Role of Myxicola infundibulum (Polychaeta, Annelida) mucus: From bacterial control to nutritional home site

The polychaete Myxicola infundibulum (Renier) produces a large amount of dense mucus which forms a gelatinous envelope where the worm lives. In the present study we evaluated some of the physical-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, and protein, carbohydrate and total lipid content. The presence of an antibacterial lysozyme-like activity as well as the density of culturable bacteria at 22 °C and vibrios and associated macrofauna were also investigated. The water content of M. infundibulum mucus was 95 ± 0.5%. By dry weight, 38 ± 1.2% was protein, 2 ± 0.21% was carbohydrate and only 3% was lipid. Most of the remainder of the dry weight (about 57%) was inorganic. The mucus of M. infundibulum exerted a lysozyme-like activity evidenced on Petri dishes inoculated with Micrococcus luteus cell walls with a diameter of lysis of 8.4 ± 0.3 mm, corresponding to 1.15 mg ml− 1 of hen egg white lysozyme. Notwithstanding this high antibacterial activity, the mucous tubes of M. infundibulum contained a high density of culturable heterotrophic bacteria at 22 °C, of which presumptive culturable vibrios accounted for 4.6 ± 0.2 × 103 CFU ml− 1. Moreover, tubes were found to be colonized by several specimens of the polychaete Lumbrineris cfr. latreilli. Therefore the mucus of M. infundibulum appears to provide defence against some bacteria and food supply for the growth of others, that in turn could be utilized by macrofaunal organisms. On account of these features this matrix represents an accessible and renewable resource that could repay further exploration from several points of view.