Few species are adapted to a life in estuarine environments, which is reflected in low biodiversity compared to marine or freshwater habitats ( Remane and Schlieper, 1971). Many barnacle species are also common fouling organisms, e.g., on ship hulls ( Otani et al., 2007), where broad salinity tolerance has been a key trait for surviving long-distance transportation, making them successful invaders worldwide and causing major ecological and economic impact in coastal areas ( Lewis and Coutts, 2009).Įstuarine environments are characterized by temporary, strong environmental fluctuations in salinity, which greatly affect the organisms living there. Already Darwin (1854) noted that several barnacle species were euryhaline, i.e., displaying a high tolerance to a wide range of salinities.
Barnacles (Cirripedia, Crustacea) are like many other crustaceans among the few marine invertebrates that can invade brackish habitats ( Davenport, 1976), with species like Balanus (Amphibalanus) improvisus and Balanus (Amphibalanus) subalbidus tolerating almost freshwater conditions ( Fyhn, 1976 Poirrier and Partridge, 1979 Kennedy and di Cosimo, 1983 Dineen and Hines, 1994). Salinity plays an important role in shaping aquatic communities ( Gunter, 1961 Remane and Schlieper, 1971 Whitfield et al., 2012). Finally, we outline future research directions to identify osmoregulatory tissues, characterize physiological and molecular mechanisms, and explore ecological and evolutionary implications of osmoregulation in barnacles. Tolerance to low salinities may play a crucial role in determining future distributions of barnacles since forthcoming climate-change scenarios predict decreased salinity in shallow coastal areas. We further discuss evolutionary consequences of barnacle osmoregulation including invasion-success in new habitats and life-history evolution. Based on this current knowledge, we discuss the osmoregulatory mechanisms possibly present in barnacles. We focus on ion and water transport across epithelial cell layers, including transport mechanisms across cell membranes and paracellular transfer across tight junctions as well as on the use of intra- and extracellular osmolytes. Different mechanisms are described based on the current understanding of molecular biology and integrative physiology of osmoregulation. To stimulate future studies on barnacle euryhalinity, we briefly review and compare barnacles to other marine invertebrates with known mechanisms of osmoregulation with focus on crustaceans. This review provides an overview of available knowledge of salinity tolerance in barnacles and what is currently known about their osmoregulatory strategies. However, the physiological and/or morphological adaptations that allow barnacles to live at low salinities are poorly understood and current knowledge is largely based on classical eco-physiological studies offering limited insight into the molecular mechanisms. Several barnacle species are described as highly euryhaline and a few species even have the ability to colonize estuarine and brackish habitats below 5 PSU. 4Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Swedenīarnacles form a globally ubiquitous group of sessile crustaceans that are particularly common in the coastal intertidal.3Department of Marine Sciences, Tjärnö Marine Laboratory, University of Gothenburg, Gothenburg, Sweden.2IVL Swedish Environmental Research Institute, Fiskebäckskil, Sweden.1Department of Biological and Environmental Sciences and Swedish Mariculture Research Center (SWEMARC), University of Gothenburg, Gothenburg, Sweden.Kristina Sundell 1, Anna-Lisa Wrange 2, Per R.
0 kommentar(er)
