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Department of Botany

Dinoflagellates
Glossary

anisogamous - Sexual reproduction in which the gametes differ from each other morphologically (Taylor 1987) e.g. Alexandrium tamarense.

amphitrophy - Nutrition mode of photosynthetic dinoflagellates in which either heterotrophy or autotrophy alone can support cell functions.

antapex - The posterior-most part of the cell.

antapical - In dinokonts, the posterior pole of the cell.

antapical plates - In thecated dinokont species, the plates covering the posterior end of the cell (designated with '''') not in contact with the cingulum.

anterior - In desmokonts, the top part of the cell.

apex - The anterior-most part of the cell.

apical - In dinokonts, the anterior pole of the cell.

apical collar - A topographic feature of some prorocentroids (desmokonts). It is an extension of the intercalary band on the left valve along the anterior margin bordering the periflagellar area (e.g. P. belizeanum and P. hoffmannianum). This feature can be curved, flared, rounded or flattened. Oftentimes, this feature can only be viewed via SEM.

apical horn - A prominent apical extention of the cell formed by apical plates; it is a feature only found on thecate species. In these species, the apical horn constitutes the apex of the cell (Steidinger & Tangen 1996).

apical plates - In thecated dinokont species, the thecal plates that surround and are in contact with the apex of the cell (designated with ' ) not in contact with the cingulum. In those species with an apical pore complex (APC), the plates that touch the APC.

apical pore (ap) - Pore located on the Po plate. This feature is not always a round or oval hole, but can be long and narrow and/or curved, or even fishhook shaped. In Alexandrium spp. the ap is referred to as a foramen. If the ap is a hole, then it may have a closing/cover plate (cp) or canopy.

apical pore complex (APC) - This feature is located on the epitheca of many marine, armoured (thecated) dinokont species. It includes an apical pore plate (Po), which bears an apical pore (ap), and often times, small periferal pores. In addition, there can be a ventral apical plate or canal plate (X plate). The X plate is always posterior and ventral to the Po.

apical pore plate (Po) - Part of the apical pore complex (APC); a feature located on the epitheca of many marine, armoured (thecated) dinokont species. The Po houses an apical pore (ap), and often times, small periferal pores. The Po can be long and narrow, as in Ostreopsis spp., or wide and triangular, as in Gambierdiscus spp.

areolae - Surface ornamentation on thecal plates that approximates deep depressions with or without raised sides. The sides may be round to polygonal and are closely appressed. Areolae can contain pores, even double pores.

armoured - Dinoflagellate species that have thecal plates of varying thickness and orientation in identifiable tabulation series. Often the plates are thickened or ornamented with reticulations, spines, grooves, etc... which are often characteristic to a species.

asexual reproduction - A method of reproduction where a 1N cell produces two to four cells with the same chromosome number. This can be by binary fission of a motile stage or a nonmotile stage. In many armoured dinokonts the original cell divides along predetermined sutures and then each half produces a new half with new thin plates.

autotrophy - Photosynthetic nutritional mode in which inorganic compounds (CO2 and carbonates) are utilized for growth, metabolism and reproduction.

auxotrophy - Heterotrophic nutritional mode in which specific external organic compounds (usually the vitamins B12, biotin and thiamine) are required in small amounts by most photosynthetic dinoflagellates.

benthic - Occuring at the bottom of the water column.

binary fission - A method of asexual reproduction in which the parent cell divides into two equal, or nearly equal, parts, each of which develops to parental size and form.

bioluminescence - The emission of light from certain species of dinoflagellates by either mechanical or chemical stimulation.

bloom - High concentrations of planktonic organisms due to enhanced cell division (growth) rates. Seasonal blooms are often related to periodical increase in nutrient and light conditions (e.g. spring bloom). Exceptional blooms are often dominated by one or a few species and may discolor the water a reddish-brown color, hence the name 'red tide'.

canal plate (x-plate) - A narrow elongated plate found on the epitheca of some thecate dinokont species ventral to the APC.

catenate - Cells connected in a series; cells in chain formation.

chlorophyll - Plant pigments found in chloroplasts which function as photoreceptors of light energy for photosynthesis.

