Larval Developmental Period Research Articles

Evaluation of Groundnut Varietal Resistance against Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

A laboratory study was conducted to evaluate resistance of 10 groundnut varieties (Tsosabana, Peolwane, Nakwana, Sellie, GO74, GO15, GO73, BMM188, GO64-B and BMM268) against Plodia interpunctella using life table parameters of the insect and level of seed damage. Fecundity and survival, longevity, intrinsic rate increase (rm), net reproduction rate (R0), generation time (T), doubling time (Td) as well as finite rate of increase (λ) were used. The hypothesis of this study was that negative effects of groundnut varieties on life table parameters of P. interpunctella will indicate levels of resistance. Fecundity, survival and R0 varied significantly among varieties while the rest of parameters showed no significant differences. The lowest number of eggs laid and hatchability per female were significantly lower on variety BMM268. Gravid females stopped laying eggs by day 8 on Sellie and BMM268. The survival rates of P. interpunctella were lower on BMM268 and Sellie and the larvae were all dead by day 8. Plodia interpunctella had short life expectancy of 8 days when reared on varieties Sellie and BMM268 compared to other varieties. Variety BMM268 had significantly lower R0 than other varieties. Based on means, there was also a slightly prolonged larval developmental period on variety BMM268 than other varieties though not significant. Considering damage, varieties Sellie and BMM268 also had the lowest number of tunnels than others except G064-B. Susceptibility index ranged from 3.12–6.91 amongst varieties and the lowest was recorded on BMM268 followed by Sellie. This study shows that Sellie and BMM 268 are relatively unsuitable as hosts, indicating some level of resistance to P. interpunctella. The two groundnut varieties can be used in integrated pest management programmes to reduce damage caused by P. interpunctella during storage.

Lethal and Sublethal Effects of Chlorpyrifos on Biological Traits and Feeding of the Aphidophagous Predator Harmonia axyridis.

Except of pest control, insecticides have shown adverse effects on natural enemies as well. Thus, risk assessment of pesticides for biological control agents is critical for effective use in integrated pest management (IPM) schemes. In the present study, the lethal and sublethal effects of chlorpyrifos, a commonly used insecticide that may negatively affect biological control agents, were evaluated on a non-target predator, the Asian ladybeetle Harmonia axyridis. Previous studies have reported on lethal concentrations, but the effects of sublethal concentrations remain unclear. Lethal and sublethal concentrations of chlorpyrifos were applied to third instar larvae of H. axyridis, and different growth and developmental parameters were measured. Treatment with LC10 (4.62 mg a.i. L−1) significantly shortened the developmental period of third instar larvae, whereas it significantly prolonged those of fourth instar larvae and pupa. Treatment with LC30 (9.59 mg a.i. L−1) significantly increased the larval and pupal developmental period compared with that of the control, whereas feeding potential, female fecundity, and adult longevity significantly decreased after LC10 and LC30 treatment. The pre-oviposition period significantly increased compared with that of the control. Population growth parameters, the finite (λ) and intrinsic rate of increase (r) and the net reproductive rate (R0), decreased following exposure to sublethal concentrations of chlorpyrifos. According to the results, the use of chlorpyrifos in IPM schemes requires further research because even sublethal concentrations of this insecticide were harmful to H. axyridis population growth.

Deterioration of digestive physiology of Bactrocera cucurbitae larvae by trypsin inhibitor purified from seeds of Mucuna pruriens

