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Exclusive Gut Flagellates of Serritermitidae Suggest a Major Transfaunation Event in Lower Termites: Description of Heliconympha glossotermitis gen. nov. spec. nov
Abstract
The guts of lower termites are inhabited by host-specific consortia of cellulose-digesting flagellate protists. In this first investigation of the symbionts of the family Serritermitidae, we found that Glossotermes oculatus and Serritermes serrifer each harbor similar parabasalid morphotypes: large Pseudotrichonympha-like cells, medium-sized Leptospironympha-like cells with spiraled bands of flagella, and small Hexamastix-like cells; oxymonadid flagellates were absent. Despite their morphological resemblance to Pseudotrichonympha and Leptospironympha, a SSU rRNA-based phylogenetic analysis identified the two larger, trichonymphid flagellates as deep-branching sister groups of Teranymphidae, with Leptospironympha sp. (the only spirotrichosomid with sequence data) in a moderately supported basal position. Only the Hexamastix-like flagellates are closely related to trichomonadid flagellates from Rhinotermitidae. The presence of two deep-branching lineages of trichonymphid flagellates in Serritermitidae and the absence of all taxa characteristic of the ancestral rhinotermitids underscores that the flagellate assemblages in the hindguts of lower termites were shaped not only by a progressive loss of flagellates during vertical inheritance but also by occasional transfaunation events, where flagellates were transferred horizontally between members of different termite families. In addition to the molecular phylogenetic analyses, we present a detailed morphological characterization of the new spirotrichosomid genus Heliconympha using light and electron microscopy. This article is protected by copyright. All rights reserved.
... The cellulolytic protists found in the guts of all "lower" termites and Cryptocercus originate from two independent groups, Parabasalia and Oxymonadida (Preaxostyla) [17,18]. Gut protists have evolved through varying degrees of horizontal transfer and episodes of co-speciation with their hosts [18][19][20][21][22][23][24]. In some species of Cryptocercus, there can be up to 25 species of protists. ...
... By contrast, many termite species host a limited number of protist species. This is especially true for more phylogenetically derived species of termites [23], such as certain Rhinotermitidae that are associated with a handful of protist species, down to a single species in Termitogeton [25]. This reduction in symbiont diversity portends the complete loss of protists in one termite lineage nested within the paraphyletic Rhinotermitidae-the Termitidae (i.e., "higher" termites: Fig. 1). ...
... However, we here support the hypothesis that two distinct mutualistic shifts had a critical role within the history of termite evolution: (1) the initial acquisition of intestinal protists within the context of alloparental care as one of the key events that enabled or facilitated the emergence of eusociality in termites, and (2) the much later loss of these protists, associated with the gain of alternative mutualists, that ultimately triggered the emergence of the most successful termite group, the Termitidae. Interestingly, there is a progressive loss of protozoan diversity in more derived "lower" termites [23,25], which culminates in their complete loss in the "higher" termites. Regardless of the factors that led to this protistan disappearance from the guts, they presumably cascaded a series of changes that fundamentally altered the inherent physiology and ecological performance of Termitidae. ...
Termites are a clade of eusocial wood-feeding roaches with > 3000 described species. Eusociality emerged ~ 150 million years ago in the ancestor of modern termites, which, since then, have acquired and sometimes lost a series of adaptive traits defining of their evolution. Termites primarily feed on wood, and digest cellulose in association with their obligatory nutritional mutualistic gut microbes. Recent advances in our understanding of termite phylogenetic relationships have served to provide a tentative timeline for the emergence of innovative traits and their consequences on the ecological success of termites. While all “lower” termites rely on cellulolytic protists to digest wood, “higher” termites (Termitidae), which comprise ~ 70% of termite species, do not rely on protists for digestion. The loss of protists in Termitidae was a critical evolutionary step that fostered the emergence of novel traits, resulting in a diversification of morphology, diets, and niches to an extent unattained by “lower” termites. However, the mechanisms that led to the initial loss of protists and the succession of events that took place in the termite gut remain speculative. In this review, we provide an overview of the key innovative traits acquired by termites during their evolution, which ultimately set the stage for the emergence of “higher” termites. We then discuss two hypotheses concerning the loss of protists in Termitidae, either through an externalization of the digestion or a dietary transition. Finally, we argue that many aspects of termite evolution remain speculative, as most termite biological diversity and evolutionary trajectories have yet to be explored.
... Initial investigations on these symbioses suggested that termite-protist associations are rather specific and evolutionarily stable (Kitade, 2004). Recent phylogenetic analyses indicated that the evolutionary codiversification between lower termites and their gut protists is mostly characterized by cospeciation, although occasional events of host switching and symbiont loss were also evidenced (Desai et al., 2010;Noda et al., 2007;Radek et al., 2018;Taerum, De Martini, Liebig, & Gile, 2018). ...
... As in many other mutualistic symbioses where hosts and symbionts are mutually dependent for survival and reproduction (Moran, McCutcheon, & Nakabachi, 2008;Salem et al., 2015), it is generally assumed that co-speciation between gut protists and lower termites emerged as a direct consequence of an efficient vertical transmission of protists across termite generations (Desai et al., 2010;Noda et al., 2007;Radek et al., 2018;Taerum et al., 2018). The results of the present study constitute the first empirical evidence supporting this widely held assumption. ...
... We propose two nonexclusive hypothetical mechanisms that could provide preliminary answers to this question. First, recent phylogenetic analyses have revealed that protists can occasionally be transferred horizontally between termite species (Desai et al., 2010;Noda et al., 2007;Radek et al., 2018;Taerum et al., 2018). We cannot exclude that such horizontal transmission events also occurred within termite species. ...
Although mutualistic associations between animals and microbial symbionts are widespread in nature, the mechanisms that have promoted their evolutionary persistence remain poorly understood. A vertical mode of symbiont transmission (from parents to offspring) is thought to ensure partner fidelity and stabilisation, although the efficiency of vertical transmission has rarely been investigated, especially in cases where hosts harbour a diverse microbial community. Here we evaluated vertical transmission rates of cellulolytic gut oxymonad and parabasalid protists in the wood‐feeding termite Reticulitermes grassei. We sequenced amplicons of the 18S rRNA gene of protists from 24 colonies of R. grassei collected in two populations. For each colony, the protist community was characterised from the gut of 14 swarming reproductives and from a pool of 10 worker guts. A total of 98 OTUs belonging to 13 species‐level taxa were found. The vertical transmission rate was estimated for each protist present in a colony by its frequency among the reproductives. Results revealed that transmission rates were high, with an average of 0.897 (±0.164) per protist species. Overall, the protist community did not differ between reproductive sexes, suggesting that both the queen and king could contribute to the gut microbiota of the offspring. A positive relationship between the transmission rate of protists and their prevalence within populations was also detected. However, transmission rates alone did not explain protist prevalence. In conclusion, these findings reveal key forces behind a conserved, multi‐species mutualism, raising further questions on the roles of horizontal transfer and negative selection in shaping symbiont prevalence.
... Spirotrichonymphids are widely distributed across lower termites, except for the families Mastotermitidae and Serritermitidae, but they are most prevalent in the Rhinotermitidae (Radek et al. 2018;Yamin 1979). The widespread occurrence of these protists suggests an ancient origin, as they are known to be vertically inherited and the common ancestor of the host lineages lived roughly 130-160 million years ago (Bourguignon et al. 2015;Nalepa et al. 2001;Ware et al. 2010). ...
... It is hoped that improved taxon sampling for Spirotrichonymphea will resolve the position of Holomastigotes and clarify the relationships among the other genera. This would enable studies of evolutionary transitions, co-cladogenesis with hosts, and potential horizontal transfer events (see Radek et al. 2018). ...
Holomastigotes is a protist genus (Parabasalia: Spirotrichonymphea) that resides in the hindguts of “lower” termites. It can be distinguished from other parabasalids by spiral flagellar bands that run along the entire length of the cell, an anterior nucleus, a reduced or absent axostyle, the presence of spherical vesicles inside the cells, and the absence of ingested wood particles. Eight species have been described based on their morphology so far, although no molecular data were available prior to this study. We determined the 18S rRNA gene sequences of Holomastigotes from the hindguts of Hodotermopsis sjostedti, Reticulitermes flavipes, Reticulitermes lucifugus, and Reticulitermes tibialis. Phylogenetic analyses placed all sequences in an exclusive and well‐supported clade with the type species, Holomastigotes elongatum from R. lucifugus. However, the phylogenetic position of Holomastigotes within the Spirotrichonymphea was not resolved. We describe two new species, Holomastigotes flavipes n. sp. and Holomastigotes tibialis n. sp., inhabiting the hindguts of R. flavipes and R. tibialis, respectively.
This article is protected by copyright. All rights reserved.
