Arthropod Structure & Development最新文献

In lower termites, which exhibit a high degree of compound eye degradation or absence, antennae play a pivotal role in information acquisition. This comprehensive study investigates the olfactory system of Reticulitermes aculabialis, spanning five developmental stages and three castes. Initially, we characterize the structures and distribution of antennal sensilla across different developmental stages. Results demonstrate variations in sensilla types and distributions among stages, aligning with caste-specific division of labor and suggesting their involvement in environmental sensitivity detection, signal differentiation, and nestmate recognition. Subsequently, we explore the impact of antennal excision on olfactory gene expression in various caste categories through transcriptomics, homology analysis, and expression profiling. Findings reveal that olfactory genes expression is influenced by antennal excision, with outcomes varying according to caste and the extent of excision. Finally, utilizing fluorescence in situ hybridization, we precisely localize the expression sites of olfactory genes within the antennae. This research reveals the intricate and adaptable nature of the termite olfactory system, highlighting its significance in adapting to diverse ecological roles and demands of social living.

Factors regulating larval growth and determinants of adult body size are described for several holometabolous insects, but less is known about brain size scaling through development. Here we use the isotropic fractionation (“brain soup”) method to estimate the number of brain cells and cell density for the whitelined sphinx moth (Lepidoptera: Hyles lineata) from the first instar through the adult stage. We measure mass and brain cell number and find that, during the larval stages, body mass shows an exponential relationship with head width, while the total number of brain cells increases asymptotically. Larval brain cell number increases by a factor of ten from nearly 8000 in the first instar to over 80,000 in the fifth instar. Brain cell number increases by another factor of 10 during metamorphosis, with the adult brain containing more than 900,000 cells. This is similar to increases during development in the vinegar fly (Drosophila melanogaster) and the black soldier fly (Hermetia illucens). The adult brain falls slightly below the brain-to-body allometry for wasps and bees but is comparable in the number of cells per unit brain mass, indicating a general conservation of brain cell density across these divergent lineages.

The mouth apparatus in larvae of the freshwater mite Limnochares aquatica (L., 1758) (Acariformes, Limnocharidae), belonging to the lower Hydrachnidia, was studied with light microscopy, scanning (SEM) and transmission (TEM) electron microscopy, as well as with confocal laser scanning microscopy (CLSM) to reveal its main morphological and functional characteristics. The gnathosoma, functioning as a mouth organ takes a prognathous position, and inclines to the body axial line at the angle of around 30°. The gnathosoma is composed of segments of the two pairs of anterior appendages and their derivatives – two-segmented chelicerae lying above the infracapitulum – the compound medial portion of the palpal coxae, and five-segmented palps, articulated with the infracapitulum laterally. The palp tibia bears the bifid palpal claw facing downward nearly at right angle. The basal cheliceral segments are free, i.e., are not covered with the integumental fold posteriorly, and do not fuse with each other. Apically, they articulate with the relatively short movable digits composed of the basal portion (lever) and the distal portion (the cheliceral blades) curved upward by their ends. The flexible fixed digits protrude forward from the distal parts of the basal cheliceral segments. The ventral wall of the gnathosoma (mentum) transforms into a very specific papillary area (velum). A papillary area with long slim papillae is formed of a light cuticle and likely acts as a sucker but does not have contractile elements. The hypostome possesses the well developed lateral lips (galea) tightly embracing the distal portions of the chelicerae and hiding the movable digits. The roof of the infracapitulum (the cervix, or epistome) lying beneath the chelicerae, shows a compound structure. Anteriorly it connects with the inner hypostomal walls forming a particular pharyngeal ring framing the narrow mouth opening. We saw no evidence of a labrum. A characteristic valve projects forward from the dorsal surface of the cervix. A crescent-shaped pharynx runs along the bottom of the infracapitulum and is attached but not fused with the cuticle of the papillary area. The dorsal pharyngeal dilators originate on the cervix, sigmoid pieces and the lateral walls of the infracapitulum at their junction with the dorsal walls of the basal cheliceral segments. A pair of sigmoid pieces having small cavities inside serves for termination of the cheliceral elevators originated on the posterior portions of the dorsal walls of the basal cheliceral segments. The organizational pattern of the gnathosoma in larvae of L. aquatica is rather specific and is quite different from those of other aquatic or terrestrial parasitengonin larvae.

