Pan‐continental invasion of Pseudorasbora parva: towards a better understanding of freshwater fish invasions

In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.     

Genetic parameters for growth and survival traits in Pacific white shrimp Penaeus (Litopenaeus) vannamei from a nucleus population undergoing a two-stage selection program

A multivariate animal model and multi-generational data from a two-stage selection shrimp breeding program were used to estimate genetic parameters for a genetic nucleus of Penaeus (Litopenaeus) vannamei. A total of 408,648 records from years 2008 to 2010 production cycles provided by a Mexican hatchery were analyzed. The studied traits were survival from 0 to 28 days of age (S1), square root of body weight at 28 days of age (W1^1/2), survival from 65 to 130 days of age (S2), and body weight at 130 days of age (W2). Mean (standard deviation) for W1^1/2 and W2 were estimated as 5.4 mg^1/2 (1.55) and 13.6 g (3.1), respectively, while mean (standard deviation) for S1 and S2 (as proportions) were estimated as 0.20 (0.41) and 0.71 (0.45), respectively. Heritabilities for S1, W1^1/2, S2, and W2 were 0.03 ± 0.01, 0.13 ± 0.03, 0.04 ± 0.01, and 0.21 ± 0.04, respectively. Genetic correlations of S1 with W1^1/2, S2, and W2 were ?0.49 ± 0.21, ?0.29 ± 0. 21, and ?0.40 ± 0.16, respectively. Genetic correlations of W1^1/2 with S2, and W2 were 0.55 ± 0.17, and 0.71 ± 0.12, respectively, and genetic correlation between S2 and W2 was 0.56 ± 0.10. Results show that selection based on W2 has a positive effect on S2, while selection based on W1^1/2, as an early selection criterion, would increase the selection responses for W2 and S2.     

Insecticide resistance compromises the control of Aedes aegypti in Bangladesh

BACKGROUND

With no effective drugs or widely available vaccines, dengue control in Bangladesh is dependent on targeting the primary vector Aedes aegypti with insecticides and larval source management. Despite these interventions, the dengue burden is increasing in Bangladesh, and the country experienced its worst outbreak in 2019 with 101 354 hospitalized cases. This may be partially facilitated by the presence of intense insecticide resistance in vector populations. Here, we describe the intensity and mechanisms of resistance to insecticides commonly deployed against Ae. aegypti in Dhaka, Bangladesh.

RESULTS

Dhaka Ae. aegypti colonies exhibited high-intensity resistance to pyrethroids. Using CDC bottle assays, we recorded 2–24% mortality (recorded at 24 h) to permethrin and 48–94% mortality to deltamethrin, at 10× the diagnostic dose. Bioassays conducted using insecticide–synergist combinations suggested that metabolic mechanisms were contributing to pyrethroid resistance, specifically multi-function oxidases, esterases, and glutathione S-transferases. In addition, kdr alleles were detected, with a high frequency (78–98%) of homozygotes for the V1016G mutation. A large proportion (≤ 74%) of free-flying and resting mosquitoes from Dhaka colonies survived exposure to standard applications of pyrethroid aerosols in an experimental free-flight room. Although that exposure affected the immediate host-seeking behavior of Ae. aegypti, the effect was transient in surviving mosquitoes.

CONCLUSION

The intense resistance characterized in this study is likely compromising the operational effectiveness of pyrethroids against Ae. aegypti in Dhaka. Switching to alternative chemical classes may offer a medium-term solution, but ultimately a more sustainable and effective approach to controlling dengue vectors is required. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Genetic parameters for seedling growth in Pinus pseudostrobus families under different competitive environments

Pinus pseudostrobus Lindl. is a widely distributed species in Mexico that also occurs in Guatemala, Honduras and El Salvador and has been tested outside its natural range in Brazil, Chile, Colombia, New Zealand, South Africa and Venezuela. Due to its great potential, it is necessary to select genotypes capable of increasing its production in the shortest possible time through genetic improvement strategies, where individuals are subjected to conditions forcing them to express their growth potential in advance. The objectives of the present study were to evaluate the genetic variation among half-sib progenies and to estimate heritability (h ² ) of stem height (SH) and diameter (SD) for seedlings grown under different competitive conditions in a common garden trial. A split-plot experimental design with four replications and three competitive environments (treatments) was used: (I) low inter-family competition (0.25 × 0.12 m), (II) high inter-family competition (0.12 × 0.06 m), and (III) high intra-family competition; 13 half-sib families were assessed, carrying out monthly evaluations for 10 months. Estimated h ² at individual and family-means levels for both SH and SD varied among competitive environments. For conditions I and II, a trend towards increasing h ² with age of seedlings was shown, but for condition III, a reverse trend was observed (values close to zero). High genetic stability in SH performance was found in both I and II, and II and III, pairs of environments, as measured by the type-B genetic correlation (0.70 ≤ r _B  ≤ 1.0), but it tended to decrease after 9 months, when competition increased; genetic stability in SD was lower (0.20 ≤ r _B  ≤ 0.80) in both pairs of the environments that were sampled. It was concluded that the competition conditions used in field trials for genotype evaluation may significantly affect the variance components, estimation of genetic parameters and genotype stability.     

