Quality characteristics of cured fish of commerce

A survey was conducted at the fish curing yards at Shakthikulangara (Quilon), fish market at Vizhinjam, fish curing yards, fish market as well as dry fish godowns in and around Tuticorin. A total of 23 samples of different varieties of fishes collected from the markets and curing yards and 8 samples of anchovies collected from different godowns at Tuticorin were analysed to evaluate the quality and extent of fungal and insect infestation. Samples were analysed for proximate composition and estimated their water activity. About 70% of the 23 samples of different varieties of fish were found to be unfit for consumption and 12.5% of the samples of anchovies were found to be infested with beetle, after 3 weeks of storage after collection from these centres.

Single base-resolution methylome of the silkworm reveals a sparse epigenomic map

Epigenetic regulation in insects may have effects on diverse biological processes. Here we survey the methylome of a model insect, the silkworm Bombyx mori, at single-base resolution using Illumina high-throughput bisulfite sequencing (MethylC-Seq). We conservatively estimate that 0.11% of genomic cytosines are methylcytosines, all of which probably occur in CG dinucleotides. CG methylation is substantially enriched in gene bodies and is positively correlated with gene expression levels, suggesting it has a positive role in gene transcription. We find that transposable elements, promoters and ribosomal DNAs are hypomethylated, but in contrast, genomic loci matching small RNAs in gene bodies are densely methylated. This work contributes to our understanding of epigenetics in insects, and in contrast to previous studies of the highly methylated genomes of Arabidopsis(1) and human(2), demonstrates a strategy for sequencing the epigenomes of organisms such as insects that have low levels of methylation.

Prevention of infestation by Dermestes maculatus Degeer in east African dried fish by solar treatment

East African sun-dried fish infested by Dermestes maculatus were exposed to tropical sunlight at ambient temperature and analysed for insect mortality and weight losses. Solar treatment for 6 to 8 lo was highly effective for one layer of split sun-dried fish and 100% insect mortality was toted, while pest species were still present in the four layer batch. Weight losses between 1.2% and 10.2% were recorded, the top layer suffering the highest loss. The high surface temperature of 60°C caused fish to become brittle and quality losses occurred. A reduction in length of exposure/temperature is probably a presupposition for application of the method to local conditions.

Prevention of infestation by Dermestes maculatus Degeer in east African dried fish using pyrethrum and piperonyl butoxide

East African sun-dried fish dipped for 4 seconds in different solutions of pyrethrum and piperonyl butoxide were analysed for insecticide residue limits. All analyses showed residues above the FAO/WHO MRL; exceeding factors of between 7.6 (22.9 ppm) and 1.6 (5.3 ppm) were found for pyrethrum while exceeding factors between 5.1 (102 ppm) and 1.7 (33.1 ppm) were common for piperonyl butoxide after 6 months storage at ambient temperature. All insecticide treated fish, regardless of dip concentration, were observed to be less susceptible to infestation by Dermestes maculatus than samples of untreated fish. No dry weight losses due to insect infestation were recorded, however moisture evaporation caused weight losses between 6 and 8% during the period. Further investigations showed that careful handling and a dip concentration more in accordance with FAO/WHO MRL than the commercial practice will reduce the cost of insecticides from K.sh. 0.72 to K.sh. 0.23 per kg pyrethrum treated fish.

