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The symbiosis between termites and their hindgut protists is mutually obligate and vertically inherited. It was established by the late Jurassic in the cockroach ancestors of termites as they transitioned to wood feeding. Since then, protist symbionts have been transmitted from host generation to host generation by proctodeal trophallaxis (anal feeding). The protists belong to multiple lineages within the eukaryotic superphylum Metamonada. Most of these lineages have evolved large cells with complex morphology, unlike the non‐termite‐associated Metamonada. The species richness and taxonomic composition of symbiotic protist communities varies widely across termite lineages, especially within the deep‐branching clade Teletisoptera. In general, closely related termites tend to harbour closely related protists, and deep‐branching termites tend to harbour deep‐branching protists, reflecting their broad‐scale co‐diversification. A closer view, however, reveals a complex distribution of protist lineages across hosts. Some protist taxa are common, some are rare, some are widespread, and some are restricted to a single host family or genus. Some protist taxa can be found in only a few, distantly related, host species. Thus, the long history of co‐diversification in this symbiosis has been complicated by lineage‐specific loss of symbionts, transfer of symbionts from one host lineage to another, and by independent diversification of the symbionts relative to their hosts. This review aims to introduce the biology of this important symbiosis and serve as a gateway to the diversity and systematics literature for both termites and protists. A searchable database with all termite‐protist occurrence records and taxonomic references is provided as a supplementary file to encourage and facilitate new research in this field. [ABSTRACT FROM AUTHOR]

Intracellular endosymbionts have reduced genomes that progressively lose genes at a timescale of tens of million years. We previously reported that gene loss rate is linked to mutation rate in Blattabacterium , however, the mechanisms causing gene loss are not yet fully understood. Here, we carried out comparative genomic analyses on the complete genome sequences of a representative set of 67 Blattabacterium strains, with sizes ranging between 511 and 645 kb. We found that 200 of the 566 analyzed protein-coding genes were lost in at least one lineage of Blattabacterium , with the most extreme case being one gene that was lost independently in 24 lineages. We found evidence for three mechanisms influencing gene loss in Blattabacterium. First, gene loss rates were found to increase exponentially with the accumulation of substitutions. Second, genes involved in vitamin and amino acid metabolism experienced relaxed selection in Cryptocercus and Mastotermes , possibly triggered by their vertically inherited gut symbionts. Third, we found evidence of epistatic interactions among genes leading to a "domino effect" of gene loss within pathways. Our results highlight the complexity of the process of genome erosion in an endosymbiont. [ABSTRACT FROM AUTHOR]

The subsocial life style and wood-feeding capability of Cryptocercus gives us an evolutionary key to unlock some outstanding questions in biology. With the advent of the Genomics Era, there is an unprecedented opportunity to address the evolution of eusociality and the acquisition of lignocellulases at the genetic level. However, to quantify gene expression, an appropriate normalization strategy is warranted to control for the non-specific variations among samples across different experimental conditions. To search for the internal references, 10 housekeeping genes from a gut transcriptome of a wood-feeding cockroach, Cryptocercus punctulatus, were selected as the candidates for the RT-qPCR analysis. The expression profiles of these candidates, including ACT, EF1α, GAPDH, HSP60, HSP70, αTUB, UBC, RPS18, ATPase and GST, were analyzed using a panel of analytical tools, including geNorm, NormFinder, BestKeeper, and comparative ΔCT method. RefFinder, a comprehensive ranking system integrating all four above-mentioned algorithms, rated ACT as the most stable reference gene for different developmental stages and tissues. Expression analysis of the target genes, Hex-1 and Cell-1, using the most or the least appropriate reference genes and a single or multiple normalizers signified this research. Our finding is the first step toward establishing a standardized RT-qPCR analysis in Cryptocercus. [ABSTRACT FROM AUTHOR]

Lower termites, as well as their sister group, the subsocial wood-feeding cockroach Cryptocercus, rely on flagellated eukaryotic symbionts in the hindgut to cooperatively digest their wood diet. In Cryptocercus these flagellates undergo encystment cycles tightly coordinated with the molting cycle of their host, yet the resultant cysts play no demonstrated role in their transmission to neonates; the trophozoite stage of the flagellates is passed directly from parents to offspring via hindgut fluids (proctodeal trophallaxis). This pattern suggests that encystment is a vestige from a gregarious cockroach ancestor, when the flagellates had a functional, two-stage life cycle and the cysts were horizontally transmitted among hosts via coprophagy. The strong integration between flagellate encystment cycles and host developmental physiology in Cryptocercus indicates that the relationship of the flagellates with their proposed gregarious cockroach ancestor was not commensal, but parasitic, with flagellates likely obtaining benefits by taking advantage of host gut metabolites and ingested plant debris. When vertical transmission evolved the parasites were ‘captured,’ and their fitness became inescapably embedded in the fitness of their host. The vertical transmission of gut flagellates and the origin of host subsociality via proctodeal trophallaxis can be considered two sides of the same coin. From the host point of view proctodeal trophallaxis marks the origination of parental care by provisioning neonates with nourishment, metabolites and beneficial microbiota. From the flagellate point of view, proctodeal trophallaxis was a shift from horizontal to vertical transmission, pushing them from the parasitic to the mutualistic end of the symbiotic spectrum, arguably making this host behavioral change the most critical juncture in the evolutionary trajectory of the termite lineage.

