Life History Parameters Research Articles

Life-history traits of the invasive and biggest European freshwater fish, the wels catfish (Silurus glanis) show high potential for colonisation in Southern Europe

Context The invasive wels catfish is spreading to many European waterbodies and is the subject of controversy concerning its environmental impact. Aims The objective was to investigate its life-history traits (growth and reproduction) for the first time in southern France. Methods A culling action was used to assess the key life-history traits, using sections of pectoral spines for age and growth estimations, and gonad macroscopic examination for the reproduction parameters. Key results The biggest individual was a 227-cm male. The age was accurately estimated from clear translucent marks on spines, with a maximum of 13 years for both sexes. The growth appeared to be extremely rapid and was the highest at old ages recorded from both the native and the invasive distribution range. The length and age at first sexual maturity, 70.1 cm for 4–5-year-old females, and 54.1 cm for 2–3-year-old males, were the lowest recorded in Europe, indicating an early maturity. Conclusions The life-history parameters (rapid growth, early maturation, high fecundity) showed a very high potential for adaptation and colonisation. Implications The cost and management required to regulate the species appear not easily feasible, particularly when combined with its high growth rate.

EFFECTS OF PROPOLİS ON THE DEVELOPMENTAL STAGES AND BİOCHEMİCAL COMPOSİTİON OF Musca domestica LİNNAEUS, 1758 (DİPTERA: MUSCİDAE)

The housefly (Musca domestica L.) is well known a global pest of animals and humans. The houseflies contain high purity chitin and protein which are widely used in industry, and medicine. Their larvae can produce animal protein in the biodegradation of organic waste . House flies provide an alternative for recycling nutrients while also generating multiple income streams, so their large-scale production is important. In this study, the effects of different doses of propolis applied to a wheat bran diet on the developmental stages (larval and pupal development time, larval, pupal, and adult weight, and larval, pupal, and adult survival) and the protein, carbohydrate, and lipid content in Musca domestica larvae were examined under laboratory conditions (62±0.2% humidity and 25.06 ± 0.8°C temperature). Thirty Musca domestica larvae were reared on substrates exposed to four different propolis concentrations. One-way ANOVA was used to compare life history and biochemical parameters. The results showed that increasing concentrations of propolis reduced larval length and weight. While a decrease in the number of pupae and adults was observed, a significant increase in pupal weight was noted. Larval development time was not affected by propolis diets compared to the control, but pupal development time was shortened. In biochemical composition, no significant difference in protein content in Musca domestica larvae was observed with increasing propolis concentrations. However, compared to the control, increasing propolis concentrations increased carbohydrate content and decreased lipid content in Musca domestica larvae.

Biological performance of Bollgard II® Bt-resistant vs susceptible population of pink bollworm, Pectinophora gossypiella (Saunders) on non-toxic diet

BackgroundThe pink bollworm, Pectinophora gossypiella (Saunders), is a devastating global pest of cotton that has caused substantial economic damage to Bt Bollgard-II® cotton plants in recent years due to the evolution of Bt resistance. The associated fitness cost is assumed to be one of the factors delaying the development of resistance against Bt transgenic crops. Hence, the present study was undertaken to assess the biological performance of pink bollworms by comparing the life history and demographic parameters of a resistant (Field-R) and susceptible (Lab-S) population.ResultsProlonged larval duration (23.40 days in Field-R vs 18.80 days in Lab-S population), total life cycle (male = 50.00 vs 42.80 days; female = 53.60 vs 46.20 days), reduced fecundity (100.60 vs 154.20 eggs/female) and fertility (88.00 vs 138.00 fertile eggs/female) was observed. The demographic parameters indicated a significant reduction in the net reproductive rate (184.27 vs 276.72), innate capacity for increase in number (0.11 vs 0.15), finite rate of increase in number (1.12 vs 1.16 female progenies produced/female/day), weekly multiplication rate (2.16 vs 2.86), potential fecundity (545.06 vs 634.11 eggs), number of hypothetical F2 females (33 955.65 vs 76 572.41), but longer mean length of generation (47.54 vs 37.74 days) and population doubling time (6.30 vs 4.62 days) in Field-R compared with Lab-S population. A stage-specific life table demonstrated the differences in survival rates between susceptible and resistant populations at various life stages, with the resistant population having higher generation mortality (0.22 vs 0.19).ConclusionsThe study confirms the involvement of fitness costs associated with Bt resistance in P. gossypiella. Despite reduced reproductive fitness, the resistant population tried prolonging the larval stage as a compensatory mechanism to repair the damaged host tissues due to Bt intoxication and for accumulation of enough nutrient reserves for normal pupation and adult emergence. Presence of a high proportion of double Bt-resistant larvae in the field coupled with continued noncompliance with refug planting certainly favours the flaring up of this monophagous pest despite the observed fitness costs. The resistance cannot be effectively reversed unless suitable alternative management strategies are deployed.

