Yungia aurantiaca is a solitary and free-living planarian, classified in the Polycladida order and within the Pseudocerotidae family. Geographically we find specimens of this species in the waters of the Mediterranean Sea and in the temperate waters of the northeastern Atlantic Ocean, where they prefer rocky sedimentary bottoms with an abundance of algae from 5 to 20 meters deep.
With up to 4 cm maximum total length, specimens of Yungia aurantiaca have an oval body and very flattened dorsoventrally, whose central part longitudinally is somewhat thicker than the edges. The margins of the body are wavy and the dorsal surface completely smooth. In the head region there are two folds on the margin that form small tentacles. In the vicinity of these we find the ocelli or simple eyes, as well as chemoreceptors with which they detect the species on which they feed. On the opposite side, the ventral side, we only find a single opening that serves as both mouth and anus.
The coloration of Yungia aurantiaca is orange with very small white dots on the dorsal side and with the margins decorated with a thin white line. The ventral surface, on the other hand, is a homogeneous whitish color.
They are carnivorous and feed on sponges, bryozoans, tunicates and small crustaceans, among others. They usually detect food at a certain distance thanks to chemoreceptors present in their tentacles. Yungia aurantiaca specimens are capable of projecting their pharynx to the outside, and sucking their food with it. Everything they cannot digest will be returned to the outside through the same mouth, due to the lack of anus.
As is common with planarians, Yungia aurantiaca is a hermaphrodite species although it requires cross-fertilization by which both specimens inject sperm (hypodermic insemination) which is stored until its later use to fertilize the eggs.
It is important to highlight the great capacity for regeneration, that is, to split in half and originate two individuals exactly the same as the original. If it feels threatened, it will not hesitate to fragment the body, regenerating the whole specimen from each section.
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