Protein synthesis in ‘fat body’ and ovary of the physogastric queen of Macrotermes subhyalinus

In the physogastric queen of Macrotermes subhyalinus the fat body, when incubated in vitro with [¹⁴C] amino acids, synthesizes proteins at a much slower rate than ovarian tissue under the same conditions. Only a very small amount of the labelled proteins is released into the incubation medium. Oxygen consumption of the queen fat body is higher than that of ovarian tissue and the fat body of the king. At 3 hr after injection of [¹⁴C] amino acids in vivo the total fat body of the queen contains three to six times less labelled proteins than the two entire ovaries. It is assumed that in contrast to other insects the physogastric termite queen synthesizes vitellogenins mainly in the ovarian follicle cells and not in the fat body.The fat body of the king with a high incorporation rate of [¹⁴C] amino acids and a rapid release of synthesized protein into the incubation medium is comparable to the fat body of other insects.     

Origin and formation of the royal fat body of the higher termite queens

The formation of the royal fat body was studied by electron microscopy in three species of higher termites (Macrotermes bellicosus, Macrotermes subhyalinus, and Cubitermes fungifaber). The swarming alate imago has a storage fat body typical of most insects. In non-physogastric young queens, during the fasting period, the adipocytes deplete their reserves and then, along with the increased vitellogenesis, acquire protein-synthesizing structures (R.E.R.). During the development of physogastry they progressively specialize in protein synthesis and secretion and undergo many cell divisions. The cytological change is paralleled by a spatial reorganization of the fat body. Observations on the transformation of imaginal adipocytes into royal adipocytes show that the royal fat body is derived from the imaginal fat body and not from the tracheal cells as previously claimed.     

Head-butting as an Early Indicator of Reproductive Disinhibition in the Termite Zootermopsis nevadensis

In lower termites, functionally sterile larval helpers are totipotent—capable of becoming reproductively active with the loss of their colony’s king or queen. Full reproductive development may take several weeks, but initiation of this developmental response most likely occurs shortly after colony members detect when a reproductive-specific signal is missing. We investigated the early response of termite helpers to the removal of their king and queen in the basal termite species Zootermopsis nevadensis. Within 6–12 h after reproductives were removed, helpers displayed an increase in head-butting—a behavior associated with dominance in other termite species as well as in closely related roaches. The loss of just one reproductive, either the king or queen, was also sufficient to cause an increase in head-butting. We did not find evidence, however, that this response was sex-specific: males and females were equally likely to increase head-butting independent of the sex of the reproductive that was removed. Finally, we discovered that reproductive-specific compounds present on the cuticle of king and queen termites were also present in their feces, but the presence of the feces did not seem sufficient to inhibit the increased head-butting after the reproductives were removed. Collectively, these results indicate that termite workers readily detect the loss of reproductives in their colony and that they at least initially respond in a non sex-specific manner.     

家白蚁群体数增长的生殖生理特点

家白蚁Coptotermes formosanus Shiraki营大巢生活,由于雌虫生殖潜能很大,群体蚁数极多.群体蚁数的逐年增长和雌蚁卵巢内卵巢管的数目增长有密切关系.实验表明,分飞时的雌虫卵巢有8条卵巢管,初建群体,半年内一群体的蚁数仅为57个.经过四年后发育的群体,蚁数是1,767个,这时的蚁后卵巢管数是75条.二年群体的年幼蚁后腹部稍膨大,三年以上的群体,蚁后的1腹部膨大较显著.一年的群体,雌虫体长是0.78厘米,雄虫体长0.71厘米.九年后的群体,蚁后体长是2.1厘米,蚁王体长为1.2厘米.和卵巢相似,雄虫精巢叶的数目也随时间而增加.     

