Lower Egg Hatching Rate Research Articles

Bdyof is a Y-chromosome-specific gene required for male development in Bactrocera dorsalis.

In many organisms, the Y chromosome contains important genes associated with sex determination and male reproductive development. However, there have been few studies of Y-chromosome-specific genes in non-model species due to the incomplete information of Y chromosome genome and difficulty in sequencing. Here, we screened 90 candidate Y-specific sequences in a constructed transcriptome assembly library by using the chromosome quotient method, among which 11 were unreported sequences associated with male reproductive development, including Bactrocera dorsalis Y-specific Oligozoospermia factor (Bdyof) with the highest expression in the testis. CRISPR/Cas9-mediated knockout of Bdyof resulted in abnormal testis development, significantly reduced sperm count, and obviously lower egg hatching rate in homozygous mutant flies. In addition, Bdyof knockout decreased the expression of dsx-M. This results provides new insights into the biological processes related to male reproductive development controlled by the Y-chromosome-specific gene Bdyof, thus providing a promising molecular target for the study of agricultural pests. © 2024 Society of Chemical Industry.

CRISPR-Cas9 knockout of membrane-bound alkaline phosphatase or cadherin does not confer resistance to Cry toxins in Aedes aegypti.

The Aedes aegypti cadherin-like protein (Aae-Cad) and the membrane-bound alkaline phosphatase (Aae-mALP) are membrane proteins identified as putative receptors for the larvicidal Cry toxins produced by Bacillus thuringiensis subsp. israelensis bacteria. Cry toxins are the most used toxins in the control of different agricultural pest and mosquitos. Despite the relevance of Aae-Cad and Aae-mALP as possible toxin-receptors in mosquitoes, previous efforts to establish a clear functional connection among them and Cry toxins activity have been relatively limited. In this study, we used CRISPR-Cas9 to generate knockout (KO) mutations of Aae-Cad and Aae-mALP. The Aae-mALP KO was successfully generated, in contrast to the Aae-Cad KO which was obtained only in females. The female-linked genotype was due to the proximity of aae-cad gene to the sex-determining loci (M:m). Both A. aegypti KO mutant populations were viable and their insect-development was not affected, although a tendency on lower egg hatching rate was observed. Bioassays were performed to assess the effects of these KO mutations on the susceptibility of A. aegypti to Cry toxins, showing that the Aae-Cad female KO or Aae-mALP KO mutations did not significantly alter the susceptibility of A. aegypti larvae to the mosquitocidal Cry toxins, including Cry11Aa, Cry11Ba, Cry4Ba, and Cry4Aa. These findings suggest that besides the potential participation of Aae-Cad and Aae-mALP as Cry toxin receptors in A. aegypti, additional midgut membrane proteins are involved in the mode of action of these insecticidal toxins.

Effect of Pb, Cd and Cu on survival and development of Culex quinquefasciatus (Diptera: Culicidae)

ABSTRACTThe present research aimed to determine the lowest levels of three heavy metals (Pb, Cd and Cu) to which the larvae of Southern House Mosquito, Culex quinquefasciatus are susceptible in water. The study also aimed to investigate the effects of these heavy metals on the development of Cx. quinquefasciatus at concentrations set by Pakistan Environmental Protection Agency (Pak-EPA) as permissible levels for liquid industrial effluents. The 2nd instar larvae of Cx. quinquefasciatus were exposed to different concentrations of Pb, Cd and Cu and their effects on oviposition preference, egg hatching rate and larval development were studied. The LC50 values of Pb, Cd and Cu were 12.6, 6.3 and 2.6 ppm, respectively. Gravid female mosquito adults deposited a significantly lower number of egg rafts in containers containing 0.50 ppm Pb or 1.0 ppm Cu in water. Each of the heavy metals in water resulted in significantly (p < 0.05) lower egg hatching rate, prolonged time to pupation, lower pupation rate, prolonged time to adult emergence, lower adult emergence rate and higher female to male ratio. It is concluded that the 2nd instar larvae of Cx. quinquefasciatus are susceptible to Pak-EPA permissible levels of Pb, Cd and Cu in municipal and liquid industrial effluents.

