Stylodictya

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Stylodictya
Scientific classification
Domain:
Eukaryota
(unranked):
SAR
(unranked):
Rhizaria
Phylum:
Retaria
Subphylum:
Radiolaria
Class:
Polycystinea
Order:
Spumellaria
Family:
Spongodiscidae
Genus:
Stylodictya

Ehrenberg, 1847 emend. Kozlova, 1972

The genus Stylodictya belongs to a group of organisms called the Radiolaria. Radiolarians are amoeboid protists found as zooplankton in oceans around the world and are typically identified by their ornate skeletons.

Contents

History

Polycistine radiolarians were first popularized by Ernst Haeckel, a German biologist who drew Radiolaria in detail and described 2775 new polycystine species. However the first taxonomic descriptions of Radiolarians were done by Christian Gottfried Ehrenberg from 1838 to 1876. Ehrenberg was the first to describe Stylodictya with what is now the lectotype species Stylodictya gracilis. Early classifications of radiolarians were somewhat arbitrary and have been improved upon since the mid-nineteenth century drawings by Ehrenberg and Haeckel. Improvements in microscopy technology have allowed more specific morphological descriptions of pre-described radiolarian genera. In addition, new species of Stylodictya and other radiolarians are constantly being discovered from both live samples and fossil evidence. [1]

Ecology

Two species of Stylodictya, Stylodictya multispina and Stylodictya validispina, are quite prevalent in ecological literature regarding Radiolarian diversity. These two species are found quite commonly in the western Pacific, [2] particularly extending from equatorial regions east of Java to south of New Zealand. Stylodictya multispina is also known to be found in the central equatorial Pacific and in the Gulf of Mexico, [2] however the full distribution of the genus is not wholly understood. Based on data from the western Pacific correlating Stylodictya distribution with upwelling zones, the appearance of the genus is likely highly dependent on upwelling. Upwelling is known to have a drastic effect on phytoplankton blooms and evidence suggests that Stylodictya is one of the genera of zooplankton that is heavily controlled by upwelling-related phytoplankton blooms. [2]

The cause of Stylodictya’s dependence on upwelling is a result of the vertical distribution of the genus. Stylodictya is a surface-dwelling plankton, reaching at absolute limit as far down as 750 meters, but being heavily concentrated in the upper 200 meters of the photic zone. [2] Being restricted to the upper edge of the vertical column means that Stylodictya’s prey is relatively wealthy in energy from sunlight but is ecologically restricted from population growth by a scarcity of nutrients (e.g. nitrates and phosphates). Therefore in upwelling zones where nutrients rise to the surface of the ocean, Stylodictya is able to proliferate extensively.

Stylodictya, like other radiolarians, is a particle feeder and a predator of other planktonic organisms such as diatoms. [3] The geologic age of the oldest Stylodictya-type fossils are evidence of the lasting ecological significance of Stylodictya and Radiolarians as a whole on the oceanic ecosystem. Stylodictya is food for a variety of organisms, from other zooplankton to filter feeders.

Morphology

Morphological terms regarding radiolarians have evolved to be more precise since the 19th-century descriptions. Terminology is inconsistent over time, as multiple terms are often used to describe a singular structure. Therefore, each morphological term used here will be accompanied by a description of the structure.

The species Stylodictya gracilis has been described by Ogane and Suzuki [4] and Ogane et al [1] as a coin-shaped discoidal spumellarian (circular radiolarian, as opposed to the cone-shaped nasselarians). At the center of the disc is a microsphere (sphere of silica that houses the nucleus and endoplasm). Surrounding the microsphere is the biretta, which is a porous rectangular box-shaped shell. Four radial beams connect the microsphere to the biretta. Surrounding the biretta are three hoops, circular rings of silica that are concave toward the center (microsphere) of the skeleton. The three hoops are connected at the top and bottom in equatorial view (viewing the side of the coin-shaped disc instead of the face) by the roof, which is also porous. There are two concentric rings of pores in the roof of each of the three hoops. Ten secondary radial beams connect the biretta through the hoops all the way to the flange (outer edge of the side of the coin shape). Four of those secondary radial beams reach past the flange outside of the rest of the skeleton and act as radial spines. [1] [4] Other species of Stylodictya have a similar overall coin-shaped morphology, but with slightly different characteristics. A common way to tell species of Stylodictya apart is by the number of radial spines that species possesses (e.g. Stylodictya multispina has 16 radial spines).

