SUBSTRATUM RECOGNITION AS SETTLEMENT CUE FOR LARVAE OF DENDROPOMA CRISTATUM (BIONDI, 1859) RICONOSCIMENTO DEL SUBSTRATO COME STIMOLO PER IL SETTLEMENT DI LARVE DI DENDROPOMA CRISTATUM(BIONDI, 1859)

Despite the ecological relevance of the vermetid bioconstructions in the Mediterranean, little is known about the early life stage of Dendropoma cristatum. This study describes the preference for settlement substrata from D. cristatumlarvae. A field experiment was carried out to test the suitability of crustose coralline algae (CCA), D. cristatumadults and two inorganic substrata as settlement surfaces. The number of settling larvae varied among the four treatments with higher settlement success on organic surfaces. CCA and D. cristatumindividuals seem to promote attachment of young larvae and to induce the metamorphosis in recruits. This is probably due to biological or physical properties of the preferred substrata which result essential for the early development of the vermetid bioconstruction

CONSERVATION NEEDS FOR THE VERMETID REEFS IN THE MEDITERRANEAN SEA

Vermetid reefs are intertidal bioconstructions typical of many subtropical and temperate coastal areas worldwide. Distributed in the warmest waters of the Mediterranean Sea, the reefs are built by the vermetid gastropod Dendropoma petraeum and the coralline alga Neogoniolithon brassica-florida, two species included in the annexes of the Berna Convention. Vermetid reefs provide a wide set of ecosystem services, such as coastal protection from erosion, regulation of sediment transport and accumulation, serving as carbon deposit and increasing biodiversity at the intertidal level. Despite its vulnerability to several threats, such as pollution, spread of invasive species, ocean acidification and anthropic use of rocky shores, the vermetid reef is only generically protected under the European Habitat Directive (92/43/EEC, code 1170), but not explicitly taken into account in many conservation management plans. On 112 censused reefs, the percentage of protected sites varies among countries. About 50 % of the reefs are officially protected in Italy, Malta, Spain, Morocco and Syria, but less than 20 % is protected in Lebanon, Tunisia and Turkey, and no protection is ensured in Algeria, Cyprus and Libya. In Israel, where protection regards more than 50 % of the reefs, Dendropoma petraeum got recently extinct. Up to date, less than 30 % of vermetid reefs in the Mediterranean are apparently protected by means of MPAs or coastal reserves, but a lack of information on the reef conservation status for the coastal areas of northern Africa and the eastern basin is clear. These data marks the need to extend action plans to protect the vermetid reefs and to improve its management in the Mediterranean. Developing a conservation strategy at basin scale and implementing monitoring of protected and not protected reefs are essential to guarantee an effective and sufficient protection of this neglected but relevant coastal key habitat

Recruitment patterns in an intertidal species with low dispersal ability: the reef-building Dendropoma cristatum (Biondi, 1859) (Mollusca: Gastropoda)

In the Mediterranean, the gastropod Dendropoma cristatum (sin. D. petraeum (Monterosato, 1884)) is the primary builder of the vermetid reef, an intertidal bioconstruction of exceptional ecological importance. Despite awareness of the need for conservation of this key species, the biology of D. cristatum remains poorly understood. The recruitment of D. cristatum deserves particular attention because the absence of a planktonic larval stage limits its dispersal ability. We examined the temporal pattern of recruitment during the breeding season of D. cristatum from June to September in 2013. Specifically, we compared the two portions of the vermetid reef (i.e. the inner edge and the outer edge) at localities with different exposures to wave motion. The number of recruits peaked in July, when it was significantly higher in the outer than in the inner edge. No differences emerged between localities with different wave exposures; however, the width of the reef was significantly related to the exposure index. Although there are still several gaps in our knowledge of the recruitment dynamics of D. cristatum, this study contributes to characterising recruitment rate variation at small spatial and temporal scales