TY - JOUR

T1 - Comparative studies of ovicell anatomy and reproductive patterns in Cribrilina annulata and Celleporella hyalina (Bryozoa

T2 - Cheilostomatida)

AU - Ostrovsky, Andrew N.

N1 - Funding Information: I wish to sincerely thank Professor Dr Claus Nielsen and Karen Bille Hansen, Zoological Museum, University of Copenhagen, for providing working facilities and for valuable aid, advice and useful discussion. I also thank Natalja N. Shunatova, Department of Invertebrate Zoology, St Petersburg State University, for collecting and sorting the material. Thanks are also given to Nickolai P. Lutov and Eckaterina V. Lobastova, Department of Invertebrate Zoology, St Petersburg State University, for using unpublished data, Vibe Lund Hansen, Tom Schiφtte and Geert Brovad, Zoological Museum, University of Copenhagen, for help with making sections and SEM and photoworks. I greatly appreciate Dr Dennis P. Gordon, National Institute of Water and Atmospheric Research, Wellington, and Professor Dr John S. Ryland, School of Biological Sciences, University of Wales, for reading the early draft of the manuscript, and useful comments and criticism. I also wish to thank Dr Paul D. Taylor, The Natural Hstory Museum, London, for useful discussion. Financial support was provided by the Danish National Science Research Council (post-doctoral grant in Evolutionary Zoomorphology).

PY - 1998/10

Y1 - 1998/10

N2 - Investigations of the common boreal-arctic cheilostomate bryozoans Cribrilina annulata and Celleporella hyalina have shown that the two species possess similar ovicell structures and reproductive patterns. Both species are characterized by frontal dwarf ovicellate zooids, that are female autozooidal polymorphs in C. hyalina and simultaneous hermaphroditic autozooids in C. annulata. The latter species in addition has ovicellate autozooids of the usual type. Each ovicell is formed from a maternal zooid only, and its cavity is lined by the outer hemispherical fold (ooecium) and the distal zooidal wall. The coelomic cavity of the ooecium is separated from the body cavity of the maternal zooid by a transverse wall with simple pores. Each pore is closed by a cell plug, and the ooecia may be considered as kenozooids. Each oocyte is accompanied by a single nurse cell that degenerates after ovulation. The eggs are macrolecithal in C. annulata and microlecithal in C. hyalina, and the former species is a non-placental brooder whereas the latter forms a placenta. Fertilization is precocious. Possible mechanisms of sperm entry as well as oviposition are discussed. The literature concerning ovicell structure and development in cheilostomates is analysed. It is proposed that the brood chamber of cribrimorphs evolved by a fusion of costae and a reduction of the daughter zooid in ancestral forms.

AB - Investigations of the common boreal-arctic cheilostomate bryozoans Cribrilina annulata and Celleporella hyalina have shown that the two species possess similar ovicell structures and reproductive patterns. Both species are characterized by frontal dwarf ovicellate zooids, that are female autozooidal polymorphs in C. hyalina and simultaneous hermaphroditic autozooids in C. annulata. The latter species in addition has ovicellate autozooids of the usual type. Each ovicell is formed from a maternal zooid only, and its cavity is lined by the outer hemispherical fold (ooecium) and the distal zooidal wall. The coelomic cavity of the ooecium is separated from the body cavity of the maternal zooid by a transverse wall with simple pores. Each pore is closed by a cell plug, and the ooecia may be considered as kenozooids. Each oocyte is accompanied by a single nurse cell that degenerates after ovulation. The eggs are macrolecithal in C. annulata and microlecithal in C. hyalina, and the former species is a non-placental brooder whereas the latter forms a placenta. Fertilization is precocious. Possible mechanisms of sperm entry as well as oviposition are discussed. The literature concerning ovicell structure and development in cheilostomates is analysed. It is proposed that the brood chamber of cribrimorphs evolved by a fusion of costae and a reduction of the daughter zooid in ancestral forms.

UR - http://www.scopus.com/inward/record.url?scp=0031661673&partnerID=8YFLogxK

U2 - 10.1111/j.1463-6395.1998.tb01280.x

DO - 10.1111/j.1463-6395.1998.tb01280.x

M3 - Article

VL - 79

SP - 287

EP - 318

JO - Acta Zoologica

JF - Acta Zoologica

SN - 0001-7272

IS - 4

ER -