The genera Omosita and Nitidula from the family Nitidulidae, are often reported to be associated with rotten animal carcasses. However, morphological descriptions of their larval stages are limited and are usually only from the third instar larvae, which does not provide enough systematic data. In this study, the overall structure of three instar larvae from the four Nitidulidae species was compared using optical microscopy, and the resolution was not satisfactory. To compensate, a large number of structures and organs were observed by scanning electron microscopy (SEM). Results showed that the number and distribution of chaetotaxy in different parts, including the macrosetae, setae, and microtrichia, have important identification values between the genera, species, and even instars. We also discuss the possible role of microtrichia in the biology of Nitidulidae larvae. Additionally, we described the number and types of sensilla in three sensory organs, and the morphologic parameters of the head capsule and urogomphi as determined by SEM images, are provided. An identification key with application value for storage products and forensic entomology was also compiled.

The Asian corn borer, Ostrinia furnacalis (Guenée), is one of the most destructive lepidopteran pests affecting maize in Asia. Previous research on the feeding behavior of O. furnacalis has mostly focused on larvae, but the adult feeding preference has been unclear hitherto. In this study, we investigated the ultramorphology of the proboscis and sensilla of O. furnacalis using scanning electron microscopy and made morphological comparisons between the sexes, attempting to make predictions on the food preference and feeding behavior of the adults. The proboscis of O. furnacalis is divided into zones 1 and 2 with three types of sensilla, namely chaetica, basiconica, and styloconica. The entire proboscis and zone 2 of the females are significantly longer than those of the males. The main sexual difference in the sensilla is shown in the number of sensilla styloconica, which are eight in females but nine in males. The feeding preference of adult O. furnacalis is discussed based on the morphology of the proboscis and sensilla.

Some Pyrochroidae species are known as “canthariphilous” for their attraction to cantharidin (CTD), a toxic terpene with anti-predatory effects, produced in nature by only two beetle families (Meloidae and Oedemeridae). It has been demonstrated that males of Neopyrochroa flabellata ingesting CTD are positively selected by females. Indeed, the compound is re-emitted from a glandular cranial apparatus as secretions that are licked up by females during courtship behaviour, inducing copulation. Herein, we provide the first description of the glands associated to the cranial apparatus of male Pyrochroinae using the European species Pyrochroa coccinea as a model. Morphological analyses show that the cranial apparatus consists of a concave pit lined with short setae retaining secretions emitted through numerous glandular pores. Ultrastructural investigations reveal the presence of two different class 3 glands (Gl.A and Gl.B), intermixed at the level of the pit but exhibiting distinct features. Gl.A are mainly characterised by short conducting canals, rounded nuclei and electrondense vesicles while Gl.B are characterised by long conducting canals, irregular nuclei, vesicles containing a particulate substance and a multifolded plasma membrane. Observations of sexual behaviour are also reported for P. coccinea and compared to N. flabellata, confirming the involvement of cranial apparatus secretions in courtship behaviour.

The morphology of the immature stages of Utetes anastrephae (Hymenoptera: Braconidae), a native parasitoid of larvae of flies of the Neotropical genus Anastrepha (Diptera: Tephritidae), is shown. This study aimed to characterize the immature stages and morphological changes in the development of the koinobiont endoparasitoid in two species of larval hosts, Anastrepha obliqua and Anastrepha ludens. The definition of structures and morphological changes during development was made through daily microscopic observations and photographs of dissected hosts. The immature development of the parasitoid corresponds to a holometabolous insect with three well-defined stages: egg (two days), larva with three larval instars (approximately eight days), and pupa (six days). Similar development times were obtained in the two host species. Males and females completed their cycle in 17 and 18 days, respectively. During egg-first instar development, host antagonistic activity through melanization and encapsulation as mortality factors was evident and frequent only in A. obliqua. These results serve as basic knowledge for the use of this parasitoid in the biological control of fruit flies.

