Journal of Experimental Marine Biology and Ecology 461 (2014) 344–349

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Journal of Experimental Marine Biology and Ecology

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

Loredana Stabili a,b,⁎, Roberto Schirosi b, Margherita Licciano b, Adriana Giangrande b

a Istituto per l'Ambiente Marino Costiero, U.O.S. di Taranto, CNR, Via Roma 3, 74100 Taranto, Italyb Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Prov.le Lecce Monteroni, 73100 Lecce, Italy

⁎ Corresponding author at: Istituto per l'Ambiente MaCNR, Via Roma 3, 74100 Taranto, Italy. Tel.: +39 0832 29

E-mail addresses: loredana.stabili@iamc.cnr.it (L. Stabi(R. Schirosi), margherita.licciano@unisalento.it (M. Liccianadriana.giangrande@unisalento.it (A. Giangrande).

http://dx.doi.org/10.1016/j.jembe.2014.09.0050022-0981/© 2014 Elsevier B.V. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 21 May 2014Received in revised form 9 September 2014Accepted 10 September 2014Available online xxxx

Keywords:Antibacterial activityCulturable bacteriaLumbrineris cfr. latreilliMacrofaunaMucusMyxicola infundibulum

The polychaeteMyxicola infundibulum (Renier) produces a large amount of dense mucus which forms a gelatinousenvelopewhere theworm lives. In the present studywe evaluated some of the physical–chemical properties of thismatrix such as viscosity, osmolarity, electrical conductivity, and protein, carbohydrate and total lipid content. Thepresence of an antibacterial lysozyme-like activity as well as the density of culturable bacteria at 22 °C and vibriosand 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 remainderof the dry weight (about 57%) was inorganic. The mucus of M. infundibulum exerted a lysozyme-like activity evi-denced on Petri dishes inoculatedwithMicrococcus luteus cell walls with a diameter of lysis of 8.4 ± 0.3mm, corre-sponding to 1.15 mgml−1 of hen egg white lysozyme. Notwithstanding this high antibacterial activity, the mucoustubes ofM. infundibulum contained a high density of culturable heterotrophic bacteria at 22 °C, of which presump-tive culturable vibrios accounted for 4.6± 0.2 × 103 CFUml−1. Moreover, tubes were found to be colonized by sev-eral specimens of the polychaete Lumbrineris cfr. latreilli. Therefore themucus ofM. infundibulum appears to providedefence against somebacteria and food supply for the growth of others, that in turn could beutilized bymacrofaunalorganisms. On account of these features this matrix represents an accessible and renewable resource that couldrepay further exploration from several points of view.

© 2014 Elsevier B.V. All rights reserved.

1. Introduction

The mucus, a secretion produced by mucous glands, is a network ofproteins and polysaccharides entangled to form a weak gel containingmore than 95% water (Davies et al., 1990; Davis and Viney, 1998;Smith et al., 1999; Wainwright et al., 1976). In marine invertebratesmucus has a wide range of attributes and functions, making it both ver-satile and essential to several invertebrate ways of life for various rea-sons, e.g. to reduce drag, prevent sedimentation, enhance adhesion,limit water loss and facilitate locomotion (Branch, 1981; Santos et al.,2009). In addition, mucus can serve as a “scaffolding” that provides an-chorage and protection for eggs and a barrier against infection and mi-crobial attack (Davis and Viney, 1998; Stabili et al., 2009).

Mucus production involves a significant loss of energy in marine in-vertebrates. Probably the best documented case of mucus release is thatof corals, which may consume up to 50% of assimilated energy in pro-ducing mucus (Wild et al., 2004). In some marine invertebrates,