Noninvasive, epigenetic age estimation in an elasmobranch, the cownose ray (Rhinoptera bonasus)

Age data are essential for estimating life history parameters and are thus critical for population assessment, management, and conservation. Traditional vertebrae-based age estimation in elasmobranchs can be costly, time intensive, of low accuracy, and is by necessity lethal. Herein, epigenetic clocks were developed for an elasmobranch, the cownose ray (Rhinoptera bonasus), using aquarium-born individuals (n = 42) with known dates of birth (age range: 7−7,878 days or 0−21 years) and two tissue types (fin clips and whole blood) that can be sampled in a relatively non-invasive manner. Enzymatically-converted restriction site-associated DNA sequencing (ECrad-seq) was used to identify CpG sites that exhibited age-correlated DNA methylation. The epigenetic clocks developed were highly accurate (mean absolute error, MAE, < 0.75 years) and precise (R2 > 0.98). Age-associated CpG sites were identified across tissues, and a multi-tissue clock was also highly accurate (MAE < 1 year) and precise (R2 = 0.97). Using the developed fin clip clock, three wild-caught individuals of unknown age but managed in aquariums for > 22 years were predicted to be 22.10−23.49 years old. Overall, the results have important implications for future epigenetic clock development and noninvasive age estimation in elasmobranchs.

Bone labeling experiments and intraskeletal growth patterns in captive leopard geckos (Eublepharis macularius).

An understanding of the dynamics of bone growth is key to interpreting life-history parameters of vertebrates. In this study, we used fluorochrome labels in captive leopard geckos (Eublepharis macularius) to track bone growth and intraskeletal variability from embryonic to adult growth stages. Thirteen individuals were administered fluorochromes from pre-hatching to 4 years of age. The left tibia, fibula, femur, humerus, radius, and ulna were examined histologically and compared for differences in the number of labels within and between individuals at each sampled growth stage, and the amount of bone growth between labels was calculated. Results suggest that limb elements had differing growth rates; the fibula grew the fastest per day on average and the femur grew the slowest per day on average. All labels administered in ovo were still present in all limb elements in adults except for the tibia, suggesting growth marks are not lost in most elements and accurate calculations of growth rates could be performed in individuals up to 3 years old. All ex ovo labels were accounted for; however, when two fluorochromes were administered 3 weeks apart, the labels could not be differentiated from each other due to the new bone not being deposited at a quantifiable level. Overall, the tibia in leopard geckos is the least reliable limb bone to use for skeletochronology and the humerus, radius, and fibula preserve the longest growth record. This research highlights that, as in other extinct and extant animals, patterns of bone growth are not consistent across reptiles. This study adds to the growing body of knowledge on growth variability in reptiles.

Effects of development and parental care on Hamilton's force of selection.

The force of selection describes the sensitivity of population growth to changes in life history parameters, with a focus usually on the survival probabilities from one age class to the next. Importantly, according to Hamilton the force of selection generally decreases after the onset of reproduction, thereby providing a possible explanation for patterns of senescence. A second characteristic feature is that the force of selection remains constant up to the age of first re- production. This latter observation, however, rests on the assumption that offspring become independent from their parents right after birth. I show here in a minimal model that if offspring are fully reliant on their parents, either during early embryonal development or via parental care at later stages, and during this time prevent their parents from entering a new bout of repro- duction, the force of selection on offspring survival generally increases up until the age at which offspring become independent. This provides a possible explanation for the commonly observed pattern of decreasing mortality during early ontogeny. Further, genes acting during recurrent life stages are observed to experience a heightened force of selection compared to genes that act strictly age-specifically, demonstrating the need to develop a mechanistic understanding of gene activation patterns through which to consider life history evolution.

