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3258369 
Journal Article 
Biomineralization in bryozoans: present, past and future 
Taylor, PD; Lombardi, C; Cocito, S 
2015 
Yes 
Biological Reviews
ISSN: 1464-7931
EISSN: 1469-185X 
90 
4 
1118-1150 
WOS:000362735300006 
Many animal phyla have the physiological ability to produce
biomineralized skeletons with functional roles that have been shaped by natural selection for
more than 500 million years. Among these are bryozoans, a moderately diverse phylum of aquatic
invertebrates with a rich fossil record and importance today as bioconstructors in some shallow-
water marine habitats. Biomineralizational patterns and, especially, processes are poorly
understood in bryozoans but are conventionally believed to be similar to those of the related
lophotrochozoan phyla Brachiopoda and Mollusca. However, bryozoan skeletons are more intricate
than those of these two phyla. Calcareous skeletons have been acquired independently in two
bryozoan clades - Stenolaemata in the Ordovician and Cheilostomata in the Jurassic - providing an
evolutionary replicate. This review aims to highlight the importance of biomineralization in
bryozoans and focuses on their skeletal ultrastructures, mineralogy and chemistry, the roles of
organic components, the evolutionary history of bimineralization in bryozoans with respect to
changes in seawater chemistry, and the impact of contemporary global changes, especially ocean
acidification, on bryozoan skeletons. Bryozoan skeletons are constructed from three different
wall types (exterior, interior and compound) differing in the presence/absence and location of
organic cuticular layers. Skeletal ultrastructures can be classified into wall-parallel (i.e.
laminated) and wall-perpendicular (i.e. prismatic) fabrics, the latter apparently found in only
one of the two biomineralizing clades (Cheilostomata), which is also the only clade to
biomineralize aragonite. A plethora of ultrastructural fabrics can be recognized and most occur
in combination with other fabrics to constitute a fabric suite. The proportion of aragonitic and
bimineralic bryozoans, as well as the Mg content of bryozoan skeletons, show a latitudinal
increase into the warmer waters of the tropics. Responses of bryozoan mineralogy and skeletal
thickness to oscillations between calcite and aragonite seas through geological time are
equivocal. Field and laboratory studies of living bryozoans have shown that predicted future
changes in pH (ocean acidification) combined with global warming are likely to have detrimental
effects on calcification, growth rate and production of polymorphic zooids for defence and
reproduction, although some species exhibit reasonable levels of resilience. Some key questions
about bryozoan biomineralization that need to be addressed are identified. 
biomineralization; Bryozoa; skeletal ultrastructure; evolution; fossil record; climate change