Cryptocercus cockroaches are remarkable for their similarity in external morphology while having a diversity in chromosome numbers. Most species are therefore delimited by karyotyping combined with phylogenetics. However, the investigation of chromosome diversity within a limited region is not well-studied, and the causes of their geographic distribution patterns remain unclear. Here, we applied a multipronged set of analyses that included external morphological analysis, chromosomal data, molecular species-delimitation methods and phylogenetic reconstruction after extensive sampling on the Western Sichuan Plateau (WSP) in western China. As a result, six new species were discovered, which increases the known species in WSP to 15. Multiple extinction-isolation events caused by the lifting of the Qinghai-Tibetan Plateau and by glacial periods likely account for the present-day distribution of WSP species. For Manchurian species, major extinctions may have been caused by the Quaternary glaciation and Cenozoic volcanic activities. We believe that three factors shaped the current distribution of Cryptocercus karyotypes: (1) a variability of chromosomes, (2) their low capability for dispersal, and (3) their vulnerability to climate change. [ABSTRACT FROM AUTHOR]

Sterile castes are a defining criterion of eusociality; investigating their evolutionary origins can critically advance theory. In termites, the soldier caste is regarded as the first acquired permanently sterile caste. Previous studies showed that juvenile hormone (JH) is the primary factor inducing soldier differentiation, and treatment of workers with artificial JH can generate presoldier differentiation. It follows that a shift from a typical hemimetabolous JH response might be required for soldier formation during the course of termite evolution within the cockroach clade. To address this possibility, analysis of the role of JH and its signaling pathway was performed in the termite Zootermopsis nevadensis and compared with the wood roach Cryptocercus punctulatus, a member of the sister group of termites. Treatment with a JH analog (JHA) induced a nymphal molt in C. punctulatus. RNA interference (RNAi) of JH receptor Methoprene tolerant (Met) was then performed, and it inhibited the presoldier molt in Z. nevadensis and the nymphal molt in C. punctulatus. Knockdown of Met in both species inhibited expression of 20-hydroxyecdysone (20E; the active form of ecdysone) synthesis genes. However, in Z. nevadensis, several 20E signaling genes were specifically inhibited by Met RNAi. Consequently, RNAi of these genes were performed in JHA-treated termite individuals. Knockdown of 20E signaling and nuclear receptor gene, Hormone receptor 39 (HR39/FTZ-F1β) resulted in newly molted individuals with normal worker phenotypes. This is the first report of the JH--Met signaling feature in termites and Cryptocercus. JH-dependent molting activation is shared by both taxa and mediation between JH receptor and 20E signalings for soldier morphogenesis is specific to termites. [ABSTRACT FROM AUTHOR]

Almost all examined cockroaches harbor an obligate intracellular endosymbiont, Blattabacterium cuenoti. On the basis of genome content, Blattabacteriumhas been inferred to recycle nitrogenwastes and provide amino acids and cofactors for its hosts. Most Blattabacterium strains sequenced to date harbor a genome of ~630 kbp, with the exception of the termite Mastotermes darwiniensis (~590 kbp) and Cryptocercus punctulatus (~614 kbp), a representative of the sister group of termites. Such genome reductionmay have led to the ultimate loss of Blattabacteriumin all termites other thanMastotermes. In this study, we sequenced 11 newBlattabacteriumgenomes fromthree species of Cryptocercus in order to shed light on the genomic evolution of Blattabacterium in termites and Cryptocercus. All genomes of Cryptocercus-derived Blattabacterium genomes were reduced (~614 kbp), except for that associated with Cryptocercus kyebangensis, which comprised 637 kbp. Phylogenetic analysis of these genomes and their content indicates that Blattabacterium experienced parallel genome reduction in Mastotermes and Cryptocercus, possibly due to similar selective forces. We found evidence of ongoing genome reduction in Blattabacterium from three lineages of the C. punctulatus species complex, which independently lost one cysteine biosynthetic gene. We also sequenced the genome of the Blattabacterium associated with Salganea taiwanensis, a subsocial xylophagous cockroach that does not vertically transmit gut symbionts via proctodeal trophallaxis. This genome was 632 kbp, typical of that of nonsubsocial cockroaches. Overall, our results show that genome reduction occurred on multiple occasions in Blattabacterium, and is still ongoing, possibly because of new associations with gut symbionts in some lineages. [ABSTRACT FROM AUTHOR]

Woodroaches from the genus Cryptocercus Scudder, 1862 are known to display low levels of morphological divergence, yet significant genetic divergence and variability in chromosome number. Compared with Cryptocercus taxa from North America, the diversity of the genus in Asia has received relatively little attention. We performed morphological and karyotypic examinations of multiple taxa from several previously unsampled mountainous areas of central and southwestern China, and identified nine candidate species primarily on the basis of chromosome number. We then investigated diversity across all Asian Cryptocercus, through phylogenetic analyses of 135 COI sequences and 74 28S rRNA sequences from individuals of 28 localities, including species delimitation analysis in General Mixed Yule Coalescent (GMYC) and Automatic Barcode Gap Discovery (ABGD). Phylogenetic results indicated that individuals from the same locality constituted well supported clades. The congruence of GMYC and ABGD results were in almost perfect accord, with 28 candidate species described on the basis of karyotypes (including the nine identified in this study). We provide evidence that each valley population in the Hengduan Mountains contains a separate evolving lineage. We conclude that the principal cause of the rich Cryptocercus diversity in China has been the uplift of the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

