Hexapod Orders Research Articles

Revisiting the four Hexapoda classes: Protura as the sister group to all other hexapods

Insects represent the most diverse animal group, yet previous phylogenetic analyses based on morphological and molecular data have failed to agree on the evolutionary relationships of early insects and their six-legged relatives (together constituting the clade Hexapoda). In particular, the phylogenetic positions of the three early-diverging hexapod lineages-the coneheads (Protura), springtails (Collembola), and two-pronged bristletails (Diplura)-have been debated for over a century, with alternative topologies implying drastically different scenarios of the evolution of the insect body plan and hexapod terrestrialization. We addressed this issue by sampling all hexapod orders and experimenting with a broad range of across-site compositional heterogeneous models designed to tackle ancient divergences. Our analyses support Protura as the earliest-diverging hexapod lineage ("Protura-sister") and Collembola as a sister group to Diplura, a clade corresponding to the original composition of Entognatha, and characterized by the shared possession of internal muscles in the antennal flagellum. The previously recognized 'Elliplura' hypothesis is recovered only under the site-homogeneous substitution models with partial supermatrices. Our cross-validation analysis shows that the site-heterogeneous CAT-GTR model, which recovers "Protura-sister," fits significantly better than homogeneous models. Furthermore, the morphologically unusual Protura are also supported as the earliest-diverging hexapod lineage by other lines of evidence, such as mitogenomes, comparative embryology, and sperm morphology, which produced results similar to those in this study. Our backbone phylogeny of hexapods will facilitate the exploration of the underpinnings of hexapod terrestrialization and megadiversity.

The ecological function of insect egg micropyles

Abstract Insect egg micropyles are openings through the chorion allowing sperm entry for fertilisation. Micropyles are diverse structures showing remarkable variation in number, spatial arrangement and physical structure across extant insect orders. Despite being almost ubiquitous across insects, they have received little attention. As key morphological features of an immobile life stage, it is plausible that part of the diversity exhibited by micropyles is adaptive, supporting other egg structures during embryo development. So, while egg fertilization is the primary function of micropyles, they could aid embryo development and be shaped by natural, as well as sexual selection. Here I first used ancestral reconstruction to investigate micropyle presence, number and variation in primitive insects. Then, I used phylogenetic comparative analyses to explore the ecological function of micropyle number. I hypothesised that micropyle number correlated with (1) aeropyle presence facilitating oxygen exchange; (2) aquatic oviposition supporting development in water and is influenced by (3) critical bioclimatic variables. Across 24 hexapod orders, the most likely ancestral state was one or two micropyles, interspecific variation was high and intraspecific variation was low. Mean micropyle number ranged from zero in Entognatha, Strepsiptera and Thysanoptera to 120 in Panstrongylus geniculatus, Hemiptera, and over 100 on average for Apidae, Hymenoptera. Micropyle number was strongly positively related to (1) egg size, with larger eggs having more micropyles; (2) the presence of aeropyles; (3) annual precipitation, with eggs developing in habitats with low annual precipitation exhibiting fewer micropyles; and (4) negatively related to micropyle width, insect eggs having fewer larger micropyles or numerous smaller ones. However, aquatic oviposition did not affect micropyle number. Overall these findings point to an adaptive ecological function of egg micropyles in addition to their primary fertilisation function. This is consistent with the hypothesis that micropyles aid embryo survival, and so this almost‐ubiquitous trait across insects is shaped by sexual and natural selection pressures during this critical life stage. Read the free Plain Language Summary for this article on the Journal blog.