chloroplast - Membrane-bound organelle found in the cytoplasm of various eukaryotic organisms that contain the chlorophyll pigments and the enzyme systems for photosynthesis.

chromosomes - Complex, helical structures in plant and animal nuclei that carry the linearly arranged genetic units, DNA and RNA.

ciguatera - A human intoxication caused by ingestion of tropical piscivorous reef fishes contaminated with toxin-producing benthic/epiphytic dinoflagellates. These fish accumulate biotoxins through the food chain (Steidinger 1993). More than 175 separate gastrointestinal, neurotoxic, or cardiovascular symptoms may be associated with this poisoning (Becker & Sanders 1991). In extreme cases death can result from respiratory failure. Although incidence is high, human mortality is low (Hallegraeff 1995).

cingular plates - In thecate dinokont species, the plates that make up the cingulum (designated with a 'c').

cingulum - In dinokont species, this structure is usually a furrow (girdle) encircling the cell once or several times, and it can be displaced. In thecated species, the cingulum is made up of plates. This structure is missing in some desmokont-type cells (e.g. Prorocentrum).

closing plate (cp) - A small plate located in the apical pore complex (APC) of some marine, armoured dinokont species, and associated with the apical pore (ap).

concave - Hollowed or rounded inward resembling the inside of a bowl.

convex - Curved or rounded resembling the exterior of a sphere or circle.

costae - A rib or rib-like structure, often located in the apical pore complex of thecated species; e.g. Coolia monotis.

cyst - Any dormant or resting nonmotile cell possessing a distinct cell wall.

cytoplasm - Protoplasm within a plant or animal cell external to the nucleur membrane.

DAPI (4',6-Diamidino-2-Phenylindole) - A highly specific and sensitive fluoresceing DNA stain used in epifluorescent microscopy to observe structures containing DNA. DAPI specifically binds to double stranded DNA, and when excited with light the DAPI-DNA complex fluoresces a bright blue (Porter & Feig 1980).

desmokont - A dinoflagellate cell type in which two dissimilar flagella emerge from the anterior part of the cell; e.g. Prorocentrum sp. This morphological type does not have a cingulum or a sulcus.

diameter - With the exception of the Prorocentroids, the maximum cell width measured between the lateral extremes of the cingular flanges (Balech 1995).

Diarrhetic Shellfish Poisoning (DSP) - A human gastrointestinal disease caused by the ingestion of toxic marine shellfish (filter-feeding bivalves) from cold and warm temperate regions of the Atlantic and Pacific Oceans (Steidinger 1993). Shellfish can accumulate and store large quantities of red tide dinoflagellate toxins without apparent harm to themselves (Steidinger & Baden 1984). Symptoms include diarrhea, nausea and vomiting lasting a few days. No human deaths have been reported (Hallegraeff 1995).

dinoflagellate - Biflagellated unicellular alga member in the Phylum Pyrrhophyta.

dinokont - A dinoflagellate cell type in which two flagella are inserted ventrally; one flagellum is transverse and housed in a cingulum and the other is longitudinal and housed in a sulcus. A dinokont dinoflagellate can be a thecate species (with thecal plates) or an athecate species (without thecal plates)(Steidinger & Tangen 1996).

dinophysoid - Group of dinokont type dinoflagellates. Members of this group are the only thecate dinoflagellates fundamentally divisible into two lateral halves and have an anterior cingulum and a narrow sulcus. They are laterally compressed, and their shapes in lateral view are essential for genus and species identification (Taylor et al. 1995).

diploid - A cell that has a nucleus with two sets of chromosomes (2N).

dorsal - Of or relating to the back side of an organism. In dinokonts, opposite the ventral side (front side) (Steidinger & Tangen 1996).

dorsoventral - Extending along the axis joining the dorsal and ventral sides.

encystment - To form or become enclosed in a cyst (resting spore). There are several types of encystment. Stressed cells can 'round up' and settle out of the water column and yet be viable if the stress conditions are removed. Others involve temporary cysts for asexual reproduction, flotation, and other functional aspects of individual survival. Yet another type of encystment involves sexual reproduction and the production of thick-walled hypnozygotes which can remain encysted for months, even years (Steidinger & Tangen 1996).

