Coralline red algae—a new host taxon for burrowing barnacles (Cirripedia, Acrothoracica)

Abstract

To date, living acrothoracican barnacles have only been directly observed burrowing into the skeletons of marine animals or into calcareous rocks. While surveying the Acrothoracica of South Africa, we recorded live Weltneria spinosa Berndt, 1907, burrowed into a beach-cast rhodolith, comprising non-geniculate coralline red algae from the genus Lithophyllum Philippi, 1837. Unoccupied holes of the same acrothoracican were also found in another rhodolith identified as Neogoniolithon brassica-florida (Harvey) Setchell & L.R.Mason, 1943. A search of herbarium material also revealed the same acrothoracican species burrowing into two thick discoid coralline algal species, Lithophyllum neoatalayense Masaki, 1968, and Heydrichia woelkerlingii R.A.Townsend, Y.M.Chamberlain & Keats, 1994. These are the first unequivocal records of living acrothoracicans burrowing into coralline red algae. The fact that several algal species were colonized and that these were found across a range of sites suggests that coralline algae represent a previously unknown habitat type for this group of barnacles and that this habitat greatly increases the known range of substrates available for colonization. Further inspections of coralline algae in this and other regions will likely reveal many more new host records and possibly new host-specific acrothoracican species.