Roundshell Shrewvs
The Roundshell Shrewvs have moved into the wetlands and Watersheds of Wright, spreading across the continent. Changes in salinity in their new environment drove the development of electrolyte production, the concentrations of which provide the cell with a simple osmoregulation system. They range in size from 1 to 4 centimetres wide, with polar species generally being smaller than their tropical and temperate relatives. All Roundshells have a smooth shell composed of aragonite which they accrete in successive layers as they grow. They have lost their bristles so as to expedite the speed at which they can grow and repair their shells. To account for the drop in defensiveness that results in the loss of their bristles, the shells are much stronger, being on 50%-75% thicker than the shell of their ancestor. The shell has its main opening on its underside which allow the cells specialized pseudopods to extend from the main mass of the cell.
The eyestalk pseudopods have their own small openings along the lower rim of the shell, allowing the eyestalks a higher base position than if they also used the single underside opening. These eyestalks are rediliant and flexible, with light sensitive patches at their terminus that allows the Shrewv to determine light and shadow in its environment. These eyestalks are also lined with chemoreceptors which serve as a much more useful sensory system, allowing the Shrewv to identify the direction of potential food.
Growth occurs when the Shrewv buries itself, usually following a large meal but for some species this is a more regular yearly occurrence. Their diet consists of dead organisms, detritus, and microorganisms they are able to filter from the water using their mouth psuedopods. To consume more solid objects, Roundshells will secrete digestive enzymes on the food item directly to create a soup of the food item to be absorbed into the cell. The coloration of the aragonite is determined by the composition and impurities of the minerals in the substrate, so the coloration of Roundshell Shrewvs varies wildly and will result in striations in the shells. Thus the age of a Shrewv can be roughly determined by the amount of striations its shell shows.
There are hundreds of species of Roundshell Shrewvs, many of which are distinct only in genetics, shell shape, and climate adaptations. Montane and polar species tend towards flatter shells, allowing them to squeeze under ice and into crevices. Temperate species tend towards more spherical shells and like the polar and montane species will bury themselves each winter to undergo shell accretion. Tropical species have more tapered, teardrop shaped shells, and will bury themselves only after large meals.
Roundshell Shrewvs can live anywhere from 5 to 15 years. Reproduction occurs much like its ancestor, with genetic material exchanged on meeting another individual, and new cells formed and implanted into the substrate to begin accreting their shells. On death they will leave behind their shells, which litter river and lakebeds with smooth, marble like shells scattered amongst the bright shells of Wright Nautstars. These scattered shells will sometimes be utilized by young Roundshell Shrewvs as a concentrated source of calcium to build their own shells, and if the size difference is significant, a temporary shelter.