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#bryozoa

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Animal Classification

Protective covering of many ectoprocts is made of

Protective housing of individual zooids in many ectoprocts involves secretion of elaborate exoskeleton termed zooecium composed primarily of chitinous cuticle frequently impregnated with calcium carbonate forming rigid box vase or tubular case enclosing softer polypide containing lophophore and viscera. In marine Gymnolaemata calcified zooecium provides rigidity against predation abrasion, frontal wall may be membranous or calcified, while Ctenostomata maintain flexible cuticle. Some possess frontal membranes, ooecia for brooding and spines defense. Composition reflects ambient calcium availability and colony form encrusting versus erect. Protective cystid contrasts with chitinous tube of phoronids and bivalved shell of brachiopods constituting unique apomorphy.

Ref: Brusca & Brusca, Chapter 23: Bryozoa zooecium; Campbell Biology, Bryozoan exoskeleton

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Animal Classification

Most ectoprocts reproduce asexually to form

Primary mode of propagation and colony expansion in ectoprocts involves asexual budding where daughter zooids bud from parental body wall producing interconnected zoarium of polymorphic zooids specialized for feeding, defense, reproduction and support. Budding generates modular growth optimized for sessile filter feeding maximizing space capture. Sexual reproduction also present producing cyphonautes triangular shelled or coronate non-feeding larvae settling to form ancestrula founding new colony. Freshwater phylactolaemates additionally produce statoblasts as dormant chitinous propagules highly resistant to desiccation, emphasizing prevalence of asexual colony formation and resilience enabling survival in variable environments and dispersal across habitats.

Ref: Ruppert et al., Invertebrate Zoology, Chapter 23: Bryozoa budding colony formation

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