Potency of Barnacles as Aquaculture Organisms

Oral Session

Recent Challenges for Developing Barnacle Aquaculture Techniques in Japan

Symposium mini revie

Total synthesis and structure–antifouling activity relationship of scabrolide F

An efficient synthetic strategy for scabrolide F (7), a norcembranolide diterpene that was isolated from the Taiwanese soft coral Sinularia scabra, has only recently been reported by our group. Herein, we report details of the first total synthesis of 7. The tetrahydrofuran domain of 7 was stereoselectively constructed via the 5-endo-tet cyclization of a hydroxy vinyl epoxide. The reaction of alkyl iodide 30 with dithiane 38, followed by the introduction of an alkene moiety, afforded allylation precursor 41. The coupling of alkyl iodide 42 and allylic stannane 43 was examined as a model experiment of allylation. Because the desired allylated product 44 was not obtained, an alternative synthetic route toward 7 was investigated instead. In the second synthetic approach, fragment–coupling between alkyl iodide 56 and aldehyde 58, macrolactonization, and transannular ring-closing metathesis were used as the key steps to achieve the first total synthesis of 7. We hope that this synthetic strategy provides access to the total synthesis of other macrocyclic norcembranolides. We also evaluated the antifouling activity and toxicity of 7 and its synthetic intermediates toward the cypris larvae of the barnacle Amphibalanus amphitrite. This study is the first to report the antifouling activity of norcembranolides as well as the biological activity of 7

Barnacle recruit density

Barnacle recruit densit

Predator preference for prey

Predator preference for pre

Data from: Mechanisms underlying predator-driven biotic resistance against introduced barnacles on the Pacific coast of Hokkaido, Japan

Introduced species are a major threat to coastal ecosystems worldwide. Thus, understanding biotic resistance (i.e. the ability of native species to limit introduced species) is a central goal of invasion biology. This paper examines mechanisms underlying biotic resistance. Consumption can limit introduced prey provided that native predators prefer such prey. Furthermore, predator nonconsumptive effects (NCEs), mediated through predator-released cues perceived by prey, can limit prey recruitment, a key demographic process for prey populations. However, information on predator NCEs is largely absent in the context of recruitment in introduced prey. Working on the Pacific coast of Hokkaido (Japan), we addressed this knowledge gap using native predatory dogwhelks (Nucella lima) that prey on native barnacles (Chthamalus dalli) and introduced barnacles (Balanus glandula). We experimentally examined dogwhelk preferences for barnacles in the laboratory and dogwhelk NCEs on barnacle recruitment in the field. We found that N. lima preferred B. glandula over C. dalli, likely as B. glandula prey is more profitable, as suggested by previous findings in congeneric dogwhelks. Moreover, we found that N. lima NCEs limited recruit density in C. dalli and B. glandula, likely as barnacle larvae moved away from dogwhelk cues to reduce future predation risk. Our study suggests that predator prey preferences and predator nonconsumptive limitation of prey recruitment are two mechanisms that can contribute to predator-driven biotic resistance against introduced prey

Chemical synthesis and antifouling activity of monoterpene–furan hybrid molecules

Geraniol, a monoterpene, and furan are structural motifs that exhibit antifouling activity. In this study, monoterpene-furan hybrid molecules with potentially enhanced antifouling activity were designed and synthesized. The nine synthetic hybrids showed antifouling activity against the cypris larvae of the barnacle Balanus (Amphibalanus) amphitrite with EC50 values of 1.65-4.70 mu g mL(-1). This activity is higher than that of geraniol and the reference furan compound. This hybridization approach to increase antifouling activity is useful and can also be extended to other active structural units

Possible molecular mechanisms of species recognition by barnacle larvae inferred from multi-specific sequencing analysis of proteinaceous settlement-inducing pheromone

Gregarious settlement is essential for reproduction and survival of many barnacles. A glycoprotein, settlement-inducing protein complex (SIPC) has been recognized as a signal for settlement and it is expressed in both conspecific adults and larvae. Although the settlement-inducing activities of SIPC are species-specific, the molecular-based mechanism by which larvae distinguish conspecific SIPC from the SIPC of other species is still unknown. Here, the complete primary structure of the SIPC of Megabalanus coccopoma, as well as the partial structure of the SIPCs of Balanus improvisus, Megabalanus rosa, and Elminius modestus are reported. These SIPCs contain highly variable regions that possibly modulate the affinity for the receptor, resulting in the species specificity of SIPC. In addition, the distribution patterns of potential N-glycosylation sites were seen to be different among the various species. Differences in such post-translational modifications may contribute to the species specificity of SIPC