Thoracic Horn Research Articles

Histone deacetylases regulate organ-specific growth in a horned beetle

BackgroundNutrient availability is among the most widespread means by which environmental variability affects developmental outcomes. Because almost all cells within an individual organism share the same genome, structure-specific growth responses must result from changes in gene regulation. Earlier work suggested that histone deacetylases (HDACs) may serve as epigenetic regulators linking nutritional conditions to trait-specific development. Here we expand on this work by assessing the function of diverse HDACs in the structure-specific growth of both sex-shared and sex-specific traits including evolutionarily novel structures in the horned dung beetle Onthophagus taurus.ResultsWe identified five HDAC members whose downregulation yielded highly variable mortality depending on which HDAC member was targeted. We then show that HDAC1, 3, and 4 operate in both a gene- and trait-specific manner in the regulation of nutrition-responsiveness of appendage size and shape. Specifically, HDAC 1, 3, or 4 knockdown diminished wing size similarly while leg development was differentially affected by RNAi targeting HDAC3 and HDAC4. In addition, depletion of HDAC3 transcript resulted in a more rounded shape of genitalia at the pupal stage and decreased the length of adult aedeagus across all body sizes. Most importantly, we find that HDAC3 and HDAC4 pattern the morphology and regulate the scaling of evolutionarily novel head and thoracic horns as a function of nutritional variation.ConclusionCollectively, our results suggest that both functional overlap and division of labor among HDAC members contribute to morphological diversification of both conventional and recently evolved appendages. More generally, our work raises the possibility that HDAC-mediated scaling relationships and their evolution may underpin morphological diversification within and across insect species broadly.

Elucidation of the genetic determination of body weight and size in Chinese local chicken breeds by large-scale genomic analyses.

Body weight and size are important economic traits in chickens. While many growth-related quantitative trait loci (QTLs) and candidate genes have been identified, further research is needed to confirm and characterize these findings. In this study, we investigate genetic and genomic markers associated with chicken body weight and size. This study provides new insights into potential markers for genomic selection and breeding strategies to improve meat production in chickens. We performed whole-genome resequencing of and Wenshang Barred (WB) chickens (n = 596) and three additional breeds with varying body sizes (Recessive White (RW), WB, and Luxi Mini (LM) chickens; (n = 50)). We then used selective sweeps of mutations coupled with genome-wide association study (GWAS) to identify genomic markers associated with body weight and size. We identified over 9.4million high-quality single nucleotide polymorphisms (SNPs) among three chicken breeds/lines. Among these breeds, 287 protein-coding genes exhibited positive selection in the RW and WB populations, while 241 protein-coding genes showed positive selection in the LM and WB populations. Genomic heritability estimates were calculated for 26 body weight and size traits, including body weight, chest breadth, chest depth, thoracic horn, body oblique length, keel length, pelvic width, shank length, and shank circumference in the WB breed. The estimates ranged from 0.04 to 0.67. Our analysis also identified a total of 2,522 genome-wide significant SNPs, with 2,474 SNPs clustered around two genomic regions. The first region, located on chromosome 4 (7.41-7.64Mb), was linked to body weight after ten weeks and body size traits. LCORL, LDB2, and PPARGC1A were identified as candidate genes in this region. The other region, located on chromosome 1 (170.46-171.53Mb), was associated with body weight from four to eighteen weeks and body size traits. This region contained CAB39L and WDFY2 as candidate genes. Notably, LCORL, LDB2, and PPARGC1A showed highly selective signatures among the three breeds of chicken with varying body sizes. Overall this study provides a comprehensive map of genomic variants associated with body weight and size in chickens. We propose two genomic regions, one on chromosome 1 and the other on chromosome 4, that could helpful for developing genome selection breeding strategies to enhance meat yield in chickens.

Limnophyes knispelae sp. n. and L. sartorii sp. n., two new crenophilous species from the Swiss Alps (Chironomidae, Orthocladiinae)

Limnophyes knispelae sp. n and L. sartorii sp. n. are diagnosed and described based on material collected in the high Alpine valley of the Rhône river and the cirque of Macun in the Swiss National Park (alt. 1800-2616 m a.s.l.). The first new species is described only as male adult, while the second as male adult and pupal exuviae. Main distinguishing characters found in the male adult of L. knispelae sp. n. L. sartorii sp. n. are: clypeus shield-like shaped; humeral pit typically circular with 3-4 or 9 lanceolate setae; virga strong spine-like; preepisternals vary from 4-6 to 4-8. The pupal exuviae of L. sartorii sp. n. is characterized by having frontal apotome domed; thoracic horn reduced to nose-like tubercle; posterior area of tergites II-VI with 1-7 rows of minute hooks; segment VIII with 5 lateral setae; inner posterior margin of anal lobe straight. A combination of the latter relevant morphological characters has allowed us to consider each of the two new species as a local biogeographic representative of the Swiss Alps. Currently, the genus Limnophyes Eaton, 1875 is represented in Switzerland by 15 species. Consequently, the description of L. knispelae sp. n and L. sartorii sp. n. increases the total number in the genus to 17 known valid species from this country. Discussions and a differential diagnosis on the two new species are given, in which some morphological affinities and distinguishing characters with other related congeners are detailed and highlighted. Comments on the ecology and geographical distribution of the new species are also provided.

The first record of Trichotanypus Kieffer (Diptera, Chironomidae: Podonominae) in the Tibet Plateau of China, with description of a new species.

Trichotanypus hani sp. nov. is described here based on the male, pupa and larva collected in the Tibet Plateau. The new species is characteristic by the elongated posterolateral heel of gonostylus in the male, bifid thoracic horn in the pupa and 8-10 mandible teeth in the larva. This is the first formal record of Trichotanypus from East Asia, indeed the first far-outside the circum-Arctic area.

A new species of Goeldichironomus Fittkau, 1965 from Argentina (Chironomidae, Chironominae).

Goeldichironomus pampeanus n. sp. is described and figured as male, pupa and larva based on reared specimens from Buenos Aires province in Argentina. The species can be separated from its congeners on the combination of the following characters: male without dark markings on thorax and an evenly curved superior volsella projecting mesad; pupa with extensive shagreen on tergites IIVI, sternites with fine shagreen only without transverse bands of points, dorsal setae on tergite IX extending beyond anal lobe and basal ring of thoracic horn kidney-shaped; larva with bifid premandible, mentum with 6 pairs of lateral teeth, anterior pair of ventral tubules simple, labral sclerite 1 intact and labral sclerite 2 consolidated on the inner side.

Propsilocerus Kieffer, 1923 shares morphological synapomorphies with Prodiamesinae

In their comprehensive analysis Cranston et al. (2012) quite unexpectedly recovered a monophyletic Orthocladiinae, except that Propsilocerus Kieffer, 1923, was recovered as a representative of Prodiamesinae. In this short communication I show that Propsilocerus shares morphological synapomorphies with other Prodiamesinae – namely (i) an indirect tracheal connection of the pupal thoracic horn to the adult spiracle and (ii) a parallel-sided rami of female gonapophysis IX.

Life histories of Paucispinigera Freeman, Paraborniella Freeman and Paratendipes Kieffer (Diptera: Chironomidae) with phylogenetic considerations.

The immature stages of the New Zealand endemic Paucispinigera Freeman and Paraborniella Freeman, endemic to Australia, are described fully for the first time. A new species of Paratendipes Kieffer endemic to Australia is described in all life stages. Morphological support from larvae for placement in a 'Microtendipes' group in tribe Chironomini includes the 6-segmented antenna with Lauterborn organs on the 2nd and 3rd segments, and a well-demarcated, multi-toothed ventromentum. The pupa has a few-branched thoracic horn and the distribution of taeniate L-setae is informative. Significant differentiating characters of the adult male include the form of tibial apices and the structures of superior and median volsellae in the genitalia. In the wing of Paucispinigera, the squama lacks setae, contrary to the original description, and unusually has vein M1+2 setose in both sexes and also the M3+4 setose in the female. An apical spine on the gonostylus of Paucispinigera is unusual. The female genitalia are described here for the first time but lack phylogenetically informative variation. An Australian species of the widespread genus Paratendipes Kieffer, described here as Paratendipes sinespina sp. n., is provided for comparison. Paucispinigera and Paraborniella each warrant independent generic rank.

Two new endemic species of Bistriopelma (Araneae: Theraphosidae) from Peru, including a new remarkable horned tarantula

The spider genus Bistriopelma Kaderka, 2015 is endemic to Peru and includes three species known to date: Bistriopelma lamasi Kaderka, 2015, B. matuskai Kaderka, 2015 and B. titicaca Kaderka, 2017. The present contribution diagnoses, describes and illustrates two new species of Bistriopelma from Peru: B. peyoi sp. nov. and B. kiwicha sp. nov., both based on male and female. The male of B. peyoi sp. nov. is provided with a remarkable thoracic horn, and the species is the first horned tarantula for this genus. An updated distribution map for all known species is presented.

The multistep morphing of beetle horns.

Genes that specify insect wings initiate horn development in dung beetles

Phylogeny of marine Ainuyusurika tuberculata (Tokunaga) (Diptera: Chironomidae: Chironominae), with description of the immature stages.

The marine Chironomidae Ainuyusurika Sasa et Shirasaka, 1988, previously known from the adults only, is associated with its immature stages for the first time based on reared specimens from Oriental China. The larva resembles those of Sergentia Kieffer and Endochironomus Kieffer in the ventromental plate with an anteromedial projection and the 5-segmented antenna with opposite Lauterborn organs. The pupal thoracic horn has 12 branches at maximum and netted tergite spinulation which appears to be similar to those of Polypedilum Kieffer, Endotribelos Grodhaus, Phaenopsectra Kieffer and Sergentia. The phylogenetic relationship was furtherly explored through molecular analysis based on concatenation of five gene makers (18S, 28S, CAD1, CAD4 and COI-3P) using both mixed-model Bayesian and maximum likelihood inference methods. The result shows Ainuyusurika is nested with an assemblage of Endochironomus, Phaenopsectra and Endotribelos. We concluded that Ainuyusurika is a good independent genus showing affinity with Endochironomus-Phaenopsectra related genera.

Contest interactions and outcomes: relative body size and aggression independently predict contest status

In species with pronounced male armaments, body and weapon size often determine success in agonistic interactions. However, the behavioural components of interactions also play a significant role in determining outcomes and individuals that win agonistic interactions may not be the ones that start contests. In this study, we used dyadic, intrasexual assays to characterize agonistic behaviours and determine whether body size and/or the propensity to start interactions influences contest outcome. We characterized agonistic interactions from start to end in the sexually dimorphic forked fungus beetle, Bolitotherus cornutus. Males of the species are known to use their thoracic horns in intrasexual combat, but other aspects of male–male behaviour are undescribed. We created an ethogram that described transitions between behaviours and categorized actions as aggressive, nonaggressive and mounting. Individual aggressive and nonaggressive behaviours were highly repeatable between trials while mounting behaviours were not repeatable. The initiation of nonaggressive and mounting behaviours was not predictive of contest outcome. Relative body size and absolute aggression independently predicted contest outcome. Our results indicate that traits important for establishing contest outcome are not always correlated. Considering either aggression or body size alone may be misleading when determining competitor abilities.

The Insulin Signaling Substrate Chico and the Ecdysone Response Element Broad Both Regulate Growth of the Head Horns in the Asian Rhinoceros Beetle, Trypoxylus dichotomus.

Males of the Asian rhinoceros beetle, Trypoxylus dichotomus, possess exaggerated head and thoracic horns that scale dramatically out of proportion to body size. While RNAi-mediated knockdowns of the insulin receptor suggest that the insulin signaling pathway regulates nutrition-dependent growth including exaggerated horns, the genes that regulate disproportionate growth have yet to be identified. We used RNAi-mediated knockdown of several genes to investigate their potential role in growth and scaling of the sexually dimorphic, exaggerated head horns of T. dichotomus. Knockdown of the insulin signaling substrate chico and the ecdysone response element broad caused significant decreases in head horn length, while having no or minimal effects on other structures such as elytra and tibiae. However, scaling of horns to body size was not affected by either knockdown. In addition, knockdown of phosphatase and tensin homolog, a negative regulator of the insulin signaling pathway, had no significant effects on any trait. Our results do not identify any candidate genes that may specifically mediate the allometric aspect of horn growth, but they do confirm the insulin signaling pathway as a mediator of conditional trait expression, and importantly implicate the ecdysone signaling pathway, possibly in conjunction with insulin signaling, as an additional mediator of horn growth.

Precise staging of beetle horn formation in Trypoxylus dichotomus reveals the pleiotropic roles of doublesex depending on the spatiotemporal developmental contexts.

Many scarab beetles have sexually dimorphic exaggerated horns that are an evolutionary novelty. Since the shape, number, size, and location of horns are highly diverged within Scarabaeidae, beetle horns are an attractive model for studying the evolution of sexually dimorphic and novel traits. In beetles including the Japanese rhinoceros beetle Trypoxylus dichotomus, the sex differentiation gene doublesex (dsx) plays a crucial role in sexually dimorphic horn formation during larval-pupal development. However, knowledge of when and how dsx drives the gene regulatory network (GRN) for horn formation to form sexually dimorphic horns during development remains elusive. To address this issue, we identified a Trypoxylus-ortholog of the sex determination gene, transformer (tra), that regulates sex-specific splicing of the dsx pre-mRNA, and whose loss of function results in sex transformation. By knocking down tra function at multiple developmental timepoints during larval-pupal development, we estimated the onset when the sex-specific GRN for horn formation is driven. In addition, we also revealed that dsx regulates different aspects of morphogenetic activities during the prepupal and pupal developmental stages to form appropriate morphologies of pupal head and thoracic horn primordia as well as those of adult horns. Based on these findings, we discuss the evolutionary developmental background of sexually dimorphic trait growth in horned beetles.

Parapentaneura (Diptera: Chironomidae: Tanypodinae) breeding in phytotelmata and the conflictive phylogenetic relationship with Pentaneura and Hudsonimyia

A new species of Parapentaneura Stur, Fittkau et Serrano 2006 (Diptera: Chironomidae: Tanypodinae) breeding on phytotelmata of the bromeliad Aechmea distichantha Lemaire in northwestern of argentinean “Yungas” is described and adults and immatures are figured. The first formal description of a Parapentaneura female adult is conducted. Information about bionomics and distribution of the new species is provided. Notes about morphology traits of phytotelm pupae of Tanypodinae are presented. These pupae tend to have thoracic horns relatively long, non-globose, corona absent and the atrium not or slightly lobulated. The phylogenetic relationship between the genera Parapentaneura, Pentaneura Philippi and Hudsonimyia Roback is tested in a phylogenetic analysis in the context of the cladistic setting of Tanypodinae recently proposed and, characters are analyzed and discussed.

Rhinoceros beetle horn development reveals deep parallels with dung beetles.

Beetle horns are attractive models for studying the evolution of novel traits, as they display diverse shapes, sizes, and numbers among closely related species within the family Scarabaeidae. Horns radiated prolifically and independently in two distant subfamilies of scarabs, the dung beetles (Scarabaeinae), and the rhinoceros beetles (Dynastinae). However, current knowledge of the mechanisms underlying horn diversification remains limited to a single genus of dung beetles, Onthophagus. Here we unveil 11 horn formation genes in a rhinoceros beetle, Trypoxylus dichotomus. These 11 genes are mostly categorized as larval head- and appendage-patterning genes that also are involved in Onthophagus horn formation, suggesting the same suite of genes was recruited in each lineage during horn evolution. Although our RNAi analyses reveal interesting differences in the functions of a few of these genes, the overwhelming conclusion is that both head and thoracic horns develop similarly in Trypoxylus and Onthophagus, originating in the same developmental regions and deploying similar portions of appendage patterning networks during their growth. Our findings highlight deep parallels in the development of rhinoceros and dung beetle horns, suggesting either that both horn types arose in the common ancestor of all scarabs, a surprising reconstruction of horn evolution that would mean the majority of scarab species (~35,000) actively repress horn growth, or that parallel origins of these extravagant structures resulted from repeated co-option of the same underlying developmental processes.

