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1 December 2007 The Internal-Brooding Apparatus in the Bryozoan Genus Cauloramphus (Cheilostomata: Calloporidae) and Its Inferred Homology to Ovicells
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Abstract

We studied by SEM the external morphology of the ooecium in eight bryozoans of the genus Cauloramphus Norman, 1903 (Cheilostomata, Calloporidae): C. spinifer, C. variegatus, C. magnus, C. multiavicularia, C. tortilis, C. cryptoarmatus, C. niger, and C. multispinosus, and by sectioning and light microscopy the anatomy of the brooding apparatus of C. spinifer, C. cryptoarmatus, and C. niger. These species all have a brood sac, formed by invagination of the non-calcified distal body wall of the maternal zooid, located in the distal half of the maternal (egg-producing) autozooid, and a vestigial, maternally budded kenozooidal ooecium. The brood sac comprises a main chamber and a long passage (neck) opening externally independently of the introvert. The non-calcified portion of the maternal distal wall between the neck and tip of the zooidal operculum is involved in closing and opening the brood sac, and contains both musculature and a reduced sclerite that suggest homology with the ooecial vesicle of a hyperstomial ovicell. We interpret the brooding apparatus in Cauloramphus as a highly modified form of cheilostome hyperstomial ovicell, as both types share 1) a brood chamber bounded by 2) the ooecium and 3) a component of the distal wall of the maternal zooid. We discuss Cauloramphus as a hypothetical penultimate stage in ovicell reduction in calloporid bryozoans. We suggest that the internal-brooding genus Gontarella, of uncertain taxonomic affinities, is actually a calloporid and represents the ultimate stage in which no trace of the ooecium remains. Internal brooding apparently evolved several times independently within the Calloporidae.

Andrew N. Ostrovsky, Matthew H. Dick, and Shunsuke F. Mawatari "The Internal-Brooding Apparatus in the Bryozoan Genus Cauloramphus (Cheilostomata: Calloporidae) and Its Inferred Homology to Ovicells," Zoological Science 24(12), 1187-1196, (1 December 2007). https://doi.org/10.2108/zsj.24.1187
Received: 16 February 2007; Accepted: 1 August 2007; Published: 1 December 2007
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