Structure of spermatodoses in shield-back bushcrickets (Tettigoniidae, Tettigoniinae)

The Ovariol Morphology and Ultrastructure of Poecilimon ataturki Ünal, 1999 (Orthoptera, Tettigoniidae) and the Histochemical Features of the Yolk Granules

This study presents the oocyte development of Poecilimon ataturki Ünal, 1999 (Orthoptera, Tettigoniidae) with histology, morphology, and histochemistry by using a stereomicroscope, a light microscope, a scanning electron microscope, and a transmission electron microscope. The ovary in this species is a panoistic type which contains many ovarioles which consist of terminal filament, germarium, and vitellarium. Germarium is the region that has undifferentiated cells which generate the oocytes and follicular cells. In the vitellarium region, yolk granules start to cover the whole oocyte. In histochemical studies, to determine the content of the yolk granules, proteins, and carbohydrates in oocytes were treated with a bromophenol blue (BPB) method, a mercury bromophenol blue (mBPB) method, and a periodic acid Schiff (PAS) method, respectively. As a result of these methods, the yolk granules gave positive results in ovariole sections treated with the PAS and the BPB, while the mBPB staining was negative.

The mosaic distribution pattern of two sister bush-cricket species and the possible role of reproductive interference

Reproductive interference can shape regional distribution patterns in closely related species, if prezygotic isolation barriers are weak. The study of such interaction could be more challenging in nuptial gift-giving species due to the direct nutritional effects on both sexes of both species during copulation. We mapped the distribution of two sister bush-cricket species, Pholidoptera aptera and Pholidoptera transsylvanica, at the northern margin of their overlapping ranges in Europe, and with a behavioral experiment, we tested the possibility of heterospecific mating. We found a very rare coexistence of species locally (0.5%, n = 391 sites) with mostly mutually exclusive distribution patterns, resulting in a mosaic pattern of sympatry, whereas they occupied the same climate niche in forest-dominated mountain landscape. Over 14 days of a mating experiment with seven mixed groups of conspecifics and heterospecifics (n = 56 individuals in total), the number of received spermatophores per female was 3-6 in P. aptera and 1-7 in P. transsylvanica. In total, we found 8.1% of heterospecific copulations (n = 99 transferred spermatophores with genetic identification of the donor species), while we also confirmed successful transfer of heterospecific sperms into a female's reproductive system. Because bush-cricket females also obtain required nutrition from a heterospecific spermatophylax what should increase their fitness and fecundity, we suggest that their flexibility to mate with heterospecifics is beneficial and drives reproductive interference. This may substantially limit the reproductive success of the less frequent species (P. transsylvanica), coupled with eventual detrimental effects from hybridization, and result in the competitive exclusion of that species from their areas of coexistence.

Size-dependent mating pattern in a nuptial gift-giving insect

The reproductive interests of females and males often diverge in terms of the number of mating partners, an individual's phenotype, origin, genes, and parental investment. This conflict may lead to a variety of sex-specific adaptations and also affect mate choice in both sexes. We conducted an experiment with the bush-cricket Pholidoptera griseoaptera (Orthoptera, Tettigoniidae), a species in which females receive direct nutritional benefits during mating. Mated individuals could be assigned due to the genotype of male spermatodoses, which are stored in the female's spermatheca. After 3 weeks of possible copulations in established mating groups which were random replications with four females and males we did not find consistent assortative mating preference regarding to body size of mates. However, our results showed that the frequency of within-pair copulations (192 analyzed mating events in 128 possible pairwise combinations) was positively associated with the body size of both mated individuals with significant interaction between sexes (having one mate very large, association between body size and the number of copulations has weaken). Larger individuals also showed a higher degree of polygamy. This suggests that body size of this nuptial gift-giving insect species is an important sexual trait according to which both sexes choose their optimal mating partner.