Being solitary spumellarians, Stylodictya must feed using its many radiating axopodia. When a Stylodictya comes into contact with a bacterium or small algae with one of its axopodia, it contracts that axopodia into its body in order to feed on the prey. [5]

Along with other radiolarians, Stylodictya have bubble-like alveoli outside of the central capsule of the organism. These alveoli are filled with gas and act as buoyancy regulators for the organism, which is weighed down quite heavily by its silicate skeleton.

Fossils

Although the geologic history of Stylodictya is sparse, fossils of Stylodictya have been found in Switzerland that date back to the Jurassic. Stylodictya-type fossils are much more common in the Cenozoic and are found in cherty limestones in New Zealand [6] and in oceanic drill holes around the world’s oceans. [7] [8] Even this sparse paleontological evidence suggests that the Stylodictya morphology of spumellarians has been prevalent in oceanic ecosystems for many millions of years. The distribution of Stylodictya in the rock record also gives insight into the paleoclimate at the time of fossilization. This is because the most important rock type lithified from fossil skeletons, limestone, is primarily calcium carbonate, which is not able to lithify under acidic conditions. Stylodictya, like other radiolarians, forms a silicate skeleton, not a carbonate one. Thus whenever Stylodictya-bearing chert becomes more common than limestone in the stratigraphy, that may be evidence of a shifting oceanic climate. This makes radiolarians important indicators of climate change within the stratigraphical record. [9]

It is important to note that micropaleontology is an extensive and under-studied field, so the fossil evidence that has already been collected on this genus likely only represents a portion of the extent of the genus over geological time and space.

Significance to humans

In addition to the paleoecological implications of Stylodictya fossils, Stylodictya can also be used as an index fossil in stratigraphy. Radiolarians are often used as index fossils, as they are usually instantly recognizable, widespread, and individual species are restricted to a specific time frame. This may not be easy with Stylodictya, however, as the genus has existed over a long period of time and different species of Stylodictya are often not very easy to tell apart, especially in the fossil record. This may not be true in the future, as species are still being discovered, and one may yet prove to be a good index fossil.

Related Research Articles

<span class="mw-page-title-main">Acantharia</span> Class of single-celled organisms

The Acantharia are a group of radiolarian protozoa, distinguished mainly by their strontium sulfate skeletons. Acantharians are heterotrophic marine microplankton that range in size from about 200 microns in diameter up to several millimeters. Some acantharians have photosynthetic endosymbionts and hence are considered mixotrophs.

<span class="mw-page-title-main">Zooplankton</span> Heterotrophic protistan or metazoan members of the plankton ecosystem

Zooplankton are the heterotrophic component of the planktonic community, having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean, or by currents in seas, lakes or rivers.

<span class="mw-page-title-main">Chert</span> Hard, fine-grained sedimentary rock composed of cryptocrystalline silica

Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.

<span class="mw-page-title-main">Radiolaria</span> Phylum of single-celled organisms

The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The elaborate mineral skeleton is usually made of silica. They are found as zooplankton throughout the global ocean. As zooplankton, radiolarians are primarily heterotrophic, but many have photosynthetic endosymbionts and are, therefore, considered mixotrophs. The skeletal remains of some types of radiolarians make up a large part of the cover of the ocean floor as siliceous ooze. Due to their rapid change as species and intricate skeletons, radiolarians represent an important diagnostic fossil found from the Cambrian onwards.

<span class="mw-page-title-main">Humboldt Current</span> Current of the Pacific Ocean

The Humboldt Current, also called the Peru Current, is a cold, low-salinity ocean current that flows north along the western coast of South America. It is an eastern boundary current flowing in the direction of the equator, and extends 500–1,000 km (310–620 mi) offshore. The Humboldt Current is named after the German naturalist Alexander von Humboldt even though it was discovered by José de Acosta 250 years before Humboldt. In 1846, von Humboldt reported measurements of the cold-water current in his book Cosmos.