Biological Manifestation of Different Temperature Regimes and Certain Insecticides on Cheilomenes sexmaculata (Fab.) Preying on Cowpea Aphid, Aphis craccivora Koch

Background: Ladybird beetles are great bio-control agents and campodeiform grubs of these little predators are able to devour aphids in a voracious fashion. They feed on a wide array of aphid species most noticeably on the infamous black aphids or cowpea aphids Aphis craccivora (Koch). Methods: The growth and feeding potential of C. sexmaculata were studied in the laboratory of the Department of Entomology, Faculty of Agricultural Sciences (Institute of Agricultural Sciences), SOA Deemed to be University, Bhubaneswar, India at four different temperatures 20°C, 25°C, 30°C and 35°C during 2021-2022. Result: The life history parameters indicated that the duration of eggs, larvae, pupae, adult males and adult females was longest at 30°C and shortest at 20°C. Such variations were also observed in morphometry and feeding potential. The trend was 30°C greater than 25°C greater than 35°C greater than 20°C. In the case of feeding potential the trend was adult female greater than adult male greater than 4th instar greater than 3rd instar greater than 2nd instar greater than 1st instar across all temperatures. Adult females lived longer than males and thereby consumed more aphids than males. Maximum consumption was seen in case of adult female at 30°C which was 633±5.71 aphids and least feeding was seen at 20°C by 1st instar grub which was 8.9±0.56 aphids. The effect of insecticides in direct spray method indicated that dimethoate 30EC killed more ladybirds and clothianidin 50% WDG killed the least. This trend was strong across all temperatures and insect growth stages. The feed contamination method indicated that clothianidin 50% WDG, imidacloprid 17.8% SL and thiamethoxam 25% WG produced higher mortality rates than direct contamination method. All insecticides showed increased mortality up to 72 h and the mortality trend was 72 HAT greater than 48 HAT greater than 24 HAT. The mortality rate of immature individuals is higher than that of adults.

Multi-biomarker assessment of chronic toxicity induced by the chemical warfare agent adamsite in Danio rerio

Several hundred thousand tons of chemical warfare agents (CWAs) were disposed of at sea, leading to environmental contamination. Among the most toxic and persistent CWAs is adamsite; however, the ecotoxicological data on this compound is limited. Presented research focuses on the long-term effects of adamsite on fish. A 28-day exposure study was conducted, evaluating the impact of adamsite on life history parameters (body length, body mass, growth rate), tissue accumulation, and the expression/activity of detoxification-related enzymes in the model fish species, Danio rerio. Results indicate that chronic adamsite exposure significantly reduces body length, weight, and growth rate of fish at trace concentrations (0.20 and 0.25 μg × L−1). Adamsite-related compounds accumulate in fish muscle tissues, increasing by approximately 4 μg per gram (dry weight) for every microgram of adamsite per litre of water during chronic exposure. The mRNA expression and activity of detoxification-related enzymes were elevated in the gills of fish, indicating oxidative stress. This study highlights the severe chronic toxicity of adamsite, which could not be anticipated based on acute toxicity. It underscores the need for comprehensive long-term toxicity assays for CWAs and emphasizes the potential ecological and health risks posed by adamsite, necessitating more stringent risk assessments.

Estimates of life-history and growth parameters of exploited fish species in lakes Edward and George: Implications on exploitation status, population dynamics, management, and conservation of native species.