Immunohistochemical analyses on the distribution of neuropeptides in the pancrustacean brain in the past have focussed mostly on representatives of the decapod (“ten-legged”) pancrustaceans whereas other taxa are understudied in this respect. The current report examines the post-embryogenic and adult brain and ventral nerve cord of the amphipod pancrustacean Parhyale hawaiensis (Dana. 1853; Peracarida, Amphipoda, Hyalide), a subtropical species with a body size of 1.5 cm and a direct post-embryonic development using immunohistochemistry to label the neuropeptide SIFamide and synaptic proteins (synapsins). We found strong SIFamide-like labelling in proto-, deuto- and tritocerebrum, especially in the lamina, the lateral protocerebrum, lateral assessory lobe, the central body, olfactory lobe, medial antenna 1 neuropil and antenna 2 neuropil. Out of a total of 28 ± 5 (N = 12) SIFamide-positive neurons in the central brain of adult P. hawaiensis, we found three individually identifiable somata which were consistently present within the brain of adult and subadult animals. Additionally, the subesophageal and two adjacent thoracic ganglia were analysed in only adult animals and also showed a strong SIFamide-like immunoreactivity. We compare our findings to other pancrustaceans including hexapods and discuss them in an evolutionary context.

The mandibular gland is an important exocrine gland connected to the mandibles. In ants, it plays a crucial role in alarm communication and reproduction. While the overall morphology of the mandibular gland does not vary much between ant species, significant differences exist in the ultrastructural characteristics and gland size in some reported cases. However, there have been few systematic comparative studies on this subject. In this paper, we conducted microscopic observations to analyze the morphological and ultrastructural similarities and differences of the mandibular gland in different castes of Camponotus japonicus. Our findings revealed that the mandibular glands of males were significantly larger than those of females. In terms of relative size, within the female castes the mandibular glands of minor workers were the largest. Additionally, our observations of the ultrastructure showed that secretory substances were most abundant in queens. All female castes and males showed the presence of crystalline structures in the secretory cells. The content of these biocrystals decreased from minor workers to major workers, queens, and males. In males, however, crystalline structures were rare and the most abundant substances are droplet-like secretions. The differences in morphology and ultrastructure between different castes suggest that the function of the mandibular gland varies among castes. In conclusion, our study provides insights into the morphological and ultrastructural characteristics of the mandibular gland in different castes of C. japonicus. Further research is needed to fully understand the specific functions and mechanisms of this gland in ants.

Regeneration is widespread across all animal taxa, but patterns of its distribution and key factors determining regeneration capabilities stay enigmatic. A comparative approach could shed light on the problem, but its efficacy is limited by the fact that data is only available on a few species from derived taxa. Pycnogonida are nested basally within the Chelicerata. They can shed and replace their walking legs and have a high regeneration capacity. In this work, we carried careful observation on leg appendotomy and regeneration processes in a sea spider under laboratory settings. The limb structure and in vivo observation reveal autotomy as the most likely appendotomy mechanism. High regeneration capabilities were ascertained: an anatomically normal but small leg appeared in a single molting cycle and the full functionality regained in 2–3 cycles. Wound closure after appendotomy in N. brevirostre primarily relies on hemolymph coagulation, which apparently differs from both xiphosurans and crustaceans. Regeneration is provided by proliferation in the leg cutpiece. Regenerative morphogenesis resembles the normal ontogenetic morphogenesis of a walking leg, but accelerated. Unlike in most arthropods, in N. brevirostre, regeneration does not necessarily correspond to the molting cycle, inferring a plesiomorphic state.