Feeding behaviour of larval European sea bass (Dicentrarchus labrax L.) in relation to temperature and prey density

The feeding behaviour of larval European sea bass (Dicentrarchus labrax, L.) was analysed in relation to temperature and prey density under controlled laboratory conditions with the aim to assess the ability of larval fish to change the feeding tactic as a response to environmental changes. Larvae were acclimated for 20 days at three different temperatures (19, 22 and 26°C), and their feeding behaviour was then video-recorded in experimental trials, at two prey densities, consisting of swarms of 400/l and 1440/l Artemia nauplii. Results showed that there was a significant effect of the interaction between temperature and prey density on the proportion of swimming activity that was reduced at the high temperature-high prey density combination. This suggested a switching in the larval feeding behaviour from an active to an ambush tactic, when the temperature reached 26°C and the prey density was 1440 /l Artemia nauplii. These results are consistent with the current literature on fish larval behaviour in showing that the foraging tactic can be modulated by the interaction of different abiotic and biotic factors characterising the rearing environment

Environmental Effects On Drosophila Brain Development And Learning

Brain development and behavior are sensitive to a variety of environmental influences including social interactions and physicochemical stressors. Sensory input in situ is a mosaic of both enrichment and stress, yet little is known about how multiple environmental factors interact to affect brain anatomical structures, circuits and cognitive function. In this study, we addressed these issues by testing the individual and combined effects of sub-adult thermal stress, larval density and early-adult living spatial enrichment on brain anatomy and olfactory associative learning in adult Drosophila melanogaster. In response to heat stress, the mushroom bodies (MBs) were the most volumetrically impaired among all of the brain structures, an effect highly correlated with reduced odor learning performance. However, MBs were not sensitive to either larval culture density or early-adult living conditions. Extreme larval crowding reduced the volume of the antennal lobes, optic lobes and central complex. Neither larval crowding nor early-adult spatial enrichment affected olfactory learning. These results illustrate that various brain structures react differently to environmental inputs, and that MB development and learning are highly sensitive to certain stressors (pre-adult hyperthermia) and resistant to others (larval crowding). © 2018. Published by The Company of Biologists Ltd

Temperature and Crowding Effects on Virus Manifestation in Neodiprion Sertifer (Hymenoptera: Diprionidae) Larvae

Temperature and (or) crowding (larval density) functioned as stressors in the induction of symptoms associated with the nucleopolyhedrosis virus of the European pine sawfly, Neodiprion sertifer, Subsamptes of larvae maintained at 30 and 35°C, with three levels of larval density each (20, 60, and 100/shoot) which had died under these conditions, revealed the presence of polyhedral inclusion bodies under microscopic examination. In contrast, larvae maintained at 25°C with the same three larval density levels experienced no symptoms of virus infection or mortality, The latter was consistent with field observations when temperatures during larval development ranged from 14°C to 27°C and larval densities were in the same general range

Larval fish in the vicinity of aquaculture intakes

Texas Parks and Wildlife Department has recently proposed that all facilities pumping water from Texas estuaries be fitted with 0.5 mm screening to prevent larval fish mortality at these facilities. Data on larval fish distributions in Texas estuaries is quite limited (Holt et al. 1990). This report presents the results of a pilot study to examine the impact on larval fishes and shrimps of pumping water into mariculture facilities at three sites on the central and southern Texas Coast. The primary objective of this study was to determine the species composition, density and size structure of ichthyoplankton populations in the vicinity of the intake structures of the three mariculture facilities during their spring and fall pumping seasons. A secondary objective was to determine what organisms were actually being pumped through the system.Final report for contract IAC(90-91)111.5Prepared for Texas A&M Sea Grant, Texas General Land OfficeFebruary 1991Marine Scienc

The Effect of Rekattidiri Ovitrap Towards Aedes Aegypti Larval Density

Dengue Hemorrhagic Fever (DHF) is a health problem in Indonesia. The entire region of Indonesia at risk of contracting dengue disease. The study aims to prove the effect of modifications ovitrap rekattidiri on the density of larvae (HI: House Index, CI: Container Index and BI: Breteu Index) as well as comparing the differences between the mean larvae trapped between ovitrap Rekattidiri with standard ovitrap. Using a quasi experimental design, time series experimental design with Control group. Population subjects were Aedes aegypti at the endemic sites in Pontianak, West Borneo. The results showed larval density index in the intervention area decreased each ie HI from 26% to 3%, CI of 6.95% to 2.19 %, and BI from 29% to 13%. The number of larvae trapped in ovitrap rekattidiri ie 70% (12,770 larvae) more than the standard ovitrap in the control and intervention, namely: 17% (3,057 larvae) and 13% (2,334 larvae). It is concluded that there are significant modifications Rekattidiri ovitrap against larval density index (HI p-value: 0.025, CI p-value: 0.052, BI value of p: 0.04) and there are differences between the mean larvae trapped in ovitrap Rekattidiri and standard ovitrap with p value: 0.001

Increased flood frequency and magnitude decreases density of a stream-breeding salamander in urbanized watersheds

Background/Question/Methods
As urbanization increases across the globe, more ecologists have taken note of its consequences to stream systems. Sufficient data have been collected to document repeated patterns in urbanized streams for many abiotic parameters, aquatic insects, and fish. For example, we now know that urbanized streams experience more frequent and intense spates as a result of increased runoff form impervious surfaces in the urban watershed. The spates eventually lead to a more incised and wider stream bed. Such abiotic shifts consistently result in decreased aquatic invertebrate and fish diversity. More recently, stream-breeding salamanders have been observed to decrease in density in urban areas. We monitored the density of southern two-lined salamanders for the duration of two cohorts in 12 streams in western Georgia, USA. We then used path analysis to determine the relationships between land-use change, abiotic shifts in the stream environment, and larval salamander density. 

