Arthropod Structure & Development最新文献

Conflicts of interest over reproduction between males and females are widespread in sexually reproducing species. This is exemplified in water striders (Gerridae), where females vigorously resist costly mating attempts, and males and females often exhibit elaborate grasping and anti-grasping morphological traits. Like water striders, their sister-group, the ripple bugs (Veliidae), share similar life histories and are expected to face similar conflicts over mating. Veliids in the genus Nesidovelia exhibit elaborate sexual dimorphism, which is predicted to function in intersexual antagonistic struggles. This includes concealed genitalia in females, and elaborate pregenital abdominal modifications in males. By documenting mating behaviour in Nesidovelia peramoena and freezing pairs in copula, we show that males and females struggle prior to mating, and male abdominal modifications function to gain access to the female's concealed genitalia. This is consistent with, though not limited to, sexual conflict.

Male genitalia in praying mantids are highly complex, but we know little of how they function. I combined the micro-computed tomography of a copulating pair of the European mantis (Mantis religiosa) with public videos of copulation in various species of Mantodea and an analysis of literature. The function of each major element is reviewed. Copulation is divided into three phases: opening, anchoring and deposition. The opening is achieved by pulling the female subgenital plate with the male apical process. Multiple cases of female cooperation or resistance were observed and one case of coercion by the male. In species with the reduced apical process, female cooperation is mandatory. The male subgenital plate may participate in the opening as an integral part of the genitalia. After the opening, the conformation of the genitalia drastically changes, revealing activity of the genital papilla. Tight grasp on female genitalia is maintained solely by the clamp on the right phallomere, despite the overall complexity and predictions of sexual conflict theory. Other prominent elements show rhythmic motions, but their functions are not entirely clear and evidently involve spermatophore deposition, female stimulation or rival sperm removal. The opening and anchoring are similar in Mantodea and Blattodea, but achieved with non-homologous elements.

The previously published ultrastructure of Aegla spermatozoa contributed to the phylogenetics of this unique taxon. The present study describes the spermatozoa of two additional aeglids, Aegla parana and A. quilombola. The spermatozoa consist of two hemispheres of the approximate same size and a bilayered acrosomal vesicle; both characteristics of the genus Aegla. The similarity of spermatozoa ultrastructure observed between A. parana and A. quilombola and the endemic Australian anomuran, Lomis hirta (Lomidae) reflects a sister group relationship, even though both are from different regions of the world and different environments today. Aeglid spermatozoa share the same organization with Lomis including the two equal size hemispheres separated by a membrane also two layers in the acrosomal vesicle with the external layer being surrounded by another membrane. The number of spermatozoa microtubular arms is unclear in Aegla, however, they are present in both the nucleus and cytoplasm. This observation does not agree with the presence of spermatozoa arms only in the nucleus, as an exclusive character for Aegla, as proposed previously. The presence of lipid-droplets and peroxisomes was observed only in the spermatozoa of A. quilombola. The greatly reduced number of spermatozoa observed in all specimens analyzed raises concerns about the conservation of several threatened species. In addition, the absence of any spermatophores seems to be a characteristic of the Aeglidae to date.

Spiders are among the most diverse animals, which developed different morphological and behavioral traits for capturing prey. We studied the anatomy and functionality of the rare and apomorphic raptorial spider feet using 3D reconstruction modeling, among other imaging techniques. The evolutionary reconstruction of the raptorial feet (tarsus plus pretarsus) features using a composite tree of spiders, indicating that similar traits emerged three times independently in Trogloraptoridae, Gradungulinae, and Doryonychus raptor (Tetragnathidae). The characteristics defining the raptorial feet are an interlocked complex merging of the base of the elongated prolateral claw with the pretarsal sclerotized ring, with the former clasping against the tarsus. Raptorial feet even flex over robust raptorial macrosetae forming a reduced tarsal version of a catching basket to encase prey during hunting. Our results show that Celaeniini (Araneidae) and Heterogriffus berlandi (Thomisidae), taxa previously compared with raptorial spiders, lack the raptorial feet key characteristics and the tarsal-catching basket. We make predictions about the possible behavior of the abovementioned taxa that will need to be tested by observing living specimens. We conclude that multiple morphological tarsal and pretarsal micro-structures define the raptorial foot functional unit and recommend a comprehensive evaluation before assigning this configuration to any spider taxa.

