chapt 8 Dinoflagellates -.pptx

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1. Micropaleo ntology Lecturer @ SNU: Abdirizak Abdullahi CHAPTER 8

2. Organic-walled microfossils micro-organisms whose shell wall is made up of hard and tough organic or non- mineralised proteinaceous material. ( Dinoflagellates )

3. There are three main types of organic-walled microfossils as mentioned below: Dinoflagellates Pollen and Spores Acritarchs

4. What are Dinoflagellate? Introduction Dinoflagellates are minute, aquatic, single-celled organisms, belonging to Phylum Dinozoa and Subphylum Dinoflagellata . They have two whip-like tails called flagella for locomotion. It has both plant and animal characteristic.

5. They drift frequently from one place to another mainly by movements of water and live mostly as solitary organisms, but colonial forms also exist The flagella are usually located within grooves, one encircling the body like a belt, and the other perpendicular to it. By beating in their respective grooves, these flagella cause the dinoflagellate to rotate like a top as it moves

6. Cont.. Dinoflagellates are both autotrophic and heterotrophic, and several of them occur as symbionts in corals, foraminifera and several other invertebrates. They are predominantly marine, but also occur in brackish and fresh waters. Some dinoflagellates are bioluminescent and cause sparkling in seawater due to the chemical reaction of an enzyme . Dinoflagellates are among the major primary producers in the present-day oceans, along with diatoms and coccolithophores .

7. Bioluminescent

8. Most are marine plankton, but they are common in freshwater habitats as well. Their populations are distributed depending on temperature, salinity, or depth. The free-swimming (motile) cells are abundant, but the resting cysts (the dinocysts ) are resistant and occur in fossil records. The distribution of present- day dinoflagellates is limited by temperature, salinity and nutrient of the seawater and, therefore, fossil dinocysts are potential indicators of past environments.

9. Some dinoflagellates have produced fossilizable remains while many have not, and those groups that have produced fossilizable cysts have done so inconsistently ( Evitt 1985 ). This has several implications for the study of dinoflagellates, including the true assemblages and population size in the geological records, and, therefore, a cautious approach to the use of dinoflagellate data in paleoenvironmental interpretation and biostratigraphy is necessitated

10. CLASSIFICATION Domain : Eukaryota Kingdom : Protista ( Protozoa) sup kingdom : Dictyozoa phylum : Dinocoa sup phylum : Dinoflagellate

11. Geological Range Dinoflagellates are considered to be among the most primitive of the eukaryotic group, the fossil record of the group may extend into the Precambrian period. Biological and biochemical evidence indicates an ancient, Precambrian origin for dinoflagellate lineage. However virtually all fossils recognizable as dinoflagellates are from Mesozoic and Cenozoic sediments , there fore the fossil record of dinoflagellates is clearly incomplete

12. MORPHOLOGY The dinoflagellate cell contains a nucleus , an endoplasmic reticulum, a Golgi apparatus, and mitochondria. Two different cell types are distinguished. The naked or unarmoured type is fragile. The second one armoured dinoflagellate has cellulose or polysaccharides within each vesicle, called theca , making the wall more rigid.

13. Morphology The wall of the theca is commonly divided into a number of polygonal areas, termed plates and the arrangement of this plate is called tabulation The reproduction is generally A-sexual in which cell is divided into two half by binary fission and sexual also found in few form

14. Cyst is protect the dinoflagellate against adverse environment condition The cyst wall called phragma is made of organic matter called dinosporn it may consist of single or mulltible layers The surface of cyst may be smooth or have process such as granule, rigids, spine and horn

15. ECOLOGY Dinoflagellates live in all aquatic environments from normal marine to brackish and freshwaters including in snow or ice. They are also common in benthic environments and sea ice. the motile stage of the autotrophic forms lives in photic zone Some species are shallow dwellers and some one live in deeper water The warm and cold of water are also distinguished by the morphotype of ceratium species , the one of tropical water have longer horns and thinner theca compared with those from cold water

16. Three nutritional strategies are seen in dinoflagellates: Phototrophy , Mixotrophy and heterotrophy. Phototrophs can be photoautotrophs or auxotrophs . Mixotrophic dinoflagellates are photosynthetically active, but are also heterotrophic. While Some dinoflagellates may feed on other organisms as predators or parasites.

17. Dinoflagellates harmful blooms Dinoflagellates sometimes multiply rapidly, resulting in population explosions or blooms in concentrations of more than a million cells per millilitre of water. Rapid multiplication is due to the presence of abundant nutrient present in the water or might be due to human activities or other natural reasons. These blooms have known to create shellfish poisoning as they release a neurotoxin which kills the fishes. The colour of the sea appears red so it is known as “Red Tide”. This phenomenon is also referred to as “Harmful algal bloom (HAB)”.

18. Red tide

19. Some dinoflagellate blooms are not dangerous. Bluish flickers visible in ocean water at night often come from blooms of bioluminescent dinoflagellates, which emit short flashes of light when disturbed

20. APPLICATION Dinoflagellates cyst are ideal Biostratigraphical indicators Its very important to indicate for paleo-salinity Its also one of the evidence uses to identified type of source rock and its maturation Its useful for human (its generate more than 90% of oxygen) its also very useful to indicate for climate change and environment its also uses as indicator of temperature

21. 1. write short note the term dinoflagellates? 2. Identify some Morphological, ecological and economic importance of dinoflagellates? Pollen and Spores Acritarchs Assignment Class activity