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PubMed1978

Development of the filiform hairs on the cerci of Gryllus bimaculatus deg. (saltatoria, gryllidae).

The filiform hairs, mechanoreceptors of Gryllus, pass through six developmental stages during the last larval stage. The cytoplasm of their sense cells suggests intensive synthesis of protein for cellular metabolism and intercytoplasmic exchange of material via glial evaginations. Ultrahistochemical tests demonstrated acid phosphatase in the lysosomes as well as in components of the Golgi apparatus. There was no significant change in the appearance of the sense cell cytoplasm, indicating a maintained functional state also during molting. The new cuticular apparatus is formed after apolysis by the three enveloping cells. Formation of the replacement hairs is initiated by a cytoplasmic outgrowth of the trichogen cell. During morphogenesis of the new hair, the microtubules serve as a cytoskeleton and probably control the flow of vesicles, which contain phenol oxidase, also demonstrated in the Golgi apparatus, and are incorporated into the new cuticle. Bundles of microfibrils are involved in the surface sculpturing of the replacement hair. The trichogen cell also forms a number of structural elements, e.g. the "cup" and "strut" marked geometric peculiarities of which indicate that they are important in the spatial orientation of the dendrite and thus also in transduction. Reduction of the apical cell membrane of the tormogen cell after apolysis permits unrestricted growth of the new hair into the exuvial space. The tormogen cell participates in the formation of the joint membrane, parts of the socket and the articulation of the hair.

Acid Phosphatase↗
PubMed1979

Length heterogeneity of amplified circular rDNA molecules in oocytes of the house cricket Acheta domesticus (Orthoptera: Gryllidae).

Amplification of the genes coding for rRNA occurs in the oocytes of a wide variety of organisms. The amplification process appears to be mediated through a rolling-circle mechanism. The approximate molecular weight of the smallest rDNA circles is equivalent to the estimated combined molecular weight of DNA which codes for a single ribosomal RNA precursor molecule and an associated non-transcribed spacer DNA sequence. RNA-DNA hybridization studies carried out on oocytes of the house cricket, Acheta domesticus, suggest that DNA coding for rRNA accounts for only a small fraction of the rDNA satellite, all of which is amplified in the oocyte. In order to test the possibility that the remainder of the amplified rDNA represents spacer and to determine whether a rolling-circle mechanism might also be involved in amplification in A. domesticus oocytes, rDNA was isolated from ovaries of A. domesticus and spread for electron microscopy. A large proportion of the rDNA isolated from ovaries is circular, while main-band DNA and rDNA prepared from other tissues demonstrates few if any circles. The mean size of the smallest rDNA circles is approximately 8 times longer than the length estimated for DNA which codes for 18S and 28 S rRNA. Denaturation mapping shows the rDNA circles to contain two major readily denaturing regions located about equidistant from one another on the circle. Each readily denaturing region accounts for 4--6% of the total DNA in the circle. The fact that only 12% of the average molecule is required to code for A. domesticus 18S and 28S rRNA is consistent with the hybridization data. Considerable size heterogeneity exists in the length of the smallest class of rDNA molecules. In the rDNA of other species such heterogeneity has been shown to reside in the non-transcribed spacer.

Animals↗
PubMed1976

Absence of rDNA amplification in the uninucleolate oocyte of the cockroach Blattella germanica (Oorthoptera: Blattidae).

Amplification of the genes coding for ribosomal RNA oocurs in the oocytes of a wide variety of organisms. In oocytes of various species of crickets (Orthoptera: Gryllidae) the amplified DNA is contained in a large extrachromosomal DNA body. Multiple nucleoli form about the periphery of the DNA body during the diplotene stage of meiosis I. In contrast to the general pattern of orthopteran oocytes, oocytes of the cockroach Blattella germanica demonstrate a single large nucleolus instead of many nucleoli. In order to determine whether the genes coding for rRNA are amplified in the oocytes of B. germanica, the relative amount of rDNA in oocytes was compared with the rDNA content of spermatocytes and somatic cells. An extrachromosomal DNA body similar to that present in crickets is not present in B. germanica. A satellite DNA band which contains nucleotide sequences complementary to rRNA accounts for approximately 3-5% of the total DNA in somatic and in male and female gametogenic tissues. Female cells contain approximately twice as much rDNA as do male cells. An XX-XO sex-determining mechanism is operative in B. germanica. In situ hybridization with rRNA indicates that the nucleolar organizer is located on one end of the X chromosome and that oocytes do not contain more than twice the amount of rDNA found in spermato cytes. The data indicate that rDNA is not amplified in the uninucleolate oocyte of B germanica.

