Caligidae
Caligidae is a family of copepods, small crustaceans that are parasitic on fish. They are commonly known as sea lice or fish lice. Caligidae are a diverse group, with over 500 species described worldwide. They are found in all the world’s oceans, from the tropics to the polar regions, and they are a common parasite of both wild and farmed fish.
Characteristics
Caligidae have a distinctive flattened body shape, with a large, shield-like cephalothorax that covers most of the body. They have a pair of prominent antennae, a pair of mandibles, and a pair of maxillae. They also have four pairs of swimming legs and a pair of caudal rami. The mouthparts of Caligidae are adapted for feeding on the blood, mucus, and scales of their host fish.
Caligidae are generally small, with most species measuring less than 10 millimeters in length. However, some species, such as Lepeophtheirus salmonis, can reach up to 20 millimeters in length.
Environment
Caligidae are parasitic copepods, meaning that they live on or in their host fish. They typically attach themselves to the skin, fins, or gills of their host. Some species are highly host-specific, while others can parasitize a wide range of fish species. Caligidae are found in a variety of marine environments, including coastal waters, estuaries, and the open ocean.
Life Cycle
Caligidae have a complex life cycle that includes several stages. The life cycle begins when a fertilized egg hatches into a free-swimming larva called a nauplius. The nauplius feeds on plankton and molts several times, eventually developing into a copepodid larva. The copepodid larva is the infective stage of the parasite, and it must find a host fish to survive. Once a copepodid larva finds a host, it attaches itself to the skin of the fish and transforms into a chalimus. The chalimus is a non-feeding stage that remains attached to the host for several days. After several days, the chalimus molts into an adult Caligidae.
Impact on Fish
Caligidae can have a significant impact on the health of their host fish. Heavy infestations of sea lice can cause a variety of problems, including skin lesions, anemia, weight loss, and even death. In farmed fish populations, sea lice infestations can cause significant economic losses. Caligidae are also known to transmit diseases between fish.