Attractiveness of Arthropodal Hexapod Orders to Light-Emitting Diode and Incandescent Bulb Light Colours

Dearth of information on response of hexapod orders to light sources and colours informed this study. The study was conducted in Federal University Wukari, Nigeria in the month of May, 2019 to evaluate the attractiveness of hexapod orders to Light-emitting Diode (LED) and Incandescent bulb light colours. Daily sampling using fabricated light traps with 5 different colours (white, yellow, red, green and blued) for each bulb type in 6 replicates was done. A trap with no lighting source was the control. Hexapods collected were sorted into their respective orders. Of the overall 13 insect orders collected, LED bulbs attracted 11 while incandescent, 10. Even though, certain hexapod orders exhibited higher affinity to specific colours, statistical analysis revealed that of the 11 orders from LED, differences in the mean number of insects attracted among the bulb colours was significant (p<0.05) only in Coleoptera and Lepidoptera while for incandescent bulb colours, the mean number of insects attracted was significant for Coleoptera, Lepidoptera, Hemiptera, Hymenoptera, Orthoptera, Mantodea, Odonata and Homoptera. Insect orders generally had higher affinity to white and blue colours. LED bulb colours significantly attracted higher number of insects than their corresponding incandescent colours, except for white on which incandescent was more attractive (p>0.05). Overall, attractiveness to hexapod orders increases with rinsing light intensity and LED bulbs were found to be more attractive to hexapods than do incandescent bulbs. Therefore, LED bulbs of higher light intensity with colours around the blue/white spectrum show potential for use in manipulating hexapods for man’s benefit.

The ubiquity and ancestry of insect doublesex.

The doublesex (dsx) gene functions as a molecular switch at the base of the insect sex determination cascade, and triggers male or female somatic sexual differentiation in Drosophila. Having been reported from only seven current insect orders, the exact phylogenetic distribution of dsx within the largest Arthropod sub-phylum, the Hexapoda, is unknown. To understand the evolution of this integral gene relative to other arthropods, we tested for the presence of dsx within public EST and genome sequencing projects representative of all 32 hexapod orders. We find the dsx gene to be ubiquitous, with putative orthologs recovered from 30 orders. Additionally, we recovered both alternatively spliced and putative paralogous dsx transcripts from several orders of hexapods, including basal lineages, indicating the likely presence of these characteristics in the hexapod common ancestor. Of note, other arthropods such as chelicerates and crustaceans express two dsx genes, both of which are shown to lack alternative splicing. Furthermore, we discovered a large degree of length heterogeneity in the common region of dsx coding sequences within and among orders, possibly resulting from lineage-specific selective pressures inherent to each taxon. Our work serves as a valuable resource for understanding the evolution of sex determination in insects.

The incidence of bacterial endosymbionts in terrestrial arthropods.

Intracellular endosymbiotic bacteria are found in many terrestrial arthropods and have a profound influence on host biology. A basic question about these symbionts is why they infect the hosts that they do, but estimating symbiont incidence (the proportion of potential host species that are actually infected) is complicated by dynamic or low prevalence infections. We develop a maximum-likelihood approach to estimating incidence, and testing hypotheses about its variation. We apply our method to a database of screens for bacterial symbionts, containing more than 3600 distinct arthropod species and more than 150 000 individual arthropods. After accounting for sampling bias, we estimate that 52% (CIs: 48-57) of arthropod species are infected with Wolbachia, 24% (CIs: 20-42) with Rickettsia and 13% (CIs: 13-55) with Cardinium. We then show that these differences stem from the significantly reduced incidence of Rickettsia and Cardinium in most hexapod orders, which might be explained by evolutionary differences in the arthropod immune response. Finally, we test the prediction that symbiont incidence should be higher in speciose host clades. But while some groups do show a trend for more infection in species-rich families, the correlations are generally weak and inconsistent. These results argue against a major role for parasitic symbionts in driving arthropod diversification.

Expression and evolution of hexamerins from the tobacco hornworm, Manduca sexta, and other Lepidoptera

