Smithsonian Marine Station at Fort Pierce

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Figure 1.

Species Name: Actinocyclus vestigulus Watkins
Common Name: None
Synonymy: None
  1. TAXONOMY

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Protista Bacillariophyta Coscinodiscophyceae - - Actinocyclus

    Species Description

    This rare species was first described from a warm core ring (Watkins & Fryxell 1986). The valve is circular and mostly flat, curving to the mantle from just inside the rimoportulae. The areolae are irregularly fasciculate, with some areolar rows within a fascicle parallel to the middle radial row, others parallel to the end row.  The areolae become slightly smaller near the valve center, and are markedly smaller on the mantle.  There is a single ring of rimoportulae with external parts even with the valve surface, and 5.5-9.5µm apart. The orientation of rimoportulae alternates between slightly higher or lower at the mantle edge.  There is a single pseudonodulus about 5 areolae in from the valve margin (Fig. 1, arrow).

    The valve diameters seen in the IRL are 48-55µm, with central areolae 9-10 in 10µm, 8-9 in 10µm at mid radius, and about 12 in 10µm on the mantle.  This contrasts with the original description of diameters of 46-81µm, with 8-9, 6-7, and 9-10 areolae, respectively, at the center, mid-radius, and margin.  This genus is notoriously variable in morphology, and the specimens found may eventually make a better fit in a different species.  Although the illustrated specimen has small linear central areolae that are clearly fasciculate, the central annulus is indistinct in SEM.  Cells were rare in the IRL near the Sebastian Inlet in summer 2007; Watkins and Fryxell (1986) found the species in the Sargasso Sea, Gulf of Mexico, and central Pacific Ocean as well as in warm core rings, so it clearly has a tropical warm-water preference.

  2. HABITAT AND DISTRIBUTION

    No information is available at this time

  3. LIFE HISTORY AND POPULATION BIOLOGY

    No information is available at this time

  4. PHYSICAL TOLERANCES

    No information is available at this time

  5. COMMUNITY ECOLOGY

    No information is available at this time

  6. ADDITIONAL INFORMATION

    No information is available at this time

  7. REFERENCES

    Watkins TP, Fryxell GA. 1986. Generic characterization of Actinocyclus: consideration in light of three new species. Diat Res 1:291-312. DOI:10.1080/0269249X.1986.9704975.

Unless otherwise noted, all images and text by PE Hargraves
Editing and page maintenance by LH Sweat
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Page last updated: 28 April 2015

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