Time Of Oviposition Research Articles

Temperature and photoperiod differentially impact maternal phenotypes in diapause egg-laying Aedes albopictus mosquitoes.

Aedes albopictus (Skuse 1894) mosquitoes can transmit deadly arboviruses and are globally invasive due to their ability to survive in both tropical and temperate climates. Although adults cannot survive harsh winters, females are capable of anticipating seasonal change and producing overwintering diapause (DP) eggs that remain in a state of arrested development over the winter and hatch when favorable conditions return in the spring. While low temperatures can facilitate DP entry under short photoperiods, temperature signals alone are not sufficient to induce DP. To identify maternal phenotypes predictive of DP egg production in laboratory conditions, we characterized aspects of maternal physiology and behavior to identify those that correlate with DP egg production and changes in photoperiod, versus changes in temperature. Neither changes in temperature nor photoperiod impacted protein preference, blood meal consumption, or total number of eggs produced per female. Egg retention and oviposition timing were influenced by temperature, independent of DP egg production. However, females housed under short photoperiod conditions showed increased starvation resistance, despite showing similar levels of locomotor activity and internal stores of triacylglycerols, glucose, glycogen, and trehalose compared to females housed in long photoperiods. These results suggest that temperature and photoperiod differentially affect maternal phenotypes and identify starvation resistance as a maternal phenotype that is influenced by photoperiod and correlates with DP egg status.

Short-term responses of spider mites inform mechanisms of maize resistance to a generalist herbivore

Plants are attacked by diverse herbivorous pests with different host specializations. While host plant resistance influences pest pressure, how resistance impacts the behaviors of generalist and specialist herbivores, and the relationship to resistance, is less well known. Here, we investigated the short-term (< 1 h) behavioral changes of a generalist herbivore, the two-spotted spider mite (TSM), and a specialist herbivore, the Banks grass mite (BGM), after introduction to no-choice Tanglefoot leaf-arenas (2 × 2 cm) of three maize inbred lines (B73, B75, and B96). The widely-used inbred line B73 is susceptible to spider mites, while B75 and B96 are known to be mite resistant, especially to TSM. Video tracking was used to record TSM and BGM walking, probing, feeding, resting, web-building and travel distance on arenas of each line. Mite oviposition was also recorded after 72 h. B75, a resistant line, decreased the feeding behavior (i.e., time) of both mite species compared to B73 (susceptible control) and B96. Moreover, TSM appeared to be sensitive to both resistant lines (B75 and B96) with reduced oviposition, and increased resting and web-building times compared to susceptible B73. In contrast, the specialist BGM showed no difference in oviposition, resting and web-building time across all maize inbred lines. Our findings of quite broad and short-term responses of TSM to B75 and B96 are consistent with a role for constitutive or rapidly induced plant defenses in maize in conferring TSM resistance. Other mechanisms of plant resistance may be needed, however, for defense against specialists like BGM.

Mating behavior and oviposition of Palpita forficifera (Lepidoptera: Crambidae).

Palpita forficifera Munroe, 1959 (Lepidoptera: Crambidae) is considered the main pest of the olive tree (Olea europaea L., Oleaceae) in Brazil and Uruguay. The aim of this work was to study the mating and oviposition behavior of P. forficifera in the field and laboratory. In the field, the sex emitting the mating pheromone was determined and in the laboratory, the rate of emergence of males and females; the age, time and duration of mating; number of copulations and oviposition time of P. forficifera were recorded. The field results showed that it was possible to capture up to five males per trap in just one night in traps with the presence of female P. forficifera. Copulation occurs between the seventh and twenty-third day of life and is most frequent during the third and sixth hours of scotophase. The average duration of the first copulation was 174min, with 35% of couples recopulating, and there were cases of up to five copulations. Oviposition times were concentrated between 20:00 and 02:00. The results obtained provide insight into the reproductive behavior of P. forficifera and are useful for future studies aimed at identifying the sex pheromone to improve monitoring of the pest in olive orchards.

Oviposition patterns of primary lepidopteran defoliators in soybean and the impact on structured refuge recommendations.