Endosulfan: a hidden menace

A clean and healthy environment is paramount to human existence. While pesticide use has successfully sustained agricultural and food production in our lifetime as well as safeguarded human health by controlling insect pests, it has also caused many tragedies including population declines in our wildlife, fatalities in workers exposed to pesticides in its manufacture and use, and the increasing incidence of dreaded human illnesses such as cancer. A delicate balance should be achieved to mitigate the adverse impact of pesticide use to the environment and at the same time ensuring short- and long-term agricultural productivity. Endosulfan has been effectively used as a pesticide, but much evidence on its chronic and sub-lethal effects on humans and wildlife have been gathered in recent years. More research still needs to be done to determine its effects from long-term exposure at very low levels. Endosulfan is highly toxic to fish and other aquatic animals and, thus, not recommended for use in aquatic ecosystems. However, in some countries, it has been incorrectly used as a molluscicide in rice paddies, which could have an adverse impact on the rice-fish farming systems and on other surrounding aquatic ecosystems. It is clear that such practices should be stopped and users must strictly observe the recommended application methods. Agricultural productivity should be achieved with less pesticide by using integrated pest management programs which make use of biological, cultural, and physical control agents and lower doses of safer pesticide on a need only basis. The benefits of biotechnology should also be used to develop more effective and safer products and techniques. This is a valid approach and one that will require a unified and concerted effort among suppliers and users of pesticides in order to ensure that resources are used to our best advantage with minimal risk.

The role of Yssichromis species (Pisces: Cichlidae) in the trophic ecology and foodwebs of Lake Victoria

Many haplochromine cichlids coexisted in Lake Victoria before the upsurge of Nile perch. The introduction of the Nile perch led to depletion of many haplochromines and other fish species in Lake Victoria. The impact of Nile perch predation on haplochromines differed for different haplochromine trophic groups. Yssichromis fusiformis (G) and Yssichromis laparogramma (G) are among the species that have survived in the lake. Yssichromis spp. was studied with the aim of determining their trophic role, food and feeding habits. Samples were collected from Bugaia, Buvuma channel and Napoleon Gulf in the northern part of Lake Victoria. The food of Yssichromis spp. varied with size of fish. Both Y fusiformis and Y laparogramma fed on Copepods, Cladocerans, Chaoborus and Chironomids. Juvenile Yssichromis spp. fed exclusively on zooplankton comprising Cyclopoid copepods, Calanoid copepods and Cladocera. The relative importance of Chironomid larvae and Calanoid copepods was higher in Bugaia than in Buvuma channel while Cyclopoid copepods and Chironomid pupae were relatively less important in Bugaia. The main food items that Yssichromis spp. fed on in Buvuma channel were Chironomid larvae Cyclopoid copepods, Cladocerans and Calanoid copepods. In Napoleon Gulf, fish caught from commercial fishery of Rastrineobola argentea (P) had fed on Chaoborus and Chironomids. Overall, Yssichromis spp. fed on more zooplankton in Buvuma than in Bugaia. Yssichromis spp. and R. argentea are presently the most abundant zooplanktivores in the northern part of Lake Victoria and are playing an important trophic role as major consumers of zooplankton and insect larvae in the foodweb of the lake ecosystem. Yssichromis spp. are bridging the transfer of energy from the lower to the higher trophic levels as secondary consumers. The fishery is still not contributing to the direct conversion of the primary products, the phytoplankton and detritus that were efficiently utilised by the diverse haplochromine trophic groups that existed before the Nile perch boom.

Trophic interrelationships and food-webs among the fishes in ecosystems of the Victoria and Kyoga lake basin

