Xenoma

File:Glugea stephani.jpg

Glugea stephani, a microsporidian parasite, causing xenoma in fish.

A xenoma is a specialized cellular structure formed in response to infection by certain microsporidia, a group of spore-forming unicellular parasites. Xenomas are most commonly observed in fish, but can also occur in other vertebrates and invertebrates.

Formation and Structure

Xenomas are characterized by the hypertrophy of host cells, which become greatly enlarged and filled with the parasite. The formation of a xenoma begins when a microsporidian spore infects a host cell. The parasite then multiplies within the cell, causing it to grow in size and alter its normal function. The host cell's cytoplasm becomes filled with the developing spores of the microsporidian, and the cell's nucleus may become displaced or altered.

Function

The primary function of a xenoma is to serve as a "factory" for the production of microsporidian spores. The altered host cell provides a protected environment where the parasite can multiply and mature. Once the spores are fully developed, they are released from the xenoma to infect new host cells, continuing the cycle of infection.

Pathology

Xenomas can cause significant pathology in infected hosts. In fish, for example, xenomas can disrupt normal tissue function, leading to symptoms such as swelling, necrosis, and impaired organ function. The severity of the disease depends on factors such as the species of microsporidian, the number of xenomas, and the location of the infection within the host.

Examples

One well-known example of a microsporidian that causes xenomas is Glugea stephani, which infects various species of fish. Infected fish may exhibit visible lumps or nodules on their bodies, which are the result of xenoma formation.

Related Pages

• Microsporidia
• Parasitology
• Fish diseases
• Cell biology