Egg Viability Research Articles

Evaluation of the biological function of ribosomal protein S18 from cattle tick Rhipicephalus microplus

Rhipicephalus (Boophilus) microplus, also known as the cattle tick, causes severe parasitism and transmits different pathogens to vertebrate hosts, leading to massive economic losses. In the present study, we performed a functional characterization of a ribosomal protein from R. microplus to investigate its importance in blood feeding, egg production and viability. Ribosomal protein S18 (RPS18) is part of the 40S subunit, associated with 18S rRNA, and has been previously pointed to have a secondary role in different organisms. Rhipicephalus microplus RPS18 (RmRPS18) gene expression levels were modulated in female salivary glands during blood feeding. Moreover, mRNA levels in this tissue were 10 times higher than those in the midgut of fully engorged female ticks. Additionally, recombinant RmRPS18 was recognized by IgG antibodies from sera of cattle naturally or experimentally infested with ticks. RNAi-mediated knockdown of the RmRPS18 gene was performed in fully engorged females, leading to a significant (29 %) decrease in egg production. Additionally, egg hatching was completely impaired, suggesting that no viable eggs were produced by the RmRPS18-silenced group. Furthermore, antimicrobial assays revealed inhibitory activities against gram-negative Escherichia coli and gram-positive Staphylococcus aureus bacteria, affecting bacterial growth. Data presented here show the important role of RmRPS18 in tick physiology and suggest that RmRPS18 can be a potential target for the development of novel strategies for tick control.

Efficacy and Persistence of Entomopathogenic Fungi against Rhynchophorus ferrugineus on Date Palm: Host to Host Transmission

The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae), is a destructive and voracious pest of palm species worldwide. Due to environmental and regulatory concerns, ecologically safe alternatives to synthetic chemical insecticides are needed to manage this cryptic insect species. Entomopathogenic fungi have the potential to manage this pest. The scope of management and effectiveness can be improved by direct control or horizontal transmission of entomopathogenic fungal isolates. We tested in the laboratory the virulence and pathogenicity of fifteen different entomopathogenic fungal isolates belonging to the following species: Beauveria bassiana, Metarhizium anisopliae, Beauveria brongniartii and Purpureocillium lilacinum. All fungal isolates were found virulent against larvae (14.9 ± 1.06 to 81.5 ± 1.48% mortality) and adults (5.6 ± 1.12 to 51.7 ± 1.51% mortality) at 12 d post-treatment. From a screening bioassay, five M. anisopliae (WG-08, WG-09) and B. bassiana (WG-23, WG-24, WG-25) isolates were tested for their concentration response mortality against larvae and adults after 7, 14 and 21 days (d) of treatment. Mortality was found positively correlated with concentration and time. At 21 d of treatment, WG-23 and WG-25 1 × 108 conidia/mL resulted in 100% mortality against larvae while only WG-25 1 × 109 conidia/mL caused 100% mortality of adults. Along with mortality, all the potential isolates have strong ovicidal effects that reduced 81.49% at 1 × 108 conidia/mL. The horizontal transmission bioassay indicated that the infected adults transmitted the disease to healthy individuals. Horizontal transmission of fungi from infected to non-infected adults not only caused significant mortality but also had a serious sublethal impact on insect development and fitness including reduced number of eggs/d fecundity, egg viability and neonate survival. Isolate WG-25 reduced oviposition (0.5 eggs/d), fecundity (11.7 eggs/female), egg viability (11.6%) along with larval survival 25.9% when infected male mated with normal female. In semi-field trials, all fungal isolates reduced survival of larvae found inside the palms and ultimately reduced infestations over a period of two months. The results of this study indicate that entomopathogenic fungi should be further tested for sustainable and efficient control of RPW in date palm production systems.

Changes in the bacterial communities of Harmonia axyridis (Coleoptera: Coccinellidae) in response to long-term cold storage and progressive loss of egg viability in cold-stored beetles.