Hexamerins are large hemolymph-proteins that accumulate during the late larval stages of insects. Hexamerins have emerged from hemocyanin, but have lost the ability to bind oxygen. Hexamerins are mainly considered as storage proteins for non-feeding stages, but may also have other functions, e.g. in cuticle formation, transport and immune response. The genome of the hornworm Manduca sexta harbors six hexamerin genes. Two of them code for arylphorins (Msex2.01690, Msex2.15504) and two genes correspond to a methionine-rich hexamerin (Msex2.10735) and a moderately methionine-rich hexamerin (Msex2.01694), respectively. Two other genes do not correspond to any known hexamerin and distantly resemble the arylphorins (Msex2.01691, Msex2.01693). Five of the six hexamerin genes are clustered within ∼45 kb on scaffold 00023, which shows conserved synteny in various lepidopteran genomes. The methionine-rich hexamerin gene is located at a distinct site. M. sexta and other Lepidoptera have lost the riboflavin-binding hexamerin. With the exception of Msex2.01691, which displays low mRNA levels throughout the life cycle, all hexamerins are most highly expressed during pre-wandering phase of the 5th larval instar of M. sexta, supporting their role as storage proteins. Notably, Msex2.01691 is most highly expressed in the brain, suggesting a divergent function. Phylogenetic analyses showed that hexamerin evolution basically follows insect systematics. Lepidoptera display an unparalleled diversity of hexamerins, which exceeds that of other hexapod orders. In contrast to previous analyses, the lepidopteran hexamerins were found monophyletic. Five distinct types of hexamerins have been identified in this order, which differ in terms of amino acid composition and evolutionary history: i. the arylphorins, which are rich in aromatic amino acids (∼20% phenylalanine and tyrosine), ii. the distantly related arylphorin-like hexamerins, iii. the methionine-rich hexamerins, iv. the moderately methionine rich hexamerins, and v. the riboflavin-binding hexamerins.

Book review: Insect morphology and phylogeny

As the authors were driving forces in the recent revival of morphology it is just and equitable that they free us from the dependence on timeworn reams. A new standard work on insect morphology and phylogeny has been long overdue and will certainly constitute a valuable reference for future publications. This textbook is a comprehensive treatment covering morphology, phylogeny, and associated methods as traditional and modern morphological techniques and phylogenetic reconstruction. It starts with a state of the art description of general hexapod morphology, supplemented with a useful separate glossary of morphological terms. The recently defined and currently applied nomenclature for the muscles of the head and the thorax is outlined in two tables. In the section on morphological techniques the authors incorporate their personal experience and discuss advantages and problems of the respective method which gives this chapter additional value. The second part of the book deals with the 35 currently recognized hexapod orders. These chapters do not only contain detailed morphological descriptions of adults and larvae including internal anatomy if investigated, but also information on diversity and distribution, taxonomy, reproductive behaviour and development, fossil record and the economic importance of the order. The relationship of the orders is presented in several cladograms, controversial phylogenetic hypotheses are discussed and autapomorphies of the orders and higher clades are listed. In the chapter “literature“ the additional listing of textbooks, review articles and cladistic software gives students a quick overview on further reading. Generally the structure of the book is clear and intuitive. The absence of separate subtopics for the sections on phylogenetic relationships is however a neglect. The only way to find this information is paging through the whole chapter “The orders of Hexapoda“ again and again which is rather tiring. We suggest preparing some post-it notes before starting to read. Altogether, the book gives the only complete and modern reference of its kind available today. The authors manage to communicate even complicate topics in an easily understandable way, not at least by enhancing the text with numerous detailed drawings, excellent scanning electron micrographs, coloured 3-D reconstructions and photographs of living specimens. Their in-depth knowledge combined with their enthusiasm for the topic make this book attractive not only for students and researchers but for everyone interested in entomology. Dtsch. Entomol. Z. 61 (1) 2014, 85 | DOI 10.3897/dez.61.7915

On the fate of sexual traits under asexuality

Environmental shifts and life-history changes may result in formerly adaptive traits becoming non-functional or maladaptive. In the absence of pleiotropy and other constraints, such traits may decay as a consequence of neutral mutation accumulation or selective processes, highlighting the importance of natural selection for adaptations. A suite of traits are expected to lose their adaptive function in asexual organisms derived from sexual ancestors, and the many independent transitions to asexuality allow for comparative studies of parallel trait maintenance versus decay. In addition, because certain traits, notably male-specific traits, are usually not exposed to selection under asexuality, their decay would have to occur as a consequence of drift. Selective processes could drive the decay of traits associated with costs, which may be the case for the majority of sexual traits expressed in females. We review the fate of male and female sexual traits in 93 animal lineages characterized by asexual reproduction, covering a broad taxon range including molluscs, arachnids, diplopods, crustaceans and eleven different hexapod orders. Many asexual lineages are still able occasionally to produce males. These asexually produced males are often largely or even fully functional, revealing that major developmental pathways can remain quiescent and functional over extended time periods. By contrast, for asexual females, there is a parallel and rapid decay of sexual traits, especially of traits related to mate attraction and location, as expected given the considerable costs often associated with the expression of these traits. The level of decay of female sexual traits, in addition to asexual females being unable to fertilize their eggs, would severely impede reversals to sexual reproduction, even in recently derived asexual lineages. More generally, the parallel maintenance versus decay of different trait types across diverse asexual lineages suggests that neutral traits display little or no decay even after extended periods under relaxed selection, while extensive decay for selected traits occurs extremely quickly. These patterns also highlight that adaptations can fix rapidly in natural populations of asexual organisms, in spite of their mode of reproduction.