Antioxidant and antiproliferative activities of heterofucans from the seaweed Sargassum filipendula

Fucan is a term used to denominate a type of polysaccharide which contains substantial percentages of l-fucose and sulfate ester groups. We obtained five heterofucans from Sargassum filipendula by proteolytic digestion followed by sequential acetone precipitation. These heterofucans are composed mainly of fucose, glucose, glucuronic acid, galactose and sulfate. These fucans did not show anticoagulant activity in PT and aPTT tests. Their antioxidant activity was evaluated using the follow tests; total antioxidant capacity, scavenging hydroxyl and superoxide radicals, reducing power and ferrous ion [Fe(II)] chelating. All heterofucans displayed considerable activity, especially SF-1.0v which showed the most significant antioxidant potential with 90.7 ascorbic acid equivalents in a total antioxidant capacity test and similar activity when compared with vitamin C in a reducing power assay. The fucan antiproliferative activity was performed with HeLa, PC3 and HepG2 cells using MTT test. In all tested conditions the heterofucans exhibited a dose-dependent effect. The strongest inhibition was observed in HeLa cells, where SF-1.0 and SF-1.5 exhibited considerable activity with an IC50 value of 15.69 and 13.83 μM, respectively. These results clearly indicate the beneficial effect of S. filipendula polysaccharides as antiproliferative and antioxidant. Further purification steps and additional studies on structural features as well as in vivo experiments are needed to test the viability of their use as therapeutic agents.     

Assessing the risk of highly pathogenic avian influenza H5N1 transmission through poultry movements in Bali,Indonesia

Indonesia continues to report the highest number of human and poultry cases of highly pathogenic avian influenza H5N1. The disease is considered to be endemic on the island of Bali. Live bird markets are integral in the poultry supply chain on Bali and are important, nutritionally and culturally, for the rural and urban human populations. Due to the lack of biosecurity practiced along the supply chain from producer to live bird markets, there is a need to understand the risks associated with the spread of H5N1 through live bird movements for effective control. Resources to control H5N1 in Indonesia are very limited and cost effective strategies are needed. We assessed the probability a live bird market is infected through live poultry movements and assessed the effects of implementing two simple and low cost control measures on this risk. Results suggest there is a high risk a live bird market is infected (0.78), and risk mitigation strategies such as detecting and removing infected poultry from markets reduce this risk somewhat (range 0.67–0.76). The study demonstrates the key role live poultry movements play in transmitting H5N1 and the need to implement a variety of control measures to reduce disease spread.     

Environmental factors and interval from the introduction of rams to estrus in postpartum Saint Croix sheep

The objective of this study was to determine whether season and total rainfall during the breeding season, sheep parity, and/or litter size affect the interval from the introduction of rams to estrus (IRE) in hair Saint Croix sheep in northeastern Mexico. An analysis was made of 874 services performed during 9 years, introducing the rams into the sheep flock after an isolation period of 60 days during the postpartum period. Estrus was recorded twice daily during 35 days. Year and season influenced significantly on the interval between ram introduction and estrus length (P < 0.01). Winter IRE length (7.9 ± 0.1 days) was shorter than in the other three seasons (11.1 ± 0.2, 11.1 ± 0.1, and 16.2 ± 0.2 days in summer, autumn, and spring, respectively) (P < 0.01). An interaction was observed between rainfall and season, then by rainfall between 0 and 100 mm, IRE was shorter (P < 0.05) in winter (6.8 ± 0.3 days), and by rainfall between 100 and 199 mm, IRE was shorter (P < 0.05) in autumn (10.2 ± 0.5 days); however, when rainfall was beyond 200 mm, IRE length was shorter (P < 0.01) in summer (4.8 ± 0.5 days) than in autumn (14.5 ± 0.3 days). The IRE length was also longer in first lambing ewes (P < 0.05) and was not affected by litter size. In the present study, several factors, including the breeding season, rainfall and parity, directly influenced the interval between the male introduction and the onset of estrus by Saint Croix hair sheep.