rino Costiero, U.O.S. di Taranto,8971.li), roberto.schirosi@libero.ito),

mucus typically forms a slippery coating that prevents bacteria and de-bris from accumulating on the body surface (Baier et al., 1985). It is re-sponsible for a number of defence mechanisms (Clare, 1995; Stabiliet al., 2009; Suzuki et al., 2003), which these organisms require asthey are under constant threat from a rich mixture of microorganismsin the surrounding water. However, the mucus also serves as a homesite for many species (Cook et al., 1969; McFarlane, 1980). Calow(1979) proposed that themucus of some speciesmight form a site of or-ganic enrichment and hence be a potential food source. Since mucusconsists primarily of polysaccharides and proteins with C:N ratios of l–5, Connor (1986) hypothesized thatmucus trails produced by somema-rine invertebrates are readily degradable by microbes and are able tosupport significant microbial growth. As already suggested by Calow(1979) the relative susceptibility to microbial attack could depend ondifferences in biochemical composition. Some invertebrates releasemucus rich in proteins rapidly used by microbes which possess a widerange of exo-enzymes potentially capable of degrading mucoid poly-mers (Azam, 1998; Coffroth, 1990). Microbial communities colonizingsuch mucus may transform mucus-derived dissolved and particulatematter into living biomass (Azam et al., 1993). Thus the mucus can bethe basis of a chain in which microbial organisms are then used byother organisms (Davies et al., 1992; Herndl and Peduzzi, 1989; Imrie,1992; Peduzzi and Herndl, 1991).

Fig. 1. A)Map of Lake Faro (Messina, Italy). The star shows the sampling site. B) Adult spec-imens of Myxicola infundibulum in the mucous tube. Scale: 0.8 cm. C) Adult specimens ofMyxicola infundibulum removed from tubes. D) Mucus collection for antibacterial activityassay.

345L. Stabili et al. / Journal of Experimental Marine Biology and Ecology 461 (2014) 344–349

Within Polychaeta (Annelida), the mucus, produced by epidermalgland cells, constitutes a key factor in the ability of many species to sur-vive in their environment (Bonar, 1972). Mucus intervenes in fertiliza-tion and egg protection (Stabili et al., 2009), consolidates the tunnelwall of burrowing polychaetes and may also play a role in the absorp-tion of metabolites (Lewis, 1968; Mouneyrac et al., 2003; Storch,1988). In the Sabellidae family heterogeneousmucus is involved in var-ious functions, such as tube building, protection and absorption of me-tabolites and prevention of proliferation of pathogenic microorganisms(Giangrande et al., 2014; Mastrodonato et al., 2005).

The present study is focused on the widespread Mediterraneansabellid polychaeteMyxicola infundibulum already suggested to be an im-portant species in medical research and of considerable economic impor-tance (Shumway et al., 1988). This species produces a large amount ofdense mucus which forms a gelatinous envelope where the worm lives(Giangrande et al., 2014). This species is common and abundant in thesoft bottom of confined areas often showing a patchy distribution. Somepatches show thick clusters of ten to fifteen individuals with a peculiarbouquet-shapedmorphology,whereworms are imbibed in a commonge-latinous mass formed by its dense mucus (Giangrande et al., 2012).

In order to evaluate the role of the produced mucus byM. infundibulumwe investigated on some of physical and chemical prop-erties of this matrix, as well as the antibacterial lysozyme-like activity.Moreover, the density of culturable heterotrophic bacteria and vibriosand the associated macrofauna present within the mucus has also beeninvestigated.

2. Materials and methods

2.1. Animals and sample preparation

Adult specimens of the polychaeteM. infundibulumwere collected in2010 in the Lake Faro (Messina, Italy) at 5 m depth using SCUBA equip-ment (Fig. 1A). Lake Faro (Messina, Italy) is located in the North-easternmost part of Sicily, Cape Peloro. It covers a 26-ha area and isroughly circular in shape; its depth in the central part is 28 m. LakeFaro is a typical brackish coastal environment, which communicates di-rectly with another coastal lake, Lake Ganzirri, and with the TyrrhenianSea and the Straits of Messina through various shallow artificial chan-nels, and is thus strongly influenced by the marine environment.

About 100 adult specimens of M. infundibulum were collected andtransferred to the laboratory. Here worms were divided randomly intotwo groups of 50 individuals each. The animals of the first group wereimmediately deprived of their mucous envelopes (Fig. 1B), whichwere used for stereomicroscopy examinations and the determinationof bacterial concentrations. Before microbiological analyses the mucuswas washed several times with sterile seawater.

The individuals of the second group were placed in a 60 l aquariumin a temperature-controlled room (T = 22 °C). The tank water (salini-ty = 37‰) was aerated and filtered through 0.22 μm pore size mem-branes (Millipore). Animals were maintained in these conditions andemployed for both the study of the physical and chemical propertiesof the mucus and the determination of its antibacterial lysozyme-likeactivity. In order to stimulate secretion of mucus, individuals of thisgroup were removed from the tube where they live and kept for30min in a Petri dish (Fig. 1C, D). The mucus secreted by 50 individualswas collected, pooled, and centrifuged at 12,000 g for 30min at 4 °C andthe supernatant was stored at−80 °C until use.

