Introduction to Europan Biology

On Tuesday, I introduced a few online (and offline) resources about realistic alien ecosystems that I’d been using for “a project.” Well, here’s that project! This is the first in a series of in-person articles you can use as SolArchive handouts in your Eclipse Phase campaign (or steal for another setting, of course). Enjoy!

Many visitors to Europa are surprised at how much of our understanding of Earth’s oceans fits the ecology of Europa’s subsurface oceans. There are niches filled by a variety of species and a stratified water column characterized by shifting food availability and changes in both temperature and pressure. This free guide is intended to give visitors a grounding in the types of creatures that are found on Europa, particularly those near the subsurface habitats and famous lithodermic reefs.


The foundation of any ecosystem is the concentration of energy into forms that organisms can make use of. The familiar terrestrial form of producers are plants which convert sunlight into sugars and form the basis for the rest of the food web. On lightless Europa, producers make use of the volcanic vents on the ocean floor and the free-floating ions in the ocean. These chemosynthetic organisms convert these inorganic sources into compounds similar to sugars and starches from Earth-based organisms.

The largest producer populations by far are the free-floating organisms of the class Strokinovida (analogous to Earth’s protozoans) and the chemosynthetic species of the lithoderms that make up the giant reefs. After these, there are large populations of organisms that researchers have discovered to be the larval stages of larger organisms in the Biderma and Tanwhainovida classes. While these groups of creatures resemble jellyfish and sharks respectively, their life cycles are very different and they hatch as chemosynthetic organisms before transitioning to an autotrophic existence.

Primary Consumers

The small creatures that float through the subsurface oceans (collectively called “plankton” just like on Earth) are consumed by larger creatures mostly through filter mechanisms. Some sift with large bristles like some whale species while others have small-scale pumps that force water through and trap the small organisms.

Visitors to Europa are likely to see anchor-worms, welders, and net colonies as their first examples of primary consumers since these creatures attach to the underside of Europa’s ice layer. They are especially attracted to the hydrocarbons and silica dust of transhuman habitats and are even more common there where many species have become pests that local communities work hard to keep in check. In particular, the welders and the interconnected organisms of net colonies use exothermicytes to melt ice and they seem just as ready to damage equipment. Though they are more common at greater depths, latch-worms pose a hazard to equipment and transhumans alike.

Fissure Gate
Image © Posthuman Studios

Further down into the ocean, sieve-jellies and the bolatees (unofficial mascots of the moon) feed in the open waters. When one approaches the peaks of the lithodermic reefs, many more primary consumers become evident as flit-rybas, filter-skates, winged bugs, and Europan krill (these last are technically present near the ice sheets but in much smaller numbers).

Secondary Consumers

Generally larger than the primary consumers, these predators eat macroorganisms and therefore pose the largest dangers to transhuman visitors. Near the main habitats, the most common secondary consumers are some large and slow-moving examples of the jellyfish-like predators called “okhots” by locals as well as some particularly territorial species of hunter-stars. Neither population is particularly dense across the moon as a whole, but habitats attract producers which attract primary consumers and so on.

Further down at the tops of the reefs, the wide and sweeping forms of twinwings and the slender, stalking forms of sea fiends create the sort of terrifyingly alien scene that many on Earth imagined for centuries. Though less common, the hulking forms of leviathan crabs are so intimidating that most aimed the earliest reports and videos were fakes until biologists could confirm. The sinuous toothed worms and the autotrophic species of  lithoderms and pseudo-diatoms are less impressive but many are some of the most interesting species on Europa.

Eclipse Phase Digitized Mind
Image © Posthuman Studios


Species that feed on the dead are another facet of life that is repeated on Europa. Sometimes it takes on familiar forms and other times strange and alien forms. Scavenger worms and some forms of flit-rybas are examples of the former and seeing them crawl and swim around the lithodermic reefs picking up dead organisms will seem very familiar to anyone who has watched vids of old Earth. There are some filtering species of the single-celled Strokinovida class and the diatom-like Innatotheca class, as well as some filter-feeding Europan krill and lithoderms themselves.

Slightly more bizarre are the long-legged scour crabs that stride across the reef slopes like mechanical walkers and the latch-worms that quickly attach themselves to any large creatures that have died (including transhuman corpses). Most interesting (and photogenic) are the mantle jellies that use flashing bioluminescence and low-frequency EM pulses to warn would-be predators of their toxicity. Mantle jellies will envelope sections of the lithodermic reefs and slowly pull off dead material before moving on. Though they cause short-term atrophy in the reef’s growth, xenobiologists have found that they are essential to the long-term health of the reef by removing dead material and providing room for health lithoderms.


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