Bacteria have a profound influence on life history and reproduction of numerous insects, while the associations between hosts and bacteria are substantially influenced by environmental pressures. Cold storage is crucial for extending the shelf life of insects used as tools for biological control, but mostly causes detrimental effects. In this study, we observed a great decrease in egg hatch rate of cold-stored Harmonia axyridis during the later oviposition periods. Furthermore, most eggs produced by their F1 offspring exhibited complete loss of hatchability. We hypothesized that long-term exposure to cold may greatly alter the bacterial community within the reproductive tracts of H. axyridis, which may be an important factor contributing to the loss of egg viability. Through sequencing of the 16S rRNA gene, we discovered considerable changes in the bacterial structure within the reproductive tracts of female cold-stored beetles (LCS_F) compared to non-stored beetles (Control_F), with a notable increase in unclassified_f_Enterobacteriaceae in LCS_F. Furthermore, in accordance with the change of egg hatchability, we observed a slight variation in the microbial community of eggs produced by cold-stored beetles in early (Egg_E) and later (Egg_L) oviposition periods as well as in eggs produced by their F1 offspring (Egg_F1). Functional predictions of the microbial communities revealed a significant decrease in the relative abundance of substance dependence pathway in LCS_F. Moreover, this pathway exhibited relatively lower abundance levels in both Egg_L and Egg_F1 compared to Egg_E. These findings validate that long-term cold storage can greatly modify the bacterial composition within H. axyridis, thereby expanding our understanding of the intricate bacteria-insect host interactions.

Effects of structurally distinct human HDAC6 and HDAC6/HDAC8 inhibitors against S. mansoni larval and adult worm stages.

Schistosomiasis is a major neglected parasitic disease that affects more than 240 million people worldwide caused by Platyhelminthes of the genus Schistosoma. The treatment of schistosomiasis relies on the long-term application of a single safe drug, praziquantel (PZQ). Unfortunately, PZQ is very effective on adult parasites and poorly on larval stage and immature juvenile worms; this can partially explain the re-infection in endemic areas where patients are likely to host parasites at different developmental stages concurrently. Moreover, the risk of development of drug resistance because of the widespread use of a single drug in a large population is nowadays a serious threat. Hence, research aimed at identifying novel drugs to be used alone or in combination with PZQ is needed. Schistosomes display morphologically distinct stages during their life cycle and epigenetic mechanisms are known to play important roles in parasite growth, survival, and development. Histone deacetylase (HDAC) enzymes, particularly HDAC8, are considered valuable for therapeutic intervention for the treatment of schistosomiasis. Herein, we report the phenotypic screening on both larvae and adult Schistosoma mansoni stages of structurally different HDAC inhibitors selected from the in-house Siena library. All molecules have previously shown inhibition profiles on human HDAC6 and/or HDAC8 enzymes. Among them we identified a quinolone-based HDAC inhibitor, NF2839, that impacts larval and adult parasites as well as egg viability and maturation in vitro. Importantly, this quinolone-based compound also increases histone and tubulin acetylation in S. mansoni parasites, thus representing a leading candidate for the development of new generation anti-Schistosoma chemotherapeutics.

Fecundity decline is male derived following transfluthrin exposures in a field strain of Aedes albopictus (Diptera: Culicidae).

Volatile pyrethroids are effective in reducing mosquito populations and repelling vectors away from hosts. However, many gaps in knowledge exist for the sublethal impacts of volatile pyrethroids on mosquitoes. To that end, transfluthrin exposures were conducted on a field strain of Aedes albopictus (Skuse) held as a laboratory colony. Dose-response analysis was conducted on both sexes at either 1-4 days old or 5-10 days old. Resultant concentration data were used to evaluate the LC20 and LC50 values in various mate pairings of treatments and controls in which either the male or female was from a selectively treated group and mated with a counterpart that was treated independently. Blood feeding proportion, delayed mortality after a 24-h recovery period, egg collection totals, and F1 larval survival were determined following transfluthrin treatment in the F0, but outcomes were not significant. In contrast, sterility was predicated on male treatment, with treated females resulting in higher overall egg viability. Treated males in the mating pair resulted in significantly lower egg viability and accelerated larval hatch in the F1. Additionally, the presence of sperm in female spermathecae was significantly diminished in test groups containing treated male mosquitoes. Male sublethal effects may be a critical determinant of a mixed population's reproductive success.

