Fig 11 - uploaded by Brendon E Boudinot
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Muscles of metathorax and propodeum of Formica rufa, sagittal view, anterior to the left. (A) The simplified diagram of skeletomuscular system redrawn from the work of Markl (1966: Fig. 23). (B) The 3D reconstruction of the metathoracic and propodeal muscles.
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The mesosoma is the power core of the ant, containing critical structural and muscular elements for the movement
of the head, legs, and metasoma. It has been hypothesized that adaptation to ground locomotion and
the loss of flight led to the substantial rearrangements in the mesosoma in worker ants and that it is likely the
ant mesosoma has undergo...
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The global Insects as Food and Feed (IAFF) industry currently farms over a trillion individual insects a year and is growing rapidly. Intensive animal production systems are known to cause a range of negative affective states in livestock; given the potential scale of the IAFF industry, it is urgent to consider the welfare of the industry’s insect...
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... No such count is available for ants. However, as a composite across studies Aibekova et al., 2022;Lieberman et al., 2022), we here estimate for the first time that the body of a single adult ant of the worker caste may comprise at least 325 separate sclerites (59 of the head, 8 of the mesosoma, 156 of the legs, 24 of the metasoma) and 316 muscle groups (67 of the head, 74 of the mesosoma, 66 of the legs, 109 of the metasoma). We note 'at least', because the state of ant anatomy is such that no study has accounted for all of the sclerites and muscles of a single ant, whether worker, queen or male. ...
... Not only did the (spectacular!) work of Janet incompletely document the sclerites and muscles for each tagma examined due to technological limitation (see, e.g., Aibekova et al., 2022), but the documentation of ant morphologydin the sense of accounting for externally visible anatomical parts and variation thereofdhas progressed in the form of character matrices in steps from Baroni Urbani et al. (1992) to Keller et al. (2014). Now ant morphology cannot be comprehensively understood without manual or digital dissection, which has revealed an order of magnitude more variation than historically appreciated for each system that has been evaluated thus far (e.g., the head: Richter et al., 2022, the prosternum: unpubl. ...
... data). The estimate of sclerites and muscles above is summarized across recent phenome-scale studies using multiple modes of imaging, most prominently being micro-computed tomography (m-CT), which have comparatively documented the head Boudinot et al., 2021), mesosoma Aibekova et al., 2022), and metasoma (Lieberman et al., 2022) of worker ants for various species, and do not include the flight system nor the anatomical treatments of the male genitalia (Boudinot, 2013;Griebenow et al., 2023). With the immature yet pronouncedly advancing stage of ant anatomy here recognized, we may ask: How do these parts work? ...
The overarching objective of this chapter is to provide a survey of the developmental-functional axis of morphology for ants to provide a direct link between anatomy and ecology. It considers variables of function, biomechanics and interaction with the environment, whether through traction, space traversal (locomotion), sensation and response, or manipulation (such as stinging or mastication). Because the consequences of these functional variables extend essentially to all of ant natural history, we must restrict our scope to a set of examples, which we frame from the developmental-anatomical and evolutionary morphological perspective.
... The extrinsic muscles are named following the nomenclature established by Friedrich and Beutel (2008). The naming of the intrinsic muscles is based on the descriptions of Aibekova et al. (2022) and, following Friedrich and Beutel (2008), documented in supplementary online material Information 1. The terminology of cuticular structures employs the revised terminology introduced by Brannoch et al. (2017), supplemented by studies from Snodgrass (1935), Levereault (1936), Carbonell (1947), Gray and Mill (1985), Beutel et al. (2014) and Wieland (2013). ...
... Especially the elaborations of Carbonell (1947) proved to be extremely helpful and served as a primary reference for our comparisons. In Supporting Information S1: 1, we combined the information from previous works with our original results, transferring them into the current nomenclature system suggested by Friedrich and Beutel (2008) and Aibekova et al. (2022), thereby easing future comparative work that relies on musculature in Dictyoptera, and likely all Neoptera. By using the nomenclature of Friedrich and Beutel (2008), in agreement with Snodgrass (1935) definition of an individual muscle-considering a muscle as a functional group rather than individual fiber bundles-we propose a reduced set of extrinsic and intrinsic muscles in the thorax and all three pairs of walking legs for P. americana (Blattodea). ...
... For the intrinsic muscles, we adapted the basic principles of the nomenclature system introduced by Friedrich and Beutel (2008) supplemented by the approach of Aibekova et al. (2022), applying it to the previous descriptions including our new results (Supporting Information S1: 1). After careful consideration of the insights gained from the comparison with P. americana, we decided to combine the femoral reductor a and b as well as the femoral tibial flexor pennate and parallel to one muscle (trochanter femur muscle 1 [tfm1] in the trochanter and the femur tibia muscle 2 [ftm2] in the femur) respectively (Bäumler, Gorb, and Büsse 2023;Gray and Mill 1985). ...
Insect legs, as primarily locomotory devices, can show a tremendous variety of morphological modifications providing a multitude of usages. The prehensile raptorial forelegs of praying mantises (Mantodea) are a prominent example of true multifunctionality since they are used for walking while being efficient prey‐capturing and grasping devices. Although being mostly generalist arthropod predators, various morphological adaptations due to different environmental conditions occur across Mantodea. Recently, the general mantodean morphology, and particularly their raptorial forelegs, received an increased interest. Yet, knowledge about the evolutionary transition from walking to prey‐grasping legs is still scarce. From evolutionary and functional perspectives, the question arises: what changes were necessary to achieve the strongly modified raptorial forelegs—while keeping walking ability—and how does the foreleg morphology differ from the remaining four walking legs? In this context, we investigated the musculature of the raptorial forelegs in seven phylogenetically distant mantodeans, including pterothoracic legs in four of them, using high‐resolution microcomputed tomography and dissection. To understand the results from an evolutionary perspective, we additionally examined all three pairs of unmodified walking legs of the closest sister group—Blattodea. We updated the knowledge of blattodean morphology, revealing differences in cuticle structures of the coxal articulation of the first pair of legs between the two orders and a shared musculature set‐up in all pairs of legs among later‐branching mantodeans. Interestingly, the early branching species Metallyticus splendidus and Chaeteessa sp. show several muscular characteristics, otherwise found exclusively in one or the other order, with a few procoxal muscles showing an intermediate state between the two orders. Studying the evolutionary transition from a walking leg to a raptorial leg will help to understand the character evolution of this highly specialized biomechanical system from a purely locomotory appendage to a multi‐functional device with all related amenities and constraints.
... Twelve new species of Aphanerostethus are described based on specimens collected in Japan, Taiwan, Vietnam, and Malaysia, and seven of these exhibit stunning sexual dimorphism and species-specific variation in the metatibial unci. X-ray microtomography (hereafter X-ray μCT) has become a widely used tool in entomology and has broad applications including enhancing analysis of insects enclosed in amber (Kundrata et al. 2020;Kypke and Solodovnikov 2020), examination of internal morphology (Alba-Alejandre et al. 2019; Aibekova et al. 2022), and for taxonomic character discovery (Garcia et al. 2017;Lewis 2023). The great advantage of X-ray μCT is that it allows for a complete three-dimensional viewing of minute internal and external structures, including those obscured by musculature, dirt and debris, or scales, and that 3D models can be uploaded to online databases for viewing by anyone with access to a computer. ...
Weevils represent one of the most speciose and economically important animal clades, but remain poorly studied across much of the Oriental Region. Here, an integrative revision of the Oriental, flightless genus Aphanerostethus Voss, 1957 (Curculionidae: Molytinae) based on X-ray microtomography, multi-gene DNA barcoding (CO1, Cytb, 16S), and traditional morphological techniques (light microscopy, dissections) is presented. Twelve new species, namely, A. armatus Lewis & Kojima, sp. nov., A. bifidus Kojima & Lewis, sp. nov., A. darlingi Lewis, sp. nov., A. decoratus Lewis & Kojima, sp. nov., A. falcatus Kojima, Lewis & Fujisawa, sp. nov., A. incurvatus Kojima & Lewis, sp. nov., A. japonicus Lewis & Kojima, sp. nov., A. magnus Lewis & Kojima, sp. nov., A. morimotoi Kojima & Lewis, sp. nov., A. nudus Lewis & Kojima, sp. nov., A. spinosus Lewis & Kojima, sp. nov., and A. taiwanus Lewis, Fujisawa & Kojima, sp. nov. are described from Japan, Taiwan, Vietnam, and Malaysia. A neotype is designated for A. vannideki Voss, 1957. The hitherto monotypic genus Darumazo Morimoto & Miyakawa, 1985, syn. nov. is synonymized under Aphanerostethus based on new morphological data and Aphanerostethus distinctus (Morimoto & Miyakawa, 1985), comb. nov. is transferred accordingly. X-ray microtomography is successfully used to explore for stable interspecific differences in cuticular, internal and micro morphology. Remarkable species-specific sexual dimorphism in the metatibial uncus is described in seven of the newly described Aphanerostethus species and the evolution of this character is discussed.
... Our study is conducted in the emerging framework of phenomics, which relies heavily on µ-CT for the digitization of phenotypes, the documentation of fine external and internal anatomy, and the analysis of evolutionary and developmental patterns. Ants have received special interest in this regard, having been the subject of phenomic study for the head (e.g., workers: Richter et al., 2019Richter et al., , 2020Richter et al., , 2022Richter, Garcia, et al., 2021;males: Boudinot et al., 2021), the mesosoma (workers: Aibekova et al., 2022), the abdomen (workers: Lieberman et al., 2022), and recently, the male genitalia (Griebenow et al., 2023). ...
The male genitalia of insects are among the most variable, complex, and informative character systems for evolutionary analysis and taxonomic purposes. Because of these general properties, many generations of systematists have struggled to develop a theory of homology and alignment of parts. This struggle continues to the present day, where fundamentally different models and nomenclatures for the male genitalia of Hyme-noptera, for example, are applied. Here, we take a multimodal approach to digitalize and comprehensively document the genital skeletomuscular anatomy of the bullet ant (Paraponera clavata; Hymenoptera: Formicidae), including hand dissection, synchrotron radiation microcomputed tomography, microphotography, scanning electron micros-copy, confocal laser scanning microscopy, and 3D-printing. Through this work, we generate several new concepts for the structure and form of the male genitalia of Hymenoptera, such as for the endophallic sclerite (=fibula ducti), which we were able to evaluate in detail for the first time for any species. Based on this phenomic anatomical study and comparison with other Holometabola and Hexapoda, we reconsider the homologies of insect genitalia more broadly, and propose a series of clarifications in support of the penis-gonopod theory of male genital identity. Specifically, we use the male genitalia of Paraponera and insects more broadly as an empirical case for hierarchical homology by applying and refining the 5-category classification of serial homologs from DiFrisco et al. (2023) (DLW23) to all of our formalized concepts. Through this, we find that: (1) geometry is a critical attribute to account for in ontology, especially as all individually identifiable attributes are positionally indexed hence can be recognized as homomorphic; (2) the definition of "structure" proposed by DLW23 is difficult to apply, and likely heterogeneous; and (3) formative elements, or spatially defined foldings or in-or evaginations of the epidermis and cuticle, are an important yet overlooked class of homomorphs. We propose a morphogenetic model for male and female insect genitalia, and a model analogous to gene-tree species-tree mappings for the hierarchical homology of male genitalia specifically. For all of the structures evaluated in the present J. Morphol. 2024;285:e21757. wileyonlinelibrary.com/journal/jmor |
... Because µ-CT scanning and reconstruction can reveal three-dimensional (3D) details to the submicron level of resolution, this technique has become widespread in entomological research (e.g., Blanke et al., 2015;Brock et al., 2022;Hillen et al., 2023;Hörnschemeyer et al., 2002;van de Kamp et al., 2011van de Kamp et al., , 2014van de Kamp et al., , 2018van de Kamp et al., , 2022Püffel et al., 2021;Rühr et al., 2021). For the morphological study of extant Aculeata, µ-CT has been applied to Formicidae (e.g., Aibekova et al., 2022;Booher et al., 2021;Boudinot et al., 2021Boudinot et al., , 2022Griebenow et al., 2023;Klunk et al., 2023;Liu et al., 2019;Richter et al., 2020Richter et al., , 2021Richter et al., , 2022Richter et al., , 2023, spheciform Apoidea (Willsch et al., 2020, Sphecidae and Ampulicidae), and some anatomical systems of the honey bee (e.g., Alba-Tercedor & Alba-Alejandre, 2019; Berry & Ibbotson, 2010;de Paula et al., 2022;Ramirez-Esquivel & Ravi, 2023;Ribi et al., 2008). ...
... Aibekova et al. (2022) described two muscles that originate on the propleuron and insert on the postocciput: Itpm1 and Itpm2. We interpreted Itpm1 of Aibekova et al. (2022) as corresponding to our Itpm2a, and their Itpm2 as corresponding to our Itpm2b. This interpretation is based on the topology described by Aibekova et al. (2022) and as implied in Friedrich and Beutel (2008a), as both muscles originate on the ventral area of the propleuron (a common pattern for Itpm2) and none on the propleural ridge (as it would be expected for Itpm1). ...
... We interpreted Itpm1 of Aibekova et al. (2022) as corresponding to our Itpm2a, and their Itpm2 as corresponding to our Itpm2b. This interpretation is based on the topology described by Aibekova et al. (2022) and as implied in Friedrich and Beutel (2008a), as both muscles originate on the ventral area of the propleuron (a common pattern for Itpm2) and none on the propleural ridge (as it would be expected for Itpm1). ...
Although the knowledge of the skeletal morphology of bees has progressed enormously, a corresponding advance has not happened for the muscular system. Most of the knowledge about bee musculature was generated over 50 years ago, well before the digital revolution for anatomical imaging, including the application of microcomputed tomography. This technique, in particular, has made it possible to dissect small insects digitally, document anatomy efficiently and in detail, and visualize these data three dimensionally. In this study, we document the skeletomuscular system of a cuckoo bee, Thyreus albomaculatus and, with that, we provide a 3D atlas of bee skeletomuscular anatomy. The results obtained for Thyreus are compared with representatives of two other bee families (Andrenidae and Halictidae), to evaluate the generality of our morphological conclusions. Besides documenting 199 specific muscles in terms of origin, insertion, and structure, we update the interpretation of complex homologies in the maxillolabial complex of bee mouthparts. We also clarify the complicated 3D structure of the cephalic endoskeleton, identifying the tentorial, hypostomal, and postgenal structures and their connecting regions. We describe the anatomy of the medial elevator muscles of the head, precisely identifying their origins and insertions as well as their homologs in other groups of Hymenoptera. We reject the hypothesis that the synapomorphic propodeal triangle of Apoidea is homologous with the metapostnotum, and instead recognize that this is a modification of the third phragma. We recognize two previously undocumented metasomal muscle groups in bees, clarifying the serial skeletomusculature of the metasoma and revealing shortcomings of Snodgrass' “internal–external” terminological system for the abdomen. Finally, we elucidate the muscular structure of the sting apparatus, resolving previously unclear interpretations. The work conducted herein not only provides new insights into bee morphology but also represents a source for future phenomic research on Hymenoptera.
... Even if technical resources are limited, this can be extended using models from platforms like Sketchfab (Epic Games, Cary, North Carolina, USA) or MorphoSource (Morpho-Source.org). In our study as well as in previous contributions (Aibekova et al. 2022;Tröger et al. 2023;Weingardt et al. 2023), these options were used to visualize complex 3-dimensional structures in an easily accessible way to contribute to a better understanding of insect morphology. ...
