Shrubesagna
Shrubesanga has developed into an interlocking reef system with each shrube making up a single block of the layered structure. Each shrube possesses an aragonite shell measuring 1.6 cm in length and width and 1 cm in height. On its dorsal face are 4 conical studs with small openings at their tops. Through these openings the shrube will extend their feeding pseudopods to feed on planktonic organisms. Their ventral side has openings which match the shape of their studs, such that they can fit into one another. This allows each Shrube to interlock with one another to form their reefs. This interlocking is further solidified by the accretion of aragonite between the sides of each shell, gluing each shell to its neighbors. The material used to create their shells is primarily from the substrate, with secondary sources such as the shells of planktonic organisms and dissolved minerals in the water contributing to a third of the material used in construction.
Their foot pseudopods are used for motion by the young and solitary founders of a colony. Once a shrube has entered a colony, its foot pseudopods will form a connection with the shrubes underneath it, allowing for the transfer of nutrients and material between members. Roles in the colony are determined by what layer a shrube is on. Shrubes with dorsal access to water are responsible for feeding and the release of offspring. Layers situated between other shrube layers are responsible for accretion and upkeep of the shells and reproduction. Shrube on the lowest layer, connected to the substrate, are responsible for material gathering.
Shrubesanga colonies will transition through many stages as the colony grows. Colonies start with singular shrubesanga shrube settling down on the substrate and sending out chemicals to attract other shrube. Eventually they will form a collective and begin connecting to one another, first in a single layer sheet with their shells glued together. This is called the founding stage. As the colony grows, new members will anchor themselves above the first layer and the layering stage begins. As layers stack upwards and established layers grow outwards, the shrube transitions into their layer roles and the propagation state begins. As growth continues reproduction ramps up to result in large broadcasting events.
This propagation stage can last for as long as the supplies for new colony members can be resourced. If the colony is first established on a large deposit of calcium, such as the remains of shev colonies, this stage can last for decades until the supply of materials is exhausted. If the colony is on substrate, then this stage will end once the centermost lower layer shrube can extract no more material for shell building and repair. Shrube that end up in this position will terminate themselves and be eaten by their neighboring Shrube. This will begin the donut stage, in which the colony will grow outward from its original center-point, abandoning and recycling old shells as they exhaust the substrate of usable material for shell building. The colony will continue in this fashion until it eventually reaches obstacles or casualties that break up the donut shaped reef into disconnected crescent shaped reefs, which will continue on much the same trajectory they started on.
In this way, Shrubesanga forms a moving reef, inching forward in search of more building material as the years pass. Though the reefs themselves are functionally immortal due to the constant replacement of reef members, each individual shrube lives on average 10 years. Reproduction can happen for any individual shrube throughout its life, but the major reproductive events occur during the propagation stage. Once a year Shrubesanga in a region will synchronize their spawning so as to overwhelm any predators. They will release cysts from their feeding pseudopods in the span of a few nights. These cysts are produced by the reproductive layers through budding inside their shells. Just prior to broadcast the middle layers of a Shrubesanga have Shrube filled to nearly 40% of their volume with cysts. When released these cysts can remain dormant and viable for months until they land on the seabed. At that point they will transition out of their cyst state and bury themselves to begin growing their shell. Young Shrube will not fully emerge from the substrate until they have gathered all usable material within their reach. During this time they will be buried just under the surface with their feeding pseudopods filtering out food from the water to fuel their growth. Their growth rate is highly dependent on where they manage to bury themselves and can thus range from 2 months to 2 years to reach the shell size of an adult.