... For specific identification and morphological investigation of the Spirotrichonympha and Spironympha species in termites from Japan, we carried out microscopic observation of protargol-stained specimens as described previously (Kitade et al., 1997Radek et al., 2018). The hindgut contents of worker termites were suspended in 0.4% NaCl and fixed with Schaudinn's fixative prior to protargol staining (modified from procedure A; Honigberg & Davenport, 1951). ...
Spirotrichonymphea, one of the six classes of phylum Parabasalia, are characterized by bearing many flagella in spiral rows, and they occur exclusively in the guts of termites. Phylogenetic relationships among the 13 described genera are not well understood due to complex morphological evolution and a paucity of molecular data. One such understudied genus is Spironympha. It has been variously considered a valid genus, a subgenus of Spirotrichonympha, or an "immature" life cycle stage of Spirotrichonympha. To clarify this, we sequenced the small subunit (SSU) rRNA gene sequences of Spironympha and Spirotrichonympha cells isolated from the hindguts of Reticulitermes species and Hodotermopsis sjostedti and confirmed the molecular identity of H. sjostedti symbionts using fluorescence in situ hybridization. Spironympha as currently circumscribed is polyphyletic, with both H. sjostedti symbiont species branching separately from the "true" Spironympha from Reticulitermes. Similarly, the Spirotrichonympha symbiont of H. sjostedti branches separately from the "true" Spirotrichonympha found in Reticulitermes. Our data support Spironympha from Reticulitermes as a valid genus most closely related to Spirotrichonympha, though its monophyly and interspecific relationships are not resolved in our molecular phylogenetic analysis. We propose three new genera to accommodate the H. sjostedti symbionts and two new species of Spirotrichonympha from Reticulitermes.
... More recently, ultrastructural studies demonstrated that the flagella of Microjoenia arise from very short, longitudinal to slightly spiraling bands, confirming its Spirotrichonymphea affinities (Brugerolle 2001). Note that while Spirotrichosomidae (Trichonymphida, Parabasalia) also feature spiraling rows of flagella, they emerge from bilaterally symmetrical rostral structures characteristic of Trichonymphida, and their flagellar bands form a lefthanded helix (Carpenter et al. 2010;Radek et al. 2018), thus excluding Microjoenia. The simple, tubular axostyle links Microjoenia specifically with Spironympha (Brugerolle 2005; Brugerolle and Bordereau 2006), another genus that currently lacks molecular data. ...
Microjoenia are obligate symbionts of termites. The genus was erected in 1892 for small cells with many flagella that insert near, but not directly from, the cell apex, and an axostyle that can protrude from the cell posterior. Although ultrastructural studies have been carried out on three Microjoenia species to date, no molecular data have been directly attributed to any species. Microjoenia are classified within the parabasalian class Spirotrichonymphea, which is characterized by flagellar bands that emerge near the cell apex and proceed posteriorly in a right-handed helix. In Microjoenia, however, the flagellar bands are very short and proceed longitudinally or with a weakly observable helix. In this study, we have amplified and sequenced the 18S ribosomal RNA gene from individually isolated Microjoenia cells from Reticulitermes and Hodotermopsis hosts as part of an ongoing effort to understand the phylogeny of Spirotrichonymphea and their coevolution with termites. In our 18S rRNA gene phylogeny, Microjoenia forms the sister lineage to Spirotrichonympha, though many other evolutionary relationships within Spirotrichonymphea remain unresolved.
... This would explain the distinct protist community found in Reticulitermes as compared to its rhinotermitid relatives (Kitade, 2004). Another ancient HST may have occurred in the ancestor of Serritermes and Glossotermes (Serritermitidae), again explaining why the symbionts of these host genera differ from those of their rhinotermitid relatives (Radek et al., 2018). To date these are the only two documented inferences of HST in termites. ...
The eukaryotic microbiome of “lower” termites is highly stable and host-specific. This is due to the mutually obligate nature of the symbiosis and the direct inheritance of protists by proctodeal trophallaxis. However, vertical transmission is occasionally imperfect, resulting in daughter colonies that lack one or more of the expected protist species. This phenomenon could conceivably lead to regional differences in protist community composition within a host species. Here, we have characterized the protist symbiont community of Heterotermes tenuis (Hagen) (Blattodea: Rhinotermitidae) from samples spanning South and Central America. Using light microscopy, single cell isolation, and amplicon sequencing, we report eight species-level protist phylotypes belonging to four genera in the phylum Parabasalia. The diversity and distribution of each phylotype’s 18S rRNA amplicon sequence variants (ASVs) mostly did not correlate with geographical or host genetic distances according to Mantel tests, consistent with the lack of correlation we observed between host genetic and geographical distances. However, the ASV distances of Holomastigotoides Ht3 were significantly correlated with geography while those of Holomastigotoides Ht1 were significantly correlated with host phylogeny. These results suggest mechanisms by which termite-associated protist species may diversify independently of each other and of their hosts, shedding light on the coevolutionary dynamics of this important symbiosis.
... They also share a largely similar and unusual linear development combined with the presence of all-male pseudergates (Bourguignon et al. 2009;Barbosa and Constantino 2017). Finally, their gut protist consortia are highly similar and unique among "lower" termites (Radek et al. 2018). ...
The Neotropical family Serritermitidae is a monophyletic group of termites including two genera, Serritermes and Glossotermes, with different way-of-life, the former being the sole obligatory inquiline among “lower” termites, while the latter is a single-site nester feeding on dry rotten red wood. Like the most advanced termite’s family, the Termitidae, the Serritermitidae is an inner group of the paraphyletic family “Rhinotermitidae”, but unlike the Termitidae, it has been poorly studied so far. In this study, we bring new insights into the chemical ecology of this key taxon. We studied the trail-following pheromone of Serritermes serrifer and we identified (10Z,13Z)-nonadeca-10,13-dien-2-one as the only component of the trail-following pheromone of this termite species, as it is the case in Glossotermes, the other genus belonging to Serritermitidae. This result makes the family Serritermitidae clearly distinct from other Rhinotermitidae, such as the termites Psammotermes and Prorhinotermes, that use (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol and/or neocembrene as trail-following pheromones.
... Vertical transmission has led to co-speciation between bacteria and their protist hosts, and sometimes even the termite hosts [26][27][28][29]. Evidence for horizontal transfer of protists between termite species, so called transfaunations, is limited to a few exceptions [30]. Hence, the termite host species association is rather strict, leading to strong phylogenetic imprints on protist community structure [31][32][33]. ...
Background
Elucidating the interplay between hosts and their microbiomes in ecological adaptation has become a central theme in evolutionary biology. A textbook example of microbiome-mediated adaptation is the adaptation of lower termites to a wood-based diet, as they depend on their gut microbiome to digest wood. Lower termites have further adapted to different life types. Termites of the wood-dwelling life type never leave their nests and feed on a uniform diet. Termites of the foraging life type forage for food outside the nest and have access to other nutrients. Here we sought to investigate whether the microbiome that is involved in food substrate breakdown and nutrient acquisition might contribute to adaptation to these dietary differences. We reasoned that this should leave ecological imprints on the microbiome.
Results
We investigated the protist and bacterial microbiomes of a total of 29 replicate colonies from five termite species, covering both life types, using metagenomic shotgun sequencing. The microbiome of wood-dwelling species with a uniform wood diet was enriched for genes involved in lignocellulose degradation. Furthermore, metagenomic patterns suggest that the microbiome of wood-dwelling species relied primarily on direct fixation of atmospheric nitrogen, while the microbiome of foraging species entailed the necessary pathways to utilize nitrogen in the form of nitrate for example from soil.
Conclusion
Our findings are consistent with the notion that the microbiome of wood-dwelling species bears an imprint of its specialization on degrading a uniform wood diet, while the microbiome of the foraging species might reflect its adaption to access growth limiting nutrients from more diverse sources. This supports the idea that specific subsets of functions encoded by the microbiome can contribute to host adaptation.
... Previous studies described microbial community diversity in the termite gut based on 16S rRNA gene sequences [19][20][21] and whole genome sequencing (WGS) [22]. The diversity of the gut microbial community differs according to the termite subfamily [23][24][25] gut compartment [19] and dietary behaviors [26,27]. In the lower termite Reticulitermes grassei, Duarte et al. showed that the greatest impact of termite diet was on protist community richness and composition [28]. ...
Although some previous studies have described the microbial diversity of termite in Brazil, the lack of studies about this subject is still evident. In the present study, we described by whole genome sequencing, the gut microbiota of seven species of termites (Termitidae) with different feeding habits from four Brazilian locations. For the litter species, the most abundant bacterial phylum was Firmicutes, where Cornitermes cumulans and Syntermes dirus (Syntermitinae) were identified. For the humus species, the most abundant bacterial phylum was Proteobacteria where three species were studied: Cyrilliotermes strictinasus (Syntermitinae), Grigiotermes bequaerti (Apicotermitinae), and Orthognathotermes mirim (Termitinae). For the wood termites, Firmicutes and Spirochaetes were the most abundant phyla, respectively, where two species were identified: Nasutitermes aquilinus and Nasutitermes jaraguae (Nasutitermitinae). The gut microbiota of all four examined subfamilies shared a conserved functional and carbohydrate-active enzyme profile and specialized in cellulose and chitin degradation. Taken together, these results provide insight into the partnerships between termite and microbes that permit the use of refractory energy sources.
... Previous studies described microbial community diversity in the termite gut based on 16S rRNA gene sequences [19][20][21] and whole genome sequencing (WGS) [22]. The diversity of the gut microbial community differs according to the termite subfamily [23][24][25] gut compartment [19] and dietary behaviors [26,27]. In the lower termite Reticulitermes grassei, Duarte et al. showed that the greatest impact of termite diet was on protist community richness and composition [28]. ...
... Previous studies described microbial community diversity in the termite gut based on 16S rRNA gene sequences [19][20][21] and whole genome sequencing (WGS) [22]. The diversity of the gut microbial community differs according to the termite subfamily [23][24][25] gut compartment [19] and dietary behaviors [26,27]. In the lower termite Reticulitermes grassei, Duarte et al. showed that the greatest impact of termite diet was on protist community richness and composition [28]. ...
Although some previous studies have described the microbial diversity of termite in Brazil, the lack of studies about this subject is still evident. In the present study, we described by whole genome sequencing, the gut microbiota of seven species of termites (Termitidae) with different feeding habits from four Brazilian locations. For the litter species, the most abundant bacterial phylum was Firmicutes, where Cornitermes cumulans and Syntermes dirus (Syntermitinae) were identified. For the humus species, the most abundant bacterial phylum was Proteobacteria where three species were studied: Cyrilliotermes strictinasus (Syntermitinae), Grigiotermes bequaerti (Apicotermitinae), and Orthognathotermes mirim (Termitinae). For the wood termites, Firmicutes and Spirochaetes were the most abundant phyla, respectively, where two species were identified: Nasutitermes aquilinus and Nasutitermes jaraguae (Nasutitermitinae). The gut microbiota of all four examined subfamilies shared a conserved functional and carbohydrate-active enzyme profile and specialized in cellulose and chitin degradation. Taken together, these results provide insight into the partnerships between termite and microbes that permit the use of refractory energy sources.
... of gut bacteria [28] and whose flagellate hosts (together with their endosymbionts) have been transferred horizontally between lower termites of different families [29,30]. Our results are in agreement with observations in numerous earlier, clone-library-based studies of termite gut bacteria, which often showed clustering of termite-derived bacterial lineages from distantly related host taxa [4,6]. ...
The gut microbiota of animals exert major effects on host biology [1]. Although horizontal transfer is generally considered the prevalent route for the acquisition of gut bacteria in mammals [2], some bacterial lineages have co-speciated with their hosts on timescales of several million years [3]. Termites harbor a complex gut microbiota, and their advanced social behavior provides the potential for long-term vertical symbiont transmission, and co-evolution of gut symbionts and host [4–6]. Despite clear evolutionary patterns in the gut microbiota of termites
[7], a consensus on how microbial communities were assembled during termite diversification has yet to be reached. Although some studies have concluded that vertical transmission has played a major role [8, 9], others indicate that diet and gut microenvironment have been the primary determinants shaping microbial communities in termite guts [7, 10]. To address this issue, we examined the gut microbiota of 94 termite species, through 16S rRNA metabarcoding. We analyzed the phylogeny of 211 bacterial lineages obtained from termite guts, including their closest relatives from other environments, which were identified using BLAST. The results provided strong evidence for rampant horizontal transfer of gut bacteria between termite host lineages. Although the majority of termite-derived phylotypes formed large monophyletic groups, indicating high levels of niche specialization, numerous other clades were interspersed with bacterial lineages from the guts of other animals. Our results indicate that ‘‘mixed-mode’’ transmission, which combines colony-to-offspring vertical transmission with horizontal colony-to-colony transfer, has been the primary driving force shaping the gut microbiota of termites.
... Termites in the genus Reticulitermes (Holmgren; Isoptera: Rhinotermitidae) carry a symbiont assemblage that is dramatically different from the other termites in their family, Rhinotermitidae, suggesting that Reticulitermes may have replaced their gut communities via an ancient horizontal transmission event (Kitade and Matsumoto 1998, Kitade 2004, Tai et al. 2015. In addition, termites in the family Serritermitidae harbor a dramatically different flagellate community from their close relatives in the Rhinotermitidae, suggesting that the gut community in the Serritermitidae may have been shaped by horizontal transfer (Radek et al. 2017). However, it is unknown whether horizontal transfers of gut protists have occurred in lower termites outside of these examples. ...
Coevolution is a major driver of speciation in many host-associated symbionts. In the termite-protist digestive symbiosis, the protists are vertically inherited by anal feeding among nest mates. Lower termites (all termite families except Termitidae) and their symbionts have broadly co-diversified over ~170 million yr. However, this inference is based mainly on the restricted distribution of certain protist genera to certain termite families. With the exception of one study, which demonstrated congruent phylogenies for the protist Pseudotrichonympha and its Rhinotermitidae hosts, coevolution in this symbiosis has not been investigated with molecular methods. Here we have characterized the hindgut symbiotic protists (Phylum Parabasalia) across the genus Zootermopsis (Archotermopsidae) using single cell isolation, molecular phylogenetics, and high-throughput amplicon sequencing. We report that the deepest divergence in the Zootermopsis phylogeny (Zootermopsis laticeps [Banks; Isoptera: Termopsidae]) corresponds with a divergence in three of the hindgut protist species. However, the crown Zootermopsis taxa (Zootermopsis angusticollis [Hagen; Isoptera: Termopsidae], Z. nevadensis nevadensis [Hagen; Isoptera: Termopsidae], and Z. nevadensis nuttingi [Haverty & Thorne; Isoptera: Termopsidae]) share the same protist species, with no evidence of co-speciation under our methods. We interpret this pattern as incomplete co-cladogenesis, though the possibility of symbiont exchange cannot be entirely ruled out. This is the first molecular evidence that identical communities of termite-associated protist species can inhabit multiple distinct host species.
... In termites, however, the flagellates are re-circulated among colony members via trophallaxis once the colony becomes established. As expected in vertically transmitted symbionts, flagellate communities of different host lineages indicate co-speciation, with possible horizontal shifts due to stochastic, dietary or ecological effects [20][21][22][23]. ...
Abstract: Subsocial wood feeding cockroaches in the genus Cryptocercus, the sister group of termites, retain their symbiotic gut flagellates during the host molting cycle, but in lower termites closely related flagellates die prior to host ecdysis. Although the prevalent view is that termite flagellates die because of conditions of starvation and desiccation in the gut during the host molting cycle, the work of L.R. Cleveland in the 1930’s through 1960’s provides a strong alternate hypothesis: it was the changed hormonal environment associated with the origin of eusociality and its concomitant shift in termite developmental ontogeny that instigates the death of the flagellates in termites. Although the research on termite gut microbial communities has exploded since the advent of modern molecular techniques, the role of the host hormonal environment on the life cycle of its gut flagellates has been neglected. Here Cleveland’s studies are revisited to provide a basis for re-examination of the problem, and the results framed in the context of two alternate hypotheses: the flagellate symbionts are victims of the change in host social status, or the flagellates have become incorporated into the life cycle of the eusocial termite colony. Recent work on parasitic protists suggests clear paths for exploring these hypotheses and for resolving long standing issues regarding sexual-encystment cycles in flagellates of the Cryptocercus-termite lineage using molecular methodologies, bringing the problem into the modern era.
... The limitations of host taxon sampling, for any controlled experimental approach, calls for testing the impact of additional life type switches across the termite phylogeny to further generalize our results. The limited sampling might also explain that we found no evidence for the potential horizontal acquisition of protists along the Reticulitermes lineage as discussed by Kitade (2004) and Radek et al. (2017). ...
The gut microbiome of lower termites comprises protists and bacteria that help these insects to digest cellulose and to thrive on wood. The composition of the termite gut microbiome correlates with phylogenetic distance of the animal host and host ecology (diet) in termites collected from their natural environment. However, carryover of transient microbes from host collection sites are a concern and might contribute to the ecological imprints on the termite gut microbiome. Here, we set out to test whether an ecological imprint on the termite gut microbiome remains, when focusing on the persistent microbiome. Therefore, we kept termites under strictly controlled dietary conditions and subsequently profiled their protist and bacterial gut microbial communities using 18S and 16S rRNA gene amplicon sequencing. . The species differ in their ecology; while three of the investigated species are wood-dwellers that feed on the piece of wood they live in and never leave except for the mating flight, the other two species regularly leave their nests to forage food. Despite these prominent ecological differences, protist microbiome structure aligned with phylogenetic relatedness of termite host species. Conversely, bacterial communities seemed more flexible, suggesting that microbiome structure aligned more strongly with the foraging and wood-dwelling ecologies. Interestingly, protist and bacterial community alpha-diversity correlated, suggesting either putative interactions between protists and bacteria, or that both types of microbes in the termite gut follow shared structuring principles. Taken together, our results add to the notion that bacterial communities are more variable over evolutionary time than protist communities and might react more flexibly to changes in host ecology.
