Elenor R. Cox

OBSERVATIONS ON THE SYMBIOSIS OF PERIDINIUM BALTICUM AND ITS INTRACELLULAR ALGA. I. ULTRASTRUCTURE1,2

The ultrastructure of Peridinium balticum indicates that an eudosymbiont is present within the dinoflagellate. The structure and probable function of the organelles of both protists arc described and discussed. The origin of photosynthetic dinoflagellates from heterotrophic forms by means of a chrysophyte‐like endosymbiont is postulated.

PERIDINIUM BALTICUM (LEVANDER) LEMMERMANN, AN UNUSUAL DINOFLAGELLATE WITH A MESOCARYOTIC AND AN EUCARYOTIC NUCLEUS123

Light and electron microscopy indicate that Peridinium balticum possesses 2 Feulgen‐positive, membrane‐bound nuclei which divide synchronously. One nucleus has the typical structure of dinocaryotic dinoflagellates, while the other nucleus has a structure typical of eucaryotic organisms. Connections between each nucleus and the endoplasmic reticulum are common. Membrane‐bound vesicles are intimately associated with the nuclear envelope of the eucaryotic nucleus.

Ultrastructure of active and resting colonies of botryococcus braunii chlorophyceae

The ultrastructure of resting state colonies of Botryococcus braunii Kützing from two localities is compared to active state colonies maintained in the laboratory. Qualitative hydrocarbon analyses confirmed the physiological status of each sample according to the precedent in the literature; resting state colonies contained botryococcenes, while active state colonies contained a predominance of straight‐chain olefins. The ultrastructure of resting and active state colonies is fundamentally similar. The chloroplast of resting state cells contains fewer thylakoids and larger relative numbers of plastoglobuli than the chloroplast of active state cells maintained under favorable growth conditions. Previously undescribed phenomena include the cytochemical demonstration of polyphosphate bodies microbody‐like organelles and ER‐ribosomal‐mitochondrial complexes.

PIGMENTS OF THE DINOFLAGELLATE PERIDINIUM BALTICUM AND ITS PHOTOSYNTHETIC ENDOSYMBIONT1

An examination of the pigments of the binucleate dinoflagellate Peridinium balticum (Levander) Lemmerman revealed the presence of chlorophylls a, c1 and c2 and the carotenoids: fucoxanthin (most abundant), diadinoxanthin, diatoxanthin, an unidentified fucoxanthin‐like xanthophyll, β‐carotene, γ‐carotene and astaxanthin. A comparison of the pigments of P. balticum and P. foliaceum (Stein) Biecheler, also a binucleate dinoflagellate, demonstrated similar compositions. However P. balticum lacked the β‐carotene precursors (e.g. phytoene) which accumulated outside the chloroplast in P. foliaceum. This study indicates that P. balticum and P. foliaceum are closely related; each species is a heterotrophic dinoflagellate with a photosynthetic endosymbiont taxonomically affiliated with the Chrysophyta (Chrysophyceae or Bacillariophyceae).

Synchronized sexuality of an algal symbiont and its dinoflagellate host, Peridinium balticum (levander) lemmermann

We report synchronized sexual reproduction between the chlorophyll c-containing algal endosymbiont and its dinoflagellate host in Peridinium balticum (Pyrrhophyta). This organisms importance lies in that it may represent an intermediate between primitive non-photosynthetic and advanced photosynthetic dinoflagellates. Fusion of the endosymbionts and their nuclei occurred concomitantly with syngamy of the host gametes. Significant morphological changes, including condensation of chromatin and crystalline rod formation, occurred in the symbiont nucleus during zygote development. These observations provide evidence that the endosymbiotic nucleus is not passive in sexual processes, as opposed to its reported passive state during mitosis. P. balticum may not only represent an intermediate in the evolution of chloroplast acquisition by dinoflagellates, but also, an intermediate in the evolution of the peridinian dinoflagellate sexual life history.

STUDIES IN PENNATE DIATOMS: VALVE MORPHOLOGIES OF LICMOPHORA AND CAMPYLOSTYLUS1

Using scanning electron and light, microscopy, several hundred specimens of Campylostylus normanianus (Grev.) Gerloff, Licmophora abbreviata Agardh, L. gracilis var. anglica (Kütz) Per. et Per., and L. flabellata (Carm.) Agardh were examined to elucidate their valve morphology. These species were found to be heterovalvar with respect to the presence of the labiate process in the basal apices of the cell, although one was always present at the head pole of each valve. This form of heterovalvar may be one basis for partitioning the large and variable family Diatomaceae. Because of the similar valve morphologies exhibited by C. normanianus and Licmophora species examined, it is recommended that Campylostylus normanianus be placed in the older genus Licmophora, as L. normaniana (Grev.) Wahrer.

Specialization of endoplasmic reticulum architecture in response to a bacterial symbiosis in Peridinium balticum (Pyrrhophyta)

Transmission elrctron microscopy (TEM) and rapid freeze‐fracture analyses were used to provide data for a more accurate description of the relationship of Peridinium balticum (Levander) Lemmermann to endosymbiotic bacteria present in the dinoflagellates cytoplasm. Bacteria were found in all of the cells observed and were present in both gamete and zygote life cycle stages. Analysis of micrographs showed that bacteria were tightly clustered in the posterior portion of the dinoflagellate cell in numbers of 50‐200/ section. Rapid freeze‐fracture replicas re‐vealed a specialization of the endoplasmic reticulum (ER). ER surrounded each bacterium and consisted of a series of infoldings which contacted the bacterial plasma membrane in several places. Extensions of ER were common between adjacent bacteria. We have interpreted the development and specialization of endoplasmic reticulum of the dinoflagellate host as an example of a cellular response of one organism to another, supportive of the serial endosymbiotic theory. Intramembrane particles (IMP) were seen on both protoplasmic (P) and exoplasmic (E) faces of the bacterial plasma membrane. Aquisition of the bacterial symbiont and the effects of long term culturing are discussed.

THECAL ULTRASTRUCTURE OF THE TOXIC MARINE DINOFLAGELLATE GONYAULAX CATENELLA1

The toxic marine dinoflagellate Gonyaulax catenella Whedon & Kofoid was studied with scanning and transmission electron microscopy to describe the thecal morphology and to accurately define the taxonomic characters of the species. The closing platelet which lies in a U‐shaped apical pore was revealed to be disassociable from a partly obscured apical platelet. Two previously unreported sulcal plates were charaterized and described. The entire complement of thecal plates numbered 33.

THE DESMID GENERA SPHAEROZOSMA, ONYCHONEMA AND TEILINGIA: AN HISTORICAL APPRAISAL1

The taxonomic history of the desmid genera Onychonema Wallich, Sphaerozosma Corda and Teilingia Bourrelly is reviewed. In addition, Teilings studies on asymmetry applied to Onychonema and Sphaerozosma are considered. Observations based on SEM examination of one species each of Onychonema and of Sphaerozosma are presented to show morphological differences. Finally, an appraisal of the taxonomic proposals by Telling and Bourrelly is given.

Thecal ultrastructure ofScrippsiella faeroense

SummaryThe thecal ultrastructure ofScrippsiella faeroense (Paulsen) Balech and Oliveira Soares as seen in the electron microscope is described. Additional structural detail of the thecal plate surface, plate connections, and the apical pore, is revealed.