The Fat-Dachsous signaling pathway regulates growth of horns in Trypoxylus dichotomus, but does not affect horn allometry

Males of the Asian rhinoceros beetle, Trypoxylus dichotomus, possess exaggerated head and thoracic horns that scale dramatically out of proportion to body size. While studies of insulin signaling suggest that this pathway regulates nutrition-dependent growth including exaggerated horns, what regulates disproportionate growth has yet to be identified. The Fat signaling pathway is a potential candidate for regulating disproportionate growth of sexually-selected traits, a hypothesis we advanced in a previous paper (Gotoh et al., 2015). To investigate the role of Fat signaling in the growth and scaling of the sexually dimorphic, condition-dependent traits of the in the Asian rhinoceros beetle T. dichotomus, we used RNA interference to knock down expression of fat and its co-receptor dachsous. Knockdown of fat, and to a lesser degree dachsous, caused shortening and widening of appendages, including the head and thoracic horns. However, scaling of horns to body size was not affected. Our results show that Fat signaling regulates horn growth in T. dichotomus as it does in appendage growth in other insects. However, we provide evidence that Fat signaling does not mediate the disproportionate, positive allometric growth of horns in T. dichotomus.

Djalmabatista (Diptera: Chironomidae: Tanypodinae) from Oriental China, with the description of a new species

Abstract. Djalmabatista sinica sp. n. is described and figured based on the adult male and pupa. The male can be separated from its congeners by the characteristic banded wing and the abdominal coloration, while the pupa differs from other species in the setal arrangement on abdominal segment III and the shape of the thoracic horn and the anal lobe. In addition, the pupa of D. reidi (Freeman, 1955) collected in China is briefly redescribed and a new distribution record is given.

Denopelopia amicitia, a new Tanypodinae from Brazil (Diptera, Chironomidae)

A new species of Denopelopia from Brazil is described based on adult male and pupa. The male of the new species can be distinguished from all other species of the genus by the genitalia and fore-tibial spur morphology. The pupa is very similar to those of Denopelopia atria, but it can be distinguished by the absence of distinct constrictions in the respiratory atrium of the thoracic horn. Generic diagnosis to male and pupa of Denopelopia is emended and keys to male and pupae of known species are provided.

The importance of scanning electron microscopy (sem) in taxonomy and morphology of Chironomidae (Diptera)

The paper reports on the value of scanning electron microscopy (SEM) in the taxonomy and morphology of Chironomidae. This method has been relatively rarely used in Chironomidae studies. Our studies suggest that the SEM method provides a lot of new information. For example, the plastron plate of the thoracic horn of Macropelopia nebulosa (Meigen) under light microscopy is visible as points, while under SEM we have found that it consists of a reticular structure with holes. By using SEM a more precise picture of the body structure of Chironomidae can be revealed. It allows researchers to explain inconsistencies in the existing descriptions of species. Another advantage of the SEM method is obtaining spatial images of the body and organs of Chironomidae. However, the SEM method also has some limitations. The main problem is dirt or debris (e.g. algae, mud, secretions, mucus, bacteria, etc.), which often settles on the external surface of structures, especially those which are uneven or covered with hair. The dirt should be removed after collection of chironomid material because if left in place it can become chemically fixed to various surfaces. It unnecessarily remains at the surface and final microscopic images may contain artifacts that obscure chironomid structures being investigated. In this way many details of the surface are thus unreadable. The results reported here indicate that SEM examination helps us to identify new morphological features and details that will facilitate the identification of species of Chironomidae and may help to clarify the function of various parts of the body. Fast development of electron microscope technique allows us to learn more about structure of different organisms.

First record of a Chironomidae pupa in amber

A pupal exuviae of a non-biting midge (Chironomidae) is recorded in Eocene Rovno amber from Ukraine. The exuviae belongs to an Orthocladiinae species. It possesses several traits characteristic for terrestrial species including non-fringed anal lobes without macrosetae, tergites with only minute shagreen, bare conjunctives, and absence of thoracic horns and frontal warts. Up to now, this is the earliest record of a preimaginal stage of Orthocladiinae, and the only record of a chironomidae pupal exuviae from amber.