keelges

Keelges are a fictional group of marine invertebrates described in speculative fiction and worldbuilding literature. They are defined by a pronounced keel-shaped ridge running along their carapace and a soft, bioluminescent underside. Adults typically measure 2 to 6 centimeters in length, though sizes vary with habitat and age. The shell is smooth with fine longitudinal ridges that converge at the keel, which may extend beyond the rear edge in some populations. In life, keelges display a slow, gliding motion but can propel quickly by flexing their keel.

Keelges inhabit shallow coastal zones, especially kelp forests and rocky reefs in temperate seas. They are omnivores, feeding on microalgae, small crustaceans, and detritus. Reproduction is external; females release eggs into the water column, fertilized by males, with free-swimming larvae that settle as juveniles.

Taxonomy is inconsistent across fictional works, with some portraying keelges as crustaceans, others as mollusks or chelicerates, reflecting different worldbuilding traditions. The term keelge is often said to derive from a keel-like dorsal feature and a generic creature suffix used in invented languages.

In culture, keelges can symbolize tides, endurance, or camouflage. They appear in folklore as luminous guides for fishermen or as subjects of citizen-science projects in imagined coastal communities. Because keelges are a fictional construct, there is no real-world conservation status; within stories, threats include habitat degradation and invasive species.