides some shelter, such as rock faces, overhanging ledges and concave shorelines.

[5] On rocky beaches, settlement is dependent on larval behavior in the water column and perception of chemical cues when the larvae contact the tubes.

[6] Sandcastle worms should not be confused with the similar, but more northern Sabellaria cementarium which are found from Alaska to southern California and have an amber-colored operculum.

[4] Unlike P. californica, S. cementarium rarely forms colonies, does not settle gregariously, and its larvae do not respond to free fatty acids.

[7] In 2004, researchers from the University of California, Santa Barbara (UCSB) discovered that the glue used by the Phragmatopoma worm to build its protecting tube was made of specific proteins with opposite charges.

[11] Inspired by these results University of Utah researchers reported in 2009 that they succeeded in duplicating the glue that the worms secrete and use to stick sand grains together underwater.

[14] If found to be practicable, the synthetic glue, which is based on complex coacervates,[15] could be used to fix small bone fragments, instead of metal stabilizer devices such as pins and screws, which are challenging to use.