The protist communities of hybrid Coptotermes (Blattodea: Rhinotermitidae) colonies shed light on aspects of symbiosis in protist-dependent termites

Host-symbiont relationships are maintained through symbiont transmission. Hosts acquire their symbionts through vertical transmission, horizontal transmission, or a combination thereof, i.e., mixed-mode transmission. Protist-dependent termites are social insects that harbor mutualistic, wood-digesting protists as well as prokaryotic symbionts in their hindguts. Each protist-dependent termite species harbors a unique community of cellulolytic protists, with rare exception. These symbionts are vertically transmitted from the founding reproductives of newly established colonies to their first workers through proctodeal trophallaxis. Recent data indicate that both founding reproductives are involved in vertical transmission in protist-dependent termites, i.e., termites perform biparental transmission of symbionts. For this study, Coptotermes gestroi (Wasmann) and Coptotermes formosanus Shiraki were used to examine aspects of symbiosis in protist-dependent termites. The complete protist communities of these Coptotermes species each consist of five parabasalid species belonging to the genera Cononympha, Holomastigotoides, and Pseudotrichonympha. The protist communities of 1-month-old to 3.5-year-old hybrid Coptotermes colonies were determined through 18S rRNA amplicon sequencing. These colonies were established by heterospecific pairs of C. gestroi and C. formosanus alates. Examination of the protist communities of hybrid Coptotermes colonies shed light on several aspects of symbiosis in protist-dependent termites, including biparental transmission, horizontal transmission between kings and queens during incipient colony development, and changes in community composition over time.