Swarmerweed

Swarmerweed split from their ancestor. These colonial algae-like swarmers have developed polymorphism in their colony members, resulting in a more complex colony structure. The colony members are now interdependent on one another, so Swarmerweed zooids can only exist individually for reproductive purposes. There are now three types of zooid in a colony: gathering, spawning, and holdfast. The gathering zooid is similar to the ancestral state, but now lacking reproductive organs; it has regained the ability to consume, and the gathering zooids also serve to capture cells and even smaller fauna with their mouths. Spawning zooids, on the other hand, have lost any resemblance to a digestive system at all and serve as the colony’s reproductive organs. They lack chloroplasts and exist on the inside layer of the colony. The third type of zooid, the holdfast zooid, exists on one end of the colony and forms a holdfast organone. Holdfast zooids have suction cup-like mouths, and when the colony settles down they eat any microbes on the chosen surface before attaching to it. When it comes time to reproduce, a temporary opening forms on the aboral end of the body (opposite of the holdfast), and gametes are released inside the body cavity and squeezed out.

In order to maintain such a complex colonial zoon, Swarmerweed zooids are partially fused together, sharing their nervous and circulatory systems. They are functionally a single organism. Every colony starts from just one individual or a few which stuck together early in life, and as such the colonies can be distinctly male or female, or more rarely hermaphroditic. The founder of the colony undergoes binary fission like a flatworm, producing zooids of each type before eventually converting itself into a gatherer zooid. The colony grows into a long worm-like chain resembling the ancestor, but with a holdfast at the end. In addition to spawning, Swarmerweed colonies can also reproduce by budding; when this occurs, they briefly have a branching appearance.

Notably, though Swarmerweed have no visible macroscopic eyes, they actually have rather good eyesight. Every single gatherer zooid has a single simple eye, and with redundancy and the shared nervous system together the zoon itself is able to get a decent greyscale picture of its surroundings in all directions.

Bizarrely, the entire developmental process of the zoon, from individual zooid production to the shape of the zoon as well as reproduction by budding, is controlled by the nervous system. The zoon as a whole has some awareness of its own shape and an instinct telling it what it's "supposed" to be shaped like, and therefore it "knows" when something is missing as a result of injury or immaturity. This allows it to instruct its individual zooids to bud in order to grow or to close a gap; without this careful direction (and as is sometimes induced by mutation or disease), wounds would be left with sheet- or tag-like scars, as the zooids do not have individual awareness of the size and shape of the wound and would overshoot. It can even instruct gathering zooids, which are as close to a "stem cell" as is possible in this setup, to produce zooids of specific types. As swarmerweeds are brainless, this is all predetermined by instincts no more complex than simple computer code, but if they were more intelligent, they would have potential to do some very strange things.

There are many species of Swarmerweed. Though they attach to objects, they are not exclusively benthic and many species will also cling to large pelagic fauna, floating flora, and shrog nests. They can live in both freshwater and saltwater and may have different holdfast zooid mouth shapes for clinging to specific kinds of surfaces. Some species which live in already densely-populated habitats will cling to other benthic flora to steal sunlight.