Do All Dinoflagellates have an Extranuclear Spindle?
The syndinean dinoflagellates are a diverse assemblage of alveolate endoparasites that branch basal to the core dinoflagellates. Because of their phylogenetic position, the syndineans are considered key model microorganisms in understanding early evolution in the dinoflagellates. Closed mitosis with an extranuclear spindle that traverses the nucleus in cytoplasmic grooves or tunnels is viewed as one of the morphological features shared by syndinean and core dinoflagellates. Here we describe nuclear morphology and mitosis in the syndinean dinoflagellate Amoebophrya sp. from Akashiwo sanguinea, a member of the A. ceratii complex, as revealed by protargol silver impregnation, DNA specific fluorochromes, and transmission electron microscopy. Our observations show that not all species classified as dinoflagellates have an extranuclear spindle. In Amoebophrya sp. from A. sanguinea, an extranuclear microtubule cylinder located in a depression in the nuclear surface during interphase moves into the nucleoplasm via sequential membrane fusion events and develops into an entirely intranuclear spindle. Results suggest that the intranuclear spindle of Amoebophrya spp. may have evolved from an ancestral extranuclear spindle and indicate the need for taxonomic revision of the Amoebophryidae.
LOHABE, Department of Oceanography, Chonnam National University, Gwangju 500-757, Republic of Korea.
Eunyoung
E
Moon
Department of Biological Science, Chungnam National University, Daejeon 306-764, Republic of Korea.
Seung Won
SW
Nam
Department of Biological Science, Chungnam National University, Daejeon 306-764, Republic of Korea.
Woongghi
W
Shin
LOHABE, Department of Oceanography, Chonnam National University, Gwangju 500-757, Republic of Korea. Electronic address: mpark@chonnam.ac.kr.
Myung Gil
MG
Park
Smithsonian Environmental Research Center, P.O. Box 28, 647 Contees Wharf Rd., Edgewater, MD 21037, USA.
D Wayne
DW
Coats
D002467:Cell Nucleus / Q000502:physiology / Q000648:ultrastructure; D004141:Dinoflagellida / Q000502:physiology* / Q000648:ultrastructure; D005456:Fluorescent Dyes / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D008938:Mitosis; D010802:Phylogeny; D016622:Silver Staining; D008941:Spindle Apparatus / Q000648:ultrastructure
D005456:Fluorescent Dyes
Amoebophrya; Syndinea; dinoflagellate; mitosis; parasite; ultrastructure.