Transgenic Bt technology in soybean, with plants expressing Cry1Ac, has been adopted as an insect pest management tool. It was first adopted in large areas of South America and Asia in 2013. The risk of resistance in target pests to this technology demands insect resistance management (IRM) programs. In Brazil, a structured refuge (area of non-Bt soybean) planted adjacent to the Bt soybean crop has been an important IRM recommendation, particularly for the primary lepidopteran defoliators Anticarsia gemmatalis (Lepidoptera: Erebidae) and Chrysodeixis includens (Lepidoptera: Noctuidae). The overall goal of this study was to validate IRM recommendations to Bt soybean. The objectives were to document the impact of soybean phenology, cultivar choice and non-Bt soybean defoliation on moth oviposition. In addition, a mark-release-recapture study estimated the dispersal capacity of these species. Five field experiments per species were performed for 3 years. Our results revealed an increase in A. gemmatalis and C. includens oviposition, respectively, on Bt plants as a consequence of the difference in plant growth stage at the time of oviposition. Defoliation of non-Bt plants significantly increased the oviposition preference of both moth species for Bt plants. The mark-release-recapture experiment indicated an average dispersal distance of ~300 m from the release point for A. gemmatalis, with maximum recapture at 1000 m. Overall, our findings emphasize the importance of planting synchronization of Bt soybean and the structured refuge. In addition, when operational aspects in large soybean areas challenge this recommendation, the priority should be for planting the refuge area first. This approach will minimize the impact of selective oviposition of A. gemmatalis and C. includens. © 2024 Society of Chemical Industry.

Parasitoid-host interaction behaviors in relation to host stages in the Tamarixia triozae (Hymenoptera: Eulophidae)-Bactericera cockerelli (Hemiptera: Triozidae) system.

Females of host-feeding parasitic wasps often partition hosts of different stages for feeding and parasitization, but the underlying behavioral mechanisms are largely unknown, making it difficult to evaluate parasitoid-host interactions and their effects on biological control success. Tamarixia triozae (Burks) is an ectoparasitoid of tomato-potato psyllid Bactericera cockerelli (Šulc), which utilizes nymphs and kills them both by parasitization and host feeding. In this study, we exposed female wasps to 1st- to 5th-instar psyllid nymphs simultaneously and made 13-h continuous video recording of parasitoid-host interactions. We then quantified host stage-dependent handling time for feeding and oviposition and behaviors of parasitoid attacks and host defenses from encountering to successful feeding and oviposition. Female wasps were more likely to encounter and evaluate older hosts. However, the encounter and evaluation did not necessarily result in the success of feeding and oviposition. Our findings suggest that (i) T. triozae continues to assess the host using its ovipositor after the evaluation phase, (ii) females prefer the mid-aged hosts for feeding piercing and feeding and the later instars for oviposition probing and oviposition, (iii) the combination of stage-specific host nutrition value, integument thickness and defense behavior determines the success of feeding attacks, and (iv) the optimal host resource for parasitoid offspring fitness defines host stage selection for oviposition. This study contributes to our understanding of parasitoid-host interactions and mechanisms behind host stage selections.

Radio Telemetry and Harmonic Radar Tracking of the Spotted Lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae).

Lycorma delicatula (White) (Hemiptera: Fulgoridae), spotted lanternfly (SLF), is an invasive pest that feeds and oviposits on numerous woody and herbaceous plants important to agricultural, forest, ornamental, and nursery industries. Describing and understanding SLF movements is key to implementing surveillance and control strategies for this pest and projecting population spread. We used radio telemetry (RT) and harmonic radar (HR) to track the movements of individual SLF at field sites in eastern Pennsylvania and northwestern New Jersey. SLF equipped with HR or RT tags were tracked in 2019 and 2020 from adult emergence until oviposition time, and their movements are described. Although the bulkier RT tags disproportionately affected the distance traveled by males, which are smaller than females, both males and females were more likely to be lost due to signal attenuation when affixed with the lighter-weight HR tags. Females were tracked moving longer distances than males, with maximum distances of 434 m by a single female and 57 m by a single male. A significant positive relationship was found between their height in trees and the distance of subsequent movement. Adult SLF were found in trees predominantly at heights between 6-9 m high. For the fraction of SLF found at eye level, males, but not females, significantly moved above eye level in the weeks prior to mating, likely resulting in the observed sex ratio shift that defines the Early-2 stage. During mating time, tracked SLF were significantly higher than 8 m and oriented to trees where tight aggregations of SLF were present. This orientation towards tight aggregations started when mating began and peaked in the following 2.5 weeks for males in Late-1 and the beginning of Late-2 (after oviposition began), whereas females started this orientation behavior a half-week after males, and this activity peaked for two weeks. Male and female SLF adults exhibited slight differences in host preference, and strong preferences for wild grape, black walnut, sweet birch, and tree-of-heaven were observed. The HR-tagged nymphs moved up to 27.6 m over a five-day period in a cornfield. Nitinol wire HR tags performed better than Wollaston process or tungsten wire tags. SLF movement parameters in the field are described.

