Morphology Dinoflagellate

longitudinal (l.f.) , transverse flagellum (t.f.); sack pusule (s.p.); nucleus (n).

dinoflagellates unicellular , possess 2 dissimilar flagella arising ventral cell side (dinokont flagellation). have ribbon-like transverse flagellum multiple waves beats cell s left, , more conventional one, longitudinal flagellum, beats posteriorly. transverse flagellum wavy ribbon in outer edge undulates base tip, due action of axoneme runs along it. axonemal edge has simple hairs can of varying lengths. flagellar movement produces forward propulsion , turning force. longitudinal flagellum relatively conventional in appearance, few or no hairs. beats 1 or 2 periods wave. flagella lie in surface grooves: transverse 1 in cingulum , longitudinal 1 in sulcus, although distal portion projects freely behind cell. in dinoflagellate species desmokont flagellation (e.g., prorocentrum), 2 flagella differentiated in dinokonts, not associated grooves.

dinoflagellates have complex cell covering called amphiesma or cortex, composed of series of membranes, flattened vesicles called alveolae (= amphiesmal vesicles) , related structures. in armoured dinoflagellates, these support overlapping cellulose plates create sort of armor called theca, opposed athecate dinoflagellates. these occur in various shapes , arrangements, depending on species , on stage of dinoflagellate. conventionally, term tabulation has been used refer arrangement of thecal plates. plate configuration can denoted plate formula or tabulation formula. fibrous extrusomes found in many forms. various other structural , genetic details, organization indicates close relationship between dinoflagellates, apicomplexa, , ciliates, collectively referred alveolates.

dinoflagellate tabulations can grouped 6 tabulation types : gymnodinoid, suessoid, gonyaulacoid–peridinioid, nannoceratopsioid, dinophysioid, , prorocentroid.

the chloroplasts in photosynthetic dinoflagellates bound 3 membranes, suggesting derived ingested algae. photosynthetic species contain chlorophylls , c2, carotenoid beta-carotene, , group of xanthophylls appears unique dinoflagellates, typically peridinin, dinoxanthin, , diadinoxanthin. these pigments give many dinoflagellates typical golden brown color. however, dinoflagellates karenia brevis, karenia mikimotoi, , karlodinium micrum have acquired other pigments through endosymbiosis, including fucoxanthin. suggests chloroplasts incorporated several endosymbiotic events involving colored or secondarily colorless forms. discovery of plastids in apicomplexa has led suggest inherited ancestor common 2 groups, none of more basal lines has them. same, dinoflagellate cell consists of more common organelles such rough , smooth endoplasmic reticulum, golgi apparatus, mitochondria, lipid , starch grains, , food vacuoles. have been found light-sensitive organelle, eyespot or stigma, or larger nucleus containing prominent nucleolus. dinoflagellate erythropsidium has smallest known eye.

some athecate species have internal skeleton consisting of 2 star-like siliceous elements has unknown function, , can found microfossils. tappan gave survey of dinoflagellates internal skeletons. included first detailed description of pentasters in actiniscus pentasterias, based on scanning electron microscopy. placed within order gymnodiniales, suborder actiniscineae.

theca structure , formation

the formation of thecal plates has been studied in detail through ultrastructural studies.

the dinoflagellate nucleus: dinokaryon

most dinoflagellates have peculiar form of nucleus, called dinokaryon, in chromosomes attached nuclear membrane. these carry reduced number of histones. in place of histones, dinoflagellate nuclei contain novel, dominant family of nuclear proteins appear of viral origin, called dinoflagellate/ viral nucleoproteins (dvnps) highly basic, bind dna similar affinity histones, , occur in multiple posttranslationally modified forms. dinoflagellate nuclei remain condensed throughout interphase rather during mitosis, closed , involves uniquely extranuclear mitotic spindle. sort of nucleus once considered intermediate between nucleoid region of prokaryotes , true nuclei of eukaryotes, termed mesokaryotic, considered advanced rather primitive traits.