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Simple Summary: It is important to compare the developmental stages of lower termites and recognize the differences between parthenogenetic and sexual eggs in order to describe their embryonic development concisely. In contrast with sexual eggs, parthenogenetic eggs have a lower rate of development and hatching success. Moreover, several genes differentially expressed between the two types of embryos have been identified. By addressing such a problem in the current research, the lack of understanding in the differences and the developmental processes between the two categories of eggs can be resolved. The aim of the study was to evaluate the development, discover the differences, and determine the gene expression patterns related to the variances between the two types of eggs. The authors discovered a number of genes with differential expression between the two categories of embryos, which explain these differences. These results present important insights into the reproductive processes of termites and highlight the need to contribute further research in this area to achieve a better understanding of termite biology. Worldwide, termites are one of few social insects. In this research, the stages of embryonic development in the parthenogenetic and sexual eggs of Reticulitermes aculabialis and R. flaviceps were observed and described. In R. flaviceps, the egg development of the FF and FM groups happened during the early phases of development, whereas in R. aculabialis, this appeared mainly during the late phase of development. The variance in the number of micropyles between the R. flaviceps FF colony type and the R. aculabialis FF colony type was statistically significant. Five stages of egg development were found in both types of R. aculabialis but only the sexual eggs of R. flaviceps. In R. flaviceps, 86% of the parthenogenetic eggs stopped growing during the blastoderm development, with the yolk cell assembling frequently in the center of the egg. According to the results of the single-cell transcriptome sequencing, we investigated the egg-to-larval expression level of genes (pka, map2k1, mapk1/3, hgk, mkp, and pax6) and indicated that the levels of essential gene expression in RaFF were considerably higher than in RfFF (p < 0.05). We also discovered that the oocyte cleavage rate in the FF colony type was considerably lower in R. flaviceps compared to R. aculabialis, which gave rise to a smaller number of mature oocytes in R. flaviceps. During ovulation in both species, oocytes underwent activation and one or two cleavage events, but the development of unfertilized eggs ceased in R. flaviceps. It was shown that termite oocyte and embryonic development were heavily influenced by genes with significant expressions. Results from the databases KEGG, COG, and GO unigenes revealed the control of numerous biological processes. This study is the first to complete a database of parthenogenetic and sexual eggs of R. flaviceps and R. aculabialis. [ABSTRACT FROM AUTHOR]

The longevity phenomenon is entirely controlled by the insulin signaling pathway (IIS-pathway). Both vertebrates and invertebrates have IIS-pathways that are comparable to one another, though no one has previously described de novo transcriptome assembly of IIS-pathway-associated genes in termites. In this research, we analyzed the transcriptomes of both reproductive (primary kings "PK" and queens "PQ", secondary worker reproductive kings "SWRK" and queens "SWRQ") and non-reproductive (male "WM" and female "WF" workers) castes of the subterranean termite Reticulitermes chinensis. The goal was to identify the genes responsible for longevity in the reproductive and non-reproductive castes. Through transcriptome analysis, we annotated 103,589,264 sequence reads and 184,436 (7G) unigenes were assembled, GC performance was measured at 43.02%, and 64,046 sequences were reported as CDs sequences. Of which 35 IIS-pathway-associated genes were identified, among 35 genes, we focused on the phosphoinositide-dependent kinase-1 (Pdk1), protein kinase B2 (akt2-a), tuberous sclerosis-2 (Tsc2), mammalian target of rapamycin (mTOR), eukaryotic translation initiation factor 4E (EIF4E) and ribosomal protein S6 (RPS6) genes. Previously these genes (Pdk1, akt2-a, mTOR, EIF4E, and RPS6) were investigated in various organisms, that regulate physiological effects, growth factors, protein translation, cell survival, proliferation, protein synthesis, cell metabolism and survival, autophagy, fecundity rate, egg size, and follicle number, although the critical reason for longevity is still unclear in the termite castes. However, based on transcriptome profiling, the IIS-pathway-associated genes could prolong the reproductive caste lifespan and health span. Therefore, the transcriptomic shreds of evidence related to IIS-pathway genes provide new insights into the maintenance and relationships between biomolecular homeostasis and remarkable longevity. Finally, we propose a strategy for future research to decrypt the hidden costs associated with termite aging in reproductive and non-reproductive castes. [ABSTRACT FROM AUTHOR]