Molecular phylogenetic analyses support the monophyly of Hexapoda and suggest the paraphyly of Entognatha.

BackgroundMolecular phylogenetic analyses have revealed that Hexapoda and Crustacea form a common clade (the Pancrustacea), which is now widely accepted among zoologists; however, the origin of Hexapoda remains unresolved. The main problems are the unclear relationships among the basal hexapod lineages, Protura (proturans), Collembola (springtails), Diplura (diplurans), and Ectognatha (bristletails, silverfishes, and all winged insects). Mitogenomic analyses have challenged hexapod monophyly and suggested the reciprocal paraphyly of Hexapoda and Crustacea, whereas studies based on nuclear molecular data support the monophyletic origin of hexapods. Additionally, there are significant discrepancies with respect to these issues between the results of morphological and molecular studies. To investigate these problems, we performed phylogenetic analyses of Pancrustacea based on the protein sequences of three orthologous nuclear genes encoding the catalytic subunit of DNA polymerase delta and the largest and second largest subunits of RNA polymerase II from 64 species of arthropods, including representatives of all hexapod orders.ResultsPhylogenetic analyses were conducted based on the inferred amino acid (aa) sequences (~3400 aa in total) of the three genes using the maximum likelihood (ML) method and Bayesian inference. Analyses were also performed with additional datasets generated by excluding long-branch taxa or by using different outgroups. These analyses all yielded essentially the same results. All hexapods were clustered into a common clade, with Branchiopoda as its sister lineage, whereas Crustacea was paraphyletic. Within Hexapoda, the lineages Ectognatha, Palaeoptera, Neoptera, Polyneoptera, and Holometabola were each confirmed to be monophyletic with robust support, but monophyly was not supported for Entognatha (Protura + Collembola + Diplura), Ellipura (Protura + Collembola), or Nonoculata (Protura + Diplura). Instead, our results showed that Protura is the sister lineage to all other hexapods and that Diplura or Diplura + Collembola is closely related to Ectognatha.ConclusionThis is the first study to include all hexapod orders in a phylogenetic analysis using multiple nuclear protein-coding genes to investigate the phylogeny of Hexapoda, with an emphasis on Entognatha. The results strongly support the monophyletic origin of hexapods but reject the monophyly of Entognatha, Ellipura, and Nonoculata. Our results provided the first molecular evidence in support of Protura as the sister group to other hexapods. These findings are expected to provide additional insights into the origin of hexapods and the processes involved in the adaptation of insects to life on land.

Many hexapod groups originated earlier and withstood extinction events better than previously realized: inferences from supertrees.

Comprising over half of all described species, the hexapods are central to understanding the evolution of global biodiversity. Direct fossil evidence suggests that new hexapod orders continued to originate from the Jurassic onwards, and diversity is presently higher than ever. Previous studies also suggest that several shifts in net diversification rate have occurred at higher taxonomic levels. However, their inferred timing is phylogeny dependent. We re-examine these issues using the supertree approach to provide, to our knowledge, the first composite estimates of hexapod order-level phylogeny. The Purvis matrix representation with parsimony method provides the most optimal supertree, but alternative methods are considered. Inferring ghost ranges shows richness of terminal lineages in the order-level phylogeny to peak just before the end-Permian extinction, rather than the present day, indicating that at least 11 more lineages survived this extinction than implied by fossils alone. The major upshift in diversification is associated with the origin of wings/wing folding and for the first time, to our knowledge, significant downshifts are shown associated with the origin of species-poor taxa (e.g. Neuropterida, Zoraptera). Polyneopteran phylogeny, especially the position of Zoraptera, remains important resolve because this influences findings regarding shifts in diversification. Our study shows how combining fossil with phylogenetic information can improve macroevolutionary inferences.