2.2. Mucus physical and chemical properties

Mucus viscosity was measured at 200 rpm in 1 ml aliquot with acone-plate viscometer (cone angle of 1.565°, model LVT-C/P 42, Brook-field Engineering Laboratories, USA) connected to a circulating waterbath (Thermoline, Australia) set at 17 ± 0.1 °C. Due to differences intemperature and equipment used between studies, comparison of

viscosity data can be difficult without reference to a common, knownviscosity. Thus, we documented the relative viscosity of mucus with re-spect to the viscosity ofwater, similar to Rosen and Cornford (1971) andCone (1999). The viscosity ofwater is 1 cPs at 20 °C and only slightly de-pendent on temperature (Withers, 1992).

Osmolarity was measured using a VAPRO vapor pressure osmome-ter (model 5520, WESCOR, UT, USA), all measurements being carriedout in triplicate. Electrical conductivity was measured using a GLP 31conductimeter (Crison).

For water contentmeasurement, thewetweight ofmucuswasmea-sured on an analytical balance. It was then dehydrated in a SpeedVac,and the dry weight was measured.

The protein concentration was measured using the Bradford (1976)assay, with bovine serum albumin (BIO-RAD) as the standard. The car-bohydrate concentration of the mucus was assayed using the methoddescribed by Dubois et al. (1956) and Kennedy and Pagliuca (1994).The assay was calibrated with known amounts of D-glucose.

2.3. Lysozyme-like activity

To detect lysozyme activity, inoculated Petri dishes were used asstandard assays. 700 μl of 5 mg ml−1 of dried Micrococcus luteus cellwalls (Sigma) was diluted in 7 ml of 0.05 M Phosphate Buffer (PB)

346 L. Stabili et al. / Journal of Experimental Marine Biology and Ecology 461 (2014) 344–349

agarose (1.2%) (pH 5.0) and then spread on a Petri dish. Four wells,6.3 mm in diameter, were sunk in the agarose gel and each filled with30 μl of mucus collected from the individuals of the second group. Thediameter of the cleared zone of the four replicates was recorded afterovernight incubation at 37 °C and comparedwith that of reference sam-ples represented by hen-egg-white lysozyme (Merck, Darmstadt,Germany). The effects on lysozyme-like activity of pH, ionic strength(I) and temperature were then examined. The effect of pH was testedby dialyzing themucus in PB 0.05 M, ionic strength, I = 0.175, adjustedto pH = 4, 5, 6, 7, and 8, and by dissolving agarose in PB at the same Iand pH-values. The effect of ionic strength was tested in PB 0.05 M(pH 6.0), adjusted to I= 0.0175, 0.175, and 1.75. Agarosewas dissolvedin PB at the same I-values. The temperature effect was tested with incu-bations of samples (in PB, at pH = 6.0, and I = 0.175) at 5, 15, 22, and37 °C.

Fig. 2. Lumbrineris cfr latreilli: A) Photograph ofwhole specimen extracted from themucusof Myxicola infundibulum. Scale: 1 cm; B) anterior end, dorsal view; C) compositemultidentate hooded hooks from third chaetiger; D) simple multidentate hooded hooksfrom a posterior parapodium. E) Buccal apparatus. Scales: A) 1 cm, B) 1 mm, C and D)0.1 mm, e) 0.2 mm.

2.4. Microbiological analyses of the mucus

For enumeration of heterotrophic bacteria, the number of CFUs wasdetermined by plating 0.1 ml of undiluted mucus and serial dilutions intriplicate on Bacto Marine Agar 2216 (Becton Dickinson & Company).The plates were incubated at 22 °C for 7 days. At the end of the incuba-tion period all colonies were counted using a 10× magnification lensand the bacterial densities were expressed as CFU ml−1.

Luminous bacteria were counted on Marine Agar 2216 plates incu-bated for 24–48 h at 30 °C and observed in a dark room to assess colo-nies emitting visible light.