As the only direct records of the history of evolution, it is critical to determine the geological source of biota-bearing fossils. Through the application of synchrotron-radiation micro-computed tomography (SR-µ-CT), Fourier-transformed infrared-spectroscopy (FT-IR), visual evaluation of ultraviolet fluorescence (UV-VS), radiocarbon dating (¹⁴C quantification), and historical sleuthing, we were able to identify and sort 161 (83 Baltic amber, 71 Copal and 7 Kauri gum pieces) individually numbered and largely mislabeled pieces of East African Defaunation resin (~145 years old) and copal (~390 years old), as well as Baltic amber (~35 million years old) from the Phyletisches Museum collection. Based on this collection, we define two new species: ‡Amphientomum knorrei Weingardt, Bock & Boudinot, sp. nov. (Psocodea: Amphientomidae, copal) and †Baltistena nigrispinata Batelka, Tröger & Bock, sp. nov. (Coleoptera: Mordellidae, Baltic amber). For selected taxa, we provide systematic reviews of the fossil record, including: Amphientomidae, for which we provide a key to all species of Amphientomum, extant and extinct, and recognize the junior synonymy of Am. ectostriolatum Li, 2002 (an unjustified emendation) under Am. ectostriolate Li, 1999 (syn. nov.); the fossil ant genus †Yantaromyrmex and the clades Dorylinae, Plagiolepidini, Camponotus, Crematogaster, and Pheidole (Formicidae); the Nevrorthidae (Neuroptera); and Doliopygus (Coleoptera: Curculionidae: Platypodinae). We synonymize Palaeoseopsis Enderlein, 1925 with Amphientomum Pictet, 1854, syn. nov. and transfer one species from Amphientomum, forming Lithoseopsis indentatum (Turner, 1975), comb. nov. To prevent the uncritical usage of unidentifiable fossils attributed to Camponotus for macroevolutionary analysis, we transfer 29 species to the form genus †Camponotites Steinbach, 1967, which we consider to be most useful as incertae sedis in the Formicinae. We treat †Ctt. ullrichi (Bachmayer, 1960), comb. nov. as unidentifiable hence invalid stat. nov. We also transfer †Ca. mengei Mayr, 1868 and its junior synonym †Ca. igneus Mayr, 1868 to a new genus, †Eocamponotus Boudinot, gen. nov., which is incertae sedis in the Camponotini. Concluding our revision of Camponotus fossils, we transfer †Ca. palaeopterus (Zhang, 1989) to Liometopum (Dolichoderinae), resulting in †L. palaeopterumcomb. nov. and the junior synonymy of †Shanwangella Zhang, 1989, syn. nov. under Liometopum Mayr, 1861. Because the type specimens of the genera †Palaeosminthurus Pierce & Gibron, 1962, stat. rev. and †Pseudocamponotus Carpenter, 1930 are unidentifiable due to poor preservation, we consider these taxa unidentifiable hence invalid stat. nov. To avoid unsupported use of the available fossils names attributed to Crematogaster for divergence dating calibration points, we transfer three species to a new collective taxon that is incertae sedis in Myrmicinae, †Incertogaster Boudinot, gen. nov., forming †In. aurora (LaPolla & Greenwalt, 2015), †In. praecursor (Emery, 1891), comb. nov., and †In. primitiva (Radchenko & Dlussky, 2019), comb. nov. Finally, we transfer †Ph. cordata (Holl, 1829) back to Pheidole, and designate a neotype from our copal collection based on all available evidence. All new species plus the neotype of ‡Ph. cordata are depicted with 3D cybertypes from our µ-CT scan data. We introduce the convention of a double dagger symbol (‡) to indicate fossils in copal or Defaunation resin, as these may yet be extant. To further contextualize our results, we provide a discussion of amber history and classification, as well as the Kleinkuhren locality, to which multiple specimens were attributed. We conclude with conspecti on key biological problems and increasing potential of µ-CT for phylogenetic paleontology.