The University of Puerto Rico at Mayagüez Insect Collection — Then and Now

The origin, historical trajectory, and present status of the insect collection of the University of Puerto Rico at Mayagüez (collection coden: UPRM) are reviewed. The collection initiated in the mid 1920s and has grown relatively continuously thanks to efforts by several outstanding entomologists working at UPRM. As of 2007, the collection includes more than 130,000 objects (individual specimens, slides, or vials) pertaining to 25 hexapod orders. The numbers of collection objects per order are listed. The geographic emphasis is on Puerto Rico and surrounding islands. The auchenorrhynchous Hemiptera, Collembola, and Coleoptera are particularly well represented. The collection is in a process of reorganization and is available for specimen loans and related collaborative activities.

Phylogenetic relationships of the orders of Hexapoda: Contributions from the circulatory organs for a morphological data matrix

Discussions of phylogenetic studies based on morphological data focus mainly on results of the cladistic analysis while selection and evaluation of characters themselves are often underrepresented. Our paper seeks to address this with a survey of characters of the circulatory organs to contribute to the analysis of phylogenetic relationships of hexapod orders. The survey is based on examination of literature and includes, in addition, numerous unpublished data. Of 38 variable traits of the dorsal vessel and the various accessory circulatory organs, we selected 11 which are potentially informative at supraordinal level. They are critically discussed and coded as characters for use in comprehensive future cladistic analyses employing greater sets of morphological data. It must be stated that many features of circulatory organs for higher systematic categories are still based on one or few species for most orders of hexapods; this defi ciency is due to the great methodological effort required to investigate internal organs. In general, circulatory organs of hexapods are simply organized making it diffi cult to discriminate homology from convergence. In addition to phylogeny, general aspects of the evolution of the circulatory system are outlined. In an appendix we provide comprehensive information on the traits, characters and the species in which they occur.

Exon-intron structure, paralogy and sequenced regions of elongation factor-1 alpha in Hexapoda

Elongation factor-1 alpha (EF-1α) is already widely used and shows even more promise for phylogenetic studies of Hexapoda. However, paralogous copies and the presence of introns pose problems. We survey exon-intron structure, presence of paralogous copies and the number and extent of sequenced regions in all hexapod orders. We assess the phylogenetic utility of the exon-intron structure of EF-1α, which is unexpectedly dynamic with widespread losses and several independent instances of intron gain. Paralogous copies of EF-1α are present in Hemiptera, Thysanoptera, Neuropterida, Coleoptera, Hymenoptera and Diptera. With the presented information about exon-intron structure and paralogous copies, researchers will be able to realise the full phylogenetic potential of EF-1α, including exon-intron structure as this can provide additional characters and help to define clades and paralogous copies. We recommend a suitable focus region of 500 bp for future studies of EF-1α in Hexapoda.

The evolution of hexapod engrailed-family genes: evidence for conservation and concerted evolution.

Phylogenetic analyses imply that multiple engrailed-family gene duplications occurred during hexapod evolution, a view supported by previous reports of only a single engrailed-family gene in members of the grasshopper genus Schistocerca and in the beetle Tribolium castaneum. Here, we report the cloning of a second engrailed-family gene from Schistocerca gregaria and present evidence for two engrailed-family genes from four additional hexapod species. We also report the existence of a second engrailed-family gene in the Tribolium genome. We suggest that the engrailed and invected genes of Drosophila melanogaster have existed as a conserved gene cassette throughout holometabolous insect evolution. In total 11 phylogenetically diverse hexapod orders are now known to contain species that possess two engrailed-family paralogues, with in each case only one paralogue encoding the RS-motif, a characteristic feature of holometabolous insect invected proteins. We propose that the homeoboxes of hexapod engrailed-family paralogues are evolving in a concerted fashion, resulting in gene trees that overestimate the frequency of gene duplication. We present new phylogenetic analyses using non-homeodomain amino acid sequence that support this view. The S. gregaria engrailed-family paralogues provide strong evidence that concerted evolution might in part be explained by recurrent gene conversion. Finally, we hypothesize that the RS-motif is part of a serine-rich domain targeted for phosphorylation.