Peptidase inhibitors (PIs) are plant proteins that are found to be effective against various digestive peptidases of insects. The present study isolated and characterized a trypsin inhibitor from mature dry seeds of Mucuna pruriens and investigated its effect against Bactrocera cucurbitae larvae, a major pest of cucurbitaceae crops, for its inhibitory activity. The purified trypsin inhibitor from M. pruriens seeds gave a molecular weight of ~11 kDa on SDS-PAGE. M. pruriens trypsin inhibitor (MPTI) exhibited inhibitory effect on growth of melon fruit fly larvae (64-72 h old) as it resulted in prolongation of larval, pupal and total development period. There was a significant increase in larval mortality with increase in concentration of MPTI. Nutritional indices decreased significantly at all the concentrations of MPTI. Quantitative RT- PCR revealed that the mRNA expression level of trypsin and chymotrypsin genes was reduced while that of GST, esterases, AP, SOD and catalase were enhanced. It can therefore be inferred that MPTI can serve as a promising agent for biocontrol that can reduce the problems caused by fruit fly and other similar catastrophic pests. This study provides the fundamental information for future successful strategies for pest management.

Lethal and sub-lethal effects of bio-and chemical insecticides on the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a destructive pest affecting the tomato crop causing a loss of 60–100% of the tomato crop production. In the present study, the lethal and sub-lethal effects of Bacillus thuringiensis (Bt), spinosad, and emamectin benzoate as bio-insecticides comparing with 2 synthetic insecticides: chlorpyrifos and indoxacarb against T. absoluta under laboratory conditions were evaluated. Take in consideration, life tables and reproductive parameters of treated larvae with LC30 for each pesticide (bio- and chemical insecticides) by using leaf dipping technique were calculated. The results showed that Lepinox formulation of Bt was the most effective one against the early 2nd instar larvae with 0.01 × 10−2 mg/l (ppm), followed by spinosad with 0.07 × 10−2 ppm comparing to indoxacarb and chlorpyrifos (0.01 and 11.44 μg/ml, respectively). Sub-lethal effect of the Bt formulations significantly increased pupal mortality by 29.77, 33.30, and 26.94% for Lepinox, Dipel 2×, and Protecto, respectively. In addition to their efficiency, Bt formulations and emamectin benzoate increased larval developmental period and reduced adult emergency percentage to 70.28, 66.70, 73.06, and 75.55% for Lepinox, Dipel 2×, Protecto, and emamectin benzoate, respectively. All bio-insecticides including Bt, spinosad, and emamectin benzoate caused abnormalities in different life stages. The results suggest these bio-insecticides are promising alternatives to synthetic insecticides for T. absoluta management.

Biochemical components of wild relatives of chickpea confer resistance to pod borer, Helicoverpa armigera

Efforts are being made to develop chickpea varieties with resistance to the pod borer, Helicoverpa armigera for reducing pesticide use and minimizing the extent of losses due to this pest. However, only low to moderate levels of resistance have been observed in the cultivated chickpea to this polyphagous pest. Hence, it is important to explore wild relatives as resistance sources to develop insect-resistant cultivars. Therefore, we studied different biochemical components that confer resistance to H. armigera in a diverse array of wild relatives of chickpea. Accessions belonging to wild relatives of chickpea exhibited high levels of resistance to H. armigera as compared to cultivated chickpea genotypes in terms of lower larval survival, pupation and adult emergence, decreased larval and pupal weights, prolonged larval and pupal developmental periods and reduced fecundity of the H. armigera when reared on artificial diet impregnated with lyophilized leaf powders. Amounts of proteins and phenols in different accessions of chickpea wild relatives were significantly and negatively correlated with larval weight, pupation and adult emergence. Phenols showed a negative correlation with pupal weight and fecundity, but positive correlation with pupal period. Total soluble sugars showed a negative correlation with larval period, but positive correlation with pupation and pupal weight, while tannins showed a positive correlation with larval weight, pupation and adult emergence. The flavonoid compounds such as chlorogenic acid, ferulic acid, naringin, 3,4-dihydroxy flavones, quercetin, naringenin, genistein, biochanin-A and formononetin that were identified through HPLC fingerprints, exhibited negative effects on survival and development of H. armigera reared on artificial diet impregnated with lyophilized leaf powders. The wild relatives with diverse mechanisms of resistance conferred by different biochemical components can be used as sources of resistance in chickpea breeding programs to develop cultivars with durable resistance to H. armigera for sustainable crop production.

Potential insecticidal activity of Sarocladium strictum, an endophyte of Cynanchum acutum, against Spodoptera littoralis, a polyphagous insect pest

Abstract Spodoptera littoralis has been recognized as the major destructive cause of various economic crops in Egypt. Chemical insecticides have been frequently used, however, the development of insecticidal resistance is the current challenge, thus searching for novel ecofriendly biocontrol agents is the prospective challenge. Fungal endophytes of plants have been recognized as a repertoire for bioactive metabolites. Thus, the objective of this study was to isolate a potential endophytic fungal isolates from different medicinal plants, with an efficient insecticidal activity against S. littoralis. Fifteen plant genera were selected, and their endogenous endophytic fungi were recovered, and their insecticidal activity were resolved. Forty-five isolates were recovered from these plants, Sarocladium strictum, endophyte of Cynancum acutum, and Aspergillus nidulans, endophyte of Lantana camara, displayed the highest insecticidal activity against 2nd larval instar of S. littoralis. The identity of S. strictum and A. nidulans has been confirmed based on their ITS sequence and deposited on genbank with accession # MK367604 and MK367603, and deposition # AUMC14096 and AUMC14095, respectively. The EtOAc and DCM extracts of S. strictum exhibited a strong effect on the total larval period, pupal period and development period of S. littoralis immature. The LC50 were 11.8, 15.3 mg/ml for S. strictum EtOAc and DCM extracts, while it was 22.6 and 34.4 mg/ml for A. nidulans DCM and EtOAc extract. A strong deformation was observed to the adults of S. littoralis by about 25.1% individuals descending from larvae treated with S. strictum EtOAc. The four major compounds from S. strictum EtOAc extract were resolved as Cis-13-octadecenoic acid, sebacic acid, pentamethoxy flavone and n-hexadecanoic acid.

Biology of the cucurbit fruit fly, Bactrocera cucurbitae (Coq) on host bottle gourd, Lagenaria siceraria

We investigated the biology of the cucurbit fruit fly, Bactrocera cucurbitae (coq) on bottle gourd, Lagenaria siceraria, using variety ‘BARI-Lau 1’. The mean incubation period, larval (1st, 2nd and 3rd instars), pre-pupal, pupal and total developmental periods of B. cucurbitae were 1.69±0.28, (1.72±0.33, 1.41±0.31, 2.31±0.51), 0.74±0.28, 9.2±0.78 and 36±1.69 days, respectively. The mean adult longevity, with food and without food was 14.1±1.28 and 5.0±0.81 days, respectively. The lengths of all three larval instars were 1.1± 0.9, 3.03 ± 0.95 and 6.42 ± 0.90 mm, and the widths were 0.22 ±0.11, 1.12 ± 0.01 and 2.13 ± 0.20 mm, respectively. The length and width of the pre-pupa and the pupa were 5.86 ±0.48, 5.68± 0.26 mm and 1.94 ± 0.23, 2.39±0.20 mm respectively. The length of male and female were 6.61±0.59 and 8.28±0.52 mm. The widths of males and females with wingspan were 10.97 ± 0.43 and 13.02±1.28 mm respectively. The incidence of B. cucurbitae as maggot population in bottle gourd was higher in January during the study period from December 2018 to March 2019.

Occurrence, damage pattern and biology of fall armyworm, Spodoptera frugiperda (J.E. smith) (Lepidoptera: Noctuidae) on fodder crops and green amaranth in Goa, India

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is an economically important polyphagous pest native to the Americas. The pest has recently introduced to India and causing severe damage to maize and other crops. The occurrence of fall armyworm on fodder maize (Zea mays L), Guinea grass (Megathyrsus maximus) (Jacq.), para grass (Brachiaria mutica) (Forssk.) and green amaranth (Amaranthus viridis L) is reported first time from Goa, India. The damage incidence of 16 to 52% was recorded on fodder maize. The other host plants viz., Guinea grass, para grass and green amaranth recorded damage incidences of 9.0, 4.0 and 13.0%, respectively. The pest was identified based on morphological characters and molecular techniques. Phylogenetic analysis of COI gene sequence revealed that fall armyworm on fodder maize from Goa is clustering with the fall armyworm isolates from India, Nigeria, Ghana, Kenya, Canada and Brazil. Goa isolate is aligning with the “Rice” strain of fall armyworm and not with “Corn” strain. Studies on the biology of fall armyworm indicated that longer larval and pupal developmental period (18.6 and 10.7 days) was recorded on Guinea grass and green amaranth, respectively. The highest number of eggs was recorded from fall armyworm population reared on fodder maize as compared to those reared on other host plants. Longer life cycle was recorded on Guinea grass and green amaranth. Shortest larval and pupal period and faster life cycle of fall armyworm was recorded on fodder maize compared to other host plants indicating that fodder maize was the most preferred host for S. frugiperda in India.

Cocoon production efficiency of silkworm (Bombyx mori L.) in response to host shift between two selected mulberry varieties

Silkworm Bombyx mori L. (Lepidoptera: Bombycidae) is a monophagous insect that feeds only on mulberry leaf. During rearing, shortage of a variety may engender a shift to another available mulberry variety to complete the rearing process. This study was carried out to assess the effect of host shift on B. mori fifth larval instar and the quality of cocoon produced. Silkworm eggs incubation and rearing of larvae were carried out following the standard procedures. There were four treatments consisting of different feeding components: sole mulberry variety S30, sole mulberry variety S14, host shift from mulberry variety S30 to S14 and host shift from mulberry variety S14 to S30. The treatments were arranged in a Completely Randomized Design with three replicates. At the fifth larval stage the worms were mounted on mountage and the spurned cocoons were harvested five days after. Host shift from mulberry S30 to S14 gave the highest fifth larval weight (2.29 ± 0.0 g) which was significantly higher than 1.99 ± 0.02 recorded on S14 sole feeding. The smallest single cocoon weight (1.07 ± 0.01 g), single pupal weight (0.96 ± 0.02 g) and single shell weight (0.10 ± 0.01 g) were obtained from sole feeding on mulberry S14.There was no significant difference in the total cocoon weight across the treatments. Silkworm larval survival, larval developmental period and number of cocoon formed were not negatively influenced either by sole feeding or shift in varietal feeding. Therefore, rearing process of silkworm that commenced with S14 or S30 can be completed with either of the varieties in the absence of one.

Standardizing a Non-Lethal Method for Characterizing the Reproductive Status and Larval Development of Freshwater Mussels (Bivalvia: Unionida).

Actively monitoring the timing, development, and reproductive patterns of endangered species is critical when managing for population recovery. Freshwater mussels are among the most imperiled organisms in the world, but information about early larval (glochidial) development and brooding periods is still lacking for many species. Previous studies have focused on the complex life history stage when female mussels are ready to parasitize host fish, but few studies have focused on the brooding period and timing of larval development. The protocol described here allows researchers to non-lethally evaluate the state of gravidity for female mussels. The results of this study show that this method does not affect a female mussel's ability to stay gravid or become gravid again after sampling has been performed. The advantage of this method may permit its use on federally threatened or endangered species or other populations of high conservation concern. This protocol can be adapted for use on both preserved or live individuals and was tested on a variety of mussel species. The database provided is a repository for a breadth of information on timing of reproductive habits and will facilitate future freshwater mussel research, conservation, and recovery efforts.