Lower termites harbor diverse consortia of symbiotic gut flagellates. Despite numerous evidence for co-cladogenesis, the evolutionary history of these associations remains unclear. Here, we present Retractinymphidae fam. nov., a monogeneric lineage of Trichonymphida from Serritermitidae. Although Retractinympha glossotermitis gen. nov. sp. nov. morphologically resembles members of the genus Pseudotrichonympha , phylogenetic analysis identified it as sister group of the Teranymphidae. We compared morphology and ultrastructure of R . glossotermitis to that of Pseudotrichonympha and other Teranymphidae, including the so-far undescribed Pseudotrichonympha solitaria sp. nov. from Termitogeton planus (Rhinotermitidae). Like all Teranymphidae, R . glossotermitis is a large, elongated flagellate with a bilaterally symmetric rostrum, an anterior, flagella-free operculum, and an internal rostral tube. However, it is readily distinguished by the length of its rostral flagella, which never exceeds that of the postrostral flagella, and its retractable anterior end. Inclusion of the hitherto unstudied Stylotermes halumicus (Stylotermitidae) in our survey of trichonymphid flagellates in Neoisoptera confirmed that the combined presence of Heliconympha and Retractinympha and absence of Pseudotrichonympha is unique to Serritermitidae. The close phylogenetic relatedness of Heliconympha in Serritermitidae to the spirotrichosomid flagellates in Stolotermitidae provides strong support for their acquisition by horizontal transmission.
Symbiotic protists play important roles in the wood digestion of lower termites. Previous studies showed that termites generally possess host‐specific flagellate communities. The genus Reticulitermes is particularly interesting because its unique assemblage of gut flagellates bears evidence for transfaunation. The gut fauna of Reticulitermes species in Japan, Europe, and North America had been investigated, but data on species in China is scarce. For the first time we analyzed the phylogeny of protists in the hindgut of five Reticulitermes species in China. A total of 22 protist phylotypes were affiliated with the family Trichonymphidae, Teranymphidae, Trichomonadidae and Holomastigotoididae (Phylum Parabasalia), and 45 protist phylotypes were affiliated with the family Pyrsonymphidae (Phylum Preaxostyla). The protist fauna of these five Reticulitermes species is similar to those of Reticulitermes species in the other geographical regions. The topology of Trichonymphidae subtree was similar to that of Reticulitermes tree. All Preaxostyla clones were affiliated with the genera Pyrsonympha and Dinenympha (Order Oxymonadida) as in the other Reticulitermes species. The results of this study not only add to the existing information on the flagellates present in other Reticulitermes species but also offer the opportunity to test the hypotheses for the coevolution of symbiotic protists with their host termites.
Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Blattoidea: Rhinotermitidae) are invasive subterranean termite pest species with a major global economic impact. However, the descriptions of the mutualistic protist communities harbored in their respective hindguts remain fragmentary. The C. formosanus hindgut has long been considered to harbor three protist species, Pseudotrichonympha grassii (Trichonymphida), Holomastigotoides hartmanni , and Cononympha (Spirotrichonympha ) leidyi (Spirotrichonymphida), but molecular data have suggested that the diversity may be higher. Meanwhile, the C. gestroi community remains undescribed except for Pseudotrichonympha leei . To complete the characterization of these communities, hindguts of workers from both termite species were investigated using single cell PCR, microscopy, cell counts, and 18S rRNA amplicon sequencing. The two hosts were found to harbor intriguingly parallel protist communities, each consisting of one Pseudotrichonympha species, two Holomastigotoides species, and two Cononympha species. All protist species were unique to their respective hosts, which last shared a common ancestor ~ 18 MYA. The relative abundances of protist species in each hindgut differed remarkably between cell count data and 18S rRNA profiles, calling for caution in interpreting species abundances from amplicon data. This study will enable future research in C. formosanus and C. gestroi hybrids, which provide a unique opportunity to study protist community inheritance, compatibility, and potential contribution to hybrid vigor.
The symbiotic gut flagellates of lower termites form host-specific consortia composed of Parabasalia and Oxymonadida. The analysis of their coevolution with termites is hampered by a lack of information, particularly on the flagellates colonizing the basal host lineages. To date, there are no reports on the presence of oxymonads in termites of the family Stolotermitidae. We discovered three novel, deep-branching lineages of oxymonads in a member of this family, the damp-wood termite Porotermes adamsoni. One tiny species (6-10μm), Termitimonas travisi, morphologically resembles members of the genus Monocercomonoides, but its SSU rRNA genes are highly dissimilar to recently published sequences of Polymastigidae from cockroaches and vertebrates. A second small species (9-13μm), Oxynympha loricata, has a slight phylogenetic affinity to members of the Saccinobaculidae, which are found exclusively in wood-feeding cockroaches of the genus Cryptocercus, the closest relatives of termites, but shows a combination of morphological features that is unprecedented in any oxymonad family. The third, very rare species is larger and possesses a contractile axostyle; it represents a phylogenetic sister group to the Oxymonadidae. These findings significantly advance our understanding of the diversity of oxymonads in termite guts and the evolutionary history of symbiotic digestion.
Hoplonympha natator is an obligate symbiont of Paraneotermes simplicicornis (Kalotermitidae), from southwestern North America. Another Hoplonympha species inhabits Hodotermopsis sjostedti (Archotermopsidae), from montane Southeast Asia. The large phylogenetic and geographical distance between the hosts makes the distribution of Hoplonympha puzzling. Here we report the phylogenetic position of H. natator from P. simplicicornis through maximum likelihood and Bayesian analysis of 18S rRNA genes. The two Hoplonympha species form a clade with a deep node, making a recent symbiont transfer unlikely. The distribution of Hoplonympha may be due to an ancient transfer or strict vertical inheritance with differential loss from other hosts.
1. Numerous cladistic analyses have converged: termites are a monophyletic clade embedded within the paraphyletic cockroaches, and sister group to the biparental, wood-feeding cockroach Cryptocercus. The latter is therefore an appropriate model for testing assumptions regarding early termite evolution.
2. The ground plan of the termite ancestor is reviewed based on shared characters of ecology, life history and behavior in Cryptocercus and incipient termite colonies, and includes two levels of dependence: a reliance of all individuals on gut microbiota, and dependence of early instars on parental care. Both these conditions co-evolved with parent-to-offspring proctodeal trophallaxis.
3. The termite ancestor lived in a single log serving as food and nest. This ‘one-piece’ nesting ecology prioritizes nitrogen conservation and strongly influences interacting social, nutritional, and microbial environments. Each of these environments individually and in combination profoundly affect cockroach development.
4. Proctodeal trophallaxis integrates the social, nutritional, and microbial environments. A change in trophallactic behavior, from parental to alloparental, can, therefore, shift developmental trajectories, ultimately adding a third level of dependence. The death of gut protists during the host molting period and consequent interdependence of family members shifted the hierarchical level at which selection acted; fixation of eusociality quickly followed.
5. The basic nesting ecology did not change when termites evolved eusociality, the change occurred in the allocation and use of existing resources within the social group, driven by nitrogen scarcity, mediated by trophallaxis and made possible by a strongly lineage specific set of life history characteristics.
