Ecological aspects of mast-building in Dyopedos bispinis
Habitats of Dyopedos bispinisnext section
Dyopedos bispinis is abundant in conditions with strong currents; their masts are rarely observed on mud but are often on hydroids. Thus, Dyopedos bispinis habitats are more similar to those of Dyopedos porrectus than Dyopedos monacanthus (Moore and Earll, 1985; Mattson and Cedhagen, 1989). Although Dyopedos porrectus was also detected in Velikaya Salma Strait, it was absent in the biotopes studied in this paper; thus, further investigations are required.
Mast-building and foreign organisms
The masts of different dulichiids were observed on hydroids (Dyopedos porrectus, Moore and Earll, 1985), sea urchin spines (Dulichia rhabdoplastis, McCloskey, 1970), shells, polychaete tubes (Dyopedos monacantha, Mattson and Cedhagen, 1989), and amphipod tubes (Dulichia falcata (Bate, 1857), Kanneworff and Nicolaisen, 1972). Dyopedos porrectus has also been associated with bryozoans (Lincoln, 1979, cit. ex. Moore and Earll, 1985). Dyopedos bispinis, although not observed on sea urchins, uses a wide range of organisms as substrata including hydroids, bryozoans, sponges, molluscs, brachiopods and Crassicorophium tubes. Importantly, mast building on hydroids can be easily underestimated because the hydroid can be fully disguised as a part of the mast. Hydroids and bryozoans often occur immured, and it is likely that the building activity of Dyopedos bispinis negatively affects substratum organisms. Because Dyopedos bispinis is a dominant species in the Velikaya Salma Strait (Zhadan et al., 2007), the influence of masts on the benthic ecosystem might be significant.
McCloskey (1970) reported that numerous diatoms cover the surfaces of the masts of Dulichia rhaboplastis, but diatoms are usually only sparsely present on masts of other Dulichiidae (Moore and Earll, 1985; Mattson and Cedhagen, 1989). Additionally, Dyopedos bispinis masts do not have abundant diatom epiflora. Nevertheless, diatoms are abundant in the detritus used to form masts (Fig. 3D-G), and some of pelagic forms likely remain alive for some time because they have mucous pads (arrowheads, Fig. 3E). It is not known whether this is a frequent occurrence or how long these forms survive, but these “former pelagic” algae likely require further attention in the descriptions of community structure.