Zygotessa

Zygotessa is a fictional genus of marine invertebrates created for speculative biology and science fiction settings. In its canonical appearances, species of Zygotessa are noted for a paired, symmetrical body form and bioluminescent markings that run along the shell margins.

Taxonomy in the fictional world places Zygotessa in the phylum Zygotta, class Zygothea, family Zygotidae. The name combines zyg- from zygote and -tessa, a feminine suffix common in the setting. This framework is not part of real-world biology.

Morphology: Zygotessa individuals typically range from 3 to 12 cm in length. They possess a compact, cap-like shell with two hinged valves. The mantle forms paired lobes surrounding two siphons; many species exhibit blue-green bioluminescent spots along the margins and a faint axial stripe that resembles a stitched line.

Ecology and life history: Zygotessa are benthic or slow-swimming, living among rocky reefs in temperate to subtropical waters. They are filter feeders past the larval stage and often engage in mutualisms with bioluminescent bacteria. Reproduction is external, with free-swimming trochophore or veliger larvae in many depictions.

In fiction and world-building, Zygotessa serves as a case study in symmetrical morphology and bioluminescence. It has appeared in field guides, short stories, and visual media within the setting, prompting discussion of evolutionary constraints and ecosystem roles.