Gleba Heliolevidea is a species of Gleba genus, a pelagic "sea butterfly". These are holoplanktonic opisthobranch molluscs belonging to the family Cymbuliidae.
1. Distribution and habitat
Heliolevidea were encountered in deep waters, from 100 m up to 2.000 m. Following the planktonic prey they might follow it to the surface at night, but return to deeper water in the morning.
Heliolevidea shed their shells and develop a cartilaginous pseudoconch, as most of the Cymbulioidea. The lateral and posterior foot lobes are joined as a ciliated proboscis that leads to the mouth, and the wings are united ventrally to form a single plate. Furthermore this species is characterized by an esca-like tissue bundle protruding on a translucent extremity from their head that possesses the ability to lighten up and has been recorded to change light frequencies.
Heliolevidea emit a pale yellow light when disturbed or attacked. The light is produced from the mantle tissue and shines through the pale cartilaginous cocon, which acts to diffuse the light so that the whole body glows. The light may serve to startle or dazzle a potential predator, and is emitted while the soft parts of the animal remain protected. It has been found that all other wavelengths of light are transmitted through the harder cartilaginous material and it is only the yellow wavelength that is selectively diffused, effectively amplifying it and making its originator seem larger.
Heliolevidea are protandrious and like most of the relative Thecosomata start their post larval life as a small male. Heliolevidea usually feed and migrate in constant groups of approximately 5-8 same-gender individuals. Whenever the current brings them into a new group they mate this often requires them to switch sex. We assume that it is the light emitting escas on their heads that helps them distinguish if an individual belongs to the group. Scientists suppose that individuals within groups synch their light frequencies, similar to some anglerfish species.
After fertilization, a gelatinous egg band is produced that is ejected into open waters where it is to float freely until hatching.