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Figure 1. Oxyphysis oxytoxoides, typical elongate form from the Indian River Lagoon.

Figure 2. O. oxytoxoides, showing recently divided cells (mirror images).

Figure 3a Schematic illustration of the aerolate theca of O. oxytoxoides. Image modified from Kofoid 1926.

Figure 3b Detail of the thecal plate structure of O. oxytoxoides. Image modified from Tai & Skogsberg 1934.

Figure 4. O. oxytoxoides image via scanning electron microscope (SEM). Total length is 56.3 µm.

Species Name: Oxyphysis oxytoxoides Kofoid, 1926
Common Name: Dinoflagellate
Synonymy: None

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Protista Dinophyta Dinophyceae Dinophysiales Oxyphysis

    Use your mouse to rollover the terms in purple for their definitions. If this feature is not supported by your browser, please refer to the accompanying glossary for terminology.

    Species Description

    Oxyphysis oxytoxoides is a unicellular thecate (having a membrane with armored cellulose plates) dinoflagellate - more or less fusiform, or spindle-like, in shape and laterally compressed (Figure 1). The membrane encompassing the entire cell, called the theca, is composed of two large plates and a number of smaller ones, most of which are not normally discernible (Figures 3b & 4).  The cell surface is areolate and is covered with pores (Figures 3a & 4), which are probably the sites of ejectile organelles that release substances from the cell. The anterior portion of the cell, known as the epitheca, is narrower than the posterior section called the hypotheca. Both parts often bear a small spine at the tip.

    Potentially Misidentified Species

    O. oxytoxoides is the only described species of this genus. However, recent research (Gomez et al. 2011) argues that, based on small subunit (SSU) and large subunit (LSU) rDNA data that show a close relationship to the type species of the genus Phalacroma, O. oxytoxoides should be transferred to the former genus as Phalacroma oxytoxoides (Kofoid) Gomez, Lopez-Garcia et Moreira.



    O. oxytoxoides is a planktonic species.

    Regional Occurrence

    O. oxytoxoides was formerly considered to be endemic to “cool coastal waters” of the Pacific Ocean (Taylor 1987), possibly as a result of being overlooked elsewhere. Conversely, the species may be an introduced or invasive species to other areas where it is now well known. Originally, the dinoflagellate was described from the west coast of the United States (Kofoid 1926), but is currently reported throughout the temperate to subtropical coastal waters of the Atlantic Ocean and Mediterranean Sea.

    Indian River Lagoon Distribution

    O. oxytoxoides is only occasionally seen in the IRL, possibly entering the lagoon via the inlets from source populations residing in cool nearshore waters.



    The cell length, ranging from 50 to 70 µm, is usually 3.5 to 5 times the cell width.


    Although O. oxytoxoides is more prominent in the IRL in the cooler months of the year, the dinoflagellate is never highly abundant, reaching maximum concentrations of only 100s per liter.


    O. oxytoxoides reproduces by binary fission, with each cell half forming a new half. Daughter cells are mirror images (Figure 2).


    No information is available at this time


    Trophic Mode

    This species is non-photosynthetic, and is predatory on ciliates and other protists by means of a feeding tube (Inoue et al.1993).


    No information is available at this time


    Gomez, F, Lopez-Garcia, P & D Moreira. 2011. Molecular phylogeny of dinophysioid dinoflagellates:  The systematic position of Oxyphysis oxytoxoides and the Dinophysis hastata group (Dinophysiales, Dinophyceae).  J. Phycol. 47: 393-406.

    Inoue, H, Fukuyo, Y & Y Nimura. 1993. Feeding behavior of dinoflagellate Oxyphysis oxytoxoides on ciliates. Bull. Plankton Soc. Japan 40: 9-17.

    Kofoid, CA 1926. On Oxyphysis oxytoxoides gen. nov., sp. nov. A dinophysioid dinoflagellate convergent toward the peridinioid type. Univ. Calif. Pub. Zool. 28: 203-216.

    Tai, L & T Skogsberg. 1934. Studies on the Dinophysoidae, marine armored dinoflagellates of Monterey Bay, California. Archive fuer Protistenkunde 82: 380-482.

    Taylor, FJR. 1987. Ecology of Dinoflagellates, A. General and Marine Systems. 398-502 In: Taylor, FJR (Ed.) The Biology of Dinoflagellates. Blackwell Scientific Publications, Oxford. 785 pp.

Unless otherwise noted, all images and text by PE Hargraves
Editing and page maintenance by LH Sweat
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Page last updated: 14 June 2011


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.

The part of a dinoflagellate cell above the cingulum. Usually refers to a thecate (with cellulose plates) cell. May also be known as the epicone or episome.

Ornamentation of the thecal plates that consists of depressions of variable depth and form.

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.

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