Is Ellipura monophyletic? A combined analysis of basal hexapod relationships with emphasis on the origin of insects

Hexapoda includes 33 commonly recognized orders, most of them insects. Ongoing controversy concerns the grouping of Protura and Collembola as a taxon Ellipura, the monophyly of Diplura, a single or multiple origins of entognathy, and the monophyly or paraphyly of the silverfish (Lepidotrichidae and Zygentoma s.s.) with respect to other dicondylous insects. Here we analyze relationships among basal hexapod orders via a cladistic analysis of sequence data for five molecular markers and 189 morphological characters in a simultaneous analysis framework using myriapod and crustacean outgroups. Using a sensitivity analysis approach and testing for stability, the most congruent parameters resolve Tricholepidion as sister group to the remaining Dicondylia, whereas most suboptimal parameter sets group Tricholepidion with Zygentoma. Stable hypotheses include the monophyly of Diplura, and a sister group relationship between Diplura and Protura, contradicting the Ellipura hypothesis. Hexapod monophyly is contradicted by an alliance between Collembola, Crustacea and Ectognatha (i.e., exclusive of Diplura and Protura) in molecular and combined analyses.

A tale of two analyses: estimating the consequences of shifts in hexapod diversification

I present a novel descriptive (non-statistical) method to help identify the location and importance of shifts in diversification across a phylogeny. The method first estimates radiation rates across terminal higher taxa and then subjects these rates to a parsimony analysis across the phylogeny. The reconstructions define the magnitude, direction and influence of past shifts in realized diversification rates across nodes. I apply the method to data on the extant hexapod orders. The results indicate that the Coleoptera (beetles) and Diptera (flies) have contributed large upward shifts in diversification tendency, without which, under the model employed, global species richness would be reduced by 20% and 6%, respectively. The origin of Neoptera (insects with wing flexion), identified elsewhere as a significant radiation, may represent a large positive, a large negative or zero influence on current species richness, depending on the assumed phylogeny and parsimony method. The most influential radiations are attributable to the origin of the Eumetabola (insects with complete metamorphosis plus bugs and their relatives) and Pterygota (winged insects), but there is presently only weak evidence that they represent significant shifts in underlying diversification tendency. These analyses support some but not all results of previous phylogenetic analyses and the identity of the most important shift therefore remains elusive. New methodology involving comparisons across multiple taxa is likely to be necessary. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 23–36.

Shifts in hexapod diversification and what Haldane could have said.

Data on species richness and taxon age are assembled for the extant hexapod orders (insects and their six-legged relatives). Coupled with estimates of phylogenetic relatedness, and simple statistical null models, these data are used to locate where, on the hexapod tree, significant changes in the rate of cladogenesis (speciation-minus-extinction rate) have occurred. Significant differences are found between many successive pairs of sister taxa near the base of the hexapod tree, all of which are attributable to a shift in diversification rate after the origin of the Neoptera (insects with wing flexion) and before the origin of the Holometabola (insects with complete metamorphosis). No other shifts are identifiable amongst supraordinal taxa. Whilst the Coleoptera have probably diversified faster than either of their putative sister lineages, they do not stand out relative to other closely related clades. These results suggest that any Creator had a fondness for a much more inclusive clade than the Coleoptera, definitely as large as the Eumetabola (Holometabola plus bugs and their relatives), and possibly as large as the entire Neoptera. Simultaneous, hence probable causative events are discussed, of which the origin of wing flexion has been the focus of much attention.