In this study, the complete mitochondrial genome of Cryptocercus meridianus was sequenced. The circular mitochondrial genome is 15,322 bp in size and contains 13 protein-coding genes, two ribosomal RNA genes (12S rRNA and 16S rRNA), 22 transfer RNA genes, and one D-loop region. We compare the mitogenome of C. meridianus with that of C. relictus and C. kyebangensis. The base composition of the whole genome was 45.20%, 9.74%, 16.06%, and 29.00% for A, G, C, and T, respectively; it shows a high AT content (74.2%), similar to the mitogenomes of C. relictus and C. kyebangensis. The protein-coding genes are initiated with typical mitochondrial start codons except for cox1 with TTG. The gene order of the C. meridianus mitogenome differs from the typical insect pattern for the translocation of tRNA-SerAGN, while the mitogenomes of the other two Cryptocercus species, C. relictus and C. kyebangensis, are consistent with the typical insect pattern. There are two very long non-coding intergenic regions lying on both sides of the rearranged gene tRNA-SerAGN. The phylogenetic relationships were constructed based on the nucleotide sequence of 13 protein-coding genes and two ribosomal RNA genes. The mitogenome of C. meridianus is the first representative of the order Blattodea that demonstrates rearrangement, and it will contribute to the further study of the phylogeny and evolution of the genus Cryptocercus and related taxa. [ABSTRACT FROM AUTHOR]

The wood-feeding cockroach Cryptocercus punctulatus Scudder (Blattodea: Cryptocercidae) is an important member of the dead wood (saproxylic) community in montane forests of the southeastern United States. However, its population biology remains poorly understood. Here, aspects of family group co-occurrence were characterized to provide basic information that can be extended by studies on the evolution and maintenance of sub-sociality. Broad sampling across the species’ range was coupled with molecular data (mitochondrial DNA (mtDNA) sequences). The primary questions were: (1) what proportion of rotting logs contain two or more different mtDNA haplotypes and how often can this be attributed to multiple families inhabiting the same log, (2) are multi-family logs spatially clustered, and (3) what levels of genetic differentiation among haplotypes exist within a log, and how genetically similar are matrilines of co-occurring family groups? Multi-family logs were identified on the premise that three different mtDNA haplotypes, or two different haplotypes among adult females, is inconsistent with a single family group founded by one male–female pair. Results showed that of the 88 rotting logs from which multiple adult C. punctulatus were sampled, 41 logs (47%) contained two or more mtDNA haplotypes, and at least 19 of these logs (22% overall) were inferred to be inhabited by multiple families. There was no strong evidence for spatial clustering of the latter class of logs. The frequency distribution of nucleotide differences between co-occurring haplotypes was strongly right-skewed, such that most haplotypes were only one or two mutations apart, but more substantial divergences (up to 18 mutations, or 1.6% uncorrected sequence divergence) do occasionally occur within logs. This work represents the first explicit investigation of family group co-occurrence in C. punctulatus, providing a valuable baseline for follow-up studies.

Aim We analysed data from an insect host ( Cryptocercus punctulatus) and its maternally-inherited obligate bacterial endosymbiont ( Blattabacterium cuenoti str . punctulatus) to address the following: (1) to what extent do these species exhibit cophylogenetic structure, (2) do the spatial-genetic structures of these species differ, and (3) what is the relative importance of codivergence versus other events in explaining congruence, or instances of incongruence, between their molecular phylogenies? Location The southern Appalachian Mountains, USA. Methods We conducted fine-scale population-level sampling and screening of DNA sequence variation in two mitochondrial genes from the host, and four genic or intergenic regions from the endosymbiont. Inferences were made using analyses that have the potential to identify isolated instances of cophylogenetic discord, uncover subtle differences in geographic locations of genetic discontinuities, and disentangle different evolutionary processes that contributed to observed patterns. Results The host and its endosymbiont showed similar phylogenetic and geographic patterns. Cophylogenetic analyses revealed that while topological discord is rare (and restricted within major clades), some instances are potentially non-negligible. Assessments of spatial-genetic structure showed that most abrupt breaks occur in the same locations, but they differ in strength, again underscoring some subtle discordance. The main process generating observed patterns was inferred to be codivergence due to host-tracking; however, incomplete lineage sorting seems likely to have also played a minor role. Main conclusions Our overarching finding of strong congruence is reflected by broader-scale cophylogenetic studies of related Cryptocercus and Blattabacterium taxa. Accordingly, we suggest that members of this symbiosis may provide an excellent opportunity for investigating geographic scaling of processes that affect biogeographic patterns. However, fine-scale sampling coupled with geospatial analyses detected rare and/or minor discordances that appeared to be localized within the most deeply dissected topographic regions of the southern Appalachian Mountains, and these warrant further exploration. [ABSTRACT FROM AUTHOR]

Approximately two-dozen species in three genera of the Neotropical suckermouth armored catfish family Loricariidae are the only described fishes known to specialize on diets consisting largely of wood. We conducted a molecular phylogenetic analysis of 10 described species and 14 undescribed species or morphotypes assigned to the wood-eating catfish genus Panaqolus , and four described species and three undescribed species or morphotypes assigned to the distantly related wood-eating catfish genus Panaque . Our analyses included individuals and species from both genera that are broadly distributed throughout tropical South America east of the Andes Mountains and 13 additional genera hypothesized to have also descended from the most recent common ancestor of Panaqolus and Panaque . Bayesian and maximum likelihood analyses of two mitochondrial and three nuclear loci totaling 4293 bp confirmed respective monophyly of Panaqolus , exclusive of the putative congener ‘ Panaqolus ’ koko , and Panaque . Members of Panaqolus sensu stricto were distributed across three strongly monophyletic clades: a clade of 10 generally darkly colored, lyretail species distributed across western headwaters of the Amazon Basin, a clade of three irregularly and narrowly banded species from the western Orinoco Basin, and a clade of 11 generally brown, broadly banded species that are widely distributed throughout the Amazon Basin. We erect new subgenera for each of these clades and a new genus for the morphologically, biogeographically and ecologically distinct species ‘ Panaqolus ’ koko . Our finding that perhaps half of the species-level diversity in the widespread genus Panaqolus remains undescribed illustrates the extent to which total taxonomic diversity of small and philopatric, yet apparently widely distributed, Amazonian fishes may remain underestimated. Ranges for two Panaqolus subgenera and the genus Panaque overlap with the wood-eating genus Cochliodon in central Andean tributaries of the upper Amazon Basin, which appear to be a global epicenter of wood-eating catfish diversity. [ABSTRACT FROM AUTHOR]

We identified the antifungal gene termicin in three species of Cryptocercus woodroaches. Cryptocercus represents the closest living cockroach lineage of termites, which suggests that the antifungal role of termicin evolved prior to the divergence of termites from other cockroaches. An analysis of Cryptocercus termicin and two β-1,3-glucanase genes ( GNBP1 and GNBP2), which appear to work synergistically with termicin in termites, revealed evidence of selection in these proteins. We identified the signature of past selective sweeps within GNBP2 from Cryptocercus punctulatus and Cryptocercus wrighti. The signature of past selective sweeps was also found within termicin from Cryptocercus punctulatus and Cryptocercus darwini. Our analysis further suggests a phenotypically identical variant of GNBP2 was maintained within Cryptocercus punctulatus, Cryptocercus wrighti, and Cryptocercus darwini while synonymous sites diverged. Cryptocercus termicin and GNBP2 appear to have experienced similar selective pressure to that of their termite orthologues in Reticulitermes. This selective pressure may be a result of ubiquitous entomopathogenic fungal pathogens such as Metarhizium. This study further reveals the similarities between Cryptocercus woodroaches and termites. [ABSTRACT FROM AUTHOR]

Cryptocercus is a genus of sub-social wood-feeding cockroaches that represents the sister group to the eusocial termites. We generated mitochondrial (12S + 16S rRNA, COII), nuclear (28S rRNA) and Blattbacterium endosymbiont (16S + 23S rRNA) sequence data for 8 new Chinese species, and combined these with previously available data to undertake the most extensive analysis of phylogenetic relationships within the genus to date. As expected, phylogenetic relationships among Blattabacterium strains were found to be congruent with those of their hosts. Three major clades were found to exist in Asian populations, one representing taxa from the Hengduan mountains in Southwestern China, a second including taxa from Russia, Korea, Northeastern China, and Yunnan in the Hengduan Mountains, and a third including taxa from the Qinling Mountains and Daba Mountains in Central China. A molecular dating analysis using 7 termite fossils to calibrate the molecular clock indicated that the divergence of American and Asian Cryptocercus occurred 55.09 Ma (41.55–72.28 Ma 95% CI), and that the radiations of American and Asian taxa occurred 28.48 Ma (20.83–37.95 Ma 95% CI) and 20.97 Ma (15.78–27.21 Ma 95% CI) respectively. Reconstruction of ancestral geographic distributions using S-DIVA suggested Cryptocercus was originally distributed across both continents, as opposed to ancestral migration of Cryptocercus from one continent to the other. The last common ancestor of Asian Cryptocercus was inferred to have existed in Central China. An examination of male chromosome numbers in Asian Cryptocercus showed that diploid numbers vary from 2 n = 15 to 2 n = 41, and indicates the presence of eight new species. Our study represents the most comprehensive phylogenetic and biogeographic study yet performed for this important group of cockroaches. [ABSTRACT FROM AUTHOR]

The rapid growth in microbiome research, particularly during the last 15 years, has revealed the crucial contributions of microbial communities to numerous physiological functions in animals, including digestion, immunity and reproduction. The permanent coexistence of these various bionts forms the holobiont (namely, the host and its microbiota). This review describes the relationships between xylophagous insects and their microbiota in an attempt to understand the characteristics that have determined bacterial fidelity over generations and throughout evolutionary history. Symbiotic interactions have probably played a central role in the evolutionary success of these insects, allowing their adaptation to unexploited ecological niches that are nutritionally deficient and/or unbalanced. Moreover, insect symbionts have provided the enzymatic capabilities that enable the synthesis of nutrients (carbon and nitrogen sources for the host) from recalcitrant plant polymers (cellulose, hemicellulose, pectin or lignin). [ABSTRACT FROM AUTHOR]

The complete mitogenome of the subsocial wood-eating cockroachCryptocercus kyebangensiswas sequenced and compared with that of another Asian cockroach,Cryptocercus relictusand the primitive termiteMastotermes darwiniensis. The complete mitogenome ofC. kyebangensisis a closed circular molecule of 15,720 bp, containing13 protein-coding genes, two ribosomal RNA genes (12S rRNA and 16S rRNA), 22 transfer RNA genes, and one D-loop region. Nucleotide composition of theC. kyebangensismitogenome shows an AT bias (74.4%), in particular, 46.0% A, 28.4% T, 9.7% G, and 15.9% C. GC skews are similar among the mitogenomes ofC. kyebangensis,C. relictus, andM. darwiniensis, but AT skew is stronger inCryptocercusmitogenomes than in theM. darwiniensismitogenome. The whole mitogenome ofC. kyebangensisshowed 88.8% nucleotide similarity to that ofC. relictusbut only 74.9% similarity to that ofM. darwiniensis. Phylogenetic analyses, based on amino acid sequences of the 13 mitochondrial proteins, showed that theCryptocercusclade has a sister relation with termites, including the primitive termiteM. darwiniensis. Sister relations of Blattidae and Blattellidae, with the clade Cryptocercidae + Isoptera as a sister group, are also evident. Polyphagidae (Eupolyphaga sinensis) appears to be most basal in the phylogenetic trees, showing sister relations with the remaining cockroaches. [ABSTRACT FROM AUTHOR]

