Host interactions The two species of
Maullinia has been shown to successfully parasitize a wide range of brown algal hosts, spanning multiple brown algal orders, such as the
Ectocarpales,
Fucales, and
Laminariales Maullinia infections of non-filamentous brown algae primarily target adult hosts, and are mostly absent during their reproductive periods. and as such provide a vector for viral infections to enter the brown alga alongside
Maullinia.
Nutrition As a parasitic genus,
Maullinia derives its nutrition from the host cells it inhabits. Initially, the sole mode of nutrition was thought to be absorptive
osmotrophy.
Maullinia appears to engulf the host organelles whole as it extends through the cell, with a preference for
plastids being clear. This preference could be due to several factors, namely active targeting by
Maullinia, the widespread nature of plastids within brown algal cells, or simply a slower digestion process of these complex pigment-containing organelles. Evidence that there is some targeting of plastids comes from the host cell actively producing smaller plastids as the infection proceeds. Outside of the plastid preference, one of the first intracellular structures to be engulfed is the large storage
vacuole. This vacuole contains many complex
polysaccharides, and as such its consumption provides the infecting
Maullinia with a boost in energy. This energy boost near the beginning of the infection, alongside the loss of a key energy source for the host cell, allows
Maullinia to expand quickly.
Distribution and habitat Maullinia is found across much of the Southern Hemisphere, with infected brown algal populations in Chile, The Prince Edward Islands, South Africa, Australia, and New Zealand currently known. Within these regions
Maullinia prevalence increases with
latitude, becoming more dominant in southern populations as compared to more tropical ones. This is likely due to a combination of two key factors: the increased density of southern populations and increased
Maullinia virulence in cooler waters. While many parasites prefer warmer environments,
Maullinia appears to thrive in lower temperatures, having greatest infection rates during the winter months and at greater latitude. The two species of
Maullinia appear to have some preference for habitat, based on the brown algal hosts which they each primarily infect.
M. ectocarpii prefers sandy, shallow, sheltered regions where more filamentous brown algae tend to thrive. However,
M. ectocarpii is a more generalist species and can adapt to more
rocky intertidal species such as
Durvillaea amatheiae and
Durvillaea potatorum.
M. braseltonii is much more specialist, and exclusively infects
Durvillaea hosts stemming from rocky intertidal habitats. As many
Durvillaea species are buoyant,
M. braseltonii is often found infecting drift as well. The role of drift in distributing
Maullinia and providing a vector for novel infections is critical. Rafting is the primary way by which new populations of brown algae are infected by
Maullinia, and this process is supported by the
physiological changes infected hosts undergo. With the hypertrophied cells forming galls, a greater buoyancy is achieved in infected individuals, allowing them a wider distribution capability. The likelihood of the mechanism is strengthened by the genetic evidence which links the New Zealand population of
Maullinia to the Chile population. The role of rafting, alongside the widespread populations separated by thousands of kilometers, implies that
Maullinia may be capable of achieving global distribution along
cold-temperate coasts. ==Description==