Though the transparent apposition eyes of larval stomatopod crustaceans lack most of the unique retinal specializations known from their adult counterparts, increasing evidence suggests that these tiny pelagic organisms possess their own version of retinal complexity. In this paper, we examined the structural organization of larval eyes in six species of stomatopod crustaceans across three stomatopod superfamilies using transmission electron microscopy. The primary focus was to examine retinular cell arrangement of the larval eyes and characterize the presence of an eighth retinular cell (R8), which is typically responsible for UV vision in crustaceans. For all species investigated, we identified R8 photoreceptor cells positioned distal to the main rhabdom of R1-7 cells. This is the first evidence that R8 photoreceptor cells exist in larval stomatopod retinas, and among the first identified in any larval crustacean. Considering recent studies that identified UV sensitivity in larval stomatopods, we propose that this sensitivity is driven by this putative R8 photoreceptor cell. Additionally, we identified a potentially unique crystalline cone structure in each of the species examined, the function of which is still not understood.

The insect cuticle is multifunctional and often includes projections used for support, communication or protection. Ants in the genus Strumigenys exhibit a peculiar honeycomb-like spongiform tissue that covers their petiole, postpetiole and sometimes also the posterior mesosoma and anterior part of the first gastral segment. The tissue is abundantly developed in workers and queens, and much reduced in males. We found this spongiform tissue is associated with a novel exocrine gland that is made up by class-3 secretory cells that are clustered underneath the major pillars of the cuticular extensions, their associated narrow ducts enter these extensions and open at the surface through small pores. The chemical nature and function of the secretion are still unknown. The honeycomb texture may act in the storage and dispersion of the glandular secretions. In addition to the spongiform tissue gland, the posterior region of the petiole and postpetiole also contain intersegmental petiole and postpetiole glands, of which the ducts open through the intersegmental membrane that forms the connection with the next segment. Future work aimed at identifying the chemicals secreted by these glands will shed light onto the function of these unusual structures.

Zygentoma is an order of wingless insects, representing the sister group of Pterygota and constituting Dicondylia together with Pterygota. Contrasting views exist regarding midgut epithelium formation in Zygentoma. According to some reports, in Zygentoma, the midgut epithelium is entirely derived from yolk cells as in other wingless orders; however, according to other reports, the midgut epithelium is of dual origin in Zygentoma, similar to that in Palaeoptera of Pterygota, i.e., the anterior and posterior midgut epithelia are stomodaeal and proctodaeal respectively, whereas the middle part of the midgut originates from yolk cells. Aiming to provide a sound basis to evaluate the true image of midgut epithelium formation in Zygentoma, we examined the formation of the midgut epithelium in detail in Thermobia domestica, and concluded that the midgut epithelium is exclusively derived from yolk cells in Zygentoma, without the stomodaeal and proctodaeal elements involved in its formation. The participation of the anlagen differentiated at or around the stomodaeal and proctodaeal extremities in the formation of the midgut epithelium (bipolar formation) may be regarded as having first appeared not in Dicondylia but in Pterygota, of which the major part is represented by Neoptera with the midgut epithelium formed through bipolar formation.

The general organization of the female genital system of the diving beetle Stictonectes optatus was studied, clarifying the complex structure of the spermatheca and spermathecal gland. The two structures adhere closely to each other, sharing a small area of their cuticular epithelium. A long duct connects the bursa copulatrix to the spermatheca, where the sperm are stored. The sperm reach the common oviduct, where egg fertilization occurs, via a fertilization duct. The spermathecal gland cells have extracellular cisterns where secretions are stored. Thin ducts composed of duct-forming cells transport these secretions to the apical gland region and into the spermathecal lumen. Soon after mating, the bursa copulatrix is almost completely occupied by a plug secreted by the male accessory glands. The secretions of the bursa epithelium seem to contribute to plug formation. Later this plug becomes large and spherical, obstructing the bursa copulatrix.

The woodwasp Sirex noctilio Fabricius is a major quarantine pest that was reported in China in 2013 and mostly damages Pinus sylvestris var. mongolica. Reverse chemical ecology, which uses chemical lures to catch or block insects from mating is the classic way to control forestry pests. This indicates that insect sensilla play a crucial role in detecting external chemical and physical stimuli. Nonetheless, the categorization and distribution of sensilla on the antennae and ovipositor of S. noctilio are insufficiently specific. In this paper, scanning electron microscopy (SEM) was used to observe the ultrastructure of the sensilla of S. noctilio on the antenna and ovipositor. It was found that the types and distribution of sensilla on the antennae of S. noctilio male and female are consistent, and six types of sensilla are found: sensilla trichodea (ST), sensilla chaetica (SC), Böhm bristles (BB), sensilla basiconica (SB), sensilla ampullacea (SA), and contact chemoreceptors (CC). Besides, there are five types of sensilla on the female ovipositor. In addition to ST, SC and BB, two more types of sensilla are also found: sensilla cavity (SCa) and sensilla coeloconica (SCo). Through identification of the morphology and distribution of the sensilla, the functions of different sensilla in the mating and host selection mechanisms of S. noctilio are proposed, thereby establishing a foundation for S. noctilio chemical communication research.