Mound Shev

The Mound Shev has become a fully sessile colony, at least as an adult. It is much the same colonial structure as its ancestor: many individual Shevs with mortared together shells, growing into a large structure. Its foot pseudopods produce aragonite in layers below each Shev, building the colony upward rather than outward. Each individual Shev is composed of one foot psuedopod, a single shell, and multiple feeding psuedopods and spines.The Mound Shev can reach a height of 30 cm and be 50 cm wide at the base, creating a shallow cone-shaped mound. It also now uses the foot pseudopods to transfer nutrients and nuclei between cells. Reproduction of new cells for the colony is much the same as its ancestor, through sexual budding. This only occurs where space is available, such as at the edge of the colony or where cracks have occurred, with the new cell budding from the foot pseudopods to then grow up into the crack and establish itself. To found new colonies, sexual budding occurs in the feeding pseudopods, and forms a cyst. The cyst is durable and can remain viable for several weeks in the water column. When the cyst lands on substrate it will develop into a juvenile Mound Shev. This juvenile is motile and will slowly crawl to the best location it can find: somewhere in direct current and with access to abundant shell building nutrients. Once it has found a location, it will become rooted and start reproducing from its foot pseudopod to grow the colony. Growth is slow however as even with the abundance of food to filter feed with, building shells and support mounds takes time. It can take 15-20 years for the Mound Shev to reach full size. Each cell only lives for 5 years on average so shells, when left empty of a cell can be filled with a new cell. In a sense the colony is immortal through this process, but predation and acidic events can damage or kill off all the cells resulting in the colony's death. New Mound Shevs will often take over the remains of old colonies and continue to grow the base, filling in the old shells. The coloration of the shells are dictated by impurities in the aragonite used to construct them. Colors range from oranges and reds to teal blues. Reefs usually become monochromatic over time as aragonite from lower layers are absorbed by the surface colonies and any impurities are concentrated. So while newly founded Mound Shevs may possess a range of shell colors, established reefs tend to have many Mound Shevs all of the same colors.

The image shows a cross section of the Mound Shev. The aragonite base they produce to build the colony upward is much the same material as what is use to construct their shells.