Initial investigations into the production of triploid sunshine bass using temperature shock

AbstractObjectiveThe sunshine bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) is an important food fish raised in U.S. aquaculture. Spawning is performed by manually stripping and fertilizing White Bass eggs with Striped Bass sperm. Embryos hatch in approximately 48 h. Mature sunshine bass females can become fertile and produce viable eggs, which is problematic in commercial food‐fish production; therefore, triploid fish are desired.MethodsThe present nonreplicated study incorporated three warm and three cold temperature shocks, along with three postfertilization initiation times and three exposure times for each temperature, during initial stages of incubation to induce triploidy. After exposure to temperature shocks, fertilized eggs were incubated in experimental hatching systems. The best performing cold and warm temperatures and times (and an ambient diploid control) were then used to incubate fertilized eggs in a commercial‐scale trial using standard industry practices with a single batch of eggs. Larvae were stocked at about 185,000 larvae/ha (75,000 larvae/acre) in newly filled and fertilized ponds. Fry were sampled weekly and harvested at 30 days.ResultThere were 15 survivors from the pond containing fish derived from cold‐shocked fertilized eggs; these individuals were tested via Coulter Counter, and no triploids were detected. Testing of 50 survivors from the pond containing fish derived from warm‐shocked fertilized eggs indicated that 14% were triploid.ConclusionTherefore, initial trials indicate that warm temperature shock is preferable to cold shock for inducing a greater percentage of triploid sunshine bass.

Bt Soybean Cry1Ac Does Not Affect Development, Reproduction, or Feeding Behavior of Red-Banded Stink Bug Piezodorus guildinii (Hemiptera: Pentatomidae).

Bt soybean cultivation is increasing worldwide. The Cry1Ac protein expressed in Bt soybean efficiently controls several lepidopteran pests. The stink bug, Piezodorus guildinii (Westwood), a major pest for soybean in the Americas, is not controlled by Bt crops, although possible sub-lethal effects may occur. Even if there were no negative effects for sting bug, ingesting toxins could affect its bio-controllers. We tested through ELISA detection if P. guildinii ingests Cry1Ac from Bt soybean and possible effects on its development, reproduction, survival, and feeding behavior. Biological traits were evaluated under controlled conditions of nymphs and adults feeding on pods of near-isogenic cultivars DM5958iPRO (Bt) and DM59i (non-Bt). Feeding behavior was recorded using an AC-DC electropenetrography (EPG) device. Results indicated that P. guildinii ingested the Cry1Ac protein; however, nymphal period and accumulated survival percentage did not differ between cultivars. Feeding on Bt soybean pods did not affect fecundity (i.e., number of egg masses and eggs/female) nor egg viability. Different feeding behaviors were only detected on the pathway phase (stylet penetration into plant tissue), which was more pronounced in the Bt cultivar. However, the total duration of the feeding activities on seeds was numerically higher (ca. 2X) on Bt plants compared to non-Bt. This is the first study to demonstrate that P. guildinii does ingest the Cry1Ac protein and excrete it without being absorbed, probably explaining the lack of direct adverse effects on its biological parameters. EPG could indicate that Bt soybean plants might be less palatable than non-Bt to red-banded stink bug.

Formulating Parasiticidal Fungi in Dried Edible Gelatins to Reduce the Risk of Infection by Trichuris sp. among Continuous Grazing Bison.

Control of infection by gastrointestinal nematodes remains a big problem in ruminants under continuous grazing. For the purpose of decreasing the risk of infection by Trichuris sp. in captive bison (Bison bison) always maintained in the same plot, dried gelatins having ≥106 chlamydospores of both Mucor circinelloides and Duddingtonia flagrans were given to them for one week, and at the end, fecal samples (FF) collected each week for four weeks were analyzed immediately. Feces taken one week prior to gelatin administration served as controls (CF). Eggs of Trichuris sp. were sorted into non-viable and viable, then classified into viable undeveloped (VU), viable with cellular development (VCD), or viable infective (VI). Ovistatic and ovicidal effects were determined throughout the study. In FF, viability of Trichuris eggs decreased between 9% (first week) and 57% (fourth week), egg development was delayed during the first two weeks, and VI percentages were significantly lower than in CF (p = 0.001). It is concluded that the preparation of gelatins with chlamydospores of parasiticidal fungi and their subsequent dehydration offer an edible formulation that is ready to use, stress-free to supply, and easy to store, as well as being well-accepted by ruminants and highly efficient to reduce the risk of Trichuris sp. infection among animals under continuous grazing regimes.

Responses of two Anastrepha species' immature stages infesting preferential hosts to different temperature exposures.

