| Synchroma | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Stramenopiles |
| Phylum: | Gyrista |
| Subphylum: | Ochrophytina |
| Class: | Picophagea |
| Order: | Synchromales Schnetter & Ehlers in Horn et al., 2007 |
| Family: | Synchromaceae Schnetter & Ehlers in Horn et al., 2007 |
| Genus: | Synchroma Schnetter in Horn et al., 2007[1] |
| Type species | |
| Synchroma grande Schnetter in Horn et al., 2007 | |
| Species[2] | |
| Diversity | |
| 2 species | |
Synchroma (from Greek syn- 'with, together' and chroma 'color') is agenus ofmarinestramenopilealgae containing twospecies withamoeboid morphology. They are grouped within the monotypic familySynchromaceae and orderSynchromales as part of an independentclade ofochrophytes known asPicophagea or Synchromophyceae.
They are distinguished by theirplastid complexes, composed of severalchloroplasts grouped together and collectively enveloped by the samemembranes. Within theirlife cycle,Synchroma cells are usually sessile and protected by alorica. These cells can join theirreticulopodia in a network known as meroplasmodium, or they can become migrating amoebae capable of fusing to each other.
Synchroma areeukaryoticalgae composed ofamoeboidcells with noflagella and multiple yellowish-greenchloroplasts containingchlorophylla andc2,fucoxanthin,violaxanthin,antheraxanthin,zeaxanthin andb-carotene.[3] Each cell presents plastid complexes of 6-8 chloroplasts each. Within the complexes, the pigmented lobes of the chloroplasts radiate from the center. Each pigmented lobe has longitudinally arrangedlamellae, without a girdle lamella (i.e. a peripherical lamella that surrounds all other lamellae, characteristic of someochrophytes). In the center of the complex, the non-pigmentedpyrenoids of all chloroplasts are tightly grouped and surrounded by a single vesicle. Each chloroplast is surrounded by two 'inner'membranes, while the entire plastid complex is surrounded by two 'outer' membranes, with the outermost membrane as therough endoplasmic reticulum.[1][2]
The main appearance ofSynchroma is as sessile,amoeboid cells of around 16[3] or 22μm[1] in diameter on average, depending on the culture conditions. The cell body is attached throughcytoplasmic strands to a flattened sphericallorica, 26 μm in diameter, which in turn is attached to the substrate. Multiple sessile cells can form a meroplasmodium,[3] an association of several spherical cell bodies through a common network ofreticulopodia,[4] which allows the capture and transport of food particles. The sessile cells can undergobinary cell division (asexual reproduction).[3]
Another sessile stage ofSynchroma is thecyst, a spherical cell with a highlygranularcytoplasm and no reticulopodia, surrounded by a multilayeredcell wall. This has been interpreted as the resting stage ofSynchroma, sometimes occurring within a lorica.[3]
Afterbinary cell division of a sessileSynchroma cell, while one of the daughter cells remains in the lorica, the other one hatches through the opening and becomes a migratingamoeba. These migrating cells without a lorica have a dynamic cell shape and size, capable of stretching and reaching five times their initial length. When attached to the substrate, they appear flattened. Within minutes, they can begin to float on the medium and switch to a 'heliozoa'-like form, with a spherical cell shape and 6-30axopodia, sometimes fixing to the substrate through one or two of these axopodia. The floating cells can switch back into the migrating amoebae. After some period of time, the hatched amoebae form a lorica and become sessile cells.[3]
The migrating amoeboid cells can fuse by contacting their filopodia together, then fusing the ectoplasm of several cells, then fusing the endoplasm. The fused cells can become sessile by forming a lorica. If two cells merge, they can undergokaryogamy (sexual reproduction) anddifferentiate into a tetrad, and three or all four of the daughter cells can hatch out of the lorica. Large cell aggregates can reach over 60 μm in size.[3]
Synchroma cells feed byphagotrophy ofbacteria and otheralgae such asPhaeodactylum tricornutum. The cytoplasmic strands attach to the prey cells and are then hauled toward the main cell body until they reach the lorica, where they are digested. The reticulopodia can absorb cytoplasmic material of other cells without killing them.[3]
Thismarine genus of algae displays sessile and non-sessile cell stages within its life cycle, with a dominating sessile amoeboid stage. It is assumed that it lives mainlybenthic onsublittoral rocks. The strong adhesion of the lorica on the substrate could prevent cells from being washed away.[3]
Synchroma is a genus ofstramenopilealgae belonging to the classSynchromophyceae, of whichPicophagea is a synonym.[5] The evolutionary origin of the plastid complexes found inSynchroma is still an enigma.[2]Synchroma is the only case of multiplastidicstramenopilealgae where the plastids are retained together in a common compartment.[1]
Synchroma contains two species: