, for which the oldest name appears to be
Description
Dictyochida Borgert , 1891 , p. 66 1 SILICOFLAGELLATA (=Dictyochaceae in the botanical nomenclature , Dictyochidae in the zoological nomenclature). They belong to a single genus Dictyocha . ... .... ... ..... . tyochales in . ....... ............. . linida t 8 Skeleton-bearing stage; B. Naked stage. ch , chloro- plast ; fl, long flagellum ; n, nucleus; t, tentacle ; v , vacuole . Arrow indicates direction of swimming. Not to scale. (From Moestrup and Thomsen , 1990) Key characters 1. Only a single (hairy) flagellum is present , but a second, barren , basal body is located within the cell. Cells of the skeleton-lacking stage have two flagella , a long hairy flagellum and a very short stubby one. The flagella insert in an apical pit (Fig . 1B). The hairy flagellum SILICOFLAGEL and a very short stubby one. The flagella insert in an apical pit (Fig . 1B). The hairy flagellum membrane extends into a wing-like structure supported by a cross-banded paraxonemal rod, as in the order Pedinellales. Microtubular flag- ellar roots are unknown and a distinct rhizoplast has not been identified (Moestrup and Thomsen, 1990). crographs of th e siliceous skeleton , in B showing the cavity that houses the living cell. x3600. (From Moestrup and Thomsen , 1990). 2. Many chloroplasts , located peripherally (Fig . 1), each containing a single embedded pyrenoid. 3. Numerous Golgi bodies located as an anterior collar around the centrally located nucleus. 4. No cell wall , but cell surrounded by external silicified skeleton (Figs 1A, 2A, B) or naked (Fig . 1 B) (see below) . 5. No eyespot or ejectile organelles. 6. The naked stage of the life cycle with an ex- tensive layer of vacuoles between the outer layer of chloroplasts and the central part (Fig . 1B) which comprises the nucleus and the Golgi apparatus . 7. The skeleton-bearing stage with an internal canal system surrounding the central nucleus and Golgi apparatus-containing region. The canal system is connected by radial canals to the ex- terior . 8. Tentacles (Fig . 1A) supported by variable number of microtubules that extend from the nuclear envelope. Tentacles apparently emerging from any part of the cell. 9. The life cycle not yet fully understood, but comprising at least three main stages: the t y pi- cal skeletonbearing stage, the naked stage, and a multinucleate stage which may reach 500 1-1m in diameter (Moestrup and Thomsen, 1990; Hen- riksen et al. , 1993). All stages are present in marine plankton . A multinucleate, amoeboid stage has been seen in culture. 10. Classification based mainly on morphology of the siliceous skeleton . This can be highly variable (see e.g. Boney, 1973; van Valkenburg and Norris , 1970) and in large populations , specimens which cannot be referred to species level may occur.
Type species
Figures
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Raw text
Dictyochida Borgert , 1891 , p. 66 1 SILICOFLAGELLATA (=Dictyochaceae in the botanical nomenclature , Dictyochidae in the zoological nomenclature). They belong to a single genus Dictyocha . ... .... ... ..... . tyochales in . ....... ............. . linida t 8 Skeleton-bearing stage; B. Naked stage. ch , chloro- plast ; fl, long flagellum ; n, nucleus; t, tentacle ; v , vacuole . Arrow indicates direction of swimming. Not to scale. (From Moestrup and Thomsen , 1990) Key characters 1. Only a single (hairy) flagellum is present , but a second, barren , basal body is located within the cell. Cells of the skeleton-lacking stage have two flagella , a long hairy flagellum and a very short stubby one. The flagella insert in an apical pit (Fig . 1B). The hairy flagellum SILICOFLAGEL and a very short stubby one. The flagella insert in an apical pit (Fig . 1B). The hairy flagellum membrane extends into a wing-like structure supported by a cross-banded paraxonemal rod, as in the order Pedinellales. Microtubular flag- ellar roots are unknown and a distinct rhizoplast has not been identified (Moestrup and Thomsen, 1990). crographs of th e siliceous skeleton , in B showing the cavity that houses the living cell. x3600. (From Moestrup and Thomsen , 1990). 2. Many chloroplasts , located peripherally (Fig . 1), each containing a single embedded pyrenoid. 3. Numerous Golgi bodies located as an anterior collar around the centrally located nucleus. 4. No cell wall , but cell surrounded by external silicified skeleton (Figs 1A, 2A, B) or naked (Fig . 1 B) (see below) . 5. No eyespot or ejectile organelles. 6. The naked stage of the life cycle with an ex- tensive layer of vacuoles between the outer layer of chloroplasts and the central part (Fig . 1B) which comprises the nucleus and the Golgi apparatus . 7. The skeleton-bearing stage with an internal canal system surrounding the central nucleus and Golgi apparatus-containing region. The canal system is connected by radial canals to the ex- terior . 8. Tentacles (Fig . 1A) supported by variable number of microtubules that extend from the nuclear envelope. Tentacles apparently emerging from any part of the cell. 9. The life cycle not yet fully understood, but comprising at least three main stages: the t y pi- cal skeletonbearing stage, the naked stage, and a multinucleate stage which may reach 500 1-1m in diameter (Moestrup and Thomsen, 1990; Hen- riksen et al. , 1993). All stages are present in marine plankton . A multinucleate, amoeboid stage has been seen in culture. 10. Classification based mainly on morphology of the siliceous skeleton . This can be highly variable (see e.g. Boney, 1973; van Valkenburg and Norris , 1970) and in large populations , specimens which cannot be referred to species level may occur.