Anastrepha fraterculus (Wiedemann) and A. obliqua (Macquart) are important pests of fruit crops. In Brazil, these species cause damage to fruit growing in the South (annual average temperature of 20.9°C) and Northeast (average yearly temperature of 24°C). We evaluated the effect of temperature on the viability and development time of A. fraterculus and A. obliqua immature stages in their respective preferred hosts, guava (Psidium guajava L., Myrtaceae) and mango (Mangifera indica L., Anacardiaceae). The duration of egg and pupal stages, egg to pre-pupa, and viability of egg and pupal stages under different temperatures (15, 20, 25, 30, and 35°C) were assessed. For both species, development time decreased with increasing temperature. Viability in the evaluated stages was only observed between 15 and 30°C. However, the species responded differently to the exposure temperatures (15 and 30°C), especially in the pupal stage and from egg to pre-pupa. Anastrepha fraterculus showed a lower tolerance to high temperatures, especially in the pupal stage and from egg to pre-pupa, which may explain its lower importance and economic impact in warmer Brazilian regions. Anastrepha obliqua had a lower tolerance at 15°C, indicating greater adequacy for temperatures above 20°C, characteristic of Northeast Brazil, suggesting the capacity to spread to cooler areas with rising temperatures.

Alterations in the rate of fertility, egg viability, and hatch parameters of adult geese exposed to different breeding methods.

In a 10-wk study, alterations in the rate of fertility, egg viability, and hatch parameters of adult geese exposed to different breeding methods were investigated. Twenty-four matured geese (4.0 ± 0.45 average weight) were randomly divided into three groups (TNM-natural mating group, TIM-artificial insemination group, TNI-natural mating and insemination group) of two replicates with four geese per replicate in a completely randomized design. Fresh semen collected from six ganders (5.2 ± 0.69 average weight) was pooled and used to inseminate the geese in TIM and TN1 at 0.2Ml at insemination times. The geese in TNM and TNI were allowed to mate naturally. Insemination and mating was done at 3 d interval and eggs from each treatment were collected daily. Incubation of eggs was done weekly, candling and transfer to hatcher were done on day 27 and goslings hatched out on day 30. Fertility, early embryo mortality (EEM), mid embryo mortality (MEM), late embryo mortality (LEM), hatch of fertile eggs (HOF), and hatch of set eggs (HOS) were obtained and analyzed using descriptive statistics and ANOVA and means separated using least significant difference test. Geese in TNI had significantly higher fertility (93.33 ± 10.97%) than TNM (59.67 ± 31.29%) and TIM (83.60 ± 17.14%). The EEM was higher in TIM than in the two other groups while the HOF and HOS were higher in TNM and TNI than in TIM. This study suggests that in comparison with TIM, higher fertility, hatchability, and lower embryo mortality can be obtained when geese are inseminated and naturally mated simultaneously.

Biological development of Saccharicoccus sacchari () (Hemiptera: Pseudococcidae) on sugarcane in different temperatures.

The pink sugarcane mealybug Saccharicoccus sacchari (Cockerell, 1895) (Hemiptera: Pseudococcidae) occurs practically in all sugarcane producing regions Saccharum spp. (Poaceae) causing damage. Little information is available about insect's biology under Brazilian conditions. In this work, biological development of pink sugarcane mealybug was studied at temperatures of 23 °C ± 2 °C and 28 °C ± 2 °C without photophase and relative humidity of 80%. Number and viability of eggs, incubation time, duration of the last oviposition, duration of each nymphal instar, viability of the nymphs, start of oviposition and longevity of the females were recorded. Biological development of insects was stipulated by the SAS University Edition software, version 9.4. There were differences in the life cycle of the pseudococcid at both temperatures evaluated. Females of S. sacchari had three nymphal instars and reproduce asexually. Asexual reproduction occurs in the field and under controlled conditions. By increasing the temperature increases, insect lived longer and the presence of the winged male in Brazil indicates the possibility of sexual reproduction of the species.