Two new Chinese Cryptocercus (Blattodea: Cryptocercidae) species, C. arcuatus sp. nov. and C. convexus sp. nov., are described together with photographs. This description includes the external structure of the adults and structures of the female genitalia. A comparative study of female genitalia was based on the 5 Chinese species in the family Cryptocercidae. Significant differences in female genitalia of Cryptocercidae are summarized. A key to these 5 species and a checklist of the species of Cryptocercus worldwide are provided. [ABSTRACT FROM AUTHOR]

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 compositions of the Bacteroidetes, Elusimicrobia, Tenericutes, Spirochaetes, and Synergistes were structured by host phylogeny perhaps due to their symbiotic associations with protists. All together, 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 have played a larger role in community composition than previously expected. [ABSTRACT FROM AUTHOR]

The gut of wood-feeding insects is a microhabitat for a specialized community of microbes, including bacteria and several groups of eukaryotes such as nematodes, parabasalids and fungi. The characterization of gut yeast communities from a variety of insects has shown that certain yeasts often are associated with the insects. The gut of wood-feeding insects is rich in ascomycete yeasts and in particular xylose-fermenting (X-F) and assimilating yeasts have been consistently present in the gut of lignicolous insects. The objective of this study was the characterization of the yeast flora from the gut of the wood roach Cryptocercus sp. (Blattodea: Cryptocercidae). Five wood roaches were collected along the Appalachian Trail near the border between Tennessee and North Carolina, USA. We isolated 18 yeast strains from the wood roaches identified as Sugiyamaella paludigena and Sugiyamaella lignohabitans, xylose-assimilating yeasts, and Scheffersomyces cryptocercus (NRRL Y-48824T = CBS 12658) a new species of X-F yeast. The presence of X-F and certain non X-F yeasts in the gut of the subsocial wood roach Cryptocercus sp. extends the previous findings of associations between certain ascomycete yeasts and lignicolous insects. New combinations were made for 13 asexual members of the Sugiyamaella clade. [ABSTRACT FROM AUTHOR]

The objective of this study is to elucidate the evolutionary rate ofCryptocercusSSU rDNAs based on the relative rate test (RRT) and comparative analysis of the primary sequences. In the RRTs, the evolutionary rate differences (dKs) of theCryptocercusSSU rDNAs were not statistically significant (0.107

Abstract: Despite their ecological significance as decomposers and their evolutionary significance as the most speciose eusocial insect group outside the Hymenoptera, termite (Blattodea: Termitoidae or Isoptera) evolutionary relationships have yet to be well resolved. Previous morphological and molecular analyses strongly conflict at the family level and are marked by poor support for backbone nodes. A mitochondrial (mt) genome phylogeny of termites was produced to test relationships between the recognised termite families, improve nodal support and test the phylogenetic utility of rare genomic changes found in the termite mt genome. Complete mt genomes were sequenced for 7 of the 9 extant termite families with additional representatives of each of the two most speciose families Rhinotermitidae (3 of 7 subfamilies) and Termitidae (3 of 8 subfamilies). The mt genome of the well supported sister-group of termites, the subsocial cockroach Cryptocercus, was also sequenced. A highly supported tree of termite relationships was produced by all analytical methods and data treatment approaches, however the relationship of the termites+ Cryptocercus clade to other cockroach lineages was highly affected by the strong nucleotide compositional bias found in termites relative to other dictyopterans. The phylogeny supports previously proposed suprafamilial termite lineages, the Euisoptera and Neoisoptera, a later derived Kalotermitidae as sister group of the Neoisoptera and a monophyletic clade of dampwood (Stolotermitidae, Archotermopsidae) and harvester termites (Hodotermitidae). In contrast to previous termite phylogenetic studies, nodal supports were very high for family-level relationships within termites. Two rare genomic changes in the mt genome control region were found to be molecular synapomorphies for major clades. An elongated stem-loop structure defined the clade Polyphagidae + (Cryptocercus +termites), and a further series of compensatory base changes in this stem-loop is synapomorphic for the Neoisoptera. The complicated repeat structures first identified in Reticulitermes, composed of short (A-type) and long (B-type repeats) defines the clade Heterotermitinae+Termitidae, while the secondary loss of A-type repeats is synapomorphic for the non-macrotermitine Termitidae. [Copyright &y& Elsevier]

Abstract: Recent challenges in the study of animal behavior are to detect genes related to behavior and how the genes exert their influence on morphological and behavioral plasticity, particularly as related to the mechanism of insect sociability. In this study, we discovered genes related to parental care behavior in social insects. Woodroaches of the genus Cryptocercus provide nutritious materials and symbiotic protists via proctodeal feeding to their young during early developmental stages. Thus, they are a good model species for discovering genes related to parental care behavior. We screened eight differentially expressed genes (DEG1–DEG8) from adult Cryptocercus females exhibiting maternal care behavior. Of the proteins translated from the screened genes, DEG7 showed high homology to apolipophorin-III-like proteins. Analysis of diverse molecular features revealed that DEG7 was a partial clone encoding apoLp-III, which plays essential roles in hemolymph-lipid transport processes in insects. Isolation of full-length cDNAs for the DEGs identified in this study would be very helpful for a functional annotation of the individual genes and further understanding of maternal care behavior at the molecular level in the future. [Copyright &y& Elsevier]