The Effects of Conspecific Alarm Cues on Larval Cane Toads (Rhinella marina)

Many aquatic organisms detect and avoid damage-released cues from conspecifics, but the chemical basis of such responses, and the effects of prolonged exposure to such cues, remain poorly understood. Injured tadpoles of the cane toad (Rhinella marina) produce chemical cues that induce avoidance by conspecific tadpoles; and chronic exposure to those cues decreases rates of tadpole survival and growth, and reduces body size at metamorphosis. Such effects suggest that we might be able to use the cane toads' alarm cue for biocontrol of invasive populations in Australia. In the present study, we examined behavioral and ecological effects of compounds that are present in cane toad tadpoles and thus, might trigger avoidance of crushed conspecifics. Four chemicals (L-Arg, L-Leu-L-Leu-OH, L-Leu-L-Ile-OH and suberic acid) induced behavioral avoidance in toad tadpoles at some (but not all) dosage levels, so we then exposed toad larvae to these chemicals over the entire period of larval development. Larval survival and size at metamorphosis were decreased by chronic exposure to crushed conspecifics (consistent with earlier studies), but not by exposure to any of the four chemicals. Indeed, L-Arg increased body size at metamorphosis. We conclude that the behavioral response to crushed conspecifics by cane toad tadpoles can be elicited by a variety of chemical cues, but that consistent exposure to these individual chemical cues does not affect tadpole viability or developmental trajectory. The optimal behavioral tactic of a tadpole may be to flee if it encounters even a single chemical cue likely to have come from an injured conspecific (indicative of predation risk), whereas the continuing presence of that single chemical (but no others) provides a less reliable signal of predation risk. Our data are consistent with results from studies on fish, that suggest a role for multiple chemicals in initiating alarm responses to damage-released cues.

Effect of Castanopsis megacarpa Extract on Mortality, Longevity Development and Feeding of Crocidolomia pavonana Larvae

As several reports of impacts arise due to the use of synthetic insecticides, the investigation for safer alternative insecticides should be continued. Using plant material that has several bioactivities is a promising way out to control insect pest. The objective of this study was to evaluate the effect of leaf and seed extract of Castanopsis megacarpa on mortality, longevity development and feeding preference of Crocidolomia pavonana larvae. Extraction conducted by infusion method. The bioassay assesment was carried out using the residual method. The concentration-mortality relationship was analyzed by probit. The antifeedant test was tested using choice and no-choice methods. Both extracts showed the same strong insecticidal activity, LC 50 of 0.18% (leaf) and 0.12% (seed). Leaf and seed extracts at concentrations equivalent to LC 50 and LC 75 in both methods used showed consistent antifeedant properties. The antifeedant activity of extracts in the no-choice method at both concentrations showed a range of activities of 40.1%-53.7% (leaf) and 74.4%-82.7% (seed) extracts. The leaf and seed extracts of C. megacarpa did not significantly extend the larval development period. Plant material that has more than one bioactivity will be better for suppress the insect pest populations in the field.

Fish spawning strategies in the northwestern Mediterranean Sea

The Mediterranean is globally considered an oligotrophic sea. However, there are some places or certain seasons in which mechanisms that enhance fertility may occur. These mechanisms, and related processes, are especially relevant in maintaining fish populations when they take place during the period of larval development. This contribution analyzes how environmental conditions occurring in the NW Mediterranean, at local and seasonal scales, determine the temporal and spatial patterns of fish reproductive activity in the region. The structure of the bathymetry, diversity of adult fish habitats and hydrodynamic mechanisms conditioning the primary production of the region (e.g., shelf-slope density front and associated current, continental water inflows, winter mixing, stratification of the water column) determine the location of spawning and the distribution patterns of fish eggs and larvae. A pronounced seasonal variability regarding both the number of species and the number of fish larvae in the plankton can be observed throughout the year. Most NW Mediterranean fish reproduce during the spring–summer stratification period, when the phytoplankton biomass values at the upper layers of the water column are lower than in winter. The development of the Deep Chlorophyll Maximum in this period and the high zooplankton biomass associated to it offers an important food source for the larvae. Additionally, during this period the inputs of continental waters are one of the fertilization mechanisms of surface waters and some species, as anchovy, takes advantage of this situation. Autumn–winter is the period with lower ichthyoplankton diversity, being dominated by sardine. Vertical mixing during winter is one of the mechanisms that enhance productivity. Overall, fish species show reproductive strategies and larval fish behavior that allow them to take advantage of the available resources throughout the seasonal cycle. These strategies, together with the high ecological efficiency of oligotrophic systems, contribute to the relatively high yield of Mediterranean fisheries. In a context of global change, understanding of the mechanisms relating environmental changes to the extent of spatial and temporal location of suitable spawning habitats of fish is a key first step to predicting and projecting such future changes, and thereby adapting to these changes.