<span class="mw-page-title-main">Phaeodarea</span> Class of protists

Phaeodarea or Phaeodaria is a group of amoeboid cercozoan organisms. They are traditionally considered radiolarians, but in molecular trees do not appear to be close relatives of the other groups, and are instead placed among the Cercozoa. They are distinguished by the structure of their central capsule and by the presence of a phaeodium, an aggregate of waste particles within the cell.

<span class="mw-page-title-main">Microfossil</span> Fossil that requires the use of a microscope to see it

A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, such as a hand lens, is referred to as a macrofossil.

<span class="mw-page-title-main">Biogenic silica</span> Type of biogenic mineral

Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.

<span class="mw-page-title-main">Radiolarite</span> Type of sedimentary rock

Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is also used for indurated radiolarian oozes and sometimes as a synonym of radiolarian earth. However, radiolarian earth is typically regarded by Earth scientists to be the unconsolidated equivalent of a radiolarite. A radiolarian chert is well-bedded, microcrystalline radiolarite that has a well-developed siliceous cement or groundmass.

<span class="mw-page-title-main">Marine sediment</span> Accumulated material on seafloor

Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.

<span class="mw-page-title-main">Siliceous ooze</span> Biogenic pelagic sediment located on the deep ocean floor

Siliceous ooze is a type of biogenic pelagic sediment located on the deep ocean floor. Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. Oozes are defined as sediments which contain at least 30% skeletal remains of pelagic microorganisms. Siliceous oozes are largely composed of the silica based skeletons of microscopic marine organisms such as diatoms and radiolarians. Other components of siliceous oozes near continental margins may include terrestrially derived silica particles and sponge spicules. Siliceous oozes are composed of skeletons made from opal silica SiO2·nH2O, as opposed to calcareous oozes, which are made from skeletons of calcium carbonate (CaCO3·nH2O) organisms (i.e. coccolithophores). Silica (Si) is a bioessential element and is efficiently recycled in the marine environment through the silica cycle. Distance from land masses, water depth and ocean fertility are all factors that affect the opal silica content in seawater and the presence of siliceous oozes.

<span class="mw-page-title-main">Spumellaria</span> Order of single-celled organisms

Spumellaria is an order of radiolarians in the class Polycystinea. They are ameboid protists appearing in abundance in the world's oceans, possessing a radially-symmetrical silica (opal) skeleton that has ensured their preservation in fossil records. They belong among the oldest Polycystine organisms, dating back to the lower Cambrian. Historically, many concentric radiolarians have been included in the Spumellaria order based on the absence of the initial spicular system, an early-develop structure that, by its lacking, sets them apart from Entactinaria despite their similar morphology. Living exemplars of the order feed by catching prey, such as copepod nauplii or tintinnids, on the adhesive ends of their pseudopodia extending radially from their skeleton; however, some have been observed as mixotrophs living in symbiosis with various photosynthetic algal organisms such as dinoflagellates, cyanobacteria, prasinophytes or haptophytes, which may cause their distribution to center in the greatest abundance and diversity within trophical waters.

<span class="mw-page-title-main">Nassellaria</span> Order of single-celled organisms

Nassellaria is an order of Rhizaria belonging to the class Radiolaria. The organisms of this order are characterized by a skeleton cross link with a cone or ring.

<span class="mw-page-title-main">Collodaria</span> Order of single-celled organisms

Collodaria is a unicellular order under the phylum Radiozoa and the infrakingdom Rhizaria. Like most of the Radiolaria taxonomy, Collodaria was first described by Ernst Haeckel, a German scholar who published three volumes of manuscript describing the extensive samples of Radiolaria collected by the voyage of HMS Challenger. Recent molecular phylogenetic studies concluded that there are Collodaria contains three families, Sphaerozodae, Collosphaeridae, and Collophidilidae.

