Pereonidae

Pereonidae is a family of parasitic crustaceans belonging to the order Isopoda. These marine invertebrates are exclusively parasitic on fish, and their life cycle typically involves several larval stages before maturing into a sessile adult form. The body of a pereonid is greatly modified for parasitism, often exhibiting asymmetry and reduction in certain appendages. The pereon, the thoracic region of the crustacean body, is typically the largest and most prominent part of the adult. Females are generally larger and more permanently attached to the host than males, which are often smaller and mobile, seeking out females for reproduction. Distribution of Pereonidae is widespread across the world's oceans, with different species exhibiting host specificity towards various fish families. Their parasitic nature can cause damage to their fish hosts, affecting scales, fins, and musculature, and in heavy infestations, can lead to significant health issues for the host. Research into Pereonidae continues to explore their complex life cycles, host-parasite interactions, and evolutionary relationships within the Isopoda.