The hindguts of lower termites and Cryptocercus cockroaches are home to a distinct community of archaea, bacteria, and protists (primarily parabasalids and some oxymonads). Within a host species, the composition of these hindgut communities appears relatively stable, but the evolutionary and ecological factors structuring community composition and stability are poorly understood, as are differential impacts of these factors on protists, bacteria, and archaea. We analyzed the microbial composition of parabasalids and bacteria in the hindguts of Cryptocercus punctulatus and 23 species spanning 4 families of lower termites by pyrosequencing variable regions of the small subunit rRNA gene. Especially for the parabasalids, these data revealed undiscovered taxa and provided a phylogenetic basis for a more accurate understanding of diversity, diversification, and community composition. The composition of the parabasalid communities was found to be strongly structured by the phylogeny of their hosts indicating the importance of historical effects, although exceptions were also identified. Particularly, spirotrichonymphids and trichonymphids likely were transferred between host lineages. In contrast, host phylogeny was not sufficient to explain the majority of bacterial community composition, but the composition of the Bacteroidetes, Elusimicrobia, Tenericutes, Spirochaetes, and Synergistes were structured by host phylogeny perhaps due to their symbiotic associations with protists. Altogether, historical effects probably resulting from vertical inheritance have had a prominent role in structuring the hindgut communities, especially of the parabasalids, but dispersal and environmental acquisition has played a larger role in community composition than previously expected.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
Termites have colonized many habitats and are among the most abundant animals in tropical ecosystems, which they modify considerably through their actions. The timing of their rise in abundance and of the dispersal events that gave rise to modern termite lineages is not well understood. To shed light on termite origins and diversification, we sequenced the mitochondrial genome of 48 termite species and combined them with 18 previously sequenced termite mitochondrial genomes for phylogenetic and molecular clock analyses using multiple fossil calibrations. The 66 genomes represent most major clades of termites. Unlike previous phylogenetic studies based on fewer molecular data, our phylogenetic tree is fully resolved for the lower termites. The phylogenetic positions of Macrotermitinae and Apicotermitinae are also resolved as the basal groups in the higher termites, but in the crown termitid groups, including Termitinae + Syntermitinae + Nasutitermitinae + Cubitermitinae, the position of some nodes remains uncertain. Our molecular clock tree indicates that the lineages leading to termites and Cryptocercus roaches diverged 170 Ma (153-196 Ma 95% confidence interval [CI]), that modern Termitidae arose 54 Ma (46-66 Ma 95% CI), and that the crown termitid group arose 40 Ma (35-49 Ma 95% CI). This indicates that the distribution of basal termite clades was influenced by the final stages of the breakup of Pangaea. Our inference of ancestral geographic ranges shows that the Termitidae, which includes more than 75% of extant termite species, most likely originated in Africa or Asia, and acquired their pantropical distribution after a series of dispersal and subsequent diversification events. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: [email protected]
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We describe a new species, Glossotermes sulcatus, based on samples collected in the Amazonian region with soldiers, workers, alates, and ergatoids. All the castes are described and illustrated, which is a novelty for Glossotermes Emerson as a whole, a genus described from a single soldier in 1950. The detailed study of the castes allowed us to redescribe the genus and discuss its status. There are many characters (in all castes) that reinforce our conclusion that Glossotermes is more closely related to Serritermes than to Psammotermes, contrary to what is so far accepted. Among these, mandibles of workers and alates of Glossotermes present the most conspicuous synapomorphy with Serritermes serrifer. We therefore propose to remove Glossotermes from Psammotermitinae and reassign it to the previously monotypic family Serritermitidae. We also provide a new definition for this family and the two new subfamilies (Glossotermitinae and Serritermitinae).
The parabasalian symbionts of lower termite hindgut communities are well-known for their large size and structural complexity. The most complex forms evolved multiple times independently from smaller and simpler flagellates, but we know little of the diversity of these small flagellates or their phylogenetic relationships to more complex lineages. To understand the true diversity of Parabasalia and how their unique cellular complexity arose, more data from smaller and simpler flagellates are needed. Here, we describe two new genera of small-to-intermediate size and complexity, represented by the type species Cthulhu macrofasciculumque and Cthylla microfasciculumque from Prorhinotermes simplex and Reticulitermes virginicus, respectively (both hosts confirmed by DNA barcoding). Both genera have a single anterior nucleus embeded in a robust protruding axostyle, and an anterior bundle flagella (and likely a single posterior flagellum) that emerge slightly subanteriorly and have a distinctive beat pattern. Cthulhu is relatively large and has a distinctive bundle of over 20 flagella whereas Cthylla is smaller, has only 5 anterior flagella and closely resembles several other parababsalian genera. Molecular phylogenies based on small subunit ribosomal RNA (SSU rRNA) show both genera are related to previously unidentified environmental sequences from other termites (possibly from members of the Tricercomitidae), which all branch as sisters to the Hexamastigitae. Altogether, Cthulhu likely represents another independent origin of relatively high cellular complexity within parabasalia, and points to the need for molecular characterization of other key taxa, such as Tricercomitus.
SILVA (from Latin silva, forest, http://www.arb-silva.de) is a comprehensive web resource for up to date, quality-controlled databases of aligned ribosomal RNA (rRNA) gene sequences
from the Bacteria, Archaea and Eukaryota domains and supplementary online services. The referred database release 111 (July 2012) contains 3 194 778 small subunit
and 288 717 large subunit rRNA gene sequences. Since the initial description of the project, substantial new features have
been introduced, including advanced quality control procedures, an improved rRNA gene aligner, online tools for probe and
primer evaluation and optimized browsing, searching and downloading on the website. Furthermore, the extensively curated SILVA
taxonomy and the new non-redundant SILVA datasets provide an ideal reference for high-throughput classification of data from
next-generation sequencing approaches.
Like ants, termites are entirely eusocial and have profound ecological significance in the tropics. Following upon recent studies reporting more than a quarter of all known fossil termites, we present the first phylogeny of termite lineages using exemplar Cretaceous, Tertiary, and Recent taxa. Relationships among Recent families were largely unaffected by the addition of extinct taxa, but the analysis revealed extensive grades of stem-group taxa and the divergence of some modern families in the Cretaceous. Rhinotermitidae, Serritermitidae, and the “higher” termites (family Termitidae), which comprise 84% of the world termite species, diverged and radiated entirely in the Tertiary, corresponding to a significant increase in termite individuals in the fossil record. Radiation of the higher termites may have affected the formation of terrestrial carbon reserves like oil and coal. The higher classification of Isoptera is slightly revised based on the phylogenetic results. The following new taxa are proposed: Cratomastotermitidae, new family; Euisoptera, new clade; Archotermopsidae, new family; and Neoisoptera, new clade. In addition, the families Stolotermitidae, Stylotermitidae, and Archeorhinotermitidae are newly recognized or resurrected, and the families Termopsidae and Hodotermitidae are significantly restricted in composition.
This revision of the classification of eukaryotes, which updates that of Adl et al. [J. Eukaryot. Microbiol. 52 (2005) 399], retains an emphasis on the protists and incorporates changes since 2005 that have resolved nodes and branches in phylogenetic trees. Whereas the previous revision was successful in re-introducing name stability to the classification, this revision provides a classification for lineages that were then still unresolved. The supergroups have withstood phylogenetic hypothesis testing with some modifications, but despite some progress, problematic nodes at the base of the eukaryotic tree still remain to be statistically resolved. Looking forward, subsequent transformations to our understanding of the diversity of life will be from the discovery of novel lineages in previously under-sampled areas and from environmental genomic information.
Isoptera (termites) are an ecologically important order, with both a high abundance and biomass in tropical ecosystems. However, there have been few phylogenetic hypotheses for termites, and we present here the first comprehensive cladistic analysis for the group. We analysed relationships between all seven termite families, including representatives of all known feeding group, plus a number of systematically critical taxa. Termite species richness is biased towards the higher termites (Termitidae), and our taxon sampling reflects this. Our analysis was based essentially on morphological characters (96 workers, 93 soldiers) plus seven biological characters. The cladistic analysis gave four equally parsimonious trees, representing two islands of topologies. The strict consensus tree is fully resolved for the higher termites, but less so for the lower termites. Overall there is low statistical support for the suggested topology, and this can be explained by the high incongruence between the data sets (worker, soldier and biological). This study highlights the particular problems of coding morphological characters in social insects with multiple castes. Without the input of additional data sets, e.g. alates, biological, behavioural and molecular, it will not be possible to obtain a well-supported termite phylogeny.
The soldier caste represents the most conspicuous realization of termite eusociality, characterized by an extreme anatomical, behavioural, and physiological specialization. Numerous strategies have evolved in soldiers, including extreme adaptations such as self-sacrifice by autothysis. In the present study, we investigated the structure and function of defensive glands in Glossotermes oculatus soldiers aiming to understand their use in combat. Three glands are involved in defence: labral, frontal, and labial glands. Mandibles are used to bite the enemy, whereas the secretions of labral and labial glands are discharged into the wound. A striking characteristic of G. oculatus is the lack of the frontal pore; the secretion of the frontal gland is discharged by a rupture of the body wall. We hypothesized that this self-sacrifice is an efficient way of blocking a gallery under attack. A similar development of the frontal gland occurs in Serritermes serrifer, which supports the close relationship between the two genera inferred from morphological and genetic analyses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 839–848.
Background:
Inferring the evolutionary history of phylogenetically isolated, deep-branching groups of taxa-in particular determining the root-is often extraordinarily difficult because their close relatives are unavailable as suitable outgroups. One of these taxonomic groups is the phylum Parabasalia, which comprises morphologically diverse species of flagellated protists of ecological, medical, and evolutionary significance. Indeed, previous molecular phylogenetic analyses of members of this phylum have yielded conflicting and possibly erroneous inferences. Furthermore, many species of Parabasalia are symbionts in the gut of termites and cockroaches or parasites and therefore formidably difficult to cultivate, rendering available data insufficient. Increasing the numbers of examined taxa and informative characters (e.g., genes) is likely to produce more reliable inferences.
