Brief Introduction to the Silicoflagellates.

Dictyocha fibula Ehrenberg, 1837

Silicoflagellates belong to a small group of marine planktonic organisms with siliceous skeletons composed of opaline rods. The cell size  ranges from 20 to 80 μm (1). They could be both autotrophic and heterotrophic, and live associate with blue-green algae. They have two flagella and  thin pseudopodia, but based on their pigmentation, mitochondria, chloroplasts and siliceous skeleton, silicoflagellates are considered golden algae or chrysophytes.

The basic structure for the skeleton   consist of a basal ring, with or without radial spines and accessory basal spines and an apical ring slightly curved or dome-shaped. The joints of the various types of bars generate hollows known as portals or windows (2)

Lyramula furcula

One exception to this body plan is the extinct genus Lyramula, which has no basal ring and exhibits two curving arms.

Silicoflagellates comprise only between 1 and 2% of the siliceous components of marine sediments and are more abundant in waters of the equatorial upwelling zone. They often find in diatomaceous earth deposits and are very sensitive indicators of temperature.

The first scientific reports of silicoflagellates were made by Ehrenberg in 1837. He recognized two  species of silicoflagellates: Dictyocha fibula  and D. speculum.

Dictyocha fibula Ehrenberg, 1837 and Dictyocha speculum Ehrenberg, 1839.

Silicoflagellates first appeared in Early Cretaceous sediments and extend to the present, but were more abundant during the Late Cretaceous. They are used in biostratigraphy, especially in high latitudes and deep waters, where calcareous microfossils are scarce or are dissolved. Their morphologies can be influenced by environmental factors a condition that allows them to develop  potential as environmental indicators,especially with respect to paleotemperatures.

References:

(1)  N. Taylor, Edith L. Taylor, Michael Krings: “Paleobotany: The Biology and Evolution of Fossil Plants”. 2nd ed., Academic Press 2009.

(2) ADAMONIS, S., CONCHEYRO, A. y ALDER, V. 2008. Protistas autótrofos y heterótrofos: silicoflagelados, ebridianos y tintínidos. En: H. Camacho y M. Longobucco (eds) Invertebrados fósiles. Fundación de Historia Natural Félix de Azara. Tomo I: 133-145