Biological responses in Musca domestica to fipronil and chlorfenapyr exposures

Insect populations exist under acute and chronic exposures to lethal and sublethal insecticide concentrations. Among the sublethal effects of insecticides on insects are reductions in life span, development rates, population growth, fertility, fecundity, changes in sex ratio, deformities, changes in behaviour, feeding, searching, and oviposition. These effects may differ depending on the modes of action of insecticides, their doses, and developmental stage of application. This study evaluated the life-history parameters in Musca domestica Linnaeus, 1758 (Diptera:Muscidae) strains that were exposed to two insecticides (fipronil and chlorfenapyr) with different modes of action at sublethal concentrations in each generation up to tenth. Two approaches to each insecticide’s exposure were used in this study, particularly in one approach, only adults M. domestica were exposed to fipronil or chlorfenapyr and in another approach, only larvae were exposed to each insecticide. The susceptibility of adult flies to these insecticides was assessed by resistance ratio based on results of non-choice feeding bioassays. Fipronil exposure at the sublethal concentration in each generation did not affect the susceptibility of adult M. domestica (in the tenth generation) to fipronil. The resistance ratio values revealed tolerance to chlorfenapyr in adults of M. domestica strains that were exposed to this insecticide, independent of the approach used to insecticide exposure. Most of the life-history parameters (such as durations of separate developmental stages, the emergence duration, the adult emergence ratio, the female ratio, and the number of eggs per female per day) of the second, fourth, sixth, eighth, and tenth generations of the insecticide-exposed strains were similar to those of the control strain. At the same time, the sublethal effects of both insecticides fipronil and chlorfenapyr prolonged the larval duration (1.63–2.22 times) and the number of days from egg to adult (1.18–1.39 times) compared to the control strain. Further studies are needed to investigate a possible genetic variability in M. domestica in response to exposure of parental generation to sublethal doses of fipronil and chlorfenapyr.

Climate-induced habitat suitability intensifies fishing-induced life-history variation of a migratory long-lived fish

Intense fishing pressure and climate change are major threats to coastal fisheries. Larimichthys crocea (large yellow croaker) is a long-lived fish, which performs seasonal migrations from its spawning and nursery grounds along the coast of the East China Sea (ECS) to overwintering grounds offshore. This study used length-based analysis and habitat suitability index (HSI) model to evaluate current life-history parameters and overwintering habitat suitability of L. crocea, respectively. We compared both life-history parameters and overwintering HSI between recent (2019) and historical (between 1971 to 1982) to analyze the fishing pressure and climate change effects on the overall population and overwintering phase of L. crocea. In the context of overfishing, the length-based analysis indicated serious overfishing of L. crocea, characterized by reduced catch yield, size truncation, constrained distribution, and advanced maturation in the ECS, namely recruitment bottleneck. In the context of climate change, the overwintering HSI modeling results indicated that climate change has led to decreased sea surface temperature during L. crocea overwintering phase over the last half-century, which in turn led to area decrease and an offshore-oriented shifting of optimal overwintering habitat. The fishing-caused size truncation may constrain the migratory ability and distribution of L. crocea, subsequently led to the mismatch of the optimal overwintering habitat against climate change background, namely habitat bottleneck. Hence, while heavily fishing was the major cause of L. crocea fishery collapse, climate-induced overwintering habitat suitability may have intensified the fishery collapse of L. crocea population. It is important for management to take both overfishing and climate change issues into consideration when developing stock enhancement activities and policy regulations, particularly for migratory long-lived fish that share a similar life history to L. crocea. Combined with China’s current restocking and stock enhancement initiatives, we propose recommendations for future restocking of L. crocea in China.

Preventing co-infection: a viral strategy with short-term benefits and long-term drawbacks

ABSTRACTViral co-infection occurs when multiple distinct viral particles infect the same host. This can impact viral evolution through intracellular interactions, complementation, reassortment and recombination. In nature many viral species are found to have a wide range of mechanisms to prevent co-infection, which raises the question of how viral evolution is impacted by this strategic choice. Here, we address this question in a model viral system, the ubiquitous bacteriophage and its host bacteria. Using a stochastic model of phage-host interactions in agent-based simulations, we first characterise the behaviour of neutral mutants and find that co-infection decreases the strength of genetic drift. We then quantify how variations in the phage life history parameters affect viral fitness. Importantly, we find that the growth rate (dis)advantage associated with variations in life history parameters can be dramatically different from the competitive (dis)advantage measured in direct-competition simulations. Additionally, we find that co-infection facilitates the fixation of beneficial mutations and the removal of deleterious ones, suggesting that selection is more efficient in co-infecting populations. We also observe, however, that in populations which allow co-infection, a mutant that prevents it displays a substantial competitive advantage over the rest of the population, and will eventually fix even if it displays a much lower growth rate in isolation. Our findings suggest that while preventing co-infection can have a negative impact on the long-term evolution of a viral population, in the short-term it is ultimately a winning strategy, possibly explaining the prevalence of phage capable of preventing co-infection in nature.

The Effects of Gunshot Residue Components (Pb, Ba, and Sb) on the Life History Traits of Lucilia sericata (Diptera: Calliphoridae)

The present study aimed to investigate the impact of gunshot residue (GSR) components (Pb, Sb, and Ba) on the life history parameters of Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae). This experiment was carried out at the Zoology Department, the Ondokuz Mayıs University in 2020. About 50 larvae, respectively were exposed to the chicken liver with four different concentrations of GSR particles and life history parameters recorded. A two-way analysis of variance (Two way ANOVA) was used on the larval weight, and length, development time, percentage of pupal and larval survival. Pearson’s correlation coefficient was used to assess the association between life-history parameters and the concentration of GSR. The total development times decreased with increasing Sb, Ba, and Pb concentrations in the diets 1–3 d when compared to the control The results showed that Ba and Sb significantly decreased larval and pupal survival and GSR decreased the pupa and adult weight as compared to the control. We concluded that life-history parameters of L. sericata are sensitive to GSR residue and heavy metal changes in the environment. The presence of gunshot residue in the corpse should be kept in mind in a criminal investigation.

Management Implications for Skates and Rays Based on Analysis of Life History Parameters

The life history (age and growth and reproduction) parameters of 35 species (41 stocks) of skates and rays were analyzed using multivariate analyses. Three groups were categorized by cluster analysis (CA) based on principal component scores. Empirical equation was developed for each group to describe the relationships between the predicted a finite rate of population increase (λ′) and the life history parameters: growth coefficient (k), asymptotic length (L∞), age at maturity (Tm), annual fecundity (f/Rc), ratio between size at birth (Lb), and L∞ (Lb/L∞), and ratio between size at maturity (Lm) and L∞ (Lm/L∞). Group 1 included species with slow growth rates (k < 0.011 year–1), early maturity (Lm/L∞ < 0.62), and extended longevity (Tmax > 25 years); Group 2 included species with intermediate growth rates (0.080 year–1 < k < 0.190 year–1), intermediate longevity (17 years < Tmax < 35 years), and late maturity (Lm/L∞ > 0.60); Group 3 included species with a fast growth rate (k > 0.160 year–1), short longevity (Tmax < 23 years), and large size at birth (Lb/L∞ > 0.18). The λ′ values estimated by these empirical equations showed good agreement with those calculated using conventional demographic analysis, suggesting that this approach can be applied in the implementation of management measures for data-limited skates and rays in a precautionary manner.