Selenidiidae

[[File:|250px|alt=|]] {{{subdivision_ranks}}}:

Selenidiidae
Kingdom:
Phylum:	Apicomplexa
Class:	Conoidasida
Order:	Eugregarinorida
Family:	Selenidiidae

Selenidiidae is a family of parasitic protozoa within the phylum Apicomplexa. Members of this family are known to infect the intestines of various annelids, particularly marine polychaetes. The family was first described by Labbé in 1899 and is characterized by its unique life cycle and morphological features.

Morphology

Selenidiidae are distinguished by their elongated, vermiform trophozoites, which lack septa. The trophozoites are typically found in the intestinal lumen of their hosts. They possess a simple, unsegmented body plan, which is adapted to their parasitic lifestyle. The cell structure includes a pellicle, which provides structural support, and a single nucleus.

Life Cycle

The life cycle of Selenidiidae involves both sexual and asexual reproduction. The trophozoites undergo schizogony, a form of asexual reproduction, to produce merozoites. These merozoites can then differentiate into gamonts, which pair to form gametocysts. Within the gametocysts, gametes fuse to form zygotes, which develop into oocysts. The oocysts are released into the environment through the host's feces, where they can infect new hosts.

Host Interaction

Selenidiidae primarily infect marine polychaetes, where they reside in the intestinal tract. The relationship between the parasite and its host is typically commensal, with minimal harm to the host. However, in cases of heavy infection, the parasites can cause damage to the intestinal lining, leading to malabsorption and other digestive issues.

Taxonomy

The family Selenidiidae is part of the order Eugregarinorida, which includes other gregarine parasites. Within Selenidiidae, there are several genera, including Selenidium, which is the type genus. The classification of these organisms is based on morphological characteristics and host specificity.

Research and Importance

Research on Selenidiidae is important for understanding the diversity and evolution of parasitic protozoa. These organisms serve as models for studying host-parasite interactions and the adaptations required for a parasitic lifestyle. Additionally, they provide insights into the broader ecological roles of parasites in marine ecosystems.

Also see

• Apicomplexa
• Gregarinasina
• Eugregarinorida
• Parasitism
• Polychaete

Apicomplexa Overview
Kingdom	Protista
Phylum	Apicomplexa
Characteristics	Obligate intracellular parasites, complex life cycles, apical complex structure
Notable Genera	Plasmodium, Toxoplasma, Cryptosporidium, Eimeria
Diseases Caused	Malaria, Toxoplasmosis, Cryptosporidiosis, Coccidiosis
Reproduction	Sexual and asexual phases, often involving multiple hosts
Research Importance	Study of parasitic diseases, vaccine development, drug resistance
Related Articles	Protozoa, Parasitology, Infectious disease