Results/Conclusions
We found that southern two-lined salamanders in the streams we monitored exhibited no change in reproductive output between urban and reference habitats. However, repeated sampling throughout the larval period revealed a large decline in density of larvae in urban areas prior to metamorphosis, while a similar decline was not seen in reference habitats. We evaluated several hypotheses that might explain the observed decline in urban areas, and a model in which increased impervious surface causes an increase in spate frequency and magnitude, which then leads to decreased larval density had the most support. This is the first attempt to compare multiple plausible hypotheses as to why salamander density and diversity decreases in urban habitats. By describing larval density at the beginning and end of the larval period, and by identifying a likely mechanism for the observed decline in density, species-specific and stream restoration efforts can be enhanced.
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How effective is integrated vector management against malaria and lymphatic filariasis where the diseases are transmitted by the same vector?

The opportunity to integrate vector management across multiple vector-borne diseases is particularly plausible for malaria and lymphatic filariasis (LF) control where both diseases are transmitted by the same vector. To date most examples of integrated control targeting these diseases have been unanticipated consequences of malaria vector control, rather than planned strategies that aim to maximize the efficacy and take the complex ecological and biological interactions between the two diseases into account.; We developed a general model of malaria and LF transmission and derived expressions for the basic reproductive number (R0) for each disease. Transmission of both diseases was most sensitive to vector mortality and biting rate. Simulating different levels of coverage of long lasting-insecticidal nets (LLINs) and larval control confirms the effectiveness of these interventions for the control of both diseases. When LF was maintained near the critical density of mosquitoes, minor levels of vector control (8% coverage of LLINs or treatment of 20% of larval sites) were sufficient to eliminate the disease. Malaria had a far greater R0 and required a 90% population coverage of LLINs in order to eliminate it. When the mosquito density was doubled, 36% and 58% coverage of LLINs and larval control, respectively, were required for LF elimination; and malaria elimination was possible with a combined coverage of 78% of LLINs and larval control.; Despite the low level of vector control required to eliminate LF, simulations suggest that prevalence of LF will decrease at a slower rate than malaria, even at high levels of coverage. If representative of field situations, integrated management should take into account not only how malaria control can facilitate filariasis elimination, but strike a balance between the high levels of coverage of (multiple) interventions required for malaria with the long duration predicted to be required for filariasis elimination

Eco control of agro pests using imaging, modelling & natural predators

Caterpillars in their various forms: size, shape, and colour cause significant harm to crops and humans. This paper offers a solution for the detection and control of caterpillars through the use of a sustainable pest control system that does not require the application of chemical pesticides, which damage human health and destroy the naturally beneficial insects within the environment. The proposed system is capable of controlling 80% of the population of caterpillars in less than 65 days by deploying a controlled number of larval parasitoid wasps (Cotesia Flavipes, Cameron) into the crop environment. This is made possible by using a continuous time model of the interaction between the caterpillar and the Cotesia Flavipes (Cameron) wasps using a set of simultaneous, non-linear, ordinary differential equations incorporating natural death rates based on the Weibull probability distribution function. A negative binomial distribution is used to model the efficiency and the probability that the wasp will find and parasitize a host larva. The caterpillar is presented in all its life-cycle stages of: egg, larva, pupa and adult and the Cotesia Flavipes (Cameron) wasp is present as an adult larval parasitoid. Biological control modelling is used to estimate the quantity of the Cotesia Flavipes (Cameron) wasps that should be introduced into the caterpillar infested environment to suppress its population density to an economically acceptable level within a prescribed number of days. Keywords

Dungeness crab research program: Report for the Year 1976

All larval stages of the 1976 year class, with the exception of the 5th zoeal stage, were found in Gu1f waters January through March. The first post-larval stage was collected in San Pablo Bay in May. Fifty percent of 1976 year class crabs entered the Bay complex as compared to nearly 80% in 1975. The 1976 year class appears relatively weak. No electrophoretic polymorphism was found in Cancer magister to be of value in Dungeness crab population determinations. Multi-variate correlations comparing crab landings with an array of oceanographic parameters and the crab density dependent factor were computer-run for both northern and central California. The most significant correlating factors at the time late stage larvae prevail were sea level and atmospheric pressure for central California and, for northern California, the density dependent factor and sea surface temperature. Female crabs held at controlled temperatures indicated gonad maturation and spawning may be induced by increased temperature. Analyses of crab tissues revealed burdens of petroleum hydrocarbons, silver, selenium, cadmium, and PCB's higher in central California crabs, while DDE was found in higher amounts in northern California crab tissue. Thru-flow culture systems were developed which should yield about 163 megalopae of Dungeness crabs in 63 days from 1,200 laboratory hatched zoeae.(46pp.