Moulting hormone,juvenile hormone and the ultrastructure of the fat body of adult Sarcophaga bullata (Diptera)

Summary In the ovoviviparous fly, Sarcophaga bullata, vitellogenesis is cyclic; a process reflected in ultrastructural changes in the fat body cells and oenocytes. At eclosion the larval fat body has not yet completely disappeared. During vitellogenesis the fat body cells are specialized for intensive protein synthesis showing a very extensive RER and numerous invaginations of the plasma membrane. These features disappear when the eggs descend into the oviducts to complete embryogenesis. The predominant feature of the oenocytes is their very prominent SER. The fat body cells of the males are never as specialized for protein synthesis as those of the females. Feeding of ecdysterone to males for 3 or more days induces a rather extensive subcellular apparatus for protein synthesis, i.e., invaginations of the plasma membrane and an extensive RER. Juvenile hormone is completely ineffective in this respect. Both ecdysterone and juvenile hormone have pronounced but different effects on the oenocytes of males.     

A microsatellite-based test of the <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> genetic caste determination model in <Emphasis Type="Italic">Coptotermes lacteus</Emphasis>

Coptotermes lacteus, a termite found in eastern Australia, is a central-site nester that constructs mounds up to 2 m in height. Mature colonies typically contain the primary king and queen, and up to a million or more worker and soldier offspring. Once a year, male and female nymphs are produced in approximately equal numbers and develop into new alates. Experimental removal of the queen in the field and subsequent mating of the king with a replacement queen, results in an unusual phenomenon whereby the production of female nymphs completely ceases, while the production of male nymphs, and workers of both sexes, continues. The proximate cause of this nymph male-bias is yet to be discovered. The production of male nymphs and workers of both sexes in de-queened C. lacteus colonies is equivalent to offspring production patterns in laboratory crosses of male nymphoid (nymph-derived) with female ergatoid (worker-derived) replacement reproductives in the related species Reticulitermes speratus. An X-linked genetically influenced caste determination (GCD) mechanism has been proposed to account for such offspring patterns in R. speratus. We examined microsatellite genotypes in C. lacteus to test a prediction arising from the R. speratus GCD model: that nymphs should result from reproduction by neotenics, rather than the primary pair. In five of six colonies examined, genotypes indicated that all workers and nymphs were derived from a single reproductive pair. In three of these cases, the primary queen was also located and examined; her genotype matched that inferred from worker and nymph genotypes. These results suggest that the GCD model proposed for R. speratus does not apply to C. lacteus, at least under field conditions. The male-nymph bias following queen removal therefore remains an unresolved issue in C. lacteus.     

Transcriptomic analysis of epigenetic modification genes in the termite Reticulitermes speratus

Eusocial insects display a caste system in which different castes are morpho-logically and physiologically specialized for different tasks.Recent studies have revealed that epigenetic modifications,including DNA methylation and histone modification,me-diate caste determination and differentiation,longevity,and polyethism in eusocial insects.Although there has been a growing interest in the relationship between epigenetic mech-anisms and phenotypic plasticity in termites,there is ltte information about differential expression levels among castes and expression sites for these genes in termites.Here we show royaltissuc-specific expression of epigenetic modification genes in the termite Reticulitermes speratus.Using RNA-seq,we identified 74 genes,including three DNA methyltransferases,seven sirtuins,48 Trithorax group proteins,and 16 Polycomb group proteins.Among these genes,15 showed king-specific expression,and 52 showed age-dependent differential expression in kings and queens.Quantitative real-time PCR revealed that DNA methyltransferase 3 is expressed specifically in the king's testis and fat body,whereas some histone modification genes are remarkably expressed in the king's testis and queen's ovary.These findings imply that epigenetic modification plays important roles in the gamete production process in termite kings and queens.     

Fat body of the frog Rana esculenta: An ultrastructural study

In the frog, the fat body is the largest body lipid deposit and is associated with the gonad. The aim of the present work was to investigate the fine structure of the fat body at different periods of the annual cycle and during prolonged starvation. Results indicate that fat body cells of Rana esculenta caught in autumn and after winter hibernation resemble mammalian adipocytes of white adipose tissue and contain markers of adipose tissue, such as S-100 protein and lipoproteinlipase. However, unlike mammalian adipocytes, fat body adipocytes consistently show small lipid droplets associated with their single, large lipid deposits, a lack of a definite external lamina, and the presence of cellular prolongations and spicula at their surfaces. Transmission and scanning electron microscopy in association with lanthanum tracer experiments suggest that in fat body adipocytes a vesicular-tubular system connects the cytoplasm and the interstitial space. In June (i.e., during the reproductive period), fat body adipocytes appear to have lost much of their lipid deposit and adjacent adipocytes show interdigitation of their plasma membranes and prominent Golgi complexes. In starved frogs, fat body cells can be almost devoid of lipid and in regression to a near-mesenchymal state. Nevertheless, these fat bodies still contain lipoproteinlipase activity (≈ 45% of that found in lipid-filled ones), indicating persistent adipose differentiation of the cells therein. Results presented here show that the R. esculenta fat body is an adipose organ undergoing reversible extreme changes in adipocyte fat content, which are associated with definite ultrastructural features. The fat body represents a suitable model for studying adipose tissue under different and extreme physiological conditions. © 1996 Wiley-Liss, Inc.     

Three queen morphs with alternative nest-founding behaviors in the ant, Temnothorax longispinosus

In many ant species, multiple modes of founding new colonies occur in the same population. These modes include dependent founding, independent founding by haplometrosis (single queen), and independent founding by pleometrosis (multiple queens). In several cases, a dimorphism in queen size has been found, such that each morph specializes in a particular nest-founding behavior. I investigated queen size in the ant Temnothorax longispinosus in several southern Wisconsin populations and found three distinct queen morphs: small queens with very low fat content and short wings, large queens with low fat and long wings, and large queens with high fat and very long wings. Several traits associated with founding behavior correlated with these queen sizes. Small queens were produced in lower numbers, were more common in polygynous nests, and returned to the nest in higher proportions than both large queen morphs. The size ranges and fat levels of each queen morph were similar to those of other species that specialize in either haplometrosis (very large, high fat), pleometrosis (large, low fat), or dependent founding (small and low fat). However, there was extensive overlap in several of the founding behaviors, suggesting that the morphs in these populations have some flexibility in founding behavior. The queen morphs in these populations of T. longispinosus may resemble early stages in the evolution of more specialized dispersal polymorphisms found in other ant species. Received 11 January 2006; revised 15 September 2006; accepted 18 September 2006.     

First record of intersex in neotenic reproductives of the termite Cryptotermes brevis (Isoptera: Kalotermitidae)

Drywood termites of the family Kalotermitidae present a very flexible developmental pattern, in which pseudergates are totipotent and may become reproductives. In this study, three colonies of Cryptotermes brevis headed by neotenic reproductives were used: (i) colony A, with a primary king and a neotenic queen; (ii) colony B, with a primary queen and a neotenic king; and (iii) colony C, with neotenic king and queen. The primary king from colony A and the neotenic king from colony B presented well‐developed reproductive systems, with conspicuous testicular lobes and cysts containing spermatozoa also observed in the seminal vesicles. The neotenic queen of colony A and the primary queen of colony B had ovaries with several oocytes in early developmental stages with some of them already vitellogenic and terminal, which suggests egg‐laying activity. Both of these queens presented the spermathecae lumen filled with spermatozoa. The queen of colony C had vitellogenic oocytes; however, the oocytes were not terminal and the lumen of spermathecae was devoid of spermatozoa and secretions. The seminal vesicles of colony C neotenic king have no spermatozoa. This king displayed a previtellogenic oocyte among its testicular lobes, which suggested that this individual was an intersex.     