Spermatodesm reorganization in the spermatophore and in the spermatheca of the bushcricket Tylopsis liliifolia (Fabricius) (Orthoptera, Tettigoniidae)

Spermatozoa of Tettigoniidae are usually transferred to the female by means of a spermatophore which is also the site of feather-shaped spermatodesm formation. These spermatodesms are then transferred to a spermatheca, composed of a spermathecal duct and of a seminal receptacle, involved in storing spermatozoa. In order to extend the knowledge about sperm transfer and spermatodesms reorganization in the Tettigoniidae, a morpho-structural investigation was carried out on spermatophore and spermatheca of Tylopsis liliifolia and on the reorganization of the gametes from the spermatophore. Our results show that the spermatodesms undergo disorganization in the spermatophore; unlike other Tettigoniidae, however, feather-shaped spermatodesms are never found. The epithelium of the spermatheca consists of two cell types, the cuticle-forming and the gland cells, with secretory features. The gland cells, absent in the distal tract of the seminal receptacle, release their secretion in a "reservoir" where an efferent duct opens. In the distal tract of the spermathecal duct, adjacent epithelial cells show diversified ultrastructural characteristics whose probable role is discussed. A particular feature of T. liliifolia is the genesis of the feather-shaped spermatodesms in the seminal receptacle. This feature and the peculiar organization of the feather-shaped spermatodesm are a possible autapomorphy of T. liliifolia.

Sperm storage by spermatodoses in the spermatheca of Trioza alacris (Flor, 1861) hemiptera, psylloidea, triozidae: a structural and ultrastructural study

Female insects generally store sperm received during mating in specific organs of their reproductive tract, i.e., the spermathecae, which keep the sperm alive for a long time until fertilization occurs. We investigated spermatheca morphology and ultrastructure in the psylloidean insect Trioza alacris (Flor,1861) in which spheroidal sperm packets that we refer to as 'spermatodoses' are found after mating. The ectoderm-derived epithelium of the sac-shaped spermatheca that has a proximal neck, consists of large secretory and flat cuticle-forming cells. Secretory cells are characterized by a wide extracellular cavity, bordered by microvilli, in which electron-dense secretion accumulates before discharge into the spermathecal lumen. The cuticle-forming cells produce the cuticular intima of the organ and a peculiar specialized apical structure, through which secretion flows into the lumen. At mating, the male transfers bundles of sperm cells embedded in seminal fluid into the spermathecal neck. Sperm cells proceed towards the spermathecal sac lumen, where they are progressively compacted and surrounded with an envelope that also encloses secretions of both male and female origin. We describe the formation of these sperm containing structures and document the contribution of the female secretion to spermatodose or female-determined spermatophore construction. We also discuss the choice of the term 'spermatodose' for T. alacris and suggest it be used to refer to sperm masses constructed in the female reproductive organs, at least when they involve the contribution of female secretion.

Larger ejaculate volumes are associated with a lower degree of polyandry across bushcricket taxa

In numerous insects, including bushcrickets (Tettigoniidae), males are known to transfer substances in the ejaculate that inhibit the receptivity of females to further matings, but it has not yet been established whether these substances reduce the lifetime degree of polyandry of the female. The aim of this study was to test the hypothesis that larger ejaculate volumes should be associated with a lower degree of polyandry across tettigoniid taxa, controlling for male body mass and phylogeny. Data on ejaculate mass, sperm number, nuptial gift mass and male mass were taken primarily from the literature. The degree of polyandry for 14 species of European bushcrickets was estimated by counting the number of spermatodoses within the spermathecae of field-caught females towards the end of their adult lifespans. Data for four further species were obtained from the literature. Data were analysed by using both species regression and independent contrasts to control for phylogeny. Multiple regression analysis revealed that, as predicted, there was a significant negative association between the degree of polyandry and ejaculate mass, relative to male body mass, across bushcricket taxa. Nuptial gift size and sperm number, however, did not contribute further to interspecific variation in the degree of polyandry. A positive relationship was found, across bushcricket taxa, between relative nuptial gift size and relative ejaculate mass, indicating that larger nuptial gifts allow the male to overcome female resistance to accepting large ejaculates. This appears to be the first comparative evidence that males can manipulate the lifetime degree of polyandry of their mates through the transfer of large ejaculates.