Planococcus ficus (Hemiptera: Pseudococcidae) movement and demography: methods for generating cohorts for laboratory studies.

Planococcus ficus (Signoret) is a worldwide pest of grapevine. Mealybugs overwinter under bark and move into the grape canopy as the season progresses. Because crawlers are more active than later stages, mealybug movement behavior is likely to be stage specific. To quantify P. ficus demography and movement behavior, a series of laboratory experiments were conducted. First, P. ficus populations were monitored on grapevine seedlings to describe survival, change in size, timing of male pupation, and timing of oviposition over a 6-wk period. Subsequently, cohorts of mealybugs were generated by infesting grapevines with crawlers and holding infested grapevines for a specified duration of 0 (crawlers), 1, 2, 3, or 4 wk. Crawlers (0-wk) were more likely to move upwards and towards a light source, than all other age cohorts tested. Further, mealybugs from 4-wk-old cohorts were more likely to move downward than all other age cohorts tested. Results suggest that crawlers are more likely to move to the top of grapevines by moving upwards and orienting towards either the sun or the moon than all other age cohorts tested, whereas older gravid females are more likely to move downward. Passive movement of mealybugs on farm machinery or animals requires surviving a host free period. To quantify risk of passive movement, establishment rates and effects of starvation on each age cohort were quantified. Larger and older mealybugs were more likely to establish on grapevines than smaller and younger mealybugs. Further, mealybug longevity in absence of food was greater for older cohorts compared to younger cohorts. Crawlers survived an average of 2 days without food, whereas females from 4-wk-old cohorts survived for an average of 11 days without food. Further, 70% of starved females from 4-wk-old cohorts deposited fertile eggs. In the absence of food, some mealybugs from cohorts aged 2-, 3-, and 4-wk formed pupa with viable males emerging. Adult males from starved nymphs lived for an average of 3 days post-emergence. Results provide methods for producing cohorts of mealybugs of predictable size and stage and provides insight into P. ficus demography and movement behavior.

Egg production in nests and nesting behaviour: genetic correlations with egg quality and BW for laying hens on the floor.

In laying hen production, cage-free housing is growing rapidly to provide living conditions that meet hens' needs. Unlike cages, this housing requires nests for automatic collection of eggs, as eggs laid outside nests must be collected by hand. Selecting hens for nest-related traits, such as egg production in nests and nesting behaviour, could help meet the requirements of cage-free housing. However, genetic correlations between these traits and major traits of breeding programmes, such as egg quality or BW, are poorly known. In addition, the genetic determinism of major traits has rarely been studied under cage-free conditions. The objective of the present study was to estimate the heritability of egg quality and BW measured on the floor and their genetic correlations with nest-related traits. Egg production in nests was based on the laying rate in nests, laying rhythm (clutch number and mean oviposition time), and nest acceptance. Nesting behaviour was based on nest preference (mean distance between nests used for laying) and mean laying duration (time spent in the nest for laying). Nest-related traits were recorded from 24 to 64weeks of age. BW and egg quality were measured at 50 and 55weeks of age, respectively. Nest-related traits and identification of the eggs laid by each hen (for individual measurements of egg quality) were obtained using individual electronic nests used by hens raised in groups and on the floor. The phenotypes of 1455 Rhode Island Red and 1538 White Leghorn hens were analysed. Heritability coefficients and genetic correlations were estimated using a multi-trait animal model for each line. Heritability estimates for egg quality and BW were moderate to high for both lines (0.17-0.74). Overall, weak genetic correlations were estimated between nest-related traits and egg quality or BW for both lines. However, strong and antagonistic genetic correlations were estimated between eggshell strength and laying rate in the nests (-0.46 to -0.42) or laying rhythm (+0.46 to +0.68) for both lines. Several moderate-to-strong genetic correlations were found for White Leghorn between nest-related traits and egg weight, eggshell shape, albumen height, and BW. This study shows that nest-related traits can be used to select hens better adapted to cage-free housing without degrading overall egg quality and BW. It also shows that some traits, like the eggshell strength, must be carefully monitored if these new traits are included in breeding goals. These results must now be confirmed for other populations and larger datasets.