Asexual queen succession in the higher termite Embiratermes neotenicus

Asexual queen succession (AQS), in which workers, soldiers and dispersing reproductives are produced sexually while numerous non-dispersing queens arise through thelytokous parthenogenesis, has recently been described in three species of lower termites of the genus Reticulitermes. Here, we show that AQS is not an oddity restricted to a single genus of lower termites, but a more widespread strategy occurring also in the most advanced termite group, the higher termites (Termitidae). We analysed the genetic structure in 10 colonies of the Neotropical higher termite Embiratermes neotenicus (Syntermitinae) using five newly developed polymorphic microsatellite loci. The colonies contained one primary king accompanied either by a single primary queen or by up to almost 200 neotenic queens. While the workers, the soldiers and most future dispersing reproductives were produced sexually, the non-dispersing neotenic queens originated through thelytokous parthenogenesis of the founding primary queen. Surprisingly, the mode of thelytoky observed in E. neotenicus is most probably automixis with central fusion, contrasting with the automixis with terminal fusion documented in Reticulitermes. The occurrence of AQS based on different mechanisms of ploidy restoration raises the hypothesis of an independent evolutionary origin of this unique reproductive strategy in individual lineages of lower and higher termites.     

Fat body is the site of vitellogenin synthesis in the soft tick,Ornithodoros moubata

Summary Vitellogenin (Vg) synthesis in cultured tissues was analysed biochemically in a soft tick,Ornithodoros moubata. Nine tissue fractions dissected from reproductive females were incubated in vitro in a specially designed Ringer containing³⁵S-methionine. The synthesis of total protein and Vg was assayed by the radioactivity incorporated into precipitates with trichloroacetic acid and antivitellin (Vn)-serum, respectively. Fat body was the most active tissue in Vg synthesis, which comprised 46% of the Vg synthesis by all tissues and 42% of total protein synthesis by fat body. Protein synthesized by the fat body and precipitated with anti-Vn-serum was shown by electrophoresis and fluorography, to consist of six radioactive polypeptides corresponding to the components of Vg. Vg synthesized in cultured fat body was first accumulated in the tissue and secreted into the medium during incubation. Some tissues other than fat body showed low Vg synthesis (in each, less than 12% of total protein synthesis) which, however, may be due to contamination by fat body cells as seen with the scanning electron microscope (SEM). SEM also showed that fat body cells in the active stage of Vg synthesis expanded about 10-fold in length. Immunohistochemical analysis showed a very strong reaction with anti-Vn-IgG in the cytoplasm of fat body from reproductive females. Fat body from unfed females and other tissues including midgut, did not show any specific fluorescence. A positive reaction was obtained with developing oocytes. These results indicate that the fat body is the only site of Vg synthesis in this tick.Abbreviations Vg vitellogenin - Vn vitellin - SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - SEM scanning electron microscopy - TCA trichloroacetic acid     

Lipophorin as a yolk protein precursor in the mosquito, Aedes aegypti

We examined expression of the lipophorin (Lp) gene, lipophorin (Lp) synthesis and secretion in the mosquito fat body, as well as dynamic changes in levels of this lipoprotein in the hemolymph and ovaries, during the first vitellogenic cycle of females of the yellow fever mosquito, Aedes aegypti. Lipophorin was purified by potassium bromide (KBr) density gradient ultracentrifugation and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). Polyclonal antibodies were produced against individual Lp apoproteins, apolipoprotein-I (apoLp-I) and apolipoprotein-II (apoLp-II), with molecular weights of 240 and 75 kDa, respectively. We report here that in the mosquito A. aegypti, Lp was synthesized by the fat body, with a low level of the Lp gene expression and protein synthesis being maintained in pre- and postvitellogenic females. Following a blood meal, the Lp gene expression and protein synthesis were significantly upregulated. Our findings showed that the fat body levels of Lp mRNA and the rate of Lp secretion by this tissue reached their maximum at 18 h post-blood meal (PMB). 20-Hydroxyecdysone was responsible for an increase in the Lp gene expression and Lp protein synthesis in the mosquito fat body. Finally, the immunocytochemical localization of Lp showed that in vitellogenic female mosquitoes, this protein was accumulated by developing oocytes where it was deposited in yolk granules.     

