TY - JOUR

T1 - Diversity of brood chambers in calloporid bryozoans (Gymnolaemata, Cheilostomata)

T2 - Comparative anatomy and evolutionary trends

AU - Ostrovsky, Andrew N.

AU - Nielsen, Claus

AU - Vávra, Norbert

AU - Yagunova, Ekaterina B.

N1 - Funding Information: Acknowledgments We are deeply indebted to Drs. N. N. Shunatova, Department of Invertebrate Zoology, St. Petersburg State University, D. P. Gordon, National Institute of Water and Atmospheric Research, Wellington, J.-G. Harmelin, Station Marien d’Endoume, Centre d’Océanologie Marseille, B. I. Sirenko and I. S. Smirnov, Laboratory of Marine Researches, Zoological Institute of Russian Academy of Sciences, St. Petersburg, and P. E. Bock, School of Ecology and Environment, Deakin University, Burwood, for sending us the material. We also thank two anonymous reviewers and Professor Th. Bartolomaeus, Freie Universität Berlin, whose comments substantially improved the manuscript. The research was supported by FWF grant P19337-B17 (Austria) and RFBR grants 07-04-00928a and 07-04-10046k (Russia).

PY - 2009/2

Y1 - 2009/2

N2 - Comparative anatomical studies of 12 species from 10 genera (Callopora, Tegella, Amphiblestrum, Parellisina, Corbulella, Crassimarginatella, Valdemunitella, Bryocalyx, Concertina, Cauloramphus) belonging to one of the largest and most diverse bryozoan taxa, the Calloporidae, and one species from the genus Akatopora belonging to the related taxon Antroporidae, were undertaken to elucidate the morphological diversity of brooding structures and to recognize main trends in their evolution. Most of the species studied possess ovicells (specialized brooding receptacles) formed by the distal and maternal (egg-producing) autozooids. The distal zooid can be an autozooid, a vicarious avicularium or a kenozooid. The calcified protective hood (ooecium) is an outgrowth from the distal zooid. Hyperstomial or prominent ovicells are most common. They were found in species of the genera Callopora, Tegella, Amphiblestrum, Parellisina, Corbulella, Bryocalyx and Concertina. Subimmersed ovicells were found in Valdemunitella, and immersed ovicells in Crassimarginatella and Akatopora. Cauloramphus has an internal brooding sac and a vestigial kenozooidal ooecium, budded by the maternal zooid. Based on the structure of the brooding organs, the following evolutionary trends can be recognized within the group: (1) reduction of the distal (ooecium-producing) zooid, (2) immersion of the brooding cavity correlated with a reduction of the ooecium and ooecial vesicle and with changes in the ovicell closure and the structure of the brood chamber floor, (3) reduction of the calcification of the ectooecium, and (4) transition from bilobate to entire ooecium. The trend towards immersion of the brooding cavity could have evolved repeatedly within the Calloporidae. Transition from bilobate to entire ooecium is characteristic of the related taxon Cribrilinidae, showing a good example of parallel evolution of the ooecium in two closely related clades. Possible causes for the transformations described are discussed.

AB - Comparative anatomical studies of 12 species from 10 genera (Callopora, Tegella, Amphiblestrum, Parellisina, Corbulella, Crassimarginatella, Valdemunitella, Bryocalyx, Concertina, Cauloramphus) belonging to one of the largest and most diverse bryozoan taxa, the Calloporidae, and one species from the genus Akatopora belonging to the related taxon Antroporidae, were undertaken to elucidate the morphological diversity of brooding structures and to recognize main trends in their evolution. Most of the species studied possess ovicells (specialized brooding receptacles) formed by the distal and maternal (egg-producing) autozooids. The distal zooid can be an autozooid, a vicarious avicularium or a kenozooid. The calcified protective hood (ooecium) is an outgrowth from the distal zooid. Hyperstomial or prominent ovicells are most common. They were found in species of the genera Callopora, Tegella, Amphiblestrum, Parellisina, Corbulella, Bryocalyx and Concertina. Subimmersed ovicells were found in Valdemunitella, and immersed ovicells in Crassimarginatella and Akatopora. Cauloramphus has an internal brooding sac and a vestigial kenozooidal ooecium, budded by the maternal zooid. Based on the structure of the brooding organs, the following evolutionary trends can be recognized within the group: (1) reduction of the distal (ooecium-producing) zooid, (2) immersion of the brooding cavity correlated with a reduction of the ooecium and ooecial vesicle and with changes in the ovicell closure and the structure of the brood chamber floor, (3) reduction of the calcification of the ectooecium, and (4) transition from bilobate to entire ooecium. The trend towards immersion of the brooding cavity could have evolved repeatedly within the Calloporidae. Transition from bilobate to entire ooecium is characteristic of the related taxon Cribrilinidae, showing a good example of parallel evolution of the ooecium in two closely related clades. Possible causes for the transformations described are discussed.

KW - Brooding

KW - Cheilostomata

KW - Evolution

KW - Internal sacs

KW - Ovicells

UR - http://www.scopus.com/inward/record.url?scp=58549096278&partnerID=8YFLogxK

U2 - 10.1007/s00435-008-0070-8

DO - 10.1007/s00435-008-0070-8

M3 - Article

AN - SCOPUS:58549096278

VL - 128

SP - 13

EP - 35

JO - Zoomorphology

JF - Zoomorphology

SN - 0340-6725

IS - 1

ER -