Tick (Acari: Ixodidae) infestation in cattle from Sleman, Yogyakarta Province, Indonesia

Abstract. Sahara A, Budianto BH, Kunda RM, Firdausy LW. 2023. Tick (Acari: Ixodidae) infestation in cattle from Sleman, Yogyakarta Province, Indonesia. Biodiversitas 24: 4087-4094. Massive attacks of were found Haemaphysalis bispinosa in beef cattle farms in Sleman Regency, Yogyakarta, Indonesia. Besides it makes blood loss, they also have the potential to become vectors of several diseases. The aim of this research is to evaluate the prevalence of infestation, describe the morphology, fecundity, and timing of oviposition, as well as the preferred attachment sites for ticks. The samples were collected manually, and the body of the cattle was divided into four regions to determine the preferred sites of attachment of ticks. The morphology and occurrence of tick attachment sites, egg production, and hatchability were examined macroscopically and microscopically, and the obtained data we assessed descriptively and qualitatively. The findings indicated that, in contrast to the body area and the front and back legs, the tick predilection locations were the head, ears, and neck region. An engorged female may generate an average of 731.5±106 eggs throughout her 10-day oviposition cycle. After 17-30 days, tick eggs hatch into larvae; on average, 626.3±56 eggs per tick female successfully hatch into larvae.

Can nesting behaviour allow reptiles to adapt to climate change?

A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

LIFE TABLE ATTRIBUTES AND FEEDING EFFICIENCY OF OENOPIA SAUZETI (MULSANT) (COLEOPTERA: COCCINELLIDAE) FED ON APHID (APHIS GOSSYPII)

Ladybird beetles are play vital role in agroecosystem due to successful and efficient feeding behavior against aphids, the present research experiment was carried to find out the life history and feeding efficacy of oenopiasauzetifed on Aphis gossypii,at the laboratory of Biological Control, integrated pest management programme (IPMP), National Agriculture Research Centre (NARC), Islamabad. The results of the experiment revealed that the mean developmental time of immature stage 3rd and 4th instar have a significant difference with 3.72±0.11 and 3.87±0.036 days, while the egg to adult emergence was 39±0.35 days. The longevity has significant difference in male and female with the higher values at female 34.0 days. Similarly, the feeding efficiency was maximum in O. sauzeti females which feeds on 2227.1 mean number of Aphis gossypii, while the (409.25±1.42) mean numbers of aphids were consumed by larva. The maximum aphid consumption was observed at 4th instar larva (198.98±0.51 aphid) followed by 3rd instar larva (128.57±0.59 aphid). The mean oviposition time of O. sauzetion A. gossypii was recorded as 21.36 days and average eggs laid female-1 day-1 was 20.53, while the total laid eggs given by a female were 253.60. The apparent mortality (100qx) was maximum at egg stage (24) and the mortality survival ratio (MSR) was highest at pupal stage (0.53), similarly, the indispensable mortality (IM) was also observed high at pupal stage. The maximum survival fraction (Sx) was observed at the 4th larval stage (0.91) and the maximum life expectancy (ex) was observed at 1st larval instar (4.51) days. The total killer power (k-value) of the O. sauzetifor the complete generation was 0.49. This will help to develop an ecofriendly managing approach for the minimizing the aphids infestationin economical important crops.

The effects of seasonal changes on the dynamics of a fig tree's pollination

Fig trees and their pollinating wasps are mutually dependent on each other. Both partners' reproductive success is regulated by the capacity of fig wasps to enter receptive figs at an appropriate time for pollination and oviposition. Oviposition is dependent on successful female pollinator dispersal from one tree to another and although fig wasps are slow flyers and short-lived they can be carried long distances by the wind. The relative importance of local versus long-distance pollinator dispersal is unclear, as is how this may vary with season. In the highly seasonal environment of the Makana Botanical Gardens, Grahamstown, South Africa, we recorded fruiting phenologies of all the trees in a monoecious Ficus burtt-davyi Hutchinson population together with variation in the abundance of its pollinator Elisabethiella baijnathi Wiebes. By comparing captures of fig wasps flying in the air with the numbers that emerged locally, we also examined the independence of the fig tree population, which was separated from the nearest conspecifics by more than 1 km. The abundance of pollinators flying in the air and the number of fig wasps released by figs were correlated with temperature. During winter there were times when no pollinators were released locally; however, they were still caught in the traps, showing that the wasps had dispersed from elsewhere and that the population was not totally independent. These results highlight the ability of fig wasps to disperse between populations and the likely impact of seasonal fluctuations on fig tree gene flow.

Selection on female reproductive schedules in the marula fly, Ceratitis cosyra (Diptera: Tephritidae) affects dietary optima for female reproductive traits but not lifespan.

A changing environment can select on life-history traits and trade-offs in a myriad of ways. For example, global warming may shift phenology and thus the availability of host-plants. This may alter selection on survival and fertility schedules in herbivorous insects. If selection on life-histories changes, this may in turn select for altered nutrient intake, because the blend of nutrients organisms consume helps determine the expression of life-history traits. However, we lack empirical work testing whether shifts in the timing of oviposition alter nutrient intake and life-history strategies. We tested in the marula fruit fly, Ceratitis cosyra, how upward-selection on the age of female oviposition, in comparison with laboratory adapted control flies, affects the sex-specific relationship between protein and carbohydrate intake and life-history traits including lifespan, female lifetime egg production and daily egg production. We then determined the macronutrient ratio consumed when flies from each selection line and sex were allowed to self-regulate their intake. Lifespan, lifetime egg production and daily egg production were optimised at similar protein to carbohydrate (P:C) ratios in flies from both selection lines. Likewise, females and males of both lines actively defended similar nutrient intake ratios (control =1:3.6 P:C; upward-selected = 1:3.2 P:C). Our results are comparable to those in non-selected C. cosyra, where the optima for each trait and the self-selected protein to carbohydrate ratio observed were nearly identical. The nutrient blend that needs to be ingested for optimal expression of a given trait appeared to be well conserved across laboratory adapted and experimentally selected populations. These results suggest that in C. cosyra, nutritional requirements do not respond to a temporal change in oviposition substrate availability.

Calcitriol combined with fish oil in the diet of Chukar partridge can ameliorate laying performance by improving oviduct histomorphometry and functions.

The effects of calcitriol (CT) and/or fish oil (FO) on performance, oviposition time, sex ratioand morphology of the reproductive system of laying Chukar partridges were studied. Female (n = 48) and male (n = 16) partridges were used in a completely randomised design using a 2 × 2 factorial arrangement and were randomly allocated to either of four experimental treatments with four cage replicates of three females and one male each. Female birds received no FO (CON - FO) or were orally administered with 0.2 mL (0.24 g)/500 g body weight FO (CON + FO) or 0.2 mL solution containing 10 µg CT (CT - FO), or their combination (CT + FO) for 42 successive days. The eggs were collected every two hours between 07:00 and 23:00 h. Administering FO along with CT had considerably increasing effect on the male-biased sex ratio. FO and CT administration interacted to increase serum calcium concentration. Experimental treatments increased the number of leucocytes and erythrocytes. Serum cholesterol was decreased in CON + FO partridges compared with those of the CT - FO and CON - FO birds. There was an interaction between FO and CT on the weight of eggs and hatchlings, number of medium white follicles, diameter and the number of small yellow follicles, the weight and diameter of the fifth follicles (F5), and thickness of secondary mucosal folds in both uterus and vagina. Administering CT alone or with FO increased the feed intake, egg production, oviductal weight, diameter and number of large yellow follicles, the weight and diameter of the second (F2) and first (F1) follicles compared with those of the CON - FO females. Further studies are required to elucidate the mechanisms by which such changes in the sex ratio skew, ovaryand oviduct are mediated.

Intrinsic competition between 2 pupal parasitoids of Drosophila suzukii (Diptera: Drosophilidae)

Abstract The parasitoids Pachycrepoideus vindemmiae Rondani (Hymenoptera: Pteromalidae) and Trichopria anastrephae Costa Lima (Hymenoptera: Diapriidae) have great potential in controlling Drosophila suzukii (Matsumura); however, both, compete for the same resources. In this study, we evaluated whether the different stages of development of the primary parasitoid reduce the negative effect of intrinsic competition. For this, we first defined the duration of each immature stage of both parasitoid species and then offered D. suzukii pupae containing the first parasitoid (P. vindemmiae or T. anastrephae) at different stages of development to the second parasitoid (P. vindemmiae or T. anastrephae). We also checked the second parasitoid’s preference (P. vindemmiae or T. anastrephae) for the primary parasitoid at different stages of development (P. vindemmiae or T. anastrephae) or D. suzukii pupae nonparasitized. Our evaluations showed that T. anastrephae preferred to parasitize pupae that were not previously parasitized and that had not parasitized puparia of D. suzukii when P. vindemmiae was in later stage to the 1st instar. However, P. vindemmiae preferred to parasitize pupae previously parasitized by T. anastrephae. In an environment of intrinsic competition, the first parasitoid to parasitize has an advantage, except when the pupal stage of T. anastrephae is parasitized by P. vindemmiae. The variation in the parasitoids’ oviposition time mitigates the competition effect; however, for use in biological control programs, the hyperparasitoids P. vindemmiae, does not prove to be advantageous, as they can affect the establishment of primary parasitoids such as T. anastrephae, and can act as competitors for resources.

Disturbed circadian rhythm of locomotor activity of pullets is related to feather pecking in laying hens

Various aspects of activity, such as spontaneous activity, explorative activity, activity in open-field tests, and hyperactivity syndrome have been explored as causal factors of feather pecking in laying hens, with no clear results. In all previous studies, mean values of activity over different time intervals were used as criteria. Incidental observation of alternated oviposition time in lines selected for high (HFP) and low feather pecking (LFP), supported by a recent study which showed differentially expressed genes related to the circadian clock in the same lines, led to the hypothesis that feather pecking may be related to a disturbed diurnal activity rhythm. Hence activity recordings of a previous generation of these lines have been reanalyzed. Data sets of a total of 682 pullets of 3 subsequent hatches of HFP, LFP, and an unselected control line (CONTR) were used. Locomotor activity was recorded in pullets housed in groups of mixed lines in a deep litter pen on 7 consecutive 13-h light phases, using a radio-frequency identification antenna system. The number of approaches to the antenna system was recorded as a measure of locomotor activity and analyzed using a generalized linear mixed model including hatch, line, time of day and the interactions of hatch×time of day and line×time of day as fixed effects. Significant effects were found for time and the interaction line×time of day but not for line. All lines showed a bimodal pattern of diurnal activity. The peak activity of the HFP in the morning was lower than that of the LFP and CONTR. In the afternoon peak all lines differed with the highest mean in the LFP followed by CONTR and HFP. The present results provide support for the hypothesis that a disturbed circadian clock plays a role in the development of feather pecking.