In order to enumerate the culturable vibrios, 0.1 ml ofM. infundibulum mucus or appropriate decimal dilution (using a steril-ized water sample from the collection area as the diluent) was platedonto thiosulfate–citrate–bile–sucrose–salt (TCBS) agar. Incubation wascarried out at 20–25 °C and 35 °C for 2 days and the colonies of pre-sumptive vibrios were counted in accordance with the colony-formingunit (CFU) method. The incubation temperature of 35 °C was chosento estimate the fraction of vibrios potentially pathogenic to humans.The incubation temperature of 20–25 °C was chosen since some Vibriospp., such as Vibrio anguillarum, do not grow well at higher tempera-tures (Høi et al., 1998).

Culturable bacteria were counted in accordance with the colony-forming unit (CFU)method.Mean values from three replicateswere de-termined and expressed as CFU ml−1, taking account of the dilutionfactor.

Table 1Main physical–chemical characteristics of Myxicola infundibulum mucus.

Water 95 ± 0.5%Dry weight 5 ± 0.5%Inorganic residual 57 ± 0.6%Organic residual 43 ± 0.5%Total proteins 38 ± 0.1%Total lipids 3 ± 0.2%Total carbohydrates 2 ± 0.1%Viscosity 20° (cPs) 325 ± 5Osmolarity (mOsmol l−1) 1060 ± 20Conductivity (mS cm−1) 89 ± 5

3. Results

ExaminedM. infundibulum specimensmeasured 7.84±3 cm in totallength,with amaximumwidth of 0.6 cm throughoutmost of the thorax.Mucous envelopes were longer and wider than worms and appearedexternally dirty and full of different kinds of debris, however, internalmucus was transparent and quite clean. At the stereomicroscopy exam-ination the external surface of the mucous envelopes appeared colo-nized by several polychaetes species and crustaceans, while only onepolychaete species belonging to the genus Lumbrineris (Lumbrineridae)was observed living inside the mucous matrix. Most of their featurescorresponded well to the species Lumbrineris latreilli Audouin andMilne Edwards, 1834 (Fig. 2), however, they differed from this speciesin having a shorter blade of compound hooks than that reported byCarrera-Parra (2006), for L. latreilli in the re-description of the type ma-terial. For this reason we preferred to refer to this taxon as L. cfr. latreilli.Each single envelope harbored at least two individuals. Worms had 200chaetigers and measured 5 cm in length and 2 mm in width. Wormswere completely entangled in the matrix and were particularly hardto extract, nevertheless they appearedmoving fast inside themucus, es-pecially when touched.

3.1. Mucus physical and chemical properties

The mean mucus viscosity was 325 ± 5 cPs with respect to 1 cPs ofwater measured at 20 °C (Table 1). The mean osmolarity was 1060 ±20 mOsmol l−1, showing that the mucus was iso-osmotic to seawater(1152 ± 25 mOsmol l−1). The mean electrical conductivity of mucuswas 89 ± 5 mS cm−1 while the electrical conductivity of seawater is35 mS cm−1.

The water content of M. infundibulum mucus was 95% ± 0.5(Table 1). The residual part of the dried sample (57%± 0.6%)wasmain-ly inorganic salt leftover from the evaporation of seawater (Table 1).

By dry weight, 38% ± 0.1% of M. infundibulum mucus was proteinand 2%± 0.1%was carbohydrate (Table 1). The total mean lipid contentwas 3% ± 0.2%. As already stated, most of the remainder of the dryweight was inorganic (57% ± 0.6%). Proteins thus made up 88% of theorganic material.

347L. Stabili et al. / Journal of Experimental Marine Biology and Ecology 461 (2014) 344–349

3.2. Lysozyme-like activity

The results of the standard assay on Petri dishes showed that themucus of M infundibulum exerted a natural lysozyme-like activity. Bythe standard assay a mean diameter of lysis of 8.4 ± 0.3 mm, corre-sponding to 1.15 mg ml−1 of hen egg-white lysozyme was observed(Fig. 3). The lysozyme activity of mucus was strongly affected by thepH (Fig. 4A), ionic strength (I) (Fig. 4B) and incubation temperature(Fig. 4C) of the sample and the reaction medium. The maximum diam-eter of lysis was reported after dialysis against PB at I= 0.175, pH=6.0and 37 °C.

3.3. Microbiological analyses of the mucus

Data for bacterial concentrations in M. infundibulum mucus areshown as mean values in Table 2. Culturable heterotrophic bacteria at22 °C showed a mean value of 6.8 ± 0.3 × 103 CFU ml−1. Presumptiveculturable vibrios density was 4.6 ± 0.2 × 103 CFU ml−1 (about 70% ofthe heterotrophic bacteria). The results of cultural analysis usingMarineAgar 2216 and TCBS Agar in parallel demonstrated that luminous vib-rios represented a significant fraction (1.7 ± 0.2 × 103 CFU ml−1) ofthe total heterotrophic culturable M. infundibulum mucus bacteria.