... Indeed, the load rotates possibly due to the moment of force applied by the ants. Other technics are used in ants to characterized the displacements of a subjects, such as the evolution of the variation of the center of mass (Merienne et al. 2019;Reinhardt et al. 2014;Drapin et al. 2021) using 3D kinematics (Merienne et al. 2021;Drapin et al. 2021;Arroyave-Tobon et al. 2022) and morphometry (Drapin et al. 2021;Aibekova et al. 2022). By combining the variation of the position of the center of mass with kinematics data regarding the precision of the morphometry, perspectives on the participation and influence of each individual during a load carrying in ants should be possible in term of forces and momentum. ...
... The nomenclature for the skeletal structure and muscular system of the leg primarily relies on Aibekova's and Yavorskaya's research findings (Aibekova et al., 2022;Yavorskaya et al., 2023). ...
... To investigate the positional changes in the metacoxa and metatrochanter of S. femorata's metathorax, we conducted micro-CT scans on the metathorax (Fig. 2B−L) and reconstructed the internal muscles and external cuticle during the first stage (Fig. 2H, I) and third stage (Fig. 2K, L) of rotation of the metacoxa and metatrochanter. In addition to the metacoxa and metatrochanter cuticle, there were 4 muscles in which the starting point and insertion point were in the metacoxatrochanter joint; the muscle nomenclature refers to Aibekova et al. (2022) and Yavorskaya et al. (2023): ...
Insect legs play a crucial role in various modes of locomotion, including walking, jumping, swimming, and other forms of movement. The flexibility of their leg joints is critical in enabling various modes of locomotion. The frog-legged leaf beetle Sagra femorata possesses remarkably enlarged hind legs, which are considered to be a critical adaptation that enables the species to withstand external pressures. When confronted with external threats, S. femorata initiates a stress response by rapidly rotating its hind legs backward and upward to a specific angle, thereby potentially intimidating potential assailants. Based on video analysis, we identified 4 distinct phases of the hind leg rotation process in S. femorata, which were determined by the range of rotation angles (0°-168.77°). Utilizing micro-computed tomography (micro-CT) technology, we performed a 3-dimensional (3D) reconstruction and conducted relative positioning and volumetric analysis of the metacoxa and metatrochanter of S. femorata. Our analysis revealed that the metacoxa-trochanter joint is a "screw-nut" structure connected by 4 muscles, which regulate the rotation of the legs. Further testing using a 3D-printed model of the metacoxa-trochanter joint demonstrated its possession of a self-locking mechanism capable of securing the legs in specific positions to prevent excessive rotation and dislocation. It can be envisioned that this self-locking mechanism holds potential for application in bio-inspired robotics.
... The term "chaetae" (Boudinot et al., 2020;Boudinot et al., 2022a;Boudinot et al., 2022b) was used to describe the clypeal, labral, and mandibular armature in place of denticles or spicules (Perrichot, 2013). For the mesosomal sclerites of the gynes I followed Boudinot (2015); specifically for the pleural regions of workers and gynes I followed Aibekova et al. (2022). ...
The extinct Cretaceous ant genus Zigrasimecia Barden & Grimaldi, the “iron maiden ants” from Myanmar, is revised, and five new species are described: †Z. boudinoti sp. nov., †Z. caohuijiae sp. nov.,†Z. chuyangsui sp. nov., †Z. perrichoti sp. nov., and †Z. thate sp. nov. Zigrasimecia hoelldobleri paratype (CNU-HYM-MA2019054) is removed from the type series. New diagnoses for all species are provided and species boundaries are discussed. Studied specimens that are not ideally preserved are presented and discussed, some of them are putative new species. Two identification keys for the genus are provided, a traditional, dichotomous key and an interactive, multi-entry key hosted online at the website www.Xper3.fr. I briefly discuss the unlikeliness of the genus Boltonimecia to belong to the subfamily Zigrasimeciinae, and also the taxonomic problem caused by the description of species based on alates and poorly preserved fossils.
