Tideworms
Tideworms are fundamental to the Wormwood Coast ecosystem for their role as primary producers that don’t depend on photosynthesis. Instead, they extract energy from an unlikely source - the rising and falling of the tides.
A tideworm spends its entire life anchored inside of the hard, mineralized tube it builds, encrusted onto a rock in the intertidal zone. At low tide the worms retreat into their tubes and seal the top shut to avoid desiccation, but as the tide comes in, their heads emerge and they begin to feed. Each individual has a single long feeding tendril ending in a methane-filled bladder. The core of the feeding tendril is made up of chains of spring-shaped proteins, so as their buoyant floats rise with the tide, the “springs” expand and the tendrils stretch as they’re put under tension. Then as the water recedes, the stored potential energy is released to drive the worm’s metabolism. With sufficiently high tides, a single worm can generate about 1/3 of a watt of power per cubic meter of methane, more than enough to fuel a small, sessile invertebrate.
Because the worms take so long to reach maturity and reproduce, they are highly dependent on the safety of their tube for protection from predators. However, because tube-building is so energy-intensive, several groups of tideworms have become parasitic, evicting other worms and stealing their ready-made tubes. To combat this, there has been an incredible morphological radiation in tube structure in order to make invasion and colonization difficult. For example, some worms build tubes with complex arrangements of inward-pointing spines, or coat them in secretions that are nearly impossible to adhere to, so that only the most specialized worms can inhabit them. There is also a vast range of sizes found across taxa, from less than an inch to several yards long.
Because their main limiting resource is vertical space, not horizontal, nearby tideworms have little competition and so can form dense colonies with complex social interactions. For unknown reasons, the most productive of these aggregations show high diversity of species and even genera. Uptake of inorganic nutrients from the environment (phosphorus, nitrogen, minerals, etc) appears to be regulated by the colony as a whole, implying that these “pseudo-reefs” function as distinct ecological units and that inter-species signaling among tideworms may play a major role in structuring local ecosystems.