Zoom out: Motilia
Volcanoids are a prolific phylum of sea life found all over Ilion’s depths, including the darkside hydrothermal vents. They are characterized by their mode of embryonic development in which the embryo folds twice: once to make a tube, as in all plicozoans, and again to form an O-ring. What used to be the mouth and anus of the wormlike ancestor are now linked together and no longer function as such. Volcanoids procure food and excrete waste through extensions of the gut that poke through the body wall.
Wartlets – Extinct and extant shelled volcanoids are responsible for a majority of Ilion’s limestone. They live a lifestyle similar to barnacles, cementing themselves to rocks and feeding with long, feathered gut extensions that can retract into the body cavity.
Pimplets – Pimplets are simple unshelled volcanoids. Among them are predators and suspension feeders. The only real distinctions between them are size of prey and method of capture. Suspension feeders breathe through their main opening and trap small particles on their sticky inner body wall. Predators can be active or passive. Passive predators lure prey into the body cavity and close the entrance before filling the chamber with digestive enzymes. Active predators feed like bladderworts, rapidly expanding their chamber to suck in prey as it passes by.
Zeppelins – Zeppelins are the largest animals on Ilion, though most of their body is empty space. Zeppelins are made up several individuals linked together. There are only three species. Two are plankton eaters that supplement their diet with the energy produced by symbiotic red algae. The third is a predator that engulfs prey large and small and digests its food with the help of multiple species of piranha-like animals that live inside the body cavity.
Sea Vases – Sea vases are similar to pimplets except for their bulbous shape and fringed main opening. Almost all sea vases live in colonies that carpet rocks and the backs of other sea life.
Geminids – Geminids are a type of planktonic sea vase that spends its adulthood as a medusa. When they reach maturity, sessile species detatch from their substrate and search for mates. Once paired, they fuse together and spawn inside their combined body cavity. The offspring eat their way out of the capsule when development is complete.
Seascrapers – Another giant of the sea, seascrapers grow from planktonic larvae into towering structures. Unlike other volcanoids, seascrapers and their relatives develop inside out, with the gut extensions facing the open water instead of the body cavity. They are most like sponges, with some vent species harboring thiotrophs and other chemoautotrophic microbes. Wastewater is excreted into the body cavity and exits from the top of the chimney.
Colonial Seascrapers – Colonial seascrapers are actually more closely related to fairy stumps than to seascrapers. Like their relatives, these giants develop inside out. Their mouths are on the outer body wall and are lined with tentacles for capturing prey.
Fairy Stumps – Fairy stumps are not all that different than their colonial relatives, except that their anuses develop on the outer body wall instead of the inside. Their main opening is fused shut and the body cavity is filled with calcified tissue for structure and strength.