... The accuracy of the tracing algorithm in Katzke et al. (2022) was 92% for fiber length estimation and 100% for the pennation angle estimation. Muscle identity and nomenclature follows Aibekova et al. (2022 ). Muscles most relevant in the movement of the legs were segmented (Ipcm2, Iscm4, I-, II-, IIIscm1, II-, IIIscm2, I-, II-, IIIscm3, Ipcm8, II-, IIIscm6, Ipcm4, II-, IIIpcm3_4, I-, II-, IIIctm1, I-, II-, IIIctm2, I-, II-, IIIctm3); in addition, large muscles, including the indirect muscle of the head (Idvm5), the levator (IA1), and one of the rotators (IA2) of abdomen were segmented for control. ...
... This parallelism among jumping ants with regards to the increase in relative volume of the trochanter depressors scm6 in the mid and hind legs is particularly relevant due to the anatomical peculiarities of this muscle. Unlike the other trochanter depressor (ctm3) which originates inside the coxa (as do the trochanter levator pair, ctm1-ctm2), trochanter depressor scm6 is an extrinsic muscle which originates in the thorax (e.g., dorsal pleural areas, furcal arms, and/or notum of mesosoma) ( Aibekova et al. 2022 ). This general anatomical arrangement already results in the muscle being longer than any of the other trochanter muscles in non-jumping ants, while in jumping ants it was possible for this muscle to enlarge into proportions that are effective for upward action, occupying a large portion of the otherwise free thoracic cavity. ...
Synopsis
Jumping is a rapid locomotory mode widespread in terrestrial organisms. However, it is a rare specialization in ants. Forward jumping has been reported within four distantly related ant genera: Gigantiops, Harpegnathos, Myrmecia, and Odontomachus. The temporal engagement of legs/body parts during jump, however, varies across these genera. It is unknown what morphological adaptations underlie such behaviors and whether jumping in ants is solely driven directly by muscle contraction or additionally relies on elastic recoil mechanism. We investigated the morphological adaptations for jumping behavior by comparing differences in the locomotory musculature between jumping and non-jumping relatives using X-ray micro-CT and 3D morphometrics. We found that the size-specific volumes of the trochanter depressor muscle (scm6) of the middle and hind legs are 3–5 times larger in jumping ants, and that one coxal remotor muscle (scm2) is reduced in volume in the middle and/or hind legs. Notably, the enlargement in the volume of other muscle groups is directly linked to the legs or body parts engaged during the jump. Furthermore, a direct comparison of the muscle architecture revealed two significant differences between jumping vs. non-jumping ants: First, the relative Physiological Cross-Sectional Area (PCSA) of the trochanter depressor muscles of all three legs were larger in jumping ants, except in the front legs of Odontomachus rixosus and Myrmecia nigrocincta; second, the relative muscle fiber length was shorter in jumping ants compared to non-jumping counterparts, except in the front legs of O. rixosus and M. nigrocincta. These results suggest that the difference in relative muscle volume in jumping ants is largely invested in the area (PCSA), and not in fiber length. There was no clear difference in the pennation angle between jumping and non-jumping ants. Additionally, we report that the hind leg length relative to body length was longer in jumping ants. Based on direct comparison of the observed vs. possible work and power output during jumps, we surmise that direct muscle contractions suffice to explain jumping performance in three species, except for O. rixosus, where the lack of data on jumping performance prevents us from drawing definitive conclusions for this particular species. We suggest that increased investment in jumping-relevant musculature is a primary morphological adaptation that separates jumping from non-jumping ants. These results elucidate the common and idiosyncratic morphological changes underlying this rare adaptation in ants.
まとぅみ (Okinawan language—Uchinaaguchi)
要旨 (Japanese)
РЕЗЮМЕ (Kazakh)
ZUSAMMENFASSUNG (German)
