Cube Algae
Cube Algae (Natatio quadratus) is a species of phytoplankton, found floating at or near the surface of the ocean in zone 4.
It has an unusual celular structure, comprised of individual undifferentiated algeal cells, held together with strands of citoplasm. These strands form silicate needles that form a basis for a rudimentary support lattice. The cells form these connections at 90° angles, forming near perfect cubes under ideal conditions. Where the needles intersect or terminate, they tend to form spherical "nodes" inside the algea cells.
The structure is semi-mobile, using flagella on the external layer of cells to move through the water and rotate. The flagella are absent on the cells inside the structure, though they will form, if these cells find themselves on the outer edge. Additionally, the cell walls tend to be much thicker on the outer cell layer than on the interior ones.
The structure can also control it's buoyancy by emitting pockets of gasses on it's interrior. If disturbed, such as by being hit or in rougher seas, some of this gas will be released and the structure will descend, however it will not dive beneath the depth of ca. 10-12 m.
It's translucent enough for the cell on the inside to be able to photosyntesise even through more than 5cm of thickness. In structures larger than that , the cells on the inside will be supported by nutrients provided by the outside cellular layers, and will often have a significantly reduced number of chloroplasts.
In calm seas with sufficient sunlight and nutrients, the structure can grow to over 20-25cm in diameter, although in rougher waters, it can often break apart, particularly if hitting hard objects. It is capable of fully regenerating from just a couple of cells, though, or even just one under ideal conditions.The colonies that had been regenerated from broken pieces are often no longer cubical in appearance, and tend to be asymmetrical, but will still often have a smooth edge or two.
It reproduces by periodically differentiating and releasing haploid gametes into the water from it's outer cell layer. These gametes, larger than normal cells, with more powerful cilia, will float around individually for varying periods of time until encountering another gamete, after which the two will fuse combining their DNA and begin multiplying and forming a connected cubical cellular colony.
It's generally not fed upon by larger creatures due to the sharp, but fragile, silicate lattice of the structure, which would cause damage to any unprotected creature that would attempt to bite it or even exert sufficient force against it. It is, however, fed upon by various species of zooplankton, small enough to avoid the needle lattice.
If sufficient amount of cells in the structure die, the lattice will sink to the bottom, as it will no longer be able to keep the bubbles inside it's structure that provide it with buoyancy.
It evolved from Micralgearous greana cells that had washed from zone 17 to zone 4 and adapted to their new environment. Originally these undifferentiated cells evolved into clumping together into into groups of four that remained connected via cytoplasmic channels. A later adaptation caused them to grow their silicate needle lattice within these channels and grow into larger colonies.
When the cells divide, they first produce elongated pseudopod-like tubes at 90° angles, in which they secrete the silicate. Then, if they encounter noting, the nucleus will split and it, along with some of the organelles will follow the tube and form a new cell at a set distance. If, however, they encounter another cell, and the chemical receptors identify it as belonging to the same colony (like a tube secreted by another cell), they will attach together.That's how they develop their 3D cubic shape.
They can survive easier and reproduce more efficiently as group that as individual cells.
Also, the cels that produce extra carbohydrates via photosynthesis can feed them to cells that are not in a good position to do so, therefor ensuring the survival of a larger number of cells.
The fragility of the silicate lattice not only provides protection from predators, but also allows the colonies to stay more firmly connected when they are still small in size, but also allows for easier fragmentation in larger colonies, allowing them to spread quicker.