Lophomonas striata is a multiflagellate parabasalid commensal in the hindgut of the omnivorous cockroaches Blatta orientalis and Periplaneta americana. Its closest relatives were traditionally thought to include similar multiflagellate parabasalids with a single flagellar area that degenerates during mitosis, such as Joenia and Kofoidia. However, molecular phylogenetic analyses have shown that “lophomonads” are not monophyletic. We have determined the SSU rRNA sequence of L. striata and we find that it branches sister to the Trichonymphida with strong support. This is surprising because all other lophomonads sampled to date branch within the Cristamonadida, and the order Trichonymphida (e.g. Trichonympha, Pseudotrichonympha, and Hoplonympha) is both morphologically coherent and monophyletic in SSU rRNA phylogenies. Trichonymphida, unlike the lophomonads, share a bilateral symmetry, in which their multiple flagella occur in two (or sometimes four) regions, and instead of degenerating upon mitosis, half of the flagella are passed to each daughter cell. The single apical flagellar region characteristic of lophomonads is therefore either plesiomorphic or it has arisen multiple times in parabasalids; our phylogenetic analyses and available ultrastructural evidence suggest the latter. Our results also suggest that parabasalid gut symbionts may have been vertically transmitted in cockroaches before the common ancestor of Cryptocercus and termites. [ABSTRACT FROM AUTHOR]

Basal termites possess two developmental features that eusocial Hymenoptera lack: the majority of colony members are juveniles whose somatic and reproductive development is temporarily or permanently suspended, and individual development is characterized by extreme phenotypic plasticity. An examination of the literature indicates that the basis for these unique ontogenetic characters is not the prolongation of a pronymphal stage into postembryonic development, as recently suggested. Like other hemimetabolous insects, termites have three embryonic cuticles, and the pronymphal (EC3) cuticle is shed during or shortly after hatch. Nonetheless, a different developmental landmark, dorsal closure, occurs later during embryogenesis in termites than it does in their cockroach relatives, clearly indicating ontogenetic repatterning from an ancestral state. An alternate hypothesis for the origin of isopteran phenotypic plasticity becomes apparent if we remain focused on the phylogenetic and social context of termite evolution. Altricial development occurs in both vertebrate and invertebrate taxa, evolves in response to the parental environment, and is displayed by two distantly related, biparental, wood-feeding cockroaches, including Cryptocercus, the sister-group to termites. It is therefore likely the condition was present in subsocial termite ancestors, and played a complex, multidimensional role in the transition to eusociality. Most relevant to current arguments is that a shift in responsibility for the care of altricial dependents, from parents to the first nutritionally independent nymphs in the family (alloparents), resulted in the developmental stasis of alloparents at a relatively young age. Because early instar cockroaches are not metamorphically competent, these young alloparents would have provided a novel developmental template on which selection could act. [ABSTRACT FROM AUTHOR]

Trichonympha is one of the most complex and visually striking of the hypermastigote parabasalids—a group of anaerobic flagellates found exclusively in hindguts of lower termites and the wood-feeding cockroach Cryptocercus—but it is one of only two genera common to both groups of insects. We investigated Trichonympha of Cryptocercus using light and electron microscopy (scanning and transmission), as well as molecular phylogeny, to gain a better understanding of its morphology, diversity, and evolution. Microscopy reveals numerous new features, such as previously undetected bacterial surface symbionts, adhesion of post-rostral flagella, and a distinctive frilled operculum. We also sequenced small subunit rRNA gene from manually isolated species, and carried out an environmental polymerase chain reaction (PCR) survey of Trichonympha diversity, all of which strongly supports monophyly of Trichonympha from Cryptocercus to the exclusion of those sampled from termites. Bayesian and distance methods support a relationship between Trichonympha species from termites and Cryptocercus, although likelihood analysis allies the latter with Eucomonymphidae. A monophyletic Trichonympha is of great interest because recent evidence supports a sister relationship between Cryptocercus and termites, suggesting Trichonympha predates the Cryptocercus-termite divergence. The monophyly of symbiotic bacteria of Trichonympha raises the intriguing possibility of three-way co-speciation among bacteria, Trichonympha, and insect hosts. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Examination of surface morphology of the oxymonad genus Saccinobaculus from the gut of the wood-feeding cockroach Cryptocercus punctulatus with scanning and transmission electron microscopy reveals several new characters not observable with light microscopy. These include small concavities covering the external surface, a glycocalyx, coated pinocytotic vesicles, and, in one species, unidentified, membrane-bounded organelles with a granular matrix that may represent peroxisomal or mitochondrial derivatives. Unlike representatives of some other oxymonad families, Saccinobaculus lacks extracellular surface structures, a holdfast, and, generally, ectobiotic bacteria. We examined the evolution of these and other characters in light of previously published phylogenies of oxymonads based on molecular data. The presence of concavities in Saccinobaculus and families Pyrsonymphidae and Oxymonadidae strengthens support for a clade comprising these three families. A glycocalyx appears to be a synapomorphy of all oxymonads, and the presence of ectobiotic bacteria also appears to be ancestral to oxymonads, but lost in Saccinobaculus. A holdfast appears to have arisen multiple times. We hypothesize that concavities may play a role in a two-step mechanism for the accumulation and internalization of specific solutes, and that the highly motile and morphologically plastic nature of Saccinobaculus cells limits the possibility of retaining a covering of ectobiotic bacteria. [Copyright &y& Elsevier]

