Animal-microbe symbiotic associations
Preface: Animal-microbe symbiotic associations in Zoological Science
Edited by Takema Fukatsu
Symbiosis is the condition in which different organisms live together and show spatial and temporal overlap in their interactions. The consequences of such interactions may be beneficial, detrimental, or neutral; their nature often depends on ecological and environmental contexts and may result inter alia in mutualistic, parasitic, commensal, antagonistic, or neutral relationships.
Symbiotic associations with microorganisms are found ubiquitously across the animal kingdom. For example, many corals are capable of photosynthesis despite their animal nature, owing to endosymbiotic dinoflagellate algae. Tubeworms gathering around hydrothermal vents in the oceanic floor possess neither mouth nor anus, and live exclusively on metabolites supplied by the huge amount of chemoautotrophic bacterial endosymbionts residing in their bodies. Some sponges and beetles defend themselves against predators by making use of poisonous polyketide compounds produced by symbiotic bacteria. Termites possess rich symbiotic microbiota in their highly-developed hindgut, wherein woody food materials consisting mainly of cellulose and lignin are digested by cellulolytic activities of the symbionts. In aphids and many other insects, endosymbiotic bacteria provide their hosts with nutritional components that are deficient in hosts’ food sources. The majority of millions of insect species are associated with bacterial endosymbionts of the genus Wolbachia, which can affect host reproductive modes in a variety of ways.
Given the ubiquity and the importance of symbiotic microorganisms in animals, it is unsurprising that the general zoological journal Zoological Science has published a number of papers dealing with animal-microbe symbiotic associations over the years. In this virtual issue, I have compiled 38 relevant papers published in the journal since 1995. Here four animal taxa, namely tunicates, corals, ciliates and insects, are preferentially represented. This pattern does not reflect the real diversity of animal-microbe associations, but rather reflects the concentration of researchers working on these research subjects. There are doubtless many more fascinating animal-microbe symbiotic associations that await future discovery and investigation.