CRISPR/Cas9-Mediated Vitellogenin Receptor Knockout Leads to Functional Deficiency in the Reproductive Development of Plutella xylostella.

The vitellogenin receptor (VgR) belongs to the low-density lipoprotein receptor (LDLR) gene superfamily and plays an indispensable role in Vg transport, yolk deposition, and oocyte development. For this reason, it has become a promising target for pest control. The involvement of VgR in Vg transport and reproductive functions remains unclear in diamondback moths, Plutella xylostella (L.), a destructive pest of cruciferous crops. Here, we cloned and identified the complete cDNA sequence of P. xylostella VgR, which encoded 1805 amino acid residues and contained four conserved domains of LDLR superfamily. PxVgR was mainly expressed in female adults, more specifically in the ovary. PxVgR protein also showed the similar expression profile with the PxVgR transcript. CRISPR/Cas9-mediated PxVgR knockout created a homozygous mutant of P. xylostella with 5-bp-nucleotide deletion in the PxVgR. The expression deficiency of PxVgR protein was detected in the ovaries and eggs of mutant individuals. Vg protein was still detected in the eggs of the mutant individuals, but with a decreased expression level. However, PxVg transcripts were not significantly affected by the PxVgR knockout. Knockout of PxVgR resulted in shorter ovarioles of newly emerged females. No significant difference was detected between wild and mutant individuals in terms of the number of eggs laid in the first 3 days after mating. The loss of PxVgR gene resulted in smaller and whiter eggs and lower egg hatching rate. This study represents the first report on the functions of VgR in Vg transport, ovary development, oviposition, and embryonic development of P. xylostella using CRISPR/Cas9 technology. This study lays the foundation for understanding molecular mechanisms of P. xylostella reproduction, and for making use of VgR as a potential genetic-based molecular target for better control of the P. xylostella.

A new function of immunity-related gene Zn72D in male fertility of Drosophila melanogaster.

Zn72D encodes the Drosophila zinc finger protein Zn72D. It was first identified to be involved in phagocytosis and indicated to have a role in immunity. Then it was demonstrated to have a function in RNA splicing and dosage compensation in Drosophila melanogaster. In this study, we discovered a new function of Zn72D in male fertility. We showed that knockdown of Zn72D in fly testes caused an extremely low egg hatch rate. Immunofluorescence staining of Zn72D knockdown testes exhibited scattered spermatid nuclei and no actin cones or individualization complexes (ICs) during spermiogenesis, whereas the early-stage germ cells and the spermatocytes were observed clearly. There were no mature sperms in the seminal vesicles of Zn72D knockdown fly testes, although a few sperms could be found close to the seminal vesicle. We further showed that many cytoskeleton-related genes were significantly downregulated in fly testes due to Zn72D knockdown. Taken together these findings suggest that Zn72D may have an important function in spermatogenesis by sustaining the cytoskeleton-based morphogenesis and individualization thus ensuring the proper formation of sperm in D. melanogaster.

Reproductive Cost Associated With Juvenile Hormone in Bt-Resistant Strains of Helicoverpa armigera (Lepidoptera: Noctuidae).

Transgenic Bacillus thuringiensis (Bt) crops are increasingly significant in pest control, but resistance development of target pests is a major issue in the sustainable deployment of Bt crops. The fitness cost of resistance in target pests is regarded as one of the main factors delaying resistance when adopting the refuge strategy. In this study, we compared the life-history traits of three independent sets of Helicoverpa armigera (Hübner, 1809) adults, of each there were a susceptible population and a Cry1Ac-resistant population derived by selection from it. Confirming to the previous studies, resistant individuals exhibited fewer progeny, less fecundity, lower egg hatching rate, and longer adult longevity. And poor fecundity in resistant strains was associated with the decline of the mature follicular amount, the ovarian weight ratio, and the length of the longest ovarian tubule. Interestingly, the juvenile hormone (JH) level appeared higher in resistant strains relative to susceptible strains. Application of methoprene (JH analogue) in vivo was effective in reducing fecundity and hatchability with the up-regulation of detected JH titer. These results suggested that resistance against Bt toxin reduced the reproductive capacity of H. armigera, and JH level is affected in the tradeoff between reproductive capacity and Bt resistance.

