The m e r a l o g i c a l features of the substrate were generally cons~dered a rmnor factor m structunng manne benthic communities The alm of t h~s work 1s to venfy whether the presence of quartz nunerals in rock may exphcate dlfferences, usually explamed m terms of substrate roughness or other factors In epibenthic cornrnun~hes Laboratory tests on the hydroid Eudendnum glomeratum showed that ~t s planulae settle preferentially on carbonat~c, rather than quartzltic substrates To test the Influence of quartz on established communities, we analysed the specles composition and quantitat~ve structure of subhttoral sesslle assemblages on Wferent rocks In several locahhes of the L~gurian and Tyrrhenian seas The observed dlfferences appeared to be related to the presence of quartz in the substrate rock The ~nteractions between organisms and minerals (bio-mmeralogy) mlght play a slgnlficant role on benthic communities affechng not only the inihal colonlsahon but also later assemblages This potential role has been largely neglected to date and further studies are needed to prove ~t s Impor tance KEY WORDS: Substrate colonisation . Mineral composition . Marine benthos distnbution . Hard substrates . Bio-mineralogy INTRODUCTIONThe spatial distribution and structure of marine benthic communities are due to numerous abiotic and biotic factors which, in turn, are influenced by the presence of the organisms, in a mutual exchange of inputs. Among the abiotic factors, the mineralogical features of the substrate were generally considered of scarce importance, but recent studies by Cerrano et al. (1998) have shown that the presence of quartz in the sand may affect the initial steps of infauna colonisation. Cerrano et al. (1998) introduced the term bio-mineralogy to explicate the interrelationships between biological systems at different hierarchies (cell, organism, species, community) and minerals.Bio-mineralogy could influence hard-bottom assemblages and explain some 'anomalies' in the structure of communities growing on rocks of different nature. A species assemblage, which may be slightly more attracted to a particular substrate, could affect succession by its subsequent interaction with later assemblages. A similar effect was evidenced in the colonisation of artificial substrates, with respect to both species composition and abundance (Anderson & Underwood 1994, Holm et al. 1997). Less information is available for natural substrates (McGuiness 1989), but it is common knowledge that the softness and asperity of a rock can favour or hamper biotic colonisation through selective larval settling, retention of water (in the littoral) and organic matter, and provision of refuges from predation or grazing (Den Hartog 1972, Levinton 1982, Walters & Wethey 1996.More is known about the influence of substrate mineralogy on bioboring, which is prevented by high percentages of quartzitic or pelitic components in the rock. Sublittoral endolitic communities are charac-

Marine hydroids are markedly seasonal in temperate seas, being extremely sensitive to climatic changes disrupting seasonal patterns. Modifications in the composition, seasonality, bathymetric distribution and reproductive period of hydroid assemblages are useful to evaluate the influence of global warming on the marine ecosystem. The hydroids on the rocky cliff of the Portofino Promontory (Ligurian Sea, Italy) were carefully studied between 1976 and 1983; in particular, in 1980 the study was carried out along a vertical transect. The hydroids were sampled again throughout 2004, with the same techniques and along the same transect. Species diversity decreased slightly in the 2004 survey. Some species present in 1980 had disappeared in 2004, but other species with southern affinity, never recorded from the area, became abundant in 2004. Species that were present in summer in the first period were also present in winter in the second one. Furthermore, shallow summer species widened their bathymetric distribution, reaching deeper levels. These data strongly suggest that the Portofino hydroid assemblage reacted to the water temperature increase found in the Mediterranean Sea.

Despite the hydroid fauna of the Mediterranean Sea being considered one of the best known in the world, the eastern basin of the Mediterranean Sea remains nearly unexplored. This paper reports on 38 species collected along the Levant Sea coast (mainly Lebanon), of which three are new records for the Mediterranean and nine for the Levant Sea. Six alien species, i.e. Eudendrium carneum, Sertularia marginata, Sertularia techocarpa, Macrorhynchia philippina, Diphasia digitalis and Dynamena quadridentata, are described in detail and illustrated on the basis of Levant Sea material. The last four species are considered as immigrants from the Red Sea. The synonymy of Sertularia stechowi, described from Japan, with S. techocarpa is established. Taken as a whole, the collection comprised a majority of circum-(sub)tropical species, and a reduced proportion of Atlantic-Mediterranean elements and Mediterranean endemics. The ecology (seasonality, depth distribution and habitat preference) of the indigenous species resulted similar to what is known for the more studied western Mediterranean, with some exceptions. Adding the present species inventory to the scanty published information, the total of hydroid species known from the Levant Sea rises to 70, indicating the need for future investigation in this sector of the Mediterranean Sea.

Hydroids in the genus Zanclea are a recently discovered component of the fauna associated with reef‐building corals. The phylogenetic relationships among these species are not well known. The present work is based on field surveys in the Republic of Maldives, and for the first time, morphological and molecular analyses are integrated to distinguish a new hydroid species and provide new information on the ecology of this symbiosis. This new hydroid, Zanclea gallii sp. n., was associated with the scleractinian Acropora muricata; it was living sympatrically with its congener Zanclea sango, which was observed for the first time at this locality on the new scleractinian host Pavona varians. The relationships between these two hydroids and other available scleractinian‐associated Zanclea were investigated using two molecular markers, nuclear 28S rDNA and mitochondrial 16S rRNA. Zanclea gallii sp. n. and Z. sango were recovered as distinct lineages within a monophyletic group of scleractinian‐associated Zanclea based on both molecular and morphological data. All Zanclea species that were observed living in association with scleractinians belong to the ‘polymorpha group’ and share the morphological characteristic ‘polymorphic colony’. The genus Leptoseris is the 16th host coral identified for Zanclea. Compared with the frequency of the Z. gallii sp. n. association with A. muricata and Z. sango with the scleractinian P. varians, the latter is twice as common; however, the former exhibited higher Zanclea polyps concentrations over the colony surface. Overall, the Zanclea survey indicates that these diminutive hydroids are more commonly associated with coral than previously known.

Mesophotic habitats, hosting benthic assemblages totally unknown and unexpected in the early 2000s, are attracting an increasing interest from scientists. Realizing that many long living and habitat forming species are playing a unique pocket of biodiversity in the frame of climate crisis, it is important to recognize the potential of the mesophotic zone in conservation strategies. The mesophotic zone is characterized by environmental factors generally more stable than the shallow counterpart; therefore, it represents a refuge habitat to preserve species that, in shallow waters, may be involved in bleaching events, massive mortalities or other pathologies generally triggered by thermal anomalies. The definition of the mesophotic zone in the temperate seas is confused, creating possible misunderstandings and problems not only from a scientific point of view but also in communication and outreach strategies. Here, we review the scientific literature to build the best definition possible based on the maximum consensus coming from papers analysis. Moreover, the key roles of mesophotic habitats, including ecosystem engineers as animal forests, have been schematized to enhance the perception of the potential risks we are running in case of damage or loss of these habitats.