Myzozoa

Myzozoa is a diverse phylum of eukaryotic organisms within the superphylum Alveolata, which also includes the Ciliophora and Apicomplexa. Myzozoans are primarily known for their role in marine and freshwater ecosystems, where they often function as both primary producers and consumers. This phylum includes several well-known groups such as the dinoflagellates, apicomplexans, and perkinsids.

Characteristics

Myzozoans are characterized by the presence of alveoli, which are flattened vesicles located just beneath the cell membrane. These structures are a defining feature of the Alveolata. Myzozoans exhibit a wide range of morphologies and life strategies, including both free-living and parasitic forms.

Cell Structure

The cell structure of myzozoans is complex, often featuring two flagella, one transverse and one longitudinal, which are used for locomotion. The transverse flagellum encircles the cell in a groove called the cingulum, while the longitudinal flagellum extends posteriorly from a groove called the sulcus.

Nutrition

Myzozoans display diverse nutritional strategies. Many are photosynthetic, possessing chloroplasts derived from secondary endosymbiosis with red algae. Others are heterotrophic, feeding on bacteria, other protists, or organic matter. Some myzozoans, such as the apicomplexans, are obligate parasites of animals.

Ecological Role

Myzozoans play crucial roles in aquatic ecosystems. Photosynthetic dinoflagellates are important primary producers, contributing significantly to the oceanic carbon cycle. Some species are known for forming harmful algal blooms, which can produce toxins affecting marine life and human health.

Evolution and Phylogeny

The Myzozoa are believed to have evolved from a common ancestor with other alveolates. Molecular phylogenetic studies have helped clarify the relationships within the group, revealing that the dinoflagellates and apicomplexans share a closer evolutionary relationship than previously thought.

Notable Groups

• Dinoflagellates: These are perhaps the most well-known myzozoans, with species that are both photosynthetic and heterotrophic. They are known for their bioluminescence and for causing red tides.
• Apicomplexans: This group includes important parasites such as Plasmodium, the causative agent of malaria, and Toxoplasma gondii, which causes toxoplasmosis.
• Perkinsids: A lesser-known group, some of which are parasitic on marine bivalves.

Also see

• Alveolata
• Dinoflagellate
• Apicomplexa
• Ciliophora
• SAR supergroup