Wormoss

Wormoss split from wormstems as they honed their ability to survive in tidal zones. Like their ancestor, they begin life as mobile crawlers, which traverse the shallow ocean floor. These have changed little. However, as they reach adulthood, they enter the tidal zone and may even crawl some way further onto the shore. There, they become immobile and grow upward on both the head and tail ends. Unlike wormstems, wormoss tend to keep a much longer horizontal area lying on the ground before bending upward, to maximize the area exposed to sunlight and because it is more difficult to support their height without the buoyancy of the water.

The overall body structure has stayed much the same. They grow in a series of segments (new ones formed by the base), consisting of a cylindrical outer shell, capable of photosynthesis, and a soft inner core. Strictly speaking, the shell and core are separate organisms, but they are completely integrated with one another. The outer core also grows leaf-like thorny protrusions, especially large on the head segment.

Once in the air, the outer shells seal up against each other, forming an airtight boundary. This protects the core from radiation and from drying out. The inner core requires moisture for survival. As a result, the former proboscis, now useless for filter-feeding, has redeveloped into a funnel-shape, which will collect rainwater (or tide water, if the wormoss is within the tidal zone). The soft core contains the vessel system that distributes water and nutrients from segment to segment, as well as depositing reserve tissues to store nutrients for later. This vessel system derives from what used to be the digestive tract. In juveniles, the core also contains a simple nerve network and muscles, but these atrophy by adulthood.

Wormoss are also dependent on water for reproduction. Even in the juvenile stage, they begin spawning sperm, but by adulthood, they spawn both sperm and eggs. These sex cells always come in pairs: one cell for the shell, one for the core. The sperm and eggs are water-borne, so adults can only release them when there is sufficient water to carry them to the ocean, thus restricting them to the tidal zone and areas with high rainfall. Egg cells come in packets containing several of them as well as nutrient packages. They will grow into a small group of juveniles, provided with a ready-made boost of energy. If food is scarce, the strongest juveniles may eat the weakest. In any case, they will then travel across the ocean floor until they find a beach for their new home.