<i>Cornutella profunda</i> Species of single-celled organism

Cornutella profunda is a species of radiolarian in the family Theoperidae and the genus Cornutella. The abundance and actual geographic span of C. profunda has not yet been fully explored, however few have been caught in various regions around the world. Samples have seen in larger numbers in the Adriatic Sea, the South China Sea, and far off the coast of Southern Africa near Namibia, and in smaller numbers in all other oceans around the world.

<i>Collozoum</i> Genus of radiolaria

Collozoum is a radiolarian genus formerly reported in the subfamily Sphaerozoidae, now reported descending from the order Collodaria. The genus contains bioluminescent species. It is a genus of colonial radiolarians.

Rhaphidozoum is a radiolarian genus reported in the subfamily Sphaerozoidae. The genus contains bioluminescent species. It is a genus of colonial radiolarians.

Sphaerozoum is a radiolarian genus formerly reported in the subfamily Sphaerozoidae, now reported in the Collosphaeridae. The genus contains bioluminescent species. It is a genus of colonial radiolarians.

<span class="mw-page-title-main">Protist shell</span> Protective shell of a type of eukaryotic organism

Many protists have protective shells or tests, usually made from silica (glass) or calcium carbonate (chalk). Protists are a diverse group of eukaryote organisms that are not plants, animals, or fungi. They are typically microscopic unicellular organisms that live in water or moist environments.

<span class="mw-page-title-main">Protists in the fossil record</span>

A protist is any eukaryotic organism that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor, the last eukaryotic common ancestor, the exclusion of other eukaryotes means that protists do not form a natural group, or clade. Therefore, some protists may be more closely related to animals, plants, or fungi than they are to other protists. However, like algae, invertebrates and protozoans, the grouping is used for convenience.

References

  1. 1 2 3 Ogane, K., Suzuki, N., Aita, Y., Lazarus, D., Sakai, T. (March 2009). "The ehrenberg type species of flat‐sharp radiolarian genera (spongodiscidae and stylodictyidae, spumellaria, polycystina)". Journal of Systematic Palaeontology. 7 (1): 81–94. doi:10.1017/S1477201908002575. S2CID   85745281.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. 1 2 3 4 Yamashita, Hitoshi; Takahashi, Kozo; Fujitani, Naoki (January 2002). "Zonal and vertical distribution of radiolarians in the western and central Equatorial Pacific in January 1999". Deep Sea Research Part II: Topical Studies in Oceanography. 49 (13–14): 2823–2862. Bibcode:2002DSRII..49.2823Y. doi:10.1016/s0967-0645(02)00060-7. ISSN   0967-0645.
  3. ↑ Anderson, O. R. (1983). Radiolaria. Springer Science & Business Media.
  4. 1 2 Ogane, Kaoru; Suzuki, Noritoshi (April 2006). "Morphological terms describing discoidal radiolarians". Revue de Micropaléontologie. 49 (2): 97–104. doi:10.1016/j.revmic.2006.03.001. ISSN   0035-1598.
  5. ↑ Matsuoka, Atsushi (2007-09-01). "Living radiolarian feeding mechanisms: new light on past marine ecosystems". Swiss Journal of Geosciences . 100 (2): 273–279. doi: 10.1007/s00015-007-1228-y . ISSN   1661-8726. S2CID   84159802.
  6. ↑ "Stylodictya Ehrenberg 1847 (radiolarian)".
  7. ↑ Kamikuri, Shin-Ichi; Wade, Bridget S. (2012). "Radiolarian chronology and fauna across the middle/Late Eocene boundary at ODP Hole 171-1052A". Pangaea. doi:10.1594/pangaea.811220.
  8. ↑ Lüer, Vanessa; Hollis, Christopher J.; Willems, Helmut (2008). "Late Quaternary radiolarian assemblages of ODP Site 181-1124". Pangaea. doi:10.1594/pangaea.762754.
  9. ↑ Racki, G (November 2000). "Radiolarian palaeoecology and radiolarites: is the present the key to the past?". Earth-Science Reviews. 52 (1–3): 83–120. Bibcode:2000ESRv...52...83R. doi:10.1016/s0012-8252(00)00024-6. ISSN   0012-8252.
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