Gonioinfradens
Gonioinfradens is a genus of marine isopods belonging to the family Gnathiidae. They are commonly known as gnathiid isopods or “gnathia”. These small crustaceans are parasitic during their larval stage, attaching to fish and feeding on their blood.
Characteristics
Gnathiid isopods are characterized by their small size, typically measuring less than 5 millimeters in length. Their bodies are dorsoventrally flattened and divided into a cephalon (head), pereon (thorax), and pleon (abdomen). They possess two pairs of antennae, one pair of mandibles, and two pairs of maxillae for feeding. Gnathiids are further distinguished by the presence of a prominent rostrum, a pointed projection on the head, and a pair of sharp, hook-like appendages called maxillipeds.
Environment
Gnathiid isopods are found worldwide in marine environments, primarily in shallow, coastal waters. They are often associated with rocky reefs, seagrass beds, and other habitats with abundant fish populations. Gnathiids are nocturnal and typically hide among rocks, crevices, and underseaweed during the day.
Life Cycle
Gnathiid isopods have a complex life cycle involving both parasitic and free-living stages. The parasitic stage is limited to the larval stage, known as the "praniza" stage. Praniza larvae are highly mobile and actively seek out fish hosts. They attach to the fish using their maxillipeds and feed on blood by piercing the skin with their mandibles. After feeding, the praniza detaches and molts into a non-parasitic stage called the "juvenile" stage. Juveniles are free-living and feed on detritus. They eventually molt into adults, which reproduce and continue the life cycle.
References
A new species of Gonioinfradens (Gnathiidae, Isopoda) from the Western Atlantic
Gnathiidae (Isopoda) of the North-East Atlantic