epibenthic - Attached to the bottom.

epifluorescence microscopy - A method of microscopy used to view light-excited regions of an organism stained with a fluorochrome dye.

epiphyte - An alga which attaches itself and lives nonparasitically on another plant or on some nonliving object. Cell can attach via a mucoid holdfast or thread(s).

epitheca - The anterior part of the dinokont-type cell above the cingulum.

eukaryote - A cell with a membrane-bound nucleus.

excystment - When the hypnozygote matures and is ready to produce a motile cell from the resting cell, a naked cell will emerge from an opening in the cyst wall. This emerging cell will either be flagellated or amoeboid. Typically, this cell will undergo meiosis and produce four vegetative 1N cells that are motile in the water column (Steidinger & Tangen 1996).

flagellar pore - In desmokont dinoflagellates, the pore in which flagella emerge located in the periflagellar area (flagellar pore area).

flagellum - Whip-like structures arising from the cell and responsible for propelling cells in a watery fluid. All dinoflagellates at some time in their life cycle have two dissimilar flagella: a transverse flagellum (provides propulsion) and a longitudinal flagellum (provides direction). They either emerge through one pore or two separate pores.

fluorescence - Emission of energy as visible light.

foramen - A relatively large comma-shaped cavity (apical pore) on the Po plate of Alexandrium spp. (sometimes fishhook shaped as in Alexandrium catenella and A. tamarense). It is a diagnostic feature of the APC.

gametes - In armoured and unarmoured species a 1N cell that fuses with another 1N cell to produce a zygote (2N).

geotropic - Oriented by gravity.

growth - Increase of body volume, and proliferation of a cell.

haploid - Vegetative or gametic cells that have one set of chromosomes (1N).

hepatotoxic - Toxic to the liver.

heterothallism - Sexual cycle in dinoflagellates which involves opposite mating types; e.g. Gymnodinium catenatum.

heterotrophy - Nutritional mode in which absorption of organic matter is required for growth, metabolism and reproduction; e.g. auxotrophy, mixotrophy, myzocytosis, phagotrophy and organotrophy.

horn - In armoured cells an extension of the apical or antapical plates.

hypnozygote - A thick-walled zygote formed following fusion of two motile gametes (diploid-2N).

hypotheca - The posterior part of a dinokont-type cell below the cingulum.

hystrichosphere - A fossilized dinoflagellate cyst.

intercalary band - Marginal growth zones between thecal plates; usually straited horizontally or transversely.

isogamous - Sexual reproduction in which the fusing gametes differ morphologically from the vegetative cells, but are morphologically identical to each other (Taylor 1987); e.g. Alexandrium monilatum.

lacerate - With a deeply and irregularly incised margin.

lanceolate - Tapering at both ends.

lateral - In desmokonts oriented toward the left or right side of the cell.

lenticulate - Shaped like a double convex lens; shaped like a lentil.

life cycle - A continuum of phases and cell types in the reproduction and growth of a species. The life cycle usually contains at least an asexual phase in which a cell can divide by binary fission and produce two similar cells (1N). It may also contain a sexual phase in which gametes fuse to form zygotes (2N) and these zygotes produce 1N cells.

list - Membranous thecal extensions of armoured dinoflagellates (often associated with the cingulum and sulcus); some extensions are curved or ribbed.

lobe - A rounded projection on a structure.

megacytic growth zone - The cell growth that occurs at the suture between the two valves of the Prorocentrales or the fissure halves of the Dinophysiales. When this usually horizontally striated zone is at its maximum extent, the cell will be at its greatest depth or width, respectively (Steidinger & Tangen 1996).

mesokaryotic - Dinoflagellate nucleus which possesses characteristics of both prokaryotes and eukaryotes.

mixotrophy - Heterotrophic nutritional mode of some photosynthetic dinoflagellates in which ingestion of food particles is required for existence.

mucocyst - An ejectile organelle; a minute structure that emerges through pores in the theca of armoured dinoflagellates that releases mucous or mucous threads when discharged.

myzocytosis - Heterotrophic nutritional mode in which prey is suctioned into a food vacuole via a feeding tube or peduncle, and then digested (Schnepf & Deichgraber 1983).

neritic - The region of shallow water adjoining the seacoast; e.g. bays, lagoons, mangroves, salt marshes, etc.