Principal findings:
Actin and elongation factor-1α genes were identified newly from 22 species of termite-gut symbionts through careful manipulations and seven cultured species, which covered major lineages of Parabasalia. Their protein sequences were concatenated and analyzed with sequences of previously and newly identified glyceraldehyde-3-phosphate dehydrogenase and the small-subunit rRNA gene. This concatenated dataset provided more robust phylogenetic relationships among major groups of Parabasalia and a more plausible new root position than those previously reported.
Conclusions/significance:
We conclude that increasing the number of sampled taxa as well as the addition of new sequences greatly improves the accuracy and robustness of the phylogenetic inference. A morphologically simple cell is likely the ancient form in Parabasalia as opposed to a cell with elaborate flagellar and cytoskeletal structures, which was defined as most basal in previous inferences. Nevertheless, the evolution of Parabasalia is complex owing to several independent multiplication and simplification events in these structures. Therefore, systematics based solely on morphology does not reflect the evolutionary history of parabasalids.
The onset of a specialized ("true") worker caste is a crucial step in the evolution of termite societies. Such workers, permanently excluded from wing development, repeatedly evolved from totipotent immatures, called "false" workers or pseudergates. In the family Rhinotermitidae, the presence of true workers and the level of specialization of this caste are highly variable, and key taxa illustrate transitional situations providing clues about worker evolution. Here we focused on the status of working immatures of Glossotermes oculatus, from the family Serritermitidae, now thought to represent either the sister-group of the Rhinotermitidae or a basal lineage nested within them. Contrary to previous assumptions, we show that the apterous immatures performing worker tasks in G. oculatus are the source of the single wing-budded nymphal instar preceding the alate. Consequently, they qualify as pseudergates rather than true workers. However, the sex ratio is strongly male biased in pseudergates and soldiers, which is a trait usually restricted to termites with true workers. We therefore argue that pseudergates of G. oculatus are close to a point where the species could easily shift toward the differentiation of a true worker caste, and that G. oculatus pinpoints a new possible route for the evolution of true workers from pseudergates.
Symbiotic flagellates play a major role in the digestion of lignocellulose in the hindgut of lower termites. Many termite gut flagellates harbour a distinct lineage of bacterial endosymbionts, so-called Endomicrobia, which belong to the candidate phylum Termite Group 1. Using an rRNA-based approach, we investigated the phylogeny of Trichonympha, the predominant flagellates in a wide range of termite species, and of their Endomicrobia symbionts. We found that Trichonympha species constitute three well-supported clusters in the Parabasalia tree. Endomicrobia were detected only in the apical lineage (Cluster I), which comprises flagellates present in the termite families Termopsidae and Rhinotermitidae, but apparently absent in the basal lineages (Clusters II and III) consisting of flagellates from other termite families and from the wood-feeding cockroach, Cryptocercus punctulatus. The endosymbionts of Cluster I form a monophyletic group distinct from many other lineages of Endomicrobia and seem to have cospeciated with their flagellate host. The distribution pattern of the symbiotic pairs among different termite species indicates that cospeciation of flagellates and endosymbionts is not simply the result of a spatial separation of the flagellate lineages in different termite species, but that Endomicrobia are inherited among Trichonympha species by vertical transmission. We suggest extending the previously proposed candidatus name 'Endomicrobium trichonymphae' to all Endomicrobia symbionts of Trichonympha species, and estimate that the acquisition by an ancestor of Trichonympha Cluster I must have occurred about 40-70 million years ago, long after the flagellates entered the termites.
Cryptocercus cockroaches and lower termites harbour obligate, diverse and unique symbiotic cellulolytic flagellates in their hindgut that are considered critical in the development of social behaviour in their hosts. However, there has been controversy concerning the origin of these symbiotic flagellates. Here, molecular sequences encoding small subunit rRNA and glyceraldehyde-3-phosphate dehydrogenase were identified in the symbiotic flagellates of the order Trichonymphida (phylum Parabasalia) in the gut of Cryptocercus punctulatus and compared phylogenetically to the corresponding species in termites. In each of the monophyletic lineages that represent family-level groups in Trichonymphida, the symbionts of Cryptocercus were robustly sister to those of termites. Together with the recent evidence for the sister-group relationship of the host insects, this first comprehensive study comparing symbiont molecular phylogeny strongly suggests that a set of symbiotic flagellates representative of extant diversity was already established in an ancestor common to Cryptocercus and termites, was vertically transmitted to their offspring, and subsequently became diversified to distinct levels, depending on both the host and the symbiont lineages.
Serritermitidae (Isoptera) is a small and little known Neotropical termite family which includes only two genera: Glossotermes and Serritermes. Despite the lack of detailed studies, it has been assumed that these termites have a true worker caste. A recent study revealed that Glossotermes has a linear development pathway and lacks true workers. Here, we present a study of the polymorphism of Serritermes serrifer Hagen & Bates, a species endemic to the Cerrado ecoregion of central Brazil which lives as an inquiline inside nests of Cornitermes spp. A morphometric analysis was performed based on measurements taken of 11 body parts of 544 specimens of immatures, worker-like individuals, soldiers, and alates. Sex of specimens was determined by dissection and examination of the seventh sternite. A principal component analysis (PCA) was used to evaluate morphological changes during development. Contrary with previous information from the literature and similar to Glossotermes, Serritermes shows a linear development pathway with two larval instars, two sizes of pseudergates, and a single nymphal morph. Pseudergates apparently undergo stationary molts. Sex ratio among pseudergates is male-biased, but not as strongly as in Glossotermes. Typical colonies have a single physogastric primary queen and a single primary king. Ergatoid reproductives are relatively rare and some female ergatoids may become strongly physogastric. Nymphoid reproductives were not found. All soldiers are male and bear well-developed testes.
All lower termites contain a symbiotic flagellate community in their hindguts. Yamin (1979) listed the symbiotic protistan composition of 31 species that belong to the family Rhinotermitidae. In this study, the symbiont composition of additional 23 Rhinotermitid termite species were investigated. The flagellate genera Spirotrichonympha, Pseudotrichonympha and Holomastigotoides are prevalent among Rhinotermitid hosts. Members of the genus Reticulitermes lack the latter two flagellate genera, but possess the most diverse flagellate community of the Rhinotermitids, being the only genus to contain flagellates of the order Oxymonadida. A one to one host-species to symbiont-species relationship is found within the genera Parrhinotermes and Termitogeton.
The process of symbiotic flagellate infection of newly hatched larvae was investigated on a damp wood termite Hodotermopsis japonica. Transmission of flagellate species begins from the 1st instar larvae 1-2 days after hatching. The complete fauna is established in a majority of 2nd instar larvae, and all of the 3rd instar larvae examined have the complete fauna. The time to establish the symbiont fauna is quicker than that of Reticulitermes speratus.
Termite guts harbor a dense and diverse microbiota that is essential for symbiotic digestion. The major players in lower termites are unique lineages of cellulolytic flagellates, whereas higher termites harbor only bacteria and archaea. The functions of the mostly uncultivated lineages and their distribution in different diet groups are slowly emerging. Patterns in community structure match changes in the biology of different host groups and reflect the availability of microbial habitats provided by flagellates, wood fibers, and the increasing differentiation of the intestinal tract, which also creates new niches for microbial symbionts. While the intestinal communities in the closely related cockroaches seems to be shaped primarily by the selective forces of microhabitat and functional niche, the social behavior of termites reduces the stochastic element of community assembly, which facilitates coevolution and may ultimately result in cospeciation.
Their ability to degrade lignocellulose gives termites an important place in the carbon cycle. This ability relies on their partnership with a diverse community of bacterial, archaeal and eukaryotic gut symbionts, which break down the plant fibre and ferment the products to acetate and variable amounts of methane, with hydrogen as a central intermediate. In addition, termites rely on the biosynthetic capacities of their gut microbiota as a nutritional resource. The mineralization of humus components in the guts of soil-feeding species also contributes to nitrogen cycling in tropical soils. Lastly, the high efficiency of their minute intestinal bioreactors makes termites promising models for the industrial conversion of lignocellulose into microbial products and the production of biofuels.
Resumo
A catalog of the living termites of the New World is presented, including all known synonyms, geographical distribution, type depositories, and a selected bibliography. The number of termite genera recorded for the New World is 86, and the number of species 543. The following taxonomical changes are included: Curvitermes projectidens is transferred to Armitermes, and Nasutitermes columbicus is treated as a junior synonym of N. guayanae. Most subspecies are treated as full species. Available names of uncertain taxonomic position are presented in a separate list.
