Examination of the interior of sand fly (Diptera: Psychodidae) abdomen reveals novel cuticular structures involved in pheromone release: Discovering the manifold

The males of many species of New World Phlebotomines produce volatile terpenoid chemicals, shown in Lutzomyia longipalpis s.l. to be sex/aggregation pheromones. Pheromone is produced by secretory cells which surround a cuticular reservoir which collects the pheromone and passes it through a cuticular duct to the surface of the insect. The pheromone then passes through specialised cuticular structures on the abdominal surface prior to evaporation. The shape and distribution of the specialised structures are highly diverse and differ according to species. In this study we used SEM to examine the interior cuticular pheromone collection and transport structures of 3 members of the Lu. longipalpis s.l. species complex and Migonemyia migonei. We found a new structure which we have called the manifold which appears to be a substantial extension of the interior tergal cuticle connected in-line with the cuticular duct and reservoir. The manifold of the Campo Grande member of the complex is longer and wider than the Jacobina member whereas the manifold of the Sobral member was shorter than both other members of the complex. Overall, the secretory apparatus of the Sobral member was smaller than the other two. The manifold of M. migonei was very different to those found in Lu. longipalpis s.l. and was positioned in a pit-like structure within the tergal cuticle. The secretory reservoir was connected by a short duct to the manifold. Differences in the size and shape of the manifold may be related to the chemical structure of the pheromone and may have taxonomic value. Examination of the interior cuticle by SEM may help to locate the secretory apparatus of vector species where pheromonal activity has been inferred from behavioural studies but the external secretory structures or pheromones have not yet been found.

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae)

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. We have shown that the ventral surface of the suction disc is covered by dense arrays of microtrichia, which are stiff spine-like cuticular structures that only make tip contact. Our results demonstrate the impressive performance and versatility of blepharicerid suction organs and highlight their potential as a study system to explore biological suction mechanisms.

New genus and four new species of anthuroid isopods (Crustacea: Peracarida) from southern Mexican Pacific

Anthuroid Isopoda are a poorly studied crustacean taxon in the Tropical Eastern Pacific, barely 21 species recorded, while to the southern Mexican Pacific, only eight species have been recorded. This study aims to increase knowledge of the species that inhabit the region. One hundred and one specimens from seven localities of the coast of Guerrero and Oaxaca were examined. Four new species were identified, belonging to three genera and two families: Negoescuanthura bastidai n. gen., n. sp., Colanthura gabinae n. sp., Paranthura amorensis n. sp. and P. tientai n. sp. A new genus is established, Negoescuanthura, very close to the genus Accalathura; the former is characterized by sucker-like cuticular structures on the antennal peduncle, while the latter lack these structures.

Cuticular Structures in Micropterous Crickets (Orthoptera, Gryllidae, Petaloptilini, Gryllomorphini)

Orthoptera is a very diverse group that has colonized practically all terrestrial ecosystems on the planet. They have adapted to live in the endogenous environment as well as in caves so that some species exhibit troglomorphic characteristics. This group has been extensively studied due to its economic and social importance; however, many basic morphological and biological questions remain to be solved. In this study, a comparative morphological study by scanning electron microscopy of different structures of eight species of micropteran crickets of the tribes Gryllomorphini and Petaloptilini, whose tegmina had lost their flight and song functionality was carried out. Special emphasis was placed on the tegmina and their possible relationship to reproductive functions. In addition, to assess troglomorphism in the genus Petaloptila, the biometric parameters of six other species have been considered. Actualization of the lifestyle of the studied species has also been carried out. The results show structures not previously described in this group (gland openings, setae, pores, or group of campaniform sensilla). Structures not previously described in this group have been detected, and tegmina (glandular openings and devoured tegmina) seem to confer a role in reproduction. Troglomorphisms are only observed in species of the subgenus Zapetaloptila. Statistically, significant differences have been found in characters such as cephalic elongation, ocular reduction, greater length of appendages, and depigmentation.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations resulting from the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on morphological innovations of social insects to further our understanding of the evolution of social behaviours.

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae)

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of an aquatic insect larva (Blephariceridae), which clings to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found their adhesion was much less reduced by micro-roughness than terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. Moreover, we showed that spine-like microtrichia on the organ are stiff cuticular structures that only make tip contact on smooth and microstructured substrates. Our results highlight the performance and versatility of blepharicerid suction organs and introduce a new study system to explore biological suction.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations as a result of the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on innovations of social insects as individuals at the phenotypic level to further our understanding of the evolution of social behaviours.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

Background Explanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs. Results Using X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations as a result of the lack of wing muscles. Conclusions Rather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on innovations of social insects as individuals at the phenotypic level to further our understanding of the evolution of social behaviours.

Occurrence, ecological function and medical importance of dermestid beetle hastisetae

Hastisetae are a specific group of detachable setae characterizing the larvae of Megatominae (Coleoptera: Dermestidae), commonly known as carpet and khapra beetles. These setae are located on both thoracic and abdominal tergites and they are the primary defense of the larva against invertebrate predators. According to previous studies, the main purpose of hastisetae is to work as a mechanical obstacle, but they are also capable to block and kill a predator. Hastisetae, single or aggregate, function as an extremely efficient mechanical trap, based on an entangling mechanism of cuticular structures (spines and hairs) and body appendages (antennae, legs and mouthparts). It is believed that this defensive system evolved primarily to contrast predation by invertebrates, however it has been observed that hastisetae may affect vertebrates as well. Although information on the impacts of vertebrate predators of the beetles is lacking, hastisetae have been shown to be a possible threat for human health as an important contaminant of stored products (food and fabric), work and living environment. Review of past and recent literature on dermestid larvae has revealed that despite these structures indicated as one of the distinctive characters in species identification, very little is known about their ultrastructure, evolution and mechanism of action. In the present work, we will provide the state of knowledge on hastisetae in Dermestidae and we will present and discuss future research perspectives intended to bridge the existing knowledge gaps.

The role of the foregut in digestion in the cricket Teleogryllus commodus and the locust Chortoicetes terminifera

The role of the foregut (crop and proventriculus) in mechanical processing of food has received little attention in insects. Using the Australian plague locust (Chortoicetes terminifera) and the black field cricket (Teleogryllus commodus) as models, the role of the crop in processing of wheat or rye grass was examined. Interior cuticular structures (spines) of the foregut were described using light and scanning electron microscopy, with locusts having sclerotised structures and crops of crickets being unsclerotised internally. Muscular bands on the exterior surface of the crop part of the foregut are similar in males of both species, but contractions and movements are more forceful in locusts. Passage rate from the foregut is much faster in locusts (<3 h) than in crickets (>3 h). Water within the crop is reduced compared with the water content of fresh grass within the foregut of locusts, but water is increased in cricket crops. Spines within the crops are small relative to the size of food particles in both species. Some spines of locusts contain metals. The slower passage rate from the crop of crickets may be limited by the proventriculus. Foregut structure and food processing facilitates the generalist diet of crickets, but may restrict locusts to consuming softer grasses.