Adequate knowledge is essential for responsible inland fisheries. However, many inland fisheries lack monitoring, and therefore, decision-making for fisheries management is not reliable. In this paper, we used data from surveys and literature to estimate the life-history and growth parameters of 16 exploited fish stocks in the Ugandan part of Lake Edward and Lake George (East Africa). The estimated parameters are pivotal indicators of fish stock status, particularly in data-poor fisheries. The estimated parameters included maximum length (Lmax) and mean length (Lmean) as indicators of size structure in experimental and commercial catches, coefficients of length-weight relationships, length at 50% maturity (Lm50), fecundity, von Bertalanffy parameters, total mortality (Z), and natural mortality (M). These parameters were estimated using empirical formulae, statistical methods, and analyses of length frequencies. Only two stocks of semutundu Bagrus docmak exhibited significant and increasing trends in Lmax (Lake Edward) and Lmean (Lake George). The estimates for the remaining parameters were consistent with those in FishBase and other literature resources, either for the same species or related species. This consistency indicates their reliability for application in decision-making and further assessments. Some parameters showed evidence of unsustainable fishing. For example, estimates of Lm50 for four of the assessed stocks belonging to two species (Nile tilapia Oreochromis niloticus and marbled lungfish Protopterus aethiopicus) were lower than baseline estimates in the studied waterbodies. Furthermore, the Lmean in catches for all the stocks were less than the optimum lengths (Lopt), which maximize catches with a minimal impact on biomass and size structure. No significant changes in Lmean, length-frequency distributions, and size at maturity could be attributed to the management changes implemented in 2018, probably because it is too early to observe changes in these parameters. However, there are positive signs attributable to the changes in management as shown by a high proportion of mature individuals in commercial catches for most of the stocks for which the proportion was calculated, and an increase in Lmean and Lmax for some stocks, such as B. docmak, in commercial or experimental catches. New estimates from this study will enhance decision-making and further assessments of fisheries. Routine monitoring is recommended to update and improve the estimates.

Centurial Variation in Size at Maturity of Eastern Baltic Cod (Gadus morhua) Mirrors Conditions for Growth.

The status of Eastern Baltic cod (EBC) Gadus morhua has remained poor despite low fishing mortality for over a decade, including a fishing ban since 2019. Although the decline in productivity can be explained by lower individual growth and survival rates, other aspects of life-history changes such as maturation patterns for EBC has so far not been sufficiently explored. According to current stock assessments, the median size at maturity (L 50) has halved from 40 to around 20 cm in total length since the 1990s, while the overall size distribution has become increasingly truncated. It has previously been suggested that changes in L 50 can be attributed to both fishing-induced evolution and phenotypic plasticity induced by growth rates. However, since L 50 is currently occurring around 20 cm, the maturation process must have been initiated at much smaller sizes, that is, long before the fish could be caught in the dominant trawl fishery at around 35 cm. In this study, we aimed to further investigate what drivers may have led to reduced productivity in EBC by determining variations in size at sexual maturity in longer time series than has been done before (1930s to 1980s) and include prey productivity and quality. We found that L 50 declined already in the 1930s and thereafter remained stable at around 40 cm up to the 1990s. On a centurial perspective, L 50 has been positively correlated to growth potential (L 95), length diversity, total stock biomass, total catch and yield per recruit, while Fulton's condition factor was not related to L 50. Our results suggest that the links between life-history parameters and external drivers are complex, but the present unprecedented early onset of maturity and hence decline in L 50 since the 1990s signals a decline in growth potential, which also has hampered the productivity of EBC.

Longevity records for bird species from the central Monte desert, Argentina

ABSTRACT Longevity is a key life-history parameter of bird species, highly relevant for the development of evolutionary biology, the study of ecological patterns and conservation planning. However, there is a marked paucity of data for Neotropical birds, mainly because estimating longevity requires long-term studies that are very scarce in temperate South America. We report data on the longevity of 25 bird species obtained in an 8-year long-term capture–recapture programme carried out in the Monte desert in Argentina and evaluate the influence of diet and migratory status on this life-history trait. The maximum value recorded was 105 months for Microspingus torquatus and the minimum was 13 months for Synallaxis albescens. Resident birds had higher average longevity than migratory birds, while species consuming mainly plant material had higher longevity values than those consuming mainly animal foods. Our results are similar to the few published records from temperate South America, although more data are needed to assess the impact of diet and migratory behaviour on longevity of Neotropical species.

Daphnia stress response to environmental concentrations of chloramphenicol—multi-omics approach

Commonly used medicines, when discarded or improperly disposed of, are known to contaminate freshwater ecosystems. Pharmaceuticals can be toxic and mutagenic, and can modify freshwater organisms, even at environmentally relevant concentrations. Chloramphenicol (CAP) is an antibiotic banned in Europe. However, it is still found in surface waters around the world. The aim of this study was to evaluate the impact of chloramphenicol contamination in freshwater on the model organism Daphnia magna. Specific life history parameters, proteome, and host-associated microbiome of four D. magna clones were analyzed during a three-generation exposure to CAP at environmental concentrations (32 ng L−1). In the first generation, no statistically significant CAP effect at the individual level was detected. After three generations, exposed animals were smaller at first reproduction and on average produced fewer offspring. The differences in D. magna’s life history after CAP treatment were in accordance with proteome changes. D. magna’s response to CAP presence indicates the high stress that the tested organisms are under, e.g., male production, upregulation of ubiquitin-conjugating enzyme E2 and calcium-binding protein, and downregulation of glutathione transferase. The CAP-exposed D. magna proteome profile confirms that CAP, being reactive oxygen species (ROS)-inducing compounds, contributes to structural changes in mitochondria. Microbiome analysis showed a significant difference in the Shannon index between control and CAP-exposed animals, the latter having a more diverse microbiome. Multilevel analyses, together with long exposure in the laboratory imitating conditions in a polluted environment, allow us to obtain a more complete picture of the impact of CAP on D. magna.