Abstract: Isoptera are highly specialized cockroaches and are one of the few eusocial insect lineages. Cryptocercus cockroaches have appeared to many as ideal models for inference on the early evolution of termites, due to their possible phylogenetic relationship and several shared key attributes in life history. Recently, Pellens, Grandcolas, and colleagues have proposed the blaberid cockroach Parasphaeria boleiriana to be an alternative model for the early evolution in termites. We compare the usefulness of Cryptocercus and P. boleiriana as models for termite evolution. Cryptocercus and lower Isoptera (1) can both feed on comparatively recalcitrant wood, (2) have an obligate, rich and unique hypermastigid and oxymonadid fauna in the hindgut, (3) transfer these flagellates to the next generation by anal trophallaxis, (4) have social systems that involve long-lasting biparental care, and, finally, (5) are strongly suggested to be sister groups, so that the key attributes (1)–(4) appear to be homologous between the two taxa. On the other hand, P. boleiriana (1) feeds on soft, ephemeral wood sources, (2) shows no trace of the oxymonadid and hypermastigid hindgut fauna unique to Cryptocercus and lower Isoptera, nor does it have any other demonstrated obligate relationship with hindgut flagellates, (3) is likely to lack anal trophallaxis, (4) has only a short period of uniparental brood care, and (5) is phylogenetically remote from the Cryptocercus +Isoptera clade. These facts would argue against any reasonable usage of P. boleiriana as a model for the early evolution of Isoptera or even of the clade Cryptocercus +Isoptera. Cryptocercus thus remains an appropriate model-taxon-by-homology for early termite evolution. As compared to P. boleiriana, some other Blaberidae (such as the Panesthiinae Salganea) appear more useful as model-taxa-by-homoplasy for the early evolution of the Cryptocercus +Isoptera clade, as their brooding behavior is more elaborate than in P. boleiriana. [Copyright &y& Elsevier]

Nitrogen fixation by gut microorganisms is one of the crucial aspects of symbiosis in wood-feeding termites since these termites thrive on a nitrogen-poor diet. In order to understand the evolution of this symbiosis, we analysed the nitrogenase structural gene nifH in the gut microbial communities. In conjunction with the published sequences, we compared approximately 320 putatively functional NifH protein sequences obtained from a total of 19 termite samples that represent all the major branches of their currently proposed phylogeny, and from one species of the cockroach Cryptocercus that shares a common ancestor with termites. Using multivariate techniques for clustering and ordination, a phylogeny of NifH protein sequences was created and plotted variously with host termite families, genera, and species. Close concordance was observed between NifH communities and the host termites at genus level, but family level relationships were not always congruent with accepted termite clade structure. Host groups examined included basal families (Mastotermitidae, Termopsidae, Kalotermitidae, as well as Cryptocercus), the most derived lower termite family Rhinotermitidae, and subfamilies representing the advanced and highly diverse apical family Termitidae (Macrotermitinae, Termitinae, and Nasutitermitinae). This selection encompassed the major nesting and feeding styles recognized in termites, and it was evident that NifH phylogenetic divergence, as well as the occurrence of alternative nitrogenase-type NifH, was to some extent dependent on host lifestyle as well as phylogenetic position. [ABSTRACT FROM AUTHOR]

Abstract: Cockroaches have always been used to understand the first steps of social evolution in termites because they are close relatives with less complex and integrated social behaviour. Termites are all eusocial and ingroup comparative analysis would be useless to infer the origin of their social behaviour. The cockroach genus Cryptocercus was used as a so-called “prototermite” model because it shows key-attributes similar to the termites (except Termitidae): wood-feeding, intestinal flagellates and subsocial behaviour. In spite of these comparisons between this subsocial cockroach and eusocial termites, the early and remote origin of eusocial behaviour in termites is not well understood yet and the study of other relevant “prototermite” models is however needed. A molecular phylogenetic analysis was carried out to validate a new “prototermite” model, Parasphaeria boleiriana which shows a peculiar combination of these key-attributes. It shows that these attributes of Parasphaeria boleiriana have an independent origin from those of other wood-eating cockroaches and termites. The case of P. boleiriana suggests that a short brood care was selected for with life on an ephemeral wood resource, even with the need for transmission of flagellates. These new phylogenetic insights modify evolutionary hypotheses, contradicting the assumption made with Cryptocercus model that a long brood care is necessary for cooperation between broods in the “shift-in-dependent-care” hypothesis. An ephemeral wood resource is suggested to prompt generation overlap and the evolution of cooperation, even if brood care is shortened. [Copyright &y& Elsevier]

The distribution of a species is determined by a set of ecological correlates (biotic and abiotic factors) and historical phenomena that define and constrain its ecological niche. By examining the geographical projection of the ecological niche, it is possible to identify areas that are suitable for the species ecologically but that are not actually inhabited. Previous studies have used such discords to anticipate the existence of undescribed species; the absence of species may also result from historical barriers that have prevented colonization of the area. Thus, discords between potential and realized niches of a species may result from aspects of the species’s biology (e.g. lack of dispersal ability, specific habitat requirements) or from barriers to dispersal. In this study, we developed ecological niche models of the five Nearctic species of wood-feeding cockroaches in the genus Cryptocercus. One species, C. clevelandi, occurs in the western USA and four ( C. darwini, C. garciai, C. punctulatus, C. wrighti) are distributed in the Appalachian Mountains in the eastern USA. In general, modelled niches for all species showed ecological restriction relative to the total range of available conditions. Niche models for the eastern USA species predicted the geographical distributions of the other eastern USA species, with the exception of C. garciai, suggesting general overall conservatism in ecological characteristics. Some interspecific differences in modelled niches were also apparent. In general, C. clevelandi was predicted to occupy cooler and drier areas relative to the eastern USA species; among the eastern USA species, C. darwini and C. garciai were predicted to inhabit warmer areas relative to C. punctulatus and C. wrighti. Interspecific differences and similarities were consistent with the phylogenetic relationships among Cryptocercus species previously reported. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 457–466. [ABSTRACT FROM AUTHOR]