Vertical Transmission of Zika Virus (Flaviviridae, Flavivirus) in Amazonian Aedes aegypti (Diptera: Culicidae) Delays Egg Hatching and Larval Development of Progeny.

Zika virus (ZIKV) has emerged as a globally important arbovirus and has been reported from all states of Brazil. The virus is primarily transmitted to humans through the bite of an infective Aedes aegypti (Linnaeus, 1762) or Aedes albopictus (Skuse, 1895). However, it is important to know if ZIKV transmission also occurs from Ae. aegypti through infected eggs to her offspring. Therefore, a ZIKV and dengue virus (DENV) free colony was established from eggs collected in Manaus and maintained until the third–fourth generation in order to conduct ZIKV vertical transmission (VT) experiments which used an infectious bloodmeal as the route of virus exposure. The eggs from ZIKV-infected females were allowed to hatch. The resulting F1 progeny (larvae, pupae, and adults) were quantitative polymerase chain reaction (qPCR) assayed for ZIKV. The viability of ZIKV vertically transmitted to F1 progeny was evaluated by cultivation in C6/36 cells. The effects of ZIKV on immature development of Ae. aegypti was assessed and compared with noninfected mosquitoes. AmazonianAe. aegypti were highly susceptible to ZIKV infection (96.7%), and viable virus passed to their progeny via VT. Moreover, eggs from the ZIKV-infected mosquitoes had a significantly lower hatch rate and the slowest hatching. In addition, the larval development period was slower when compared to noninfected, control mosquitoes. This is the first study to illustrate VT initiated by oral infection of the parental population by using mosquitoes, which originated from the field and a ZIKV strain that is naturally circulating in-country. Additionally, this study suggests that ZIKV present in the Ae. aegypti can modify the mosquito life cycle. The data reported here suggest that VT of ZIKV to progeny from naturally infected females may have a critical epidemiological role in the dissemination and maintenance of the virus circulating in the vector.

Peptide Transporters in the Primary Gastrointestinal Tract of Pre-Feeding Mozambique Tilapia Larva.

Fish larvae differ greatly from the adult form in their morphology and organ functionality. The functionality of the gastrointestinal tract depends on the expression of various pumps, transporters, and channels responsible for feed digestion and nutrients absorption. During the larval period, the gastrointestinal tract develops from a simple closed tube, into its complex form with differentiated segments, crypts and villi, as found in the adult. In this study, we characterized the expression of three peptide transporters (PepT1a, PepT1b, and PepT2) in the gastrointestinal tract of Mozambique tilapia (Oreochromis mossambicus) larvae along 12 days of development, from pre-hatching to the completion of yolk sac absorption. Gene expression analysis revealed differential and complimentary time-dependent expression of the PepT1 variants and PepT2 along the larval development period. Immunofluorescence analysis showed differential protein localization of the three peptide transporters (PepTs) along the gastrointestinal tract, in a similar pattern to the adult. In addition, PepT1a was localized in mucosal cells in the larvae esophagus, in much higher abundance than in the adults. The results of this study demonstrate specialization of intestinal sections and absorbance potential of the enterocytes prior to the onset of active exogenous feeding, thus pointing to an uncharacterized function and role of the gastrointestinal tract and its transporters during the larval period.