Effects of temperature and storage duration on quality of an insect artificial diet.

Artificial diets are widely used to produce insects for research and education programs. Completed diets, in which the diets are fully made from individual ingredients and ready to use, often have high water activity, making them vulnerable to degradation. Proper storage is critical to maintaining diet quality, yet the storage conditions are not well investigated. In this study, we characterized the effects of storage conditions (temperatures and storage duration) on the quality of a diet capable of rearing both specialist and generalist insect species. The completed diet, produced by both private industry and a USDA-Agricultural Research Service laboratory, was exposed to varying temperatures during a 24-hour transit over 1600km. After transit, it was stored at 4°C for a total storage period of 28 days. In a separate experiment, the completed diet was stored immediately after diet production at five fixed temperatures (-20, 4, 22, 25, and 33°C) for up to 28 days. For both experiments, at 5 intervals after storage (1, 7, 14, 21, and 28 days), diet quality was accessed by life history parameters (survival, molting, and weight) of western corn rootworm (Diabrotica virgifera virgifera LeConte) larvae, the most serious maize pest in the United States. Our results showed that exposure to varying temperatures between -2°C and 27°C for 24 hours had no significant impact on diet quality. However, extended storage (beyond 24 hours) at any of the fixed temperatures negatively affected diet quality. Insects reared on diets stored for over 24 hours at fixed temperatures ranging from -20°C to 33°C had significant declines in performance. Among the tested temperatures, -20°C and 4°C were found to be the most effective for preserving diet quality. At these low temperatures, there were no significant changes in insect weight and survival for diets stored within 21 and 28 days, respectively, though molting was significantly reduced within 7 days of storage. These findings provide the base of information on the storage conditions for completed diets, supporting the production of healthy insects.

Polygenic, autosomal, and stable spirotetramat resistance in Chrysoperla carnea resulting in increased fitness.

Green lacewing, Chrysoperla carnea (Stephens) is a generalist predator used as a biological control agent in agro ecosystems. In order to use chemical and biological control in an integrated way, it is advantageous to know about natural enemy resistance response to a selected chemical. To determine C. carnea spirotetramat resistance potential, a population collected from the field was selected in the laboratory. Then we determined how spirotetramat resistance was inherited and how much it impacts the fitness of C. carnea. After eighteen selections with spirotetramat, the selected population (Spiro-Sel) of C. carnea had a 47-fold of resistance when compared to an UNSEL population. Inheritance results showed that spirotetramat resistance was inherited as an autosomal, incompletely dominant and polygenic trait. The values of effective dominance decreased from 0.87 (incomplete dominant) to 0.00 (complete recessive) as the concentration of spirotetramat increased from 625 mg/L to 10000 mg/L. The Spiro-Sel strain had no cross resistance to chlorfenapyr (1.10-fold), deltamethrin (1.26-fold) and chlorpyrifos (1.27-fold). After 7 generations without selection pressure resistance to all experimental insecticides in the Spiro-Sel strain was stable. Fitness data of the Spiro-Sel, Cross A, Cross B, UNSEL and susceptible strains of C. carnea showed that spirotetramat resistance increased the fitness of the selected green lacewing population. Life history parameters like fecundity, net reproductive rate, and relative fitness of the Spiro-Sel strain significantly increased when compared to the susceptible or unselected strains of C. carnea. These findings show that C. carnea is a perfect candidate for integrated pest management (IPM) programmes that combine biological control methods with selective pesticide applications to manage a variety of insect pests. Additionally, it would reduce the possibility of pests developing pesticide resistance despite repeated applications. It would be an excellent choice for widespread releases and be effective in most spray programs.