Termites of most isopteran families and wood-feeding cockroaches of the genus Cryptocercus usually harbor more than one symbiotic flagellate species in their hindgut. To evaluate the similarity of their symbiont faunae, data on symbiont composition at a generic level were examined by cluster analysis and type III quantification method. In both analyses, the symbiont composition recorded from host insects belonging to the same families or monophyletic family groups tended to be similar. This tendency was particularly remarkable in the clade Kalotermitidae and the clade Rhinotermitidae plus Serritermitidae. Two basal host groups, the Cryptocercidae and the Mastotermitidae, exhibited very different symbiont compositions. These findings suggested that the symbiont faunae mainly reflect the host's phylogenetic relationships. Within the Rhinotermitid hosts, the genus Reticulitermes showed a unique symbiont fauna although it is not a basal taxon in the Rhinotermitidae. Horizontal transfers of symbiotic protists might explain such anomalistic fauna.
A technique has recently been described whereby the symbiotic protozoa of the wood-feeding roach, Cryptocercus, may be transferred from the hind-gut of one host to another per rectum (Cleveland and Nutting, J. Exp. Zool., in press) . The method has now been applied successfully in the reciprocal transfer of protozoa be tween this roach and the large, western North American termite, Zootermopsis. An earlier series of experiments by Cleveland, in which the transfer was accom plished by feeding, showed that the protozoa were capable of living in alternate hosts for some time (Cleveland et ci., 1934, p. 320) . This preliminary work called for more extensive experiments, first to determine whether the termite protozoa could indeed supplant the normal infection of the roach and vice versa. Should this then be the case, it would be a matter of considerable interest to determine the behavior of the protozoa in their new hosts during the molting period. Experimentation of this sort has been extremely limited and largely confined to determining the host specificity of protozoa from certain termites. Light and San ford (1928) reinfected oxygen-defaunated termites per rectum with a glass canula connected by rubber tubing to a mouthpiece. They found that the protozoa of Zootermopsis angusticollis could live and multiply in Kalotermes hubbardi for at least 100 days. Dropkin (1941) similarly infected Z. angusticollis with protozoa from Reticulitermes fiwipes, and Katotermes jouteli and schwarzi. None of the protozoa multiplied, and so were unable to support the new host for longer than 50 days. He therefore concluded that these unsuccessful refaunations resulted from physiological as well as morphological distinctions which must exist between the protozoa from widely different species of termites. •¿�Before describing the roach-termite transfaunations, it is pertinent to recount the natural methods for transfer of protozoa between the normal hosts. Crypto cercus harbors a large and diverse fauna composed of 13 described genera and some 30 species of hypermastigote and polymastigote flagellates. All of these genera change from asexual to sexual methods of reproduction during the molting period of their host which, in the laboratory at 210 C., lasts for about 44 days. Most of the individuals of Trichonympha encyst a few days before molting, and large num bers are usually passed in the fecal pellets within 20 to 36 hours after ecdysis. The hatching of nymphs from their oothecae coincides with the peak of the molting sea son, so that the new individuals are able to gain their initial infections, at least in
What is known of termite global diversity patterns is reviewed at a number of spatial scales (from Neotropics > Oriental tropics. This contradicts the predictions of energy-diversity theory. Both of these gradients can be described as “diversity anomalies”. Multivariate analyses of generic WORLDMAP data are reviewed showing that the latitudinal and longitudinal diversity anomalies are due to the differential distribution of termite clades in different biogeographical regions, rather than a uniform difference across all clades between regions with different diversities. Different clades may, therefore, have evolved in different areas due to particular idiosyncratic events across geological time, and then may not have dispersed significantly from their original biogeographical regions. Indeed, the limited data that are available suggest that termites are generally poor dispersers across geographical barriers. The present, admittedly incomplete data, suggest that the families of termites may have evolved on Pangaea prior to the break-up of that supercontinent, and that the major clades of the Termitidae may have evolved subsequently on the separate pieces. The characteristics of the termite fauna of the different regions are discussed, as well as the distribution of genera within the putative clades. Termites appear to represent a very good example of a group whose biology and ecology are strongly influenced by history. Some possible consequences of these historical constraints on ecological processes are briefly discussed.
The following methods for taxonomic studies of ciliated protozoa are described in detail: live observation, supravital staining with methyl green-pyronin, dry silver nitrate impregnation, wet silver nitrate impregnation, silver carbonate impregnation, protargol impregnation (three procedures), and scanning electron microscopy. Familiarity with these methods (or modifications) is an absolute prerequisite for successful taxonomic work. No staining method is equally appropriate to all kinds of ciliates. A table is provided which indicates those procedures which work best for certain groups of ciliates. A second table relates to the structures revealed by the procedures. Good descriptions usually demand at least live observation, silver nitrate and protargol or silver carbonate impregnation. Some instructions are provided for distinguishing mono- and dikinetids as well as ciliated and non-ciliated basal bodies in silvered ciliates. The brilliancy of the silver preparations has unfortunately recently tempted some taxonomists to neglect live observation. However, many important species characters cannot be seen or are changed in silvered specimens. I thus consider all species descriptions based exclusively on silver slides as incomplete and of doubtful value for both α-taxonomists and ecologists. Especially the latter are usually not trained to correlate the silvered structures with the live appearance of the cell.
The properties of the inorganic dye ruthenium red are presented with emphasis upon its use for electron microscopy of cells and tissues. Although commercial ruthenium red often can be used directly, it always contains various impurities and by-products. One of these, termed ruthenium violet, can be isolated and is useful by itself. Absorption spectra of the ruthenium dyes and common impurities are given so that an assay is possible for any sample. Convenient fixative recipes containing ruthenium red or violet are provided together with constraints necessary for a reliable reaction to label extracellular acidic mucosubstances. Perfusion was not successful. The specificity of the ruthenium red reaction was evaluated by spot testing with 57 substances, and by titration with chemically defined pectins. The results indicate that ruthenium red, as a hexavalent cation, precipitates a large variety of polyanions by ionic interaction, and that its classical reaction with pectin is typical rather than specific. New data are presented regarding its reaction with phospholipids. For electron microscopy, a further reaction with OsO4 amplifies the feeble electron density, which is the counterpart of its intense optical labeling, to a practical level resulting in strong contrast. An hypothesis is presented for the mechanism underlying this intensification.
An attempt is made to retrace the evolution of symbiotic associations in Blattopteroidea, with particular reference to Isoptera. It seems probable that double symbiosis occured in the common ancestor of Blattids and Termites: intracellular microorganisms of bacteriocytes, xylophagous intestinal Flagellates. Where as actual Blattids, exceptingCryptocercus, have only retained the former, the primitive Termites, exceptingMastotermes, have only kept the latter. Evolved Termites (fam. Termitidae) have in turn lost the symbiotic Flagellates, but have acquired a rich and complex bacterial flora. — Some of these microorganisms, mixed with their aliments, certainly aid digestion (breakdown of cellulose), whilst others, localised at a particular level of the alimentary canal and not found in the alimentary mass, presumably play a different rle. Furthermore, Protozoa are constantly associated with certains Termites (xylophagous Amoebae, humus-feeder Ciliates of the genusTermitophrya) and may play some rle in the process of digestion. Finally, an association occurs between fundgus-growing Termites (subfam. Macrotermitinae) and mushrooms (Termitomyces).
Relationships among genera in the termite family Rhinotermitidae and their relationship to the families Termitidae and Serritermitidae were investigated based on analysis of three mitochondrial genes: COI, COII and 16S rDNA. Maximum Parsimony (MP) bootstrap analysis of each of these genes indicated a low level of phylogenetic incongruence between them, and thus they were combined and analysed by MP and Bayesian analysis. Six main lineages were clearly identified, however relationships among these were not well defined. Tentative support was found for the Rhinotermitid genera Coptotermes, Heterotermes and Reticulitermes being the sister group to the Termitidae, rendering the Rhinotermitidae paraphyletic. The species Serritermes serrifer and Glossotermes oculatus were found to group with strong support, in agreement with the recent transfer of the latter species to the family Serritermitidae based on morphological characteristics. No support was found for the Rhinotermitidae being paraphyletic with respect to the Serritermitidae. A number of disagreements were found between the molecular tree and traditional classifications of genera within subfamilies.
Three genera of spirotrichonymphids: Microjoenia, Spirotrichonymphella andSpirotrichonympha, living in the termite Porotermes, were studied by electron microscopy and compared with species of Spirotrichonympha, Holomastigotoides and Micromastigotes from other termites. Microjoenia anterodepressa is a new species and Spirotrichonymphella pudibunda is the type species. All these genera share the following common features: several apical spiralled flagellar bands; basal body #2 bears preaxostylar fibres connected to the pelta-axostyle system at the origin of each flagellar band; basal bodies of flagellar bands are inserted into a gutter limited by a striated lamina associated with microfibrillar material, as is the whole complex forming a cord-like structure at the base of each flagellar band; the pelta-axostyle microtubular rows are always present at the apex and may extend in an axostylar trunk towards the posterior; Golgi bodies are not supported by a parabasal fibre; a semi-permanent microtubular bundle (paradesmosis) stretched between the striated lamina of two neighbouring flagellar bands may be present. However, each genus has particular features not found in the other genera: Microjoenia has a complete axostyle, Spirotrichonymphella has two striated roots at the base of each basal body and no axostylar trunk; in these genera 3 to 5 Golgi bodies are situated immediately posterior to the nucleus and independent of flagellar bands. In Spirotrichonympha species basal bodies are very long. In Microjoenia and in a group of Spirotrichonympha species, the structure of the gutters are complete and very similar. In Holomastigotoides the striated lamina of the gutters is associated with microfibrillar material of variable density depending on the species.The comparisons of these 5 genera, of the 9 spirotrichonymphid genera described, indicate that the suborder Spirotrichonymphina is very homogenous and probably monophyletic. The organization comprising basal body #2, preaxostylar fibres and pelta-axostyle is shared with trichomonads, but the fact that Golgi bodies are not supported by parabasal fibres and are independent of basal bodies distinguishes this suborder from Trichomonadida, Lophomonadina and Trichonymphina.