Long-chain PUFA profiles in parental diets induce long-term effects on growth, fatty acid profiles, expression of fatty acid desaturase 2 and selected immune system-related genes in the offspring of gilthead seabream

The present study investigated the effects of nutritional programming through parental feeding on offspring performance and expression of selected genes related to stress resistance in a marine teleost. Gilthead seabream broodstock were fed diets containing various fish oil (FO)/vegetable oil ratios to determine their effects on offspring performance along embryogenesis, larval development and juvenile on-growing periods. Increased substitution of dietary FO by linseed oil (LO) up to 80 % LO significantly reduced the total number of eggs produced by kg per female per spawn. Moreover, at 30 d after hatching, parental feeding with increasing LO up to 80 % led to up-regulation of the fatty acyl desaturase 2 gene (fads2) that was correlated with the increase in conversion rates of related PUFA. Besides, cyclo-oxygenase 2 (cox2) and TNF-α (tnf-α) gene expression was also up-regulated by the increase in LO in broodstock diets up to 60 or 80 %, respectively. When 4-month-old offspring were challenged with diets having different levels of FO, the lowest growth was found in juveniles from broodstock fed 100 % FO. An increase in LO levels in the broodstock diet up to 60LO raised LC-PUFA levels in the juveniles, regardless of the juvenile's diet. The results showed that it is possible to nutritionally programme gilthead seabream offspring through the modification of the fatty acid profiles of parental diets to improve the growth performance of juveniles fed low FO diets, inducing long-term changes in PUFA metabolism with up-regulation of fads2 expression. The present study provided the first pieces of evidence of the up-regulation of immune system-related genes in the offspring of parents fed increased FO replacement by LO.

Cross-shelf distribution of decapod larvae in a coastal upwelling zone of northern Chile: some oceanographic implications

The northern of Chile is one of the most productive and permanent upwelling systems of the large Humboldt Current System. However, do not investigations have been developed about the decapod larvae dynamics in this region, characterized by its narrow continental shelf and an oxygen minimal zone (OMZ) very shallow (<50 m). Four oceanographic campaigns carried out in a coastal upwelling zone off northern Chile in 2003 were used to analyze the dispersal patterns of 15 taxa from decapods larvae selected. The coastal upwelling conditions showed a maximum Ekman transport value (Mx) in January and a minimum in May, while the temperature and salinity characteristics defined four types of waters named a) cold upwelling waters (UW), b) warm trapped waters (WTW), c) upwelling front waters (UFW) and d) oceanic front waters (OFW), which showed different concentrations of dissolved oxygen, OMZ depth (<1 mL L−1) and chlorophyll-a concentrations, respectively. Decapod larvae with the highest abundance and frequency were Cancer spp., Emerita analoga, Pinnaxodes chilensis, Callianassidae sp., Pagurus sp. and Allopetrolisthes sp., from adults of diverse habitats, characterized by different development stages and periods. The offshore weighted distance (Ğ) estimated for the decapod larvae allowed the differentiation of three main groups. a) group formed by high dispersion larvae (>11 km), with five zoea stages and associated to the UFW waters, b) group formed by mean dispersion larvae (between 5 and 8 km) and distributed in upwelling waters (UW), and c) group showing lower horizontal dispersions (<4 km), which significantly and negatively correlated to the OMZ in UW and WTW-type waters. The different cross-shelf distribution patterns relative to the oceanographic conditions were compared with other upwelling system, and larval behavior, morphology, environmental requirements and development period of different decapods were discussed.

Climate warming leads to decline in frequencies of melanic individuals in subarctic leaf beetle populations

