Space Snails
MOLLUSKS to be Precise
Itinerant cosmic travelers the so-called "Space Snails" are a rare example of interstellar life. Feeding on various forms of energy and the hydrogen found in interstellar medium of the galaxy these Space Snails are extremely efficient living spacecraft.
Space Snails have been encountered by many civilizations and detailed records go back as far as there is recorded space-faring history, this marks them as one of the oldest extant species in the universe. Indeed an Ukaros researcher once tagged a specimen with a tracking device, and whilst the device subsequently ceased functioning, it was later discovered thousands of cycles later by Fulgar scavengers, still attached to it's original specimen. Effectively immortal and capable of sustaining itself on the raw environment of deep space, the Space Snail has rightly attracted a great deal of academic interest.
Unfortunately for scientists Space Snail encounters remain incredibly rare and no specimen (living or deceased) has been recovered due to a unique defense mechanism whereby any cornered specimen undergoes a process of stellar fusion... resulting in a massive explosion. Despite this, some facts have been gleaned by direct observation.
Firstly, Space Snails are large organisms contained within a hexagonal shaped tube or shell. They possess a series of tentacles that seem to act as their feeding apparatus and they clearly feed off of hydrogen (presumably to be used in a form of contained fusion within them, much like any constructed fusion core). This feeding process is fascinating as it appears that a singular Space Snail would not be able to survive off of the available hydrogen in the interstellar medium based on their dietary needs and their rate of movement. This is curious, as it would suggest that there would be no way for the species to survive alone or in groups... however their herding behavior is the very key to their survival.
It has been determined, that in groups, Space Snails are able to attract interstellar hydrogen to their location, as such, the herd simply stops moving and then simultaneously attracts and consumes hydrogen particles. Alone, a Space Snail would die of starvation, and so, if separated form the heard, they induce fusion, which essentially reseeds that region of space for future grazing by others of their kind. Interestingly some nebulae having formed less stars than what has been calculated, a mathematical mystery to an astronomer. It has been suggested that this discrepancy could be the result of Space Snails feeding off the nebula's raw materials.
Space Snails have never been directly observed breeding and it is unclear if they reproduce sexually or asexually, certainly size variations have been observed between different specimens but molecular dating of the organisms (shell scrapings via drone sampling has proved possible) has shown no correlation between the size of the specimens and their age. It is thusly unclear which individuals may be "youths" and which may be "elders". Scientists do believe that Space Snails must in fact breed, and that newborns become new members of the herd, herds are believed to split into two herds only when the original grouping has reached a size whereby the local resources cannot sustain them. This would explain why the species is not simply traveling as a single "mega herd".
Space Snails have rarely been observed within the boundaries of a solar system, instead, they tend to feed in-between stars or at their edges, and sightings are slightly more frequent within energetic nebula. One instance has been reported of Space Snails orbiting the aperture of a pulsar, however the source of this report was a particularly unscrupulous Terran trader and is not considered seriously by academics.
Further study is needed to comment further on the proclivities or the intelligence of the Space Snails, but suffice to say they are an amazing natural phenomenon and have to date posed no threat to interstellar travelers, it is unfortunate that the creatures are so rare and that some empires have destroyed Space Snails rather than attempt to study the creatures.