Animals↗
PubMed1992

Toxicokinetics of 2,2',4,4'- and 3,3',4,4'-tetrachlorobiphenyl congeners in the house cricket.

Recently, investigators have reported bioaccumulation of polychlorinated biphenyls (PCBs) in insects collected at hazardous waste sites. Little is known about differences in bioaccumulation of particular PCB congeners in insects. The authors report on the toxicokinetics of a non-coplanar ortho substituted congener, 2,2',4,4'-tetrachlorobiphenyl (PCB-47) and a coplanar non-ortho substituted PCB, 3,3',4,4'-tetrachlorobiphenyl (PCB-77) in topically treated house crickets. Penetration and excretion were more rapid for PCB-47 than for PCB-77. PCB-47 demonstrated a high affinity for abdomen, gut, and gonads, whereas, PCB-77 had a greater affinity for the head and thorax. Sex differences were observed in excretion and distribution. Females had an increased excretion of PCBs and increased accumulation in gut and gonads compared to males. Differences in lipophilicity can explain differences in distribution between sexes and of compounds within sexes. However, to explain the observed difference in penetration, it is necessary to invoke explanations based on stearic factors associated with coplanarity of the molecules. Differences in excretion are likely related to sex differences in mixed-function oxidase activities. These toxicokinetic data suggest that the more toxic coplanar congener, PCB-77, is likely to be more persistent in crickets compared to PCB-47, despite its lower lipophilicity.

Abdomen↗
PubMed2026

Gastrointestinal digestion governs insect protein hydrolysis and predicted bioactive peptide release: Species-dependent implications for functional food applications.

This study investigates the digestion of insect proteins and the release of predicted bioactive peptides during human gastrointestinal digestion. Using the Infogest in vitro model, mealworm, cricket, and black soldier fly larvae (BSFL) proteins were digested and analyzed through discovery proteomics and bioinformatics to identify predicted bioactive peptides. Sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) quantified insect proteins including predicted bioactive peptide precursor proteins, the precursors of predicted bioactive peptides. Results indicated that gastrointestinal digestion strongly influences peptide release, with the gastric phase exhibiting a richer predicted bioactive peptide profile than the small intestinal phase. Many predicted bioactive peptides were rapidly hydrolysed under small intestine conditions, which may lead to reduced stability or diminished activity in vivo, potentially explaining why certain peptides show strong bioactivity in vitro but limited effects in vivo. Additionally, predicted bioactive peptide release varied by insect species, influenced by genetic factors and peptide abundance. These findings highlight the importance of species selection and consideration of proteolytic digestion patterns in optimizing insect-derived bioactive peptides for functional foods and nutraceutical applications.

Animals↗
PubMed2026

Genomic signatures of adaptation across a landscape of crickets following the introduction of a parasitoid fly.

Novel species interactions provide an opportunity to assess the earliest stages of genetic adaptation. We combined population genomics and field selection surveys to explore the genomic and geographic landscape of adaptation in small, fragmented Hawaiian cricket populations, which are parasitized by larvae of an introduced fly that targets singing males. Multiple protective male-silencing cricket morphs have recently spread under this novel selection pressure, despite song's important roles in mate attraction. We find evidence of sharp declines in cricket effective population sizes following the fly's introduction and identify regions under spatially varying selection mediated by infestation risk, which are linked to an adaptive morph and other genes implicating in resisting infestation. Despite repeated bottlenecks, genetic variation is dominated by structural variant polymorphisms seemingly maintained under balancing selection. Our study illustrates pervasive consequences of abrupt changes in selection on small populations. Fly-mediated selection remains strong despite the spread of adaptive male-silencing phenotypes, which also reduce male fitness in the context of mate attraction.

Animals↗