The oxymonads are a group of structurally complex anaerobic flagellates about which we know very little. They are found in association with complex microbial communities in the guts of animals. There are five recognized families of oxymonads; molecular data have been acquired for four of these. Here, we describe the first molecular data from the last remaining group, represented by Saccinobaculus, an organism that is found exclusively in the hindgut of the wood-eating cockroach Cryptocercus. We sequenced small subunit ribosomal RNA (SSU rRNA) from total gut DNA to describe Saccinobaculus SSU rRNA diversity. We also sequenced SSU rRNA from manually isolated cells of the two most abundant and readily identifiable species: the type species Saccinobaculus ambloaxostylus and the taxonomically contentious Saccinobaculus doroaxostylus. We inferred phylogenetic trees including all five known oxymonad subgroups in order to elucidate the internal phylogeny of this poorly studied group, to resolve some outstanding issues of the taxonomy and identification of certain Saccinobaculus species, and to investigate the evolution of character states within it. Our analysis recovered strong support for the existence of the five subgroups of oxymonads, and consistently united the subgroups containing Monocercomonoides and Streblomastix, but was unable to resolve any further higher-order branching patterns. [Copyright &y& Elsevier]

Members of the genus Cryptocercus are xylophagous, wingless, subsocial cockroaches that inhabit decaying logs in temperate forests. Given their winglessness, subsocial living, and the patchy distribution of food resources (decomposing logs), it is likely that Cryptocercus populations are substructured. Allozyme variation at eight polymorphic loci was assayed for 10 subpopulations of Cryptocercus darwini and 13 subpopulations of Cryptocercus wrighti, both of which are distributed in the Appalachian Mountains. The mean FIS was 0.13 and FST was about 0.25 for both C. darwini and C. wrighti. The relatedness among individuals of a subpopulation of both species was not significantly different from that expected among full sibs. In terms of how genetic variation is partitioned, C. darwini and C. wrighti differed from each other substantially. Most of the genetic variation occurred among subpopulations of C. wrighti in the same region and among subpopulations of C. darwini in different regions. We discuss the factors that may have contributed to the observed similarities and differences in the breeding structure of the two species. [ABSTRACT FROM AUTHOR]

Appalachian species of Cryptocercus (Dictyoptera: Cryptocercidae) display considerable genetic variation, but little morphological variation has been reported. We employed light and scanning electron microscopy to investigate variation in male and female reproductive structures among four species of Cryptocercus. Our results indicated consistent, species-specific differences exist in the genitalia of the four species. Males exhibit moderate interspecific differences in the shape of the subgenital plate and third left phallomere hook. Females display consistent interspecific differences in the size of setae on the basivalvula and great differences in size, number, and pattern of setae on the base of the second valves. Together, the interspecific variation in female reproductive structures can be used to identify each of the four Cryptocercus species that occur in the Appalachian Mountains. [Copyright &y& Elsevier]

Phylogenetic relationships and biogeography of Northeast Asian Cryptocercus were inferred based on the DNA sequences of mitochondrial COII and 16S rRNA genes and nuclear 18S rRNA gene. The results suggest that two clades exist in Korean populations. The southwestern population (Cryptocercus from Jiri-san) was more closely related to the populations from Northeast China and eastern Russia than to all the other Korean Cryptocercus. According to molecular-based estimated divergence times, the divergence event occurred between Cryptocercus in Jiri-san, Northeast China and eastern Russia and those in the remaining South Korea during the Miocene (7.5–17.4 Myr ago), and then the divergence event between Cryptocercus in Jiri-san and those in Northeast China and eastern Russia occurred 0.8–1.9 Myr ago. In the Korean Peninsula, Jiri-san is located in the most southwestern region among the high mountains surveyed. The location is the farthest from Northeast China and eastern Russia among sampling localities in South Korea. Thus, it was unexpected that the southwestern populations are more closely related to those from Northeast China and eastern Russia rather than to the other Korean Cryptocercus. Based on Korean topography and estimated divergence times, possible scenarios are proposed for the current geographical distribution of Korean Cryptocercus. [Copyright &y& Elsevier]

In a recent paper, Kambhampati, Clark & Brock ( Biological Journal of the Linnean Society 2002; 75: 163–172) suggested that members of the wood-feeding cockroach genus Cryptocercus are differentially adapted to two features of the environment: host log species and elevation. A re-examination of the evidence, however, fails to support their hypothesis. First, their analysis of host preferences was based on a general description of forest type, rather than on the level at which host choice occurs: the dead tree on the forest floor. Cryptocercus in both East Asia and in the eastern United States have been collected from a range of evergreen and deciduous logs. Although C. clevelandi in the western United States is associated primarily with conifers, no evidence of host adaptation exists. Second, there is no support for the described evolutionary trend toward low-altitude habitats among karyotype groups of C. punctulatus in the eastern United States. The findings of Kambhampati et al. are based on inadequate sampling; they did not include the highest and most topographically complex regions of the Southern Appalachian Mountains, nor the lower elevation border regions to the north and east of the range. An analysis of elevational data from 71 collection sites revealed no significant difference in the range of altitudes at which karyotype groups of C. punctulatus are found. In contrast to the suggestions of these authors, a lack of specialization with regard to altitude and host logs was probably the factor that allowed all taxa in the genus to thrive during climatically driven shifts in the geographical location and plant species composition of northern hemisphere mesic forests. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 223–233. [ABSTRACT FROM AUTHOR]

We investigated the territorial behavior of Cryptocercus kyebangensis from the viewpoint of offspring protection. Aggressive behavior against adult intruders occurred more frequently in resident adults with their young than those without their young. Resident adults without offspring more frequently attacked intruders of the same sex than those of the opposite sex, whereas those with offspring attacked regardless of the sex of adult intruders. In paired residents, cooperative territorial behavior occurred in a higher proportion in pairs with offspring than those without offspring. Responses of residents to nymphal intruders depended on the head capsule size of the intruders. Resident adults rarely attacked intruders smaller than their own offspring but frequently attacked larger intruders. Resident nymphs frequently attacked intruders smaller than themselves, whereas they escaped or showed jerking behavior when they encountered larger intruders. [ABSTRACT FROM AUTHOR]