Workers do not mediate the inhibitory power of queens in a termite, <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera,Rhinotermitidae)

In social insects, the caste systems are based on reproductive division of labor; queens specialize in reproduction and workers primarily maintain the colony. Recently, a volatile pheromone containing n-butyl-n-butyrate and 2-methyl-1-butanol was identified as a termite queen pheromone that inhibits the differentiation of female neotenic reproductives (secondary queens). Although this volatile inhibitory pheromone regulates caste differentiation directly, the method by which it reaches members without direct contact with the queen in large colonies is not well understood. Therefore, additional mechanisms of indirect communication must exist, such as worker-mediated queen signal transport. We found that workers exposed to female reproductives did not mediate queens’ inhibitory signal in a termite Reticulitermes speratus. The experiment assessed worker transfer from direct to indirect contact groups and determined that the differentiation of new female reproductives in the indirect contact groups was not influenced by the direct contact groups, whereas direct contact with functional female reproductives and artificial queen pheromone did suppress neotenic differentiation. This suggests that worker transfer of the queen signal is unlikely and that for colony-wide inhibition direct contact by the majority of infertile members with reproductives or eggs, which emit the same volatiles as female reproductives, is necessary within a certain time interval.     

Adaptation of a radiochemical assay for juvenile hormone biosynthesis to study caste differentiation in a primitive termite

A radiochemical assay measuring juvenile hormone synthesis by corpora allata incubated in vitro was adapted for use with the termite Zootermopsis angusticollis. Corpora allata from 3–4-day old virgin female neotenic reproductives were used in these studies because this caste showed the highest rates of juvenile hormone synthesis (0.6 pmol h^?1 per pair corpora allata). Juvenile hormone-III synthesis was linear for up to 6 h over the range of concentrations of labelled l-methionine from 27–280 μM. Rates of juvenile hormone synthesis were stimulated up to 10-fold in a dose-dependent manner by the addition of farnesoic acid to the incubation medium. However, the relatively high concentration of 120 μM farnesoic acid reduced the rates of juvenile hormone synthesis. The radiochemical assay was used to determine rates of juvenile hormone synthesis in vitro by corpora allata from larvae with a queen and king vs orphaned larvae. The presence of reproductives resulted in a suppression of larval corpus allatum activity relative to orphaned controls.     

Culture of honeybee organs: Development of a new medium and the importance of tracheation

Summary A culture system for honeybeen fat body and ovary was developed that supported optimal levels of protein synthesis by the explanted tissues. Abdominal body wall preparations of honeybee workers and queens, with adhering fat body, and ovaries of egg-laying queens were incubated in a culture medium designed to match honeybee hemolymph composition as closely as possible. Incorporation of [³H]eucine into soluble tissue proteins was measured. The new medium makes possible rates of tracer incorporation into fat body proteins that are up to three times higher than other media tested. When the tracheal system of the organs was let intact and open to the air during incubation, protein synthesis increased 17-fold (fat body) or 15-fold (ovary) as compared to preparations without open tracheas. After explantation into the medium, labeled proteins were synthesized at a highly variable rate for 10 h, probably due to wound response, and at a constant rate for the next 60 h. In contrast, ovarian protein synthesis occurred at a constant rate for at least 20 h and showed no wound response. The rate of tracer incorporation into fat body proteins was 3.2 times greater in tissues from the queen. This culture system is therefore suitable for a variety of investigations in honeybeen development and reproduction. These studies were supported by grants from the Deutsche Forschungsgemeinschaft, a Senior Scientist Award from the Alexander v. Humboldt Foundation for H. H. Hagedorn, and a fellowship from the Deutscher Akademischer Austauschdienst for H. H. Kaatz.     

Polymorphism in the neotropical termite Serritermes serrifer

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.     

Variation in the quality of Vespula vulgaris (L.) queens (Hymenoptera: Vespidae) and its significance in wasp population dynamics

Abstract

Density‐related variation in queen quality has been proposed as a possible mechanism regulating population fluctuations in Vespula species. We investigated annual variation in the quality (size, weight, and fat content) of adult V. vulgaris queens representing four stages of their life cycle (spring, founding, developing, and emerged) taken from six sites in beech forest, South Island, New Zealand. For each queen the dry weight, head width, and thorax length was measured. For a subsample of queens, the fat content was determined by ether extraction. The size of queen cells was measured from a subsample of nests. Size, weight, and fat content of queens varied between wasp colonies and sites. The smallest juvenile queens were under‐represented in the reproductive population. There was no direct link between body size and food supply. Size and weight of developing queens increased as the number of cells in the nest increased. The size of the queen cells varied significantly among layers in a nest and among nests. The under‐representation of small queens in the reproductive population suggests that queen quality may affect survival and/or competitive ability by increasing winter fat storage, nest building activity, and/or success in usurpation disputes.     

Ultrastructure and formation of the physogastric termite queen cuticle

The physogastric termite queen is the most striking example in insects of growth in size without cuticular moulting. This phenomenon has been studied with electron microscopy and histochemical tests in two species of higher termites, Cubitermes fungifaber and Macrotermes bellicosus. The abdominal hypertrophy (physogastry) is allowed by growth of the arthrodial membranes of the swarming imago. The growth is slow (over several years) but important: the cuticular dry weight is multiplied by 20 in C. fungifaber, by 100-150 in M. bellicosus. The termite queen cuticle arises from the transformation of the cuticle of the swarming imago or imaginal cuticle (unfolding and growing of the epicuticle, stretching of the endocuticle, resorption of the subcuticle) and from the secretion of a new endocuticle or royal endocuticle. The termite queen is the first example known in insects of epicuticular growth. In the physogastric queen, three cuticular types are observed: the rigid cuticle of the sclerites, the soft cuticle of the arthrodial membranes and the partially rigid cuticle of special structures, the neosclerites, which show both rigidity and growth. The fibrillar architecture varies according to the abdominal zones and the position within the cuticle. It appears to be determined by the forces arising from the musculature and the anisometric abdominal growth. The king does not become physogastric, although its cuticle is also modified.     

Irreversible transfer of brood care duties and insights into the burden of caregiving in incipient subterranean termite colonies

1. In incipient termite colonies, biparental brood care rapidly shifts towards alloparental brood care. This transition was suggested to recapitulate the evolutionary trajectory from subsocial wood roach ancestors to eusociality in termites. 2. Incipient colonies of the subterranean termite Coptotermes gestroi (Wasmann) were investigated to determine if this transition was irreversible and if the burden of brood care on the first alloparents could be measured. To do so, the initial size of the work force necessary for an incipient colony to survive once the brood care became alloparental was determined. 3. The results of the study show that within 5 months after foundation, brood care duties were fully transferred to workers and the primary reproductives became irreversibly dependent on these workers for survival, reproduction, and colony growth. 4. Once the brood care became strictly alloparental, the presence of a single worker was enough to maintain the survival of the king and queen, confirming that ‘reversed parental care’ was also achieved. However, major brood loss and suppressed egg‐laying activity from the queen was observed, suggesting that the burden of brood care was too high for a single worker to absorb. Therefore, once brood care has shifted to alloparents, a critical number of workers is necessary to prevent brood loss and initiate colony growth. 5. As the initial cost of brood care is rapidly absorbed with colony growth in termites, the performance in brood care of the first few alloparents in a subsocial wood roach ancestor may have contributed to the emergence of eusociality in this clade.