TY - JOUR

T1 - Cleavage pattern in Oscarella species (Porifera, Demospongiae, Homoscleromorpha)

T2 - Transmission of maternal cells and symbiotic bacteria

AU - Ересковский, Александр Вадимович

AU - Boury-Esnault, Nicole

PY - 2002/10/20

Y1 - 2002/10/20

N2 - The cleavage and the first stages of development of larvae in five Oscarella species, from the north-west Mediterranean, O. lobularis, O. tuberculata, O. imperialis, O. microlobata and Oscarella sp., are investigated. Eggs are isolecithal, and rich in yolk inclusions. The cleavage is holoblastic, equal and asynchronous. During cleavage, there is no central cavity (blastocoel). The result of cleavage is the formation of a solid morula constituted by equal blastomeres. The polarity of the blastomeres is not expressed prior to the beginning of larva differentiation, i.e. approximately up to 64-cell stage. The superficial membrane of the blastomeres shows numerous filopodia which form blastomere contact. Symbiotic bacteria and cells with inclusions of the maternal mesohyl are present in the intercellular spaces of the embryo from the beginning of cleavage. Whereas maternal symbiotic bacteria are present in the embryo of the five species studied, maternal cells with inclusions are absent from two species (O. tuberculata and O. microlobata). The most original feature of early development in the genus Oscarella is the formation of a coeloblastula larva from a morula due to the progressive migration of the internal cells to the periphery.

AB - The cleavage and the first stages of development of larvae in five Oscarella species, from the north-west Mediterranean, O. lobularis, O. tuberculata, O. imperialis, O. microlobata and Oscarella sp., are investigated. Eggs are isolecithal, and rich in yolk inclusions. The cleavage is holoblastic, equal and asynchronous. During cleavage, there is no central cavity (blastocoel). The result of cleavage is the formation of a solid morula constituted by equal blastomeres. The polarity of the blastomeres is not expressed prior to the beginning of larva differentiation, i.e. approximately up to 64-cell stage. The superficial membrane of the blastomeres shows numerous filopodia which form blastomere contact. Symbiotic bacteria and cells with inclusions of the maternal mesohyl are present in the intercellular spaces of the embryo from the beginning of cleavage. Whereas maternal symbiotic bacteria are present in the embryo of the five species studied, maternal cells with inclusions are absent from two species (O. tuberculata and O. microlobata). The most original feature of early development in the genus Oscarella is the formation of a coeloblastula larva from a morula due to the progressive migration of the internal cells to the periphery.

KW - Cleavage

KW - Maternal cells

KW - Mediterranean sea

KW - Oscarella

KW - Sponge

KW - Symbiotic bacteria

KW - Ultrastructure

UR - http://www.scopus.com/inward/record.url?scp=0037145408&partnerID=8YFLogxK

U2 - 10.1080/00222930110069050

DO - 10.1080/00222930110069050

M3 - Article

AN - SCOPUS:0037145408

VL - 36

SP - 1761

EP - 1775

JO - Journal of Natural History

JF - Journal of Natural History

SN - 0022-2933

IS - 15

ER -