Reproductive behavioural differences between wild-caught and pond-reared Penaeus monodon prawn broodstock

Ongoing problems exist with the commercial scale domestication of Penaeus monodon. One of the major issues, in terms of reproductive performance, is the low egg hatch rate of eggs from these captive bred prawns. The current study investigated the related issue of mating success. Time lapse video observations were conducted to compare the mating behaviour of pond-reared (domesticated) and wild-caught prawn P. monodon broodstock.Mating success of the pond-reared prawns was found to be low relative to wild-caught. It was determined that both male and female prawns contributed to this low mating rate suggesting both genders were impacted negatively by the domestication process. The causative factors for the low mating success are yet to be determined, however external physical abnormalities and lack of sexual maturity did not appear to play a role. The most notable behavioural difference between wild-caught and domesticated prawns was a reduced level of pursuit behaviour by domesticated males. This and other behavioural differences are discussed in relation to an increasing body of evidence that male prawns respond to sex pheromones produced by receptive females and that males detect these chemical signals in part, via their second antennal flagella. Accordingly we hypothesise that pond-reared (domesticated) females may have a reduced ability to produce or release sex pheromones and males, a reduced ability to detect them when compared to their wild-caught counterparts.

Efeito de diferentes concentrações de óleo e tintura de citronela sobre os parâmetros reprodutivos de teleóginas de Rhipicephalus (Boophilus) microplus

The tick Rhipicephalus (Boophilus) microplus is the most important ectoparasite in cattle rising, and it is responsible for severe economic losses. Parasite control is based on chemicals, which are used indiscriminately and result in effectiveness reduction of these compounds. In order to delay the onset of parasite resistance, some alternative methods are being researched, including herbal medicine. The aim of this experiment was to evaluate the in vitro efficacy of citronella (Cymbopogon nardus) oil and tincture on R. (B) microplus by the engorged female immersion test. Four oil concentrations were tested (1; 25; 50; 100%) and the inhibition of oviposition were 16; 40; 53; 73%, egg hatch were 28; 16; 23; 6% and the effectiveness were 78; 100; 86; 98%, respectively. The gradual rise of the inhibition of oviposition and low egg hatch had a positive influence in the effectiveness of treatment. The solution at 1% of citronella oil had a partial control of the teleogines and the solution at 25% had 100% of effectiveness. Six dilutions of the tincture (1; 5; 10; 25; 50; 100%) were tested and the inhibition of oviposition were 10; 63; 80; 83; 86; 96%, egg hatch were 91; 31; 6; 26; 0; 0% and the effectiveness were 23; 93; 94; 97; 100; 100%, respectively. Most of the treatments with the citronella tincture had inhibition of oviposition higher than 80% and low egg hatch rate. The tincture at 5% had similar efficacy compared to the groups with higher concentrations. A significant association between the oil and tincture of citronella and the treatment effectiveness was observed in the statistical evaluation. It is possible to conclude that both the oil and the tincture of citronella had negative influence in the reproductive parameters of R. (B) microplus.

Gizzard Shad Thiaminase Activity and Its Effect on the Thiamine Status of Captive American Alligators Alligator mississippiensis

Adult mortality and low egg hatch rate were observed among American alligators Alligator mississippiensis in Lake Griffin, Florida, between 1998 and 2003. Previous studies show that the alligator mortality is due to neurological impairment associated with thiamine (vitamin Bt) deficiency. This study determined the rate of thiaminase activity in gizzard shad Dorosoma cepedianum, a fish often eaten by alligators, and examined the thiamine status of captive adult alligators fed only gizzard shad. We found that the thiaminase activity of gizzard shad in Lake Griffin is 16,409 +/- 2,121 pmol/g/min (mean +/- 2SEs). This high rate of thiaminase activity was present in most months and across a wide range of shad sizes. Seven alligators were captured in the wild from Lake Griffin and Lake Woodruff, held in captivity, and fed gizzard shad. We monitored blood and muscle thiamine levels throughout the experiment and liver thiamine at the end. Over a period of 6-12 months, all of the alligators maintained weight but blood and muscle thiamine levels decreased to 25-50% of the original (healthy) values. Three animals with the greatest reduction in thiamine died, demonstrating mobility impairment and neural histopathology similar to those seen in wild alligators in Lake Griffin. Two alligators were fed shad for 10 months but then treated with thiamine. These animals showed a reduction in thiamine while eating shad, but treatment restored their thiamine levels to the initial values, which were comparable to those of normal wild Lake Griffin alligators. We demonstrated that thiamine deficiency can be induced by a diet of gizzard shad and cause neurological signs and death in alligators in captivity. We conclude that the thiaminase activity in gizzard shad is high enough to cause thiamine deficiency in wild alligators when shad are a major part of their diet.

Obligate symbiont involved in pest status of host insect.

The origin of specific insect genotypes that enable efficient use of agricultural plants is an important subject not only in applied fields like pest control and management but also in basic disciplines like evolutionary biology. Conventionally, it has been presupposed that such pest-related ecological traits are attributed to genes encoded in the insect genomes. Here, however, we report that pest status of an insect is principally determined by symbiont genotype rather than by insect genotype. A pest stinkbug species, Megacopta punctatissima, performed well on crop legumes, while a closely related non-pest species, Megacopta cribraria, suffered low egg hatch rate on the plants. When their obligate gut symbiotic bacteria were experimentally exchanged between the species, their performance on the crop legumes was, strikingly, completely reversed: the pest species suffered low egg hatch rate, whereas the non-pest species restored normal egg hatch rate and showed good performance. The low egg hatch rates were attributed to nymphal mortality before or upon hatching, which were associated with the symbiont from the non-pest stinkbug irrespective of the host insect species. Our finding sheds new light on the evolutionary origin of insect pests, potentially leading to novel approaches to pest control and management.

Male-killing bacterium in a fifth ladybird beetle, Coleomegilla maculata (Coleoptera: Coccinellidae)

Inherited symbionts which selectively cause the death of male hosts are found widely across the Insecta. Previous studies have shown a single, but different micro-organism to be responsible for male-killing in each taxonomic group studied. We here produce evidence that within a group of insects, the Coccinellidae, there is more than one causal agent of male lethality. We report a novel observation of a male-killing trait in the species Coleomegilla maculata. Six of 26 crosses were found to produce a female-biased sex ratio associated with a low egg hatch-rate. The trait was matrilinearly inherited and was observed to be tetracycline-sensitive. However, tests which indicate the presence of a Rickettsia, previously found to cause male-killing in another member of the Coccinellidae, Adalia bipunctata, proved negative. We therefore conclude that the phenomenon of male-killing is multicausal, within, as well as between, taxonomic groups of the Insecta.

Egg Hatch of Honey Bees Fertilized with Frozen Spermatozoa12

Honey bee (Apis mellifera L.) semen was diluted with water (or 0.85% NaCl) and dimethyl sulfoxide in a 6:3:1 ratio and stored in liquid nitrogen (–196° C). Queens inseminated with this semen produced a higher proportion of males (unfertilized eggs) and a lower egg hatching rate than control queens. Low hatching rates were associated with the fertilized eggs rather than with the unfertilized eggs within the test group. Egg hatching rates averaged 82±11% (x±SD) in test queens and 95±2% in controls.