4. Discussion

The mucus produced by several marine invertebrates is essential fortheir vital processes such as heterotrophic feeding and defence against amultitude of environmental stressors including bacterial infections(Brown and Bythell, 2005). However, our understanding of the compo-sition, production and roles of mucus, and its relevance to the energy ofvarious marine invertebrates remain fragmentary and little is knownabout the protective properties of mucus in disease resistance. In con-trast, several studies have attempted to estimate the nutritional valueof mucus to marine invertebrates. The nutritional value of mucus ismeasured in terms of ash content, biochemical constituents, caloric con-tent and the ratio of carbon to nitrogen content. In corals, for example,estimates of the nutritional value of mucus have yielded variable results(Meikle et al., 1988). In addition, the viscosity of mucus is dictated by itshydration state, which is dependant upon the Donnan potential be-tween mucins and the surrounding water (Cone, 1999; Gupta, 1989;).M. infundibulummucus exhibits high viscosity (325±5 cPs). Moreover,

Fig. 3. Lysozyme-like activity ofMyxicola infundibulummucusmeasured by standard assayon Petri dishes inoculated with Micrococcus luteus cell walls. Note the clear zone of cellwall lysis surrounding wells on the test plate.

Fig. 4. Lysozyme-like activity ofMyxicola infundibulummucus: A) Effect of the pH. B) Effectof the ionic strength. C) Effect of the incubation temperature. Columns aremean values±Standard Deviation.

the bulk of the organic material (about 43%) is composed of proteins(38%), with carbohydrates and lipids making up about 2% and 3% re-spectively. These physical and chemical properties are different fromthose of the mucus of the polychaete Sabella spallanzanii (Stabili et al.,2011), which has lower viscosity (2.5± 0.02 cPs), similar to that of sea-water, lower protein content (about 26%) and a higher concentration ofcarbohydrate (about 8%). These differences might be due to the differ-ent roles of mucus in these two worms. S. spallanzanii mucus has alow nutritional value (Stabili et al., 2011) and plays a major role in

Table 2Bacterial densities recorded in the mucus of Myxicola infundibulum expressed as colonyforming units (CFU) ml−1.