Life History Parameters and Spawning Potential Ratio of Upeneus vittatus (Forsskål, 1775) in the Coastal Waters of Lebak and Sukabumi, Indonesia

Abstract It is necessary to obtain information regarding the life history and stock status of the yellow-striped goatfish (Upeneus vittatus) in the coastal waters of Lebak and Sukabumi, Indonesia. This study aims to determine the stock status of U. vittatus in the coastal waters of Lebak and Sukabumi based on their life history parameters and length-based spawning potential ratio (LB-SPR). Eight hundred seventy-four samples were collected from Binuangeun, Palabuhanratu Nusantara, and Ciwaru Fishing Ports. The monthly length frequency data were obtained from July to December 2022. The results show that the Von Bertalanffy growth parameter was Lt=254(1-e−(0.58(t+0.154)) for males, Lt=239(1-e−(0.42(t+0.221)) for females, and Lt = 258(1-e−(0.37(t+0.246)) for both. The mature gonads of U. vittatus were mostly obtained from October to December. The length of first maturity L50 and L95 were 158 mm and 236 mm for males and 149 mm and 229 mm for females, respectively. The exploitation rate (E) on male, female, and combined U. vittatus revealed that E values exceed 0.5 or are overexploitation. The estimated SPR of U. vittatus was 23%, lower than the target reference point of 40%. Therefore, U. vittatus was fully exploited in the coastal waters of Lebak and Sukabumi.

Estimation of life history parameters of the Gangetic leaffish, Nandus nandus from southern coastal waters of Bangladesh: Implications for sustainable management

The Nandus nandus (Hamilton, 1822) is a highly prized food fish that possesses significant nutritional and commercial worth. Bangladesh, India, Pakistan, Malaysia, Myanmar, Thailand and Viet Nam are the countries where it is endemic. The IUCN Bangladesh has classified this species as near endangered due to its current progressive decline. Hence, immediate actions are necessary to efficiently manage the fishery in this country. To address this issue, a comprehensive understanding of its life history parameters is required. This study aimed to examine the growth characteristics, recruitment length, sexual maturity, mortality, exploitation rate, and maximum sustainable production of N. nandus in Bangladesh's southern coastal waters. Samples were taken every month from January through December of 2021. Our study indicates that N. nandus grows in an isometric manner. The estimated asymptomatic length of this species is 18.0 cm in total length (TL), growing at a rate of 1.30 year−1. The growth performance index of this species was determined to be 2.62, and the projected lifespan was calculated to be 2.31 years. The initial length at recruitment was measured to be 9.5 cm TL, whie the size at first sexual maturity was recorded to be 9.4 cm TL. With the contributions of the natural mortality rate (2.26 year−1) and the fishing mortality rate (1.86 year−1) the total mortality rate was found to be 4.12 year−1. The exploitation rate, determined to be 0.45, surpasses the upper limit of sustainable yield criteria set at 0.37. Therefore, it is imperative to implement strategies to avoid excessive fishing and guarantee the long-term control of N. nandus populations.

Determining demersal fisheries status in fisheries management arena (FMA) 712 under data limited situation

Abstract Demersal fisheries in FMA 712 have been established since the early 1950’s, industrialization in demersal fisheries was started on 1970’s with the operation of trawl fleets in Java Sea. The exploitation continued until the 1980s when the Trawl Ban regulation was enacted. According to historical statical data from 1980 the number of demersal fishing fleets are still dominating and endangered the sustainability of demersal fish stock in FMA 712. This study presented alternatives approaches to determining demersal fisheries status in FMA 712 using the Bayesian surplus production model (cMSY) and Length-Based Spawning Potential Ratio (LBSPR). The cMSY analysis was conducted using time series production data and known CPUE represent the area in FMA 712 and the LBSPR model was conducted using the life-history parameters and the length frequency data. The results show that current demersal fisheries condition is overexploited, points of estimation of the Biomass condition based on 1980-2022 data: B/BMSY 0,803, F/FMSY 1,75 and MSY 323.000 ton. Additionally, the spawning potential ratio (SPR) of the dominant demersal fish species (Lutjanus malabarius and Portunus pelagicus) was lower than the limit reference point (&lt;0,20), indicating overexploited. This study demonstrates that alternatives approaches could be applied to limited data fisheries and provide useful and robust recommendations.