Genetic origins of a resurging lake whitefish, Coregonus clupeaformis, population in the Detroit River, Laurentian Great Lakes

The Detroit River connects Lake Huron and Lake Erie of the Laurentian Great Lakes. The river once supported a substantial lake whitefish (Coregonus clupeaformis) fishery until the early 1900s, when habitat loss, pollution, and overfishing contributed to the collapse of the fishery and loss of spawning populations in the river. In the early 1970s, efforts were initiated to improve water and habitat quality, and in December 2005 a spawning male lake whitefish and viable eggs were collected; the first documented evidence of spawning since 1916. Researchers have tracked the spawning magnitude of the lake whitefish population in the Detroit River since 2005 by assessing the number of eggs deposited on egg mats. Genetic analysis of larval fish hatched from eggs collected in the field between 2005 and 2018 was used to determine the relative contributions of Lake Erie and Lake Huron to the resurging population. Over 80% of the hatched larvae had parents originating from Lake Erie in all the years sampled. The estimated number of full-sibling families sampled at Belle Isle was the same in 2010 and 2014 and varied between 2009 and 2016 at Fighting Island. The estimated number of lake whitefish parents at Fighting Island decreased in the most recent collections possibly due to loss of habitat on spawning reefs due to sedimentation. Our results provide additional evidence that restored spawning habitat in the Detroit River is again being used by lake whitefish and continued reproduction at these sites may improve the Great Lakes portfolio of ecological and genetic diversity.

Reaction of potato cultivars to Potato Cyst Nematodes (Globodera rostochiensis and G. pallida) under greenhouse conditions in Kenya

Several measures have been recommended in the control of potato cyst nematodes (PCN) with resistant potato cultivars being considered as the most practical and affordable for smallholder potato farmers in Kenya. However, the level of resistance in locally grown potato varieties is yet to be established. The aim of this study was to screen Kenyan potato cultivars against PCN under greenhouse conditions. Eleven potato cultivars namely Shangi, Dutch Robijn, Sherekea, Nyota, Roseline tana, Tigoni, Unica, Asante, Chulu, Kenya Mpya and Arka were screened with Desiree (susceptible variety), Manitou (resistant cultivar) as controls. For each potato cultivar, there were two sets of plants with the first set being inoculated with 50 cysts, while the second batch was nematode-free. The treatments were arranged in a completely randomized design with three replications. A scale of 1-9, with 9 indicating the highest level of resistance was used in the assessment of disease severity. Nematode infestation caused a reduction in root mass across the 11 cultivars from 20 to 100% compared to uninoculated controls. Reproductive index of PCN viable eggs across the 11 cultivars was <1 compared to control (Desiree). Potato cultivars Shangi, Tigoni, Dutch, Chulu, Asante, Unica, Arka, Kenya Mpya, and Roseline Tana had a severity score of 1-3 (>95%), hence were considered to be susceptible to PCN. The cultivars Sherekea and Nyota had a severity score of 4-6 (<25%) and hence were considered partially resistant to PCN. The findings of this study provides a basis of integrating partially resistant potato cultivars into PCN management in smallholder farms. Keywords: Cyst viable eggs, reproductive index, resistance, susceptible, smallholder farmers, severity score.

Lipids in Insect Reproduction: Where, How, and Why.

Modern insects have inhabited the earth for hundreds of millions of years, and part of their successful adaptation lies in their many reproductive strategies. Insect reproduction is linked to a high metabolic rate that provides viable eggs in a relatively short time. In this context, an accurate interplay between the endocrine system and the nutrients synthetized and metabolized is essential to produce healthy offspring. Lipids guarantee the metabolic energy needed for egg formation and represent the main energy source consumed during embryogenesis. Lipids availability is tightly regulated by a complex network of endocrine signals primarily controlled by the central nervous system (CNS) and associated endocrine glands, the corpora allata (CA) and corpora cardiaca (CC). This endocrine axis provides hormones and neuropeptides that significatively affect tissues closely involved in successful reproduction: the fat body, which is the metabolic center supplying the lipid resources and energy demanded in egg formation, and the ovaries, where the developing oocytes recruit lipids that will be used for optimal embryogenesis. The post-genomic era and the availability of modern experimental approaches have advanced our understanding of many processes involved in lipid homeostasis; therefore, it is crucial to integrate the findings of recent years into the knowledge already acquired in the last decades. The present chapter is devoted to reviewing major recent contributions made in elucidating the impact of the CNS/CA/CC-fat body-ovary axis on lipid metabolism in the context of insect reproduction, highlighting areas of fruitful research.