Bacterial group CFU ml−1

Culturable heterotrophic bacteria 6.8 ± 0.3 × 103

Vibrios 4.6 ± 0.2 × 103

Luminous vibrios 1.7 ± 0.2 × 103

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defending the worms from microbial attack, serving as a medium intowhich antimicrobial substances are released. Indeed the mucus of thisspecies shows a hemolytic activity (Canicattì et al., 1992) and a highlysozyme-like activity (Stabili et al., 2009, 2011). Such activity is crucialto the defence of invertebrates, not having developed mechanisms ofacquired immunity and therefore reliant on mechanisms of innate im-munity (Bulet et al., 2004). As an antibacterial agent, lysozyme can actas a defence mechanism against bacteria and pathogens, via direct ac-tion or its stimulatory effects on phagocytosis. The lysozyme-like anti-bacterial activity in M. infundibulum appears slightly weaker thanS. spallanzanii mucus, with a mean diameter of lysis of 8.4 ± 0.30 mm,corresponding to 1.15 mg/ml of hen egg-white lysozyme, vs a mean di-ameter of lysis of 9.6 ± 0.02 mm, corresponding to 1.31 mg/ml of henegg white lysozyme, reported for S. spallanzanii (Stabili et al., 2009).The difference between S. spallanzanii andM. infundibulummucus com-position with a higher protein content in comparison to S. spallanzanii,suggests thatM. infundibulummucus other than having a defence activ-ity towards some bacteria, could represent a food source for others,playing a role in the structuring of specific beneficial microbial commu-nities. This hypothesis is supported by the high values of bacterial den-sities observed in itsmucus, which are comparable with those observedin other invertebrates that produce mucus of high nutritional value(Goldberg, 2002) and by the high amount of mucus producedsupporting a large number of degraders. In M. infundibulum mucus,the highest densities of culturable bacteria were observed with hetero-trophic bacteria at 22 °C. Of these, luminous vibrios accounted for a con-spicuous fraction (1.7 ± 0.2 × 102 CFU ml−1). In agreement with theresults of the present study, culturable isolates from the mucus of thecoral Oculina patagonica were also dominated by vibrios (Koren andRosenber, 2006). Vibrios are known to possess highmetabolic plasticity(Beleneva and Kukhlevskii, 2010; Stabili et al., 2008) and can degradebiopolymers (carbohydrates, complex polysaccharides and proteins),given their broad spectra of hydrolytic enzymes which are an indirectindication of their role inmucus digestion and transformation. The asso-ciation of vibrios with M. infundibulum mucus could thus be explainedwith reference to the activity of the Vibrio species feeding on themucus. Some of these Vibrio species were showed to grow well in thepresence of M. infundibulum mucus as a sole carbon source (Stabiliet al., 2014), leading to conclude that there is a feeding activity of vibrioson themucus.However, feedingmaynot be the only activity involved inthe association of vibrios with the mucus. In contrast to free livingplanktonic microorganisms, which often have to face dramatic fluctua-tions in environmental conditions, several Vibrio associated bacteriahave developed adaptations which are specific to the microenviron-ment created by the hosts. Moreover, many of the biologically activecompounds ascribed to marine invertebrates such as sponges (Flattet al., 2005; Ridley et al., 2005) and bryozoans (Hildebrand et al.,2004) have been found to be produced by their bacterial associates. In-creasingly, these associations show strong functional significance andalso have potential biotechnological implications. For instance, the bac-terial symbionts of sponges and bryozoans produce chemicals that pro-tect their hosts from heterospecific settlement of larvae (Ridley et al.,2005) and from predation (Lopanik et al., 2004) respectively. It hasalso been hypothesized that coral-associated bacteria play a role in re-sistance to disease (Reshef et al., 2006; Ritchie and Smith, 2004;Rohwer and Kelley, 2004) by competing for nutrients and/or spaceand by producing antibiotics. In the case of M. infundibulum, furtherstudies are needed to clarify whether the mucus may have a defensivefunction even if it is though providing a food source to microorganismssuch as Vibrio. The hypothetical existence inM. infundibulummucus of achain in which microbial organisms are then used by other organismspresent in the same mucus is supported by the observed presence ofseveral specimens of L. cfr. latreilli, suggesting that they toleratewell liv-ing in thematrix as ameans for nourishment and protection. L. latreilli isa detritivore species commonly found in Mediterranean on soft sub-strates especially in sheltered and lagoonal environments (Carrera-

Parra, 2006). As pointed out by Carrera-Parra (2009), lumbrinerids usu-ally live freely or within own temporary mucous tubes, and only occa-sionally can be hosted by other marine invertebrates such as sponges(Zibrowius et al., 1975). The relationship betweenM infundibulum andL. cfr. latreilli, should be specific, considering that although the formerlives in a sedimentary habitat, heavily colonized by several othermacro-invertebrates, the only species able to internally colonize this matrixwas L. cfr. latreilli. Therefore, it is possible that this last species is a differ-ent taxon from L. latreilli because of the particular habitat colonized, andthe presence of some small morphological differences. Further studieswill clarify its status and the type of association between the two poly-chaetes, taking also into account that the size of the worms hosted in-side the mucus was surprisingly quite similar to that of the host andthat each single envelope harbored up to two individuals.

As awhole, the obtained results indicate that themucus of the inves-tigated species might act as a home site with a nutritional value for cer-tain bacteria while protecting the species from others. Given thisantibacterial activity and the considerable amount ofmucus per individ-ual released byM. infundibulum (Giangrande et al., 2014), the mucus ofthis species might be proposed as an efficient tool to design novel anti-bacterials. Natural defensive substances secreted by living organisms,including lysozyme, have recently emerged as a particularly attractiveclass of biocidal agents. These enzymes are environmentally benignand actmore specifically than conventional organic biocides such as an-tibiotics and quaternary ammonium compounds (Caro et al., 2009;Conte et al., 2008; Ostroumov, 2008; Wang et al., 2009). In conclusionM. infundibulum mucus provides an accessible, renewable resourcethat could repay further exploration from several points of view.

Acknowledgments

Financial support was provided by the PRIN Project (2010–2011)and RITMARE Flagship Project both funded by the Italian Ministry ofUniversity and Research. [SS]

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