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Dinoflagellate Glossary


Species Name: 

Polykrikos schwartzii

   
Common Name:      Dinoflagellate

 

I.  TAXONOMY

KINGDOM DIVISION CLASS ORDER GENUS
Protista
Dinophyta Dinophyceae Gymnodiniales Polykrikos

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Figure 1. Polykrikos schwartzii. 8-cell pseudocolony. Image via light microscope, phase contrast.


Figure 2. P. schwartzii. 4-cell pseudocolony with refractile food vacuole. Image via light microscope, phase contrast.

 

SPECIES NAME: 
Polykrikos schwartzii Bütschli

COMMON NAME:
Dinoflagellate

SPECIES DESCRIPTION:
Polykrikos schwartzii is a barrel-shaped non-thecate pseudocolonial species with mostly 4 (Figures 2, 3 ) or 8 (Figure 1) slightly compressed cells (occasionally 16), each individual of which has the general form of a Gymnodinium.  Each individual, called a zooid, is closely appressed to its neighbor without separating cell membranes, each with a median cingulum but all sharing a common sulcus.  The number of nuclei is normally one half the number of zooids.  The zooids possess numerous prominent nematocysts, lack chloroplasts, and the cytoplasm is a transparent green or pink. Cysts are sometimes seen, and these are brown and covered with honeycomb-like ridges that produce a coarsely rugose appearance (Figure 5).

POTENTIALLY MISIDENTIFIED SPECIES:
P. schwartzii resembles P. kofoidii in general appearance, but the latter is distinctly ridged on the hypotheca (hyposome) of each zooid, the cinguli are more displaced on each zooid, and the pseudocolony normally has only 4 cells.  The cysts of the two species are almost indistinguishable. Polykrikos lebourae has 8 zooids, but has golden-brown chloroplasts (thus photosynthetic) and is benthic.

 

II.  HABITAT & DISTRIBUTION

HABITAT:
The species is planktonic, mostly confined to coastal waters and estuaries.

REGIONAL OCCURENCE:
P. schwartzii apparently has a worldwide distribution in neritic environments, except for polar seas.  However, confusion with P. kofoidii makes its exact distribution uncertain.

 
 

INDIAN RIVER LAGOON DISTRIBUTION:
P. schwartzii has been found in the central IRL, the St. Lucie estuary and near Sebastian Inlet. It has not been found in the Mosquito Lagoon or Banana River.

SIZE:
The 8-cell colony (Figure 1) is about 100-160 µm long and 40-80 µm wide.

ABUNDANCE:
Rare

 

III. LIFE HISTORY & POPULATION BIOLOGY

REPRODUCTION:
Sexual reproduction has been reported (Hoppenrath et al. 2009), but reproduction is otherwise accomplished via asexual vegetative cell division.

TROPHIC MODE:
Nutrition is holozoic, by phagocytosis of diatoms, dinoflagellates and other protists.  Prey is probably captured by means of stinging nematocysts.


 
Figure 3. P. schwartzii. 4-cell pseudocolony captured via scanning electron microscope (SEM). Image courtesy of G. Hallegraeff.   Figure 4. P. schwartzii cyst. Image via light microscope, brightfield.

 

IV. REFERENCES

Dodge, JD. 1982. Marine Dinoflagellates of the British Isles. Her Majesty’s Stationery Office, London. 303 pp.

Hoppenrath, M & BS Leander. 2007. Character evolution in polykrikoid dinoflagellates. J. Phycol. 43: 366-377.

Hoppenrath, M et al. 2009. Marine Phytoplankton. Kleine Senckenberg-Reihe 49. E. Schweizerbart Science Publishers, Stuttgart Germany. 264 pp.

 

 

 

 

Unless otherwise noted, all images and text by PE Hargraves
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Page last updated: 14 June 2011


Copyright © 2011 Smithsonian Institution
SEXUAL REPRODUCTION

Process of reproduction in dinoflagellates that involves the production of gametes that are fused to create a zygote.

HYPOTHECA

The part of a dinoflagellate cell below the cingulum. Usually refers to a thecate (with cellulose plates) cell. May also be referred to as the hypocone or hyposome.
CYST

The diploid zygotic dormant stage in the sexual life cycle. Usually morphologically dissimilar from the haploid motile stage. Also called the ‘dinocyst’ or ‘hypnozygote’.

NEMATOCYST

Ejectile organelle of some dinoflagellate genera; involved in prey capture.
SULCUS

A longitudinal furrow, often partially enclosing the propulsive flagellum.
MEDIAN CINGULUM

A cingulum that encircles approximately the midpoint of the cell.
THECATE / THECAL

Dinoflagellates possesing a cell wall comprised of cellulose plates, which have special designations and symbols according to their location on the cell. See glossary for more information.