Abstract
Polychaete annelids are a very important group of calcifiers in the modern oceans. They can produce calcite, aragonite, and amorphous phosphates. Serpulids possess very diverse tube ultra-structures, several unique to them. Serpulid tubes are composed of aragonite or calcite or a mixture of both polymorphs. The serpulid tubes with complex oriented microstructures, such as lamello fibrillar, are exclusively calcitic, whereas tubes with prismatic structures can be composed either of calcite or aragonite. In serpulids, the calcareous opercula also have complex microstructures. Evolutionarily, calcitic serpulid taxa belong to one clade and the aragonitic taxa belong to another clade. Modern ocean acidification affects serpulid biomineralization. Serpulids are capable of biomineralization in extreme environments, such as the deepest part (hadal zone) of the ocean. The tubes of calcareous sabellids are aragonitic and have two layers, the inner irregular spherulitic prismatic layer and the outer spherulitic layer. The tube wall of cirratulids is composed of aragonitic lamellae with a spherulitic prismatic structure. In some other polychaetes, biominerals are formed in different parts of the animal body, such as chaetae or body shields, or occur within the body as granule-shaped or rod-shaped inclusions.
Highlights
Calcifying polychaete annelids are a very important group of animals in the oceanic calcium sink, especially in temperate seas where they can be major calcifying invertebrates [1,2,3]
General understanding of the evolution of invertebrate biomineralization systems is mostly based on studies of molluscs (Carter et al and references therein) [6], and to a lesser extent on corals, brachiopods, bryozoans, and echinoderms
This review summarizes the most important aspects of the polychaete biomineralization currently known
Summary
Calcifying polychaete annelids are a very important group of animals in the oceanic calcium sink, especially in temperate seas where they can be major calcifying invertebrates [1,2,3]. Isotopic analyses have been used to study the stable-isotope composition of serpulid tubes for insights into calcification processes in marine organisms [4]. Serpulid tubes have been studied with plasma mass spectroscopy (IPC-MS) to analyze the anthropogenically mobilized metal content (e.g., Al, Cd, Ni, Pb, U, etc.) as an estimate of the human impact on the coastal environment of California [5]. General understanding of the evolution of invertebrate biomineralization systems is mostly based on studies of molluscs (Carter et al and references therein) [6], and to a lesser extent on corals, brachiopods, bryozoans, and echinoderms. Polychaetes, may have a different biomineralization strategy, the understanding of which would contribute significantly toward a general synthesis of biomineralogical evolution among invertebrates having calcareous skeletons
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