Egg productivity and viability of larvae of promising breeding systems obtained based on foreign silkworm breeds

This article comparatively analyzes the viability as well as the fertility of silkworms of local breeds and promising breeding systems during the egg and larval periods. Based on the results of the study, average indicators of eggs hatchability, viability and the morbidity degree of larvae of new breeding systems were identified. At the same time, according to the results obtained, new promising systems in the combination Parvoz 1 x foreign and Parvoz 2 x foreign showed an average degree in terms of fertility characteristics. Uzbek-Chinese breeds are important in the rearing of high-quality cocoon raw materials for sericulture in Uzbekistan in the future, and therefore it is advisable further development of scientific research in this direction and bring it to a new level.

STUDY OF THE EFFICIENCY AND COMPARATIVE ANALYSIS OF THE APPLICATION OF TECHNIQUES FOR EVALUATING THE QUALITY OF PHYTOPHAGES AND ENTOMOPHAGES AT DIFFERENT STAGES OF ONTOGENESIS

The concept of quality control of insect crops is proposed, which is based on a targeted approach based on the goal and objectives of the implementation of a certain breeding program and is divided into two main directions: control of phytophage production, control of entomophage production. Quality control methods are based on the general biological rule of dependence between the intensity of insect taxis and the overall viability of biomaterial. The effectiveness of methods for assessing the quality of phytophages (on the example of the mother cultures of the grain moth Sitotroga cerealella, the wax moth Galleria mellonella) and entomophages (laboratory and natural populations of P. bioculatus.) of the Center for Mother Cultures of Insects Engineering and Technological Institute “Biotekhnica” of the National Academy of Sciences (ETI “Biotekhnica”) at different stages of ontogenesis was investigated using the indicator the intensity of taxis. As a result of research conducted on the culture of phytophagous, grain moth, a significant difference with the control was established in the indicators of viability of eggs, larvae, pupae and adults: 25; 6; 33 and 11%, respectively. Studies conducted with another phytophagous representative – the wax firefly – also showed positive results (16; 17; 16; 11%, respectively). The obtained (as a result of preliminary quality control) and selection culture had significantly higher viability indicators at all stages of ontogenesis. It was established that the intensity of chemotaxis of larvae of the 1st age of entomophages directly correlates with the indicator of viability of the insect culture. When selecting the starting material for successful culture, it is possible to select by chemotaxis of the larvae after rebirth from the egg. Thus, viability when selecting for Colorado beetle eggs significantly (p<0.01) exceeds this indicator in other selection options – Colorado beetle larvae and wax firefly larvae: 82; 59; 73% respectively. When working with an artificial population of P. bioculatus, on wax moth larvae, the highest intensity of taxis was noted in the variant with wax moth larvae compared to Colorado beetle eggs and Colorado beetle larvae – 37; 34; 29% respectively. This indicates a shift in the number of the population in the direction of individuals that successfully feed on unnatural food. Their viability was significantly higher than the viability in other variants of the study with an artificial population – 78; 71; 68% respectively. The proposed method of selection of starting material for cultivation of P. bioculatus allows differentiation of individuals for further effective reproduction, and the use of such biomaterial in programs of biological protection of plants from pests. A comparative analysis of methods for assessing the quality of phytophagous and entomophagous cultures at different stages of ontogenesis was carried out using the indicator of the overall viability of insect populations. It is an integrated indicator that takes into account the viability of the population at all stages of its development. All tested objects of the study showed that control and improvement of culture quality by the proposed method lead to an increase in the viability of biomaterial by 18.71; 18.56 and 8.86%, respectively (egg, larva, pupa).

Influence of Tempetature on Viability and Deveplopment of Heterakis gallinarum (Nematoda, Heterakidae) Eggs