The Victoria and Kyoga lake basins had a high fish species diversity with many fish species that were found only in these lakes. Two Tilapiines species Oreochromis esculentus and Oreochromis variabilis were the most important commercial species in these lakes and were found nowhere else on earth except in the Victoria and Kyoga lake basins (Graham 1929, Worthington 1929). Lakes Kyoga and Nabugabo also had endemic haplochromine species (Worthington 1929, Trewavas 1933, Greenwood 1965, 1966). As stocks of introduced species increased, stocks of most of the native species declined rapidly or disappeared altogether. The study was carried out on Lakes Victoria and Kyoga, River Nile, some selected satellite lakes from the two basins namely Lakes Mburo, Kachera, Wamala, Kayanja, Kayugi, Nabugabo, Victoria, Victoria nile and River Sio(Victoria lake basin). Lakes Kyoga (Iyingo), Nawampasa, Nakuwa, Gigati, Nyaguo, Agu, Kawi and Lemwa (Kyoga lake basin). Species composillon and relative abundance of fishes were estimated by detennining the overall average total number of each species encountered. A trophic consists of species using the same food category. Shannon-Weaver Index of diversity H (Pielou, 1969) and number of trophic groups, were used to estimate the Trophic diversity of various fish species in the lakes. Food analysis has been done on some fishes in some of the sampled lakes and is still going on, on remaining fishes and in some lakes. Generally fish ingested detritus, Spirulina, Melosira, filamentous algae, Planktolyngbya, Microcysists, Anabaena, Merismopedia, Spirogyra, higher plant material, rotifers, Ostracodes, Chironomid larvae and pupae, Choaborus larvae, Odonata, Povilla, Insect remains, Caridina, fish eggs and fish. Eight trophic groups were identified from thes food items ingestes. These included detritivores, algae eaters, higher plant eaters, zooplanktivores, insectivores, molluscivores, prawn eaters, paedophages and piscivores. Trophic diversity by number of trophic groups was highest in Lake Kyoga (6) followed by lakes Kayugi, Nabugabo, River Nile and Mburo (3) and the lowest number was recorded in kachera (2).

A study of Rastrineobola argentea in the Ugandan lakes

Increased stocks of mukene Rastrineobola argentea and the subsequent interest in its fishery on Lake Victoria has been attributed to the poor performance of the endemic fishery as a result of introductions into this lake of foreign fish species Lates niloticus and Oreochromis niloticus. R. argentea now remains the only endemic fish species of economic importance ranking second to the Nile perch in this lake. Despite this importance, biological information on the species and knowledge of its fishery is scanty. Preliminary observations on the species in the Ugandan waters indicate that R. argentea feeds mainly on zooplankton (copepods) during daylight hours. Small quantities of aquatic insect larvae/pupae (chironomids and chaoborids) are also eaten mainly at night. These fishes breed just after the rainy seasons and the young eventually mature at between 43-44 mm standard length. Growth and population parameters show a rate of growth (K) of 0.92 with L of 64.5 mm S.L. Natural mortality (M) is given at 2.371 and total mortality (2) of 3.594. Two mesh size nets 10 and 5 mm are in use in the lake. The smaller mesh size which is more preferred by the artisanal fishermen however tends to capture many immature fishes. There is therefore need for a unified lakewide data collection on the species and its fishery in order to obtain more reliable biological information necessary proper management of this fast developing fishery.

La peche dans le fleuve Niger

The fish production of the River Niger can best be estimated from a country by country evaluation of the tonnage exported and that consumed locally. All exported and some locally consumed fish are preserved by smoking or sun drying, a process which entails a loss of weight. Coefficients to correct for this of between 2.6 to 4 have been calculated depending on the type of product. A further loss occurs due to handling and to insect attack, which may account for up to 40% of the production. Taking the above factors into account the productions estimated for the various countries of the Niger River basin are as follows: Guinea (3,600 t), Mali (90,000 t), Upper Volta and Ivory Coast (negligible), Niger (5,200 t), Dahomey (1,200 t), Nigeria (25,000 t), Cameroon (3,000 t). A total production of 128,000 t is, therefore, obtained for the basin as a whole, excluding the Kainji Reservoir. At this level of production, there have been no intimations of overfishing from any part of the basin, and there is unanimity that fishing could be intensified. On the basis of the estimates of existing production and local estimates of potential production it is possible that up to 200,000 t of fish could be produced annually from the basin as a whole.

Mass rearing of Aphidius gifuensis (Hymenoptera : Aphidiidae) for biological control of Myzus persicae (Homoptera : Aphididae)

The green peach aphid, Myzus persicae, is a major pest of tobacco, Nicotiana tabacum, in Yunnan province, China, where its control still depends on the use of insecticides. In recent years, the local government and farmers have sought to improve the biological control of this tobacco pest. In this paper, we present methods for mass rearing Aphidius gifuensis, a dominant endoparasitoid of M. persicae on tobacco plants in this region. The tobacco cultivar K326 (N. tabