The Symbiotic Spectrum: Where Do the Gregarines Fit?

Area of Science:

• Parasitology
• Evolutionary Biology
• Microbiology

Background:

• Gregarines are basal apicomplexans, related to significant human pathogens like Plasmodium and Toxoplasma.
• Despite their evolutionary importance, gregarines are often ignored in 'omics' studies due to their invertebrate hosts and lack of direct medical relevance.
• The Apicomplexa phylum is perceived as exclusively parasitic, but gregarines exhibit a wide range of host interactions, from mutualism to parasitism.

Purpose of the Study:

• To highlight the evolutionary significance of gregarines in understanding the origin and diversification of parasitism within Apicomplexa.
• To propose future research directions for elucidating the biology and ecological roles of gregarines.
• To investigate the complex symbiotic relationships between gregarines, their invertebrate hosts, and the host microbiota.

Main Methods:

• Comparative analysis of gregarine biology with other apicomplexans.
• Review of existing literature on gregarine-host interactions.
• Suggesting 'omics' approaches to study gregarine-host-microbiota dynamics.

Main Results:

• Gregarines represent the earliest diverging lineage within Apicomplexa, offering insights into the transition from free-living to parasitic lifestyles.
• Gregarine-host interactions span a spectrum, challenging the notion of Apicomplexa as solely parasitic.
• The role of gregarines in host-microbiota interactions remains largely unexplored.

Conclusions:

• Gregarines are essential models for studying the evolution of parasitism in Apicomplexa.
• Further research into gregarine biology, host interactions, and microbiota is critical for a comprehensive understanding of apicomplexan evolution.
• Re-evaluating the parasitic nature of Apicomplexa is necessary, considering the diverse symbiotic roles of gregarines.