98/01699 Determination of the handle-ability of a coal blend using an extrusion trough: Brown, D. W. et al. Fuel 1997, 76, (13), 1183–1186

Hexamerins are large hemolymph-proteins that accumulate during the late larval stages of insects. Hexamerins have emerged from hemocyanin, but have lost the ability to bind oxygen. Hexamerins are mainly considered as storage proteins for non-feeding stages, but may also have other functions, e.g. in cuticle formation, transport and immune response. The genome of the hornworm Manduca sexta harbors six hexamerin genes. Two of them code for arylphorins (Msex2.01690, Msex2.15504) and two genes correspond to a methionine-rich hexamerin (Msex2.10735) and a moderately methionine-rich hexamerin (Msex2.01694), respectively. Two other genes do not correspond to any known hexamerin and distantly resemble the arylphorins (Msex2.01691, Msex2.01693). Five of the six hexamerin genes are clustered within ∼45 kb on scaffold 00023, which shows conserved synteny in various lepidopteran genomes. The methionine-rich hexamerin gene is located at a distinct site. M. sexta and other Lepidoptera have lost the riboflavin-binding hexamerin. With the exception of Msex2.01691, which displays low mRNA levels throughout the life cycle, all hexamerins are most highly expressed during pre-wandering phase of the 5th larval instar of M. sexta, supporting their role as storage proteins. Notably, Msex2.01691 is most highly expressed in the brain, suggesting a divergent function. Phylogenetic analyses showed that hexamerin evolution basically follows insect systematics. Lepidoptera display an unparalleled diversity of hexamerins, which exceeds that of other hexapod orders. In contrast to previous analyses, the lepidopteran hexamerins were found monophyletic. Five distinct types of hexamerins have been identified in this order, which differ in terms of amino acid composition and evolutionary history: i. the arylphorins, which are rich in aromatic amino acids (∼20% phenylalanine and tyrosine), ii. the distantly related arylphorin-like hexamerins, iii. the methionine-rich hexamerins, iv. the moderately methionine rich hexamerins, and v. the riboflavin-binding hexamerins.

98/01693 Combined-cycle power generation plant and its operational method: Ueda, T. Jpn. Kokai Tokkyo Koho JP 09,268,294 [97,268,294] (Cl. C10J3/46), 14 Oct 1997, Appl. 96/99,562, 29 Mar 1996, 6 pp. (in Japanese)

Hexamerins are large hemolymph-proteins that accumulate during the late larval stages of insects. Hexamerins have emerged from hemocyanin, but have lost the ability to bind oxygen. Hexamerins are mainly considered as storage proteins for non-feeding stages, but may also have other functions, e.g. in cuticle formation, transport and immune response. The genome of the hornworm Manduca sexta harbors six hexamerin genes. Two of them code for arylphorins (Msex2.01690, Msex2.15504) and two genes correspond to a methionine-rich hexamerin (Msex2.10735) and a moderately methionine-rich hexamerin (Msex2.01694), respectively. Two other genes do not correspond to any known hexamerin and distantly resemble the arylphorins (Msex2.01691, Msex2.01693). Five of the six hexamerin genes are clustered within ∼45 kb on scaffold 00023, which shows conserved synteny in various lepidopteran genomes. The methionine-rich hexamerin gene is located at a distinct site. M. sexta and other Lepidoptera have lost the riboflavin-binding hexamerin. With the exception of Msex2.01691, which displays low mRNA levels throughout the life cycle, all hexamerins are most highly expressed during pre-wandering phase of the 5th larval instar of M. sexta, supporting their role as storage proteins. Notably, Msex2.01691 is most highly expressed in the brain, suggesting a divergent function. Phylogenetic analyses showed that hexamerin evolution basically follows insect systematics. Lepidoptera display an unparalleled diversity of hexamerins, which exceeds that of other hexapod orders. In contrast to previous analyses, the lepidopteran hexamerins were found monophyletic. Five distinct types of hexamerins have been identified in this order, which differ in terms of amino acid composition and evolutionary history: i. the arylphorins, which are rich in aromatic amino acids (∼20% phenylalanine and tyrosine), ii. the distantly related arylphorin-like hexamerins, iii. the methionine-rich hexamerins, iv. the moderately methionine rich hexamerins, and v. the riboflavin-binding hexamerins.