Neurotoxic Shellfish Poisoning (NSP) - A human neurological disease caused by the ingestion of toxic marine shellfish (filter-feeding bivalves). Symptoms are similar to those of ciguatera poisoning and include temperature reversal sensations, as well as headache, chills, and muscle and joint pain (Hallegraeff 1995, Steidinger 1993). Cases have been reported from the southeast US and eastern Mexico (Steidinger 1993).

nucleus - A membrane-bound organelle in eucaryotic cells which contains a large percentage of the genetic material in the cell. In dinoflagellates, it is most often referred to as a mesokaryon or a dinokaryon due to its unique feature: chromosomes are permanently condensed.

organelle - A specialized subcellular structure having a special function; e.g. mitochondria.

organotrophy - Heterotrophic nutritional mode of dinoflagellates without chloroplasts; i.e. total nutrition and growth is derived exclusively from organic compounds.

osmotrophy - Active uptake of dissolved organic substances for nutrition.

ovate - Shaped like an egg; one end broader than the other.

Paralytic Shellfish Poisoning (PSP) - A human neurological disease caused by the ingestion of toxic marine shellfish (filter-feeding bivalves) as well as other harvested seafood. PSP has been reported from cold and warm seas (Steidinger 1993). Shellfish can accumulate and store large quantities of bloom or red tide dinoflagellate toxins without apparent harm to themselves (Steidinger & Baden 1984). Symptoms include: tingling sensation around lips gradually spreading to face and neck; prickly sensation in fingertips and toes; headache, dizziness, nausea, vomiting, diarrhea. In extreme cases, muscular paralysis occurs resulting in death from respiratory paralysis (Hallegraeff 1995).

peduncle - A small, flexible, finger-like appendage located near the flagellar pores in some photosynthetic as well as nonphotosynthetic species. Its functions are not fully understood, but it has been associated with feeding behavior (phagotrophy).

pellicle - A retaining envelope which may be found around certain dinoflagellates or which can develop at a certain stage of the life history.

periflagellar area - In prorocentroids (desmokonts) this region is located on the anterior end of the right valve within a notched area (V-shaped triangular depression). It consists of several plates or platelets around one or two periflagellar pores, the auxilliary pore (A) and the flagellar pore (F). Accessory pores, apical spine(s), periflagellar collars and/or periflagellar plates may also be present.

periflagellar collar - A topographic feature of the periflagellar area of some prorocentroids (desmokonts). It is a thecal extension of a periflagellar plate that can lie adjacent to the periflagellar pores (flagellar and auxiliary) and/or surround one or both pores (e.g. Prorocentrum maculosum). A periflagellar collar can be flared and/or protuberant, or appear as a winged spine (e.g. Prorocentrum mexicanum). Oftentimes, this feature can only be viewed via SEM.

periflagellar plates - A topographic feature of the periflagellar area of some prorocentroids (desmokonts); platelets situated around the periflagellar pores.

periflagellar pores - In prorocentroids (desmokonts), large apical pores found in the periflagellar area: auxiliary pore (A) and/or the flagellar pore (F). A periflagellar collar can surround these pores; e.g. P. maculosum.

phagotrophy - Heterotrophic feeding mode of generally non-photosynthetic dinoflagellates in which whole prey (or parts of) are ingested or engulfed, with digestion occurring in phagocytic vacuoles.

photosynthesis - The use of inorganic compounds in the presence of light for growth, metabolism and reproduction.

phytoplankton - Planktonic plant life.

pigments - Any coloring matter in plant or animal cells.

plankton - Refers to free-living organisms in aquatic environments that have little or no self-motility and therefore float and drift under the action of water movement.

plastids - Cytoplasmic organelles of photosynthetic cells that serve as centers of specialized metabolic activities.

pore - Openings or channels in the theca of dinoflagellates that can be involved in extrusion of trichocysts or mucocysts and other active processes. Pore number and location are variable within a species, but in many groups, the pattern is a reliable, but variable character for identification of species (Steidinger & Tangen 1996).

poroid - Shallow surface depressions on the valve surface.