Effects of the symbiotic bacteria, Caballeronia insecticola, on the life history parameters of Riptortus pedestris (Hemiptera: Alydidae) and their implications for the host population growth.

This study aimed to investigate the effects of symbiosis on the life history of host insects and address their implications at the host population level. We evaluated the effects of symbiotic bacteria Caballeronia insecticola on its host Riptortus pedestris (Fabricus) (Hemiptera: Alydidae) from cohorts for nymphal development, adult survivorship, and female reproduction. Then, life table parameters were compared between symbiotic and apo-symbiotic groups, and the effects of symbiosis on the abundance of R. pedestris were simulated for varying proportions of symbiotic individuals in host populations. We found that symbiosis significantly accelerated the nymphal development and reproductive maturation of females. However, symbiosis incurred survival cost on adult females, reducing their longevity by 28.6%. Nonetheless, symbiotic females laid significantly greater numbers of eggs than the apo-symbiotic during early adult ages. This early reproductive investment negated the adverse effect of their reduced longevity, resulting in the mean lifetime fecundity to not significantly differ between the 2 groups. Indeed, total cohort fecundity of the symbiotic group was 1.3-fold greater than that of the apo-symbiotic group. Life table analysis demonstrated shorter generation time and greater population growth rate in the symbiotic population. Finally, the simulation model results indicate that an increase in the proportion of symbiotic R. pedestris favored the population growth, increasing the population size by 1.9 times for every 25% increase in the proportion of symbiotic individuals. Our study demonstrates that symbiont-mediated changes in the life history parameters of host individuals favor the host population growth, despite substantial reduction in the female longevity.

Anuran responses to urbanization: evaluating life history traits of Rhinella arenarum in urban wetlands

Abstract Wetlands are unique ecological environments capable of harboring high biodiversity. However, urbanization can degrade, eliminate, or transform these habitats. Although amphibians utilize habitats created by humans in urban landscapes, few studies have investigated the influence of the habitat quality on the life history of anurans. We assessed life history traits such as snout-vent length (SVL), body condition, and reproductive investment in the South American common toad Rhinella arenarum, to determine whether urbanization is harmful or beneficial to this species. We sampled wetlands with different levels of urbanization in Río Cuarto city, Córdoba, Argentina. We recorded males with lower SVL in medium urbanized wetlands and those with the highest SVL in both low and high urbanization categories, similar to what was found for body conditions with males with low body conditions inhabiting wetlands with a medium degree of urbanization. In females, lower SVL was recorded in medium urbanization and highest SVL in high and low urbanization. It is observed that females recorded in highly urbanized wetlands have a very low body condition. The reproductive investment parameters were not significantly different, but we observed an association between a greater number of eggs and clutch size with wetlands of low urbanization. These results show a variability of responses of R. arenarum to urbanization, which could be due to phenotypic plasticity in its life history parameters, allowing it to inhabit urban areas. Continuous monitoring of the species in these wetlands is needed to determine if these biological responses are temporary or persistent.

Suitability of different artificial diets for mass rearing of six lepidopteran pest species

Busseola fusca (Fuller) (Noctuidae), Chilo partellus (Swinhoe) (Crambidae), Eldana saccharina (Walker) (Pyralidae), Helicoverpa armigera (Hübner) (Noctuidae), Sesamia calamistis (Hampson) (Noctuidae) and Spodoptera frugiperda (J.E. Smith) (Noctuidae) are six of the most important insect pests of sugarcane, sorghum and maize in Africa. Suitable artificial diets are needed for the continuous rearing of these species in sufficient numbers to support research on Bt protein-incorporated artificial diet bioassays, screening for host plant resistance, as well as for monitoring of insecticide and Cry-protein resistance evolution in pest populations. This study evaluated diet protocols for rearing of these species. Different noctuid and crambid diets were evaluated and the following life history parameters were recorded: larval survival and mass, larval duration, pupation rate, pupal mass, duration of pupal period and sex ratio. Chilo partellus, E. saccharina and H. armigera excelled on a sugarcane-incorporated diet with high larval survival and mass, pupation and the quickest development to adults. Busseola fusca, S. calamistis and S. frugiperda performed better on a maize leaf-incorporated diet. These two diets are considered optimal for the respective species and are recommended for use in rearing of these species.