Blastocladiales is an order of fungi that belongs to the phylum Blastocladiomycota, one of the currently recognized phyla within the kingdom Fungi. [1] Blastocladiales was originally the order Blastocladia within the phylum Chytridiomycota until molecular and zoospore ultrastructural characters were used to demonstrate it was not monophyletic with Chytridiomycota. [2]

Blastocladiales contains 5 families and approximately 12 genera, with about 30 species in the genus Blastocladia alone. [3] [4] The members of this order are aquatic fungi that grow on submerged twigs, fruits, algae, or animals. They have a thallus that consists of a single, branched basal cell or trunk with rhizoids at one end and sporangia at the other. They produce flagellated zoospores for asexual and sexual reproduction, and some exhibit alternation of generations. [3] [4]

Some members of Blastocladiales are entomopathogenic, meaning they infect and kill insects. The most common entomopathogenic genus is Coelomomyces, which contains over 70 species that parasitize mainly mosquitoes and water bugs. Coelomomyces has a complex life cycle that involves an alternation of hosts between insects and crustaceans. [5]

Blastocladiales is an interesting and diverse group of fungi that has many ecological and evolutionary implications. They are also potential sources of biocontrol agents against insect pests and vectors of diseases. [5]

References:

1. Blastocladiomycota – Wikipedia. https://en.wikipedia.org/wiki/Blastocladiomycota
2. James TY, Kauff F, Schoch CL, et al. Reconstructing the early evolution of Fungi using a six-gene phylogeny. Nature. 2006;443(7113):818-822.
3. Blastocladia – Wikipedia. https://en.wikipedia.org/wiki/Blastocladia
4. Index Fungorum – Names Record – Blastocladiales. http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=90088
5. Blastocladiales – an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/blastocladiales

Blastocladiales have a complex and diverse life cycle that may include alternation between haploid gametothallus and diploid sporothallus generations, and in some cases, alternation of hosts as well. [6] [7] In sexual reproduction, pairs of uniflagellated gametes fuse, resulting in biflagellated zygotes. The zygotes may germinate immediately or form thick-walled resting spores that can survive harsh conditions. The germinated zygotes produce diploid thalli that produce thin-walled zoosporangia or thick-walled meiosporangia. The zoosporangia release diploid zoospores that can colonize new substrates or form new diploid thalli. The meiosporangia undergo meiosis and release haploid zoospores that can germinate into haploid thalli. [6] [7]

In some genera, such as Coelomomyces, the life cycle involves two different hosts: an insect and a crustacean. The insect host is infected by a diploid zoospore that forms a plasmodium inside the hemocoel. The plasmodium produces meiosporangia that release haploid zoospores into the hemolymph. The zoospores escape from the insect host and infect a crustacean host, where they form haploid thalli that produce gametangia and gametes. The gametes fuse to form zygotes that develop into resting spores inside the crustacean host. The resting spores are released when the crustacean dies or molts, and can infect new insect hosts. [8]

Blastocladiales are important members of aquatic ecosystems, as they decompose organic matter, recycle nutrients, and regulate the populations of their hosts. They are also potential biocontrol agents against insect pests and vectors of diseases, such as malaria and filariasis. However, they also pose a threat to some aquatic animals, such as amphibians and fish, as they can cause fatal infections. [8] [9]

References:

1. Blastocladiomycota – Wikipedia. https://en.wikipedia.org/wiki/Blastocladiomycota
2. James TY, Kauff F, Schoch CL, et al. Reconstructing the early evolution of Fungi using a six-gene phylogeny. Nature. 2006;443(7113):818-822.
3. Blastocladia – Wikipedia. https://en.wikipedia.org/wiki/Blastocladia
4. Index Fungorum – Names Record – Blastocladiales. http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=90088
5. Blastocladiales – an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/blastocladiales
6. Blastocladiomycota | SpringerLink. https://link.springer.com/referenceworkentry/10.1007/978-3-319-28149-0_17
7. Blastocladiomycota – Wikipedia.
8. Coelomomyces – an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/coelomomyces
9. Chytridiomycosis – Wikipedia. https://en.wikipedia.org/wiki/Chytridiomycosis