Pinworms of the genus Heterakis Dujardin, 1845 parasitize a wide range of hosts, including a number of species of domestic and wild birds. These nematodes are ecologically adapted to the climatic conditions of many geographical zones, which contributes to their widespread distribution. The aim of the work was to investigate the influence of different temperature regimes at laboratory conditions on the growth, development and viability of eggs isolated from the gonads of female nematodes Heterakis gallinarum Schrank, 1788. The conducted studies established that, depending on the cultivation temperature, nematode eggs developed from 6 to 56 days, and their survival rate was from 67.7 to 83.7 %. The temperature of 25 °С was the most favourable for the development of H. gallinarum eggs, the development lasted 12 days and the highest number of eggs with motile infective larvae was formed (83.7 %). It was found that the period of egg development in cultures gradually decreased with increasing temperature: it was 56 days at 15 °C, 18 days at 20 °C, 12 days at 25 °C and 6 days at 30 °C. The survival rate of H. gallinarum eggs gradually increased with increasing temperature in regimes of 15 °С, 20 °С and 25 °С to 67.7 %, 80.7 % and 83.7 %, respectively. At a temperature of 30 °C, egg survival decreased slightly to 78.7 %. It was found that the development of H. gallinarum eggs from the zygote stage to the formation of motile infective larvae, depending on the temperature regime of cultivation, is accompanied by a decrease in egg length by 4.9–5.4 %, an increase in egg width by 4.1–7.6 % and a thinning of the shell by 9.5–28.6 %. Under different temperature regimes, the morphometric parameters of eggs during their development differ in terms of their length, width and shell thickness.

Characterization of the vocal behavior of the miniature and transparent fish model, Danionella cerebruma).

Danionella cerebrum has recently been proposed as a promising model to investigate the structure and function of the adult vertebrate brain, including the development of vocal-auditory neural pathways. This genetically tractable and transparent cypriniform is highly vocal, but limited information is available on its acoustic behavior and underlying biological function. Our main goal was to characterize the acoustic repertoire and diel variation in sound production of D. cerebrum, as well as to investigate the relationship between vocal behavior and reproduction. Sound recordings demonstrated high vocal activity, with sounds varying from short sequences of pulses known as "bursts" (comprising up to 15 pulses) to notably longer sounds, termed "long bursts", which extended up to 349 pulses with over 2.7 s. Vocal activity peaked at midday and it was very low at night with only a few bursts. While the number of pulses was higher during the daytime, the interpulse interval was longer at night. In addition, calling time was positively associated with the number of viable eggs, suggesting that acoustic communication is important for reproduction. These preliminary findings reveal the potential of using D. cerebrum to investigate vocal plasticity and the implications for sexual selection and reproduction in a novel vertebrate model for neuroscience.

Sampling and Extraction of Plant Parasitic Nematodes.

The study of nematodes requires availability of nematode specimens and their population densities in plants and soil. This can be achieved using adequate sampling schemes and extraction methods. In this chapter, the most common and suitable sampling and extraction procedures and equipment are described. These include the use of Baermann's funnels, Cobb's decanting and sieving, floating methods such as the Oostenbrink method and Fenwick can, elutriators such as Seinhorst methods, centrifugation methods including that of Coolen, and mechanical and enzymatic maceration. The combination of different methods for cleaning the nematode suspensions is described, such as Cobb's sieving with Baermann's funnels or centrifugation, and for cysts combining Seinhorst's elutriator or Fenwick can with the alcohol methods. Methods for extraction of eggs and/or juveniles of cyst and egg mass forming nematodes, to be used as inoculum or to ascertain egg viability, are also described. Only little information is also noted on the use of molecular tools to identify and quantify nematode populations in soil and roots.

The influence of the toxin-producing dinoflagellate, Alexandrium catenella, on feeding, reproduction and toxin retention in Calanus helgolandicus

Copepods of the genus Calanus dominate the biomass of pelagic ecosystems from the Mediterranean Sea up into the Arctic Ocean and form an important link between phytoplankton and higher trophic levels. Impacts from toxin-producing harmful algae (HA) have been recorded throughout this region over the last 50 years, with potentially negative effects on Calanus spp. populations and the ecosystem functions and services they provide. Here we examine how ingestion, egg-production and egg-viability in Calanus helgolandicus are affected by the relative abundance of the toxin-producing dinoflagellate Alexandrium catenella in their diet. Our four-day experiments demonstrate that the ingestion rate of C. helgolandicus declined significantly as the percentage of toxin-producing A. catenella within their diet increased, whereas egg production and egg viability were unaffected. Toxin profile concentrations for A. catenella are presented alongside body toxin-loads in C. helgolandicus after 4 days of feeding on these cells. The body toxin concentrations of C. helgolandicus were 3.6–356.6 pg STX diHCl eq. copepod−1, approximately 0.02–3.3 % of the toxins ingested. Our work suggests that the effects of exposure to A. catenella may be negligible in the short-term but could manifest if bloom conditions persist for longer than our experimental duration.