It would not surprise that two related termite species are similar in many traits, especially those related to reproduction such as similarity in sexual organs, spermathecae, gametes, glands in genital organs and micropyles of eggs. Because similarities of them are thought to be directly linked to increase their reproductive fitness. Moreover, the key data showing successful hybridization between the two termite species under laboratory conditions and in the field. The present study was conducted on the base of morphometric analyses and histological examinations of the sperm, testes, vas deferens, accessory glands, ejaculatory duct and spermathecae of Reticulitermes flaviceps and R. chinensis. The accessory glands of male alates were found without spermatozoa in both termites. The patterns of spermatogenesis in the alate testes of both species were quite similar and the gametes (spermatogonia, spermatocytes, spermatids, and sperm) produced in a sequence of essential developmental processes. The aflagellated sperm were transferred by male numerous times in a day after few copulations. They were stored alive in spermatheca by female and used for fertilization of oocytes. The nutrition was obtained by the sperm from the secretory cells, for a living and being functional during storage in the spermathecae. The spermathecae have finger shape and their thick walls divided into 4 type cells. Anatomically spermathecae of the two termite species consisted of lumens, ductules, and few glands, in thick wall structures. While the entire examinations revealed no more differences in the sexual organs of the two different species since R. flaviceps and R. chinensis can hybridize under experimental conditions as well as in wild to produce offspring. The similarity in the structure of sexual organs of both heterospecies provides possible evidence for the successful hybridization. [ABSTRACT FROM AUTHOR]

The subterranean termite Reticulitermes aculabialis was firstly described from the soldier caste in 1977 and diagnose from the imago has been difficult due to the lack of description of alate. In this paper, a detailed description of alate for R. aculabialis is presented, including additional data to soldiers. The data are chiefly based on the external morphology of R. aculabialis imago, which has never been described before. All the samples of alates and soldiers were collected in Xi'an, Shaanxi province, China. All of the essential specific characteristics are illustrated for identification purposes. [ABSTRACT FROM AUTHOR]

Aging and longevity is a dynamic, chronological process assumed to originate from several hallmarks causing archetypal and beguiling cycles with incredible natural diversity. This phenomenon is widely observed in different animals, and the estimated age of Drosophila melanogaster, Caenorhabditis elegans,Daphnia longispina are a few days to weeks. Reproductive termites live for 30 years, although the root cause of longevity in termite castes is still debated for molecular and cellular changes. Insulin and insulin signaling pathway‐related (IIS) genes are important metabolic factors (glucose) highly conserved in lower to higher organisms. Therefore, in this study, we pooled Reticulitermes chinensis castes as primary king (PK), primary queen (PQ), ergatoid king "SWRK" and queen "SWRQ", male (WM), and female (WF) workers. We determined transcriptome sequencing of R. chinensis castes as a model organism for longevity to investigate the insulin signaling pathway and longevity genes. Through RNA‐sequencing, we identified 35 IIS‐pathway‐related genes out of 343 to the KEGG pathway in ergatoid king and queen, PK, PQ, WM, and WF. Among these genes, Tsc2, akt2‐a, mTOR, EIF4E, Pdk1, and RPS expressed highly in ergatoid king and queen, PK, and PQ. However, a significant cornerstone tradeoff between reproductive and non‐reproductive efforts for early life is essential for evolutionary longevity. The present study concludes that a highly conserved IIS‐pathway is evidence for the prolonged termite reproductive life span. We recommended devoting insulin signaling pathway genes to their biological function for termite survival and new insights into the maintenance and relationships between biomolecular homeostasis and remarkable longevity. [ABSTRACT FROM AUTHOR]