post-cingular plates - In thecated dinokont species, the plates touching the cingulum in the hypotheca (designated with ''' ).

posterior - In desmokonts, the bottom end of the cell.

pre-cingular plates - In thecated dinokont species, the plates touching the cingulum in the epitheca (designated with " ).

premedian cingulum - In dinokont-type cells when the cingulum is above the midpoint of the cell.

prokaryote - A cell that contains a primitive nucleus where the DNA-containing region lacks a definitive membrane; e.g. bacteria and cyanobacteria.

prorocentroids - Group of desmokont type dinoflagellate. Two anteriorly inserted flagella and two large laterally flattened valves easily distinguish the species of this group. The right valve has a small indentation, the periflagellar area, that houses the flagellar pore(s) (Taylor et al. 1995).

pustule - A small elevation on the valve surface resembling a blister or pimple.

pyrenoid - Cytoplasmic structure made of protein or appended to the chloroplasts in most phytoflagellates. They are associated with the formation or storage of polysaccharide food reserves (usually starch)(Steidinger & Tangen 1996).

reticulae - Surface ornamentation on thecal plates where raised straight lines or ridges cross one another creating a complex pattern resembling a network of fibers, veins or lines.

rugose - Uneven surface covered with shallow minute depressions.

Scanning Electron Microscopy (SEM) - Instrumentation used to observe minute surface details of small organisms/objects at high magnification by means of electron lenses. SEM techniques are often employed and needed to correctly identify a dinoflagellate species.

sexual reproduction - A method of reproduction that involves two gametes (1N) that fuse to produce a zygote (2N).

striae - Surface ornamentation on unarmoured or armoured dinoflagellates that appear as longitudinal lines, ridges or grooves; on armoured species the striae can be interrupted by pores and may be associated with other markings, such as reticulations.

sulcus - Longitudinal area on the ventral surface of dinokont-type cells that forms a pronounced furrow or depression that houses the longitudinal flagellum. In thecated species, the sulcus is made up of sulcal platelets (designated by 's'). This feature is not present in some desmokont-type cells (Steidinger & Tangen 1996).

sutures - In armored species, visible linear boundaries between thecal plates (Steidinger & Tangen 1996).

theca - Dinoflagellate membrane system encompassing the whole cell consisting of a complex of three to six membranes.

thecal plates - Plates of armoured (thecated) species which are composed of cellulose or polysaccharide microfibrils. Their particular size, shape and arrangement on the cell are characteristic to a species (Steidinger & Tangen 1996).

transdiameter - With the exception of the Prorocentrales, the cell width measured between the lateral extremes of the cingulum bottom; i.e. the flanges are excluded. Minimum cingular width; a measurement of width used in armoured dinokonts (Balech 1995).

trichocysts - A cytoplasmic ejectile organelle; a minute structure that emerges through pores in the theca of armoured dinoflagellates that releases filamentous or fibrillar threads when discharged.

tycoplanktonic - Benthic dinoflagellate species found at some time in the water column.

unarmoured - Dinokont-type cells that do not have an identifiable plate series and do not have apical pore complexes.

vacuole - A cytoplasmic membrane-bound cavity within a cell that may function in digestion, storage, secretion or excretion.

valves - In the thick-walled desmokonts, two opposing halves of the theca are called valves (right and left). The right valve is the one most indented anteriorly by the periflagellar plates.

ventral - The front side of an organism (opposite dorsal side): in dinokonts, side of sulcus and juncture of the cingulum-sulcus; in dinokonts, the side of flagellar insertion (Steidinger & Tangen 1996).

ventral pore (vp) - In some armored species, a ventral pore may be present at the juncture of the first apical plate (1') and an anterior intercalary or another apical plate on the epitheca. Sometimes the pore is in one of the apical plates. The presence of a ventral pore or its placement may be diagnostic for certain species (Steidinger & Tangen 1996).

ventral ridge - In dinokonts, an identifiable ridge on the right side of the sulcal intrusion onto the epitheca.

vermiculate - Surface ornamentation on thecal plates in which the plates are marked with irregular fine lines or with wavy impressed lines.

zygote - A cell (2N) formed by the union of two gametes (1N) during sexual reproduction.

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