A number of cophylogenetic relationships between two organisms namely a host and a symbiont or parasite have been studied to date; however, organismal interactions in nature usually involve multiple members. Here, we investigated the cospeciation of a triplex symbiotic system comprising a hierarchy of three organisms -- termites of the family Rhinotermitidae, cellulolytic protists of the genus Pseudotrichonympha in the guts of these termites, and intracellular bacterial symbionts of the protists. The molecular phylogeny was inferred based on two mitochondrial genes for the termites and nuclear small-subunit rRNA genes for the protists and their endosymbionts, and these were compared. Although intestinal microorganisms are generally considered to have looser associations with the host than intracellular symbionts, the Pseudotrichonympha protists showed almost complete codivergence with the host termites, probably due to strict transmissions by proctodeal trophallaxis or coprophagy based on the social behaviour of the termites. Except for one case, the endosymbiotic bacteria of the protists formed a monophyletic lineage in the order Bacteroidales, and the branching pattern was almost identical to those of the protists and the termites. However, some non-codivergent evolutionary events were evident. The members of this triplex symbiotic system appear to have cospeciated during their evolution with minor exceptions; the evolutionary relationships were probably established by termite sociality and the complex microbial community in the gut.
Termites thrive on dead plant matters with the aid of microorganisms resident in their gut. The gut microbiota comprises protists (single-celled eukaryotes), bacteria, and archaea, most of which are unique to the termite gut ecosystem. Although this symbiosis has long been intriguing researchers of both basic and applied sciences, its detailed mechanism remains unclear due to the enormous complexity and the unculturability of the microbiota. In the effort to overcome the difficulty, recent advances in omics, such as metagenomics, metatranscriptomics, and metaproteomics have gradually unveiled the black box of this symbiotic system. Genomics targeting a single species of the unculturable microbial members has also provided a great progress in the understanding of the symbiotic interrelationships among the gut microorganisms. In this review, the symbiotic system organized by wood-feeding termites and their gut microorganisms is outlined, focusing on the recent achievement in omics studies of this multilayered symbiotic system.
We propose a new classification of Parabasalia which is congruent with both ultrastructural and molecular-phylogenetic studies. We identify six main parabasalid lineages and give them the rank of class: Hypotrichomonadea, Trichomonadea, Tritrichomonadea, Cristamonadea, Trichonymphea, and Spirotrichonymphea. Trichomonadea is characterized by a single mastigont and by the absence of both a comb-like structure and an infrakinetosomal body. Most representatives also possess a lamelliform undulating membrane. Trichomonadea is divided into two monophyletic orders, Trichomonadida (family Trichomonadidae; with a B-type costa) and Honigbergiellida (families Honigbergiellidae, Hexamastigidae and Tricercomitidae; without a costa). The class Tritrichomonadea, with a single order Tritrichomonadida, is ancestrally characterized by a single mastigont with four flagella, and both a comb-like structure and an infrakinetosomal body. The morphologically most complex representatives (family Tritrichomonadidae) possess in addition a rail-type undulating membrane, an A-type costa, and a suprakinetosomal body. These last three characters are absent in families Monocercomonadidae and Simplicimonadidae. The remaining tritrichomonadids, Dientamoebidae, have undergone reductive evolution. Cristamonads (Cristamonadea) are morphologically derived from tritrichomonads. Because we are unable to determine morphologically homogenous monophyletic lineages within cristamonads, we classify all cristamonads into a single family, Lophomonadidae. Hypotrichomonadea, comprising the genera Trichomitus and Hypotrichomonas, resembles Tritrichomonadea by an A-type costa, and by the presence of a comb-like structure in the mastigont. However, they do not possess an infrakinetosomal body, and are not specifically related to Tritrichomonadea in molecular-phylogenetic analyses. Moreover, unlike Tritrichomonadea, Hypotrichomonadea possesses a lamelliform undulating membrane. The remaining parabasalids are of complex morphology and belong to the classes Trichonymphea and Spirotrichonymphea. A new parabasalid genus, Simplicimonas (Tritrichomonadea), and three new species, Tetratrichomonas undula, Hexamastix coercens and Simplicimonas similis, are described.
Thesis (M.A.)--University of California, Dec. 1928. "Literature cited": p. 25-26.
Parabasalia are a large, diverse clade of anaerobic flagellates, many of which inhabit the guts of wood-feeding insects. Because most are uncultivable, molecular data representing the true diversity of Parabasalia only became possible with the application of single-cell techniques, but in the last decade molecular data have accumulated rapidly. Within the Trichonymphida, the most diverse lineage of hypermastigote parabasalids, molecular data are now available from five of the six families, however, one family, the Spirotrichosomidae, has not been sampled at the molecular level, and is very little studied with electron microscopy. Here we examine a representative of Spirotrichosomidae--Leptospironympha of the wood-feeding cockroach Cryptocercus punctulatus--with scanning and transmission electron microscopy, and analyze its small subunit rRNA gene to infer its phylogenetic position. Phylogenetic analyses place Leptospironympha as sister to a clade comprising Eucomonymphidae and Teranymphidae with moderate support. Examination with scanning and transmission electron microscopy reveals new classes of previously undetected symbiotic surface bacteria, a glycocalyx, granular particles on flagella, and putative phagocytosed bacteria. The range of flagellar patterns in Spirotrichosomidae is quite wide, and the possibility that some members may be more closely related to Eucomonymphidae or Teranymphidae is addressed.
A low-viscosity embedding medium based on ERL-4206 is recommended for use in electron microscopy. The composition is: ERL-4206 (vinyl cyclohexene dioxide) 10 g, D.E.R. 736 (diglycidyl ether of polypropylene glycol) 6 g, NSA (nonenyl succinic anhydride) 26 g, and S-1 (dimethylaminoethanol or DMAE) 0.4 g. The medium is easily and rapidly prepared by dispensing the components, in turn by weight, into a single flask. The relatively low viscosity of the medium (60 cP) permits rapid mixing by shaking and swirling. The medium is infiltrated into specimens after the use of any one of several dehydrating fluids, such as ethanol, acetone, dioxan, hexylene glycol, isopropyl alcohol, propylene oxide, and tert.-butyl alcohol. It is compatible with each of these in all proportions. After infiltration the castings are polymerized at 70°C in 8 hours. Longer curing does not adversely affect the physical properties of the castings. Curing time can be reduced by increasing the temperature or the accelerator, S-1, or both; and the hardness of the castings is controlled by changes in the D.E.R. 736 flexibilizer. The medium has a long pot life of several days and infiltrates readily because of its low viscosity. The castings have good trimming and sectioning qualities. The embedding matrix of the sections is very resistant to oxidation by KMnO4 and Ba(MnO4)2, compared with resins containing NADIC methyl anhydride. Sections are tough under the electron beam and may be used without a supporting membrane on the grids. The background plastic in the sections shows no perceptible substructure at magnifications commonly used for biological materials. The medium has been used successfully with a wide range of specimens, including endosperms with a high lipid content, tissues with hard, lignified cell walls, and highly vacuolated parenchymatous tissues of ripe fruits.
The phylogeny of a symbiotic hypermastigote Trichonympha agilis (class Parabasalia; order Hypermastigida) in the hindgut of the lower termite Reticulitermes speratus was examined by a strategy that does not rely on cultivation. From mixed-population DNA obtained from the termite gut, small subunit (16S-like) ribosomal RNA sequences were directly amplified by the polymerase chain reaction method using primers specific for eukaryotes. Comparative sequence analysis of the clones revealed two kinds of sequences, one from the termite itself and the other from a symbiotic protist. A fluorescent-labeled oligonucleotide probe for the latter sequence was designed and used in whole-cell hybridization experiments to provide direct visual evidence that the sequence originated from a larger hypermastigote in the termite hindgut, Trichonympha agilis. According to the phylogenetic trees constructed, the hypermastigote represented one of the deepest branches of eukaryotes. The hypermastigote along with members of the order Trichomonadida formed a monophyletic lineage, indicating that this hypermastigote and trichomonads shared a recent common ancestry.