Nest preference and laying duration traits to select against floor eggs in laying hens

BackgroundFloor eggs, which are defined as eggs that hens lay off-nest, are a major issue in cage-free layer poultry systems. They create additional work for farmers because they must be collected by hand. They are also usually soiled or broken, which results in economic losses. Nonetheless, knowledge about the genetics of nesting behavior is limited. The aim of this study was to estimate genetic parameters for traits related to nest preference for laying and to time spent in the nests used for laying (laying duration).MethodsTwo pure lines of laying hens were studied: 927 Rhode Island Red and 980 White Leghorn. Electronic nests were used to record the nesting behavior of these hens in floor pens from 24 to 64 weeks of age. Nest preference was studied based on the mean distance between nests used for laying and the percentage of nests used for laying. Laying duration was studied based on mean laying duration, mean duration in the nest before laying, and mean duration in the nest after laying. Genetic parameters were estimated for each line using a restricted maximum-likelihood method applied to a pedigree-based multi-trait animal model.ResultsEstimates of genetic parameters were similar for the two lines. Estimates of heritability ranged from 0.18 to 0.37 for nest preference traits and from 0.54 to 0.70 for laying duration traits. Estimates of genetic correlations of these traits with clutch number or mean oviposition time were favorable. Positive genetic correlations were estimated between nest preference and laying rate in the nests or nest acceptance for laying (+ 0.06 to + 0.37).ConclusionsThese results show that genetics influences traits related to nest preference and laying duration. Selecting hens that have no preference for particular nests and spend little time laying in the nests could help optimize nest use, reduce their occupation rate, and thus decrease the incidence of floor eggs in cage-free systems. Genetic correlations of these traits with other traits of interest related to hen welfare and egg quality have yet to be estimated.

Evaluation of the susceptibility to fipronil of Rhipicephalus microplus larvae from egg masses incubated at different times of oviposition.

The objective of this work was to evaluate the susceptibility of R. microplus larvae from different oviposition times to fipronil. The LPT was performed in sextuplicate, at concentrations of 18.75, 37.5, 75, 150 and 300 µg.mL-1. The LC50 found for the egg masses incubated with +7, +14 and +21 days were respectively 105.87, 110.71 and 121.22 µg.mL-1. The larvae originating from egg masses from the same group of engorged females, incubated on different days, presented similar mortality rates compared to the evaluated fipronil concentrations, facilitating the maintenance of laboratory colonies of this tick species.

Multi-omics analysis shed light on the mechanisms of tick reproductive inhibition by antibiotics

Ticks are vector pests and their biology and control are of worldwide concern. Microbiota play an important role in tick physiology, and antibiotic treatments are mostly used to explore the interactions between ticks and symbiotic microorganisms. In addition to altering the host microbial community, antibiotics also exhibit toxic effects on the host. In the tick Haemaphysalis longicornis, the engorged female ticks showed reproductive disruption after microinjection of tetracycline, as evidenced by prolonged oviposition time, reduced reproductive efficiency and hatchability, and abnormal oocyte development.

Size distribution and reproductive phenology of the invasive Burmese python (Python molurus bivittatus) in the Greater Everglades Ecosystem, Florida, USA

The design of successful invasive species control programs is often hindered by the absence of basic demographic data on the targeted population. Establishment of invasive Burmese pythons (Python molurus bivittatus) in the Greater Everglades Ecosystem, Florida USA has led to local precipitous declines (&amp;gt; 90%) of mesomammal populations and is also a major threat to native populations of reptiles and birds. Efforts to control this species are ongoing but are hampered by the lack of access to and information on the expected biological patterns of pythons in southern Florida. We present data from more than 4,000 wild Burmese pythons that were removed in southern Florida over 26 years (1995–2021), the most robust dataset representing this invasive population to date. We used these data to characterize Burmese python size distribution, size at maturity, clutch size, and seasonal demographic and reproductive trends. We broadened the previously described size ranges by sex and, based on our newly defined size-stage classes, showed that males are smaller than females at sexual maturity, confirmed a positive correlation between maternal body size and potential clutch size, and developed predictive equations to facilitate demographic predictions. We also refined the annual breeding season (approx.100 days December into March), oviposition timing (May), and hatchling emergence and dispersal period (July through October) using correlations of capture morphometrics with observations of seasonal gonadal recrudescence (resurgence) and regression. Determination of reproductive output and timing can inform population models and help managers arrest population growth by targeting key aspects of python life history. These results define characteristics of the species in Florida and provide an enhanced understanding of the ecology and reproductive biology of Burmese pythons in their invasive Everglades range.