Intraspecific diversity buffers populations from deleterious impacts of environmental change. Nevertheless, the consequences of climate warming for phenotypic and genetic diversity within populations and species remain poorly understood. The goal of our study was to explore among-year variations in the phenotypic structure of populations and their relationships with climate variability and population dynamics. We analysed multiyear (1992–2018) data on colour morph frequencies within populations of the leaf beetle, Chrysomela lapponica, from multiple sites in the Kola Peninsula (northwestern Russia). We observed a strong decline in the proportion of dark (melanic) morphs among overwintered beetles during the study period; this decline was consistent across all study sites. Using model selection procedures, we explained declines in the dark morph of overwintered beetles by increases in minimum spring (May–June) daily temperatures. Other climatic characteristics, pollution load, and beetle population density were unrelated to variation in colour morph frequencies. Among newly emerged beetles (August), dark morph frequencies also decreased with an increase in average spring temperatures, but were unrelated to mean temperatures during the larval development period (July). These results suggest that the two-fold decline in dark morph frequencies during the past 26 years has been driven by the 2.5 °C increase in spring temperatures, most likely because dark males lose the mating advantages over light males that they obtain during cold springs. The continued loss of dark morphs and related decrease in within-population diversity may render leaf beetle populations more vulnerable to future environmental changes, in particular to those expressed in extreme weather fluctuations. Our study demonstrates that declines in within-population diversity are already underway in subarctic areas, and that these declines are likely driven by climate warming.

Effects of dietary arachidonic and eicosapentaenoic acids on common dentex (Dentex dentex Linnaeus 1758) larval performance

Oily emulsions containing constant levels of total fatty acids (FAs) and varying eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels were used to enrich rotifers. Common dentex larval survival and growth were compared between groups fed different enriched live prey. Growth, survival rate, and lipid composition of larvae suggest that feeding common dentex in the first 15 days posthatching with 2.5–3% EPA, 6–8% docosahexaenoic acid (DHA), and DHA/EPA ratio of 2.0–2.5 is sufficient to fulfill their EPA requirements. Higher amounts of dietary EPA did not result in any significant improvement in growth or survival. EPA requirement during this period of larval development does not seem to be as critical as other FAs during the first 15 days of common dentex larval development, but it does not exclude its essentiality later in development. In the case of ARA, nutritional requirements are low compared to other marine finfish species, with the upper limit of this essential FA being around 2% of total FAs provided in the live prey composition.

Inhibitory activities of proteinase inhibitors on developmental characteristics of sugarcane Chilo infuscatellus (Snellen)

A sugarcane wild relative Erianthus arundinaceus was identified as a source of resistance against Chilo infuscatellus, a major devastating pest at the early cropping stage of sugarcane. In the view of earlier studies, inhibitory activities of proteinase inhibitors (PIs) from C. infuscatellus field resistant E. arundinaceus genotypes viz., IK 76 78, IJ 76 400, IK 76 84, IK 76 88, IJ 76 370, FIJI 55, IJ 76 364 and ERI 2798 and a popular variety Co 86032 were done. Although proteinase inhibitors differed significantly among the plant parts of selected genotypes, it was comparatively higher in the apical meristem (70%) followed by leaf sheath (20%) and stalk tissues (11%). The results also showed that E. arundinaceus apical meristem PIs significantly inhibited (> 70%) the midgut proteinase of early shoot borer. Among the genotypes, IJ 76 370 and IJ 76 364 had considerably higher PIs in apical meristem and leaf sheath which showed strong inhibitory activity against gut proteinase of sugarcane shoot borer. Developmental characteristics of the borer showed a significant reduction of larval and pupal survival along with extended larval duration in the genotypes IJ 76 370 and IJ 76 364. Correlation studies indicated negative relationship with shoot borer larval (P < 0.05, r = −0.14) and pupal survival (P < 0.05, r = −0.56**) with apical meristem PIs of E. arundinaceus. Similarly, significant correlations were found between the shoot borer developmental period and apical meristem PIs of E. arundinaceus (P < 0.05, r = 0.52**, P < 0.05, r = 0.24 and P < 0.05, r = 0.56** for larval, pupal and total developmental period of the borer respectively). The study identified two elite genotypes IJ 76 370 and IJ 76 364 which could be used as donors for sugarcane pre-breeding programme for the development of shoot borer resistant varieties. Besides, it could be possible to identify novel insecticidal proteins (PIs) that may be utilized in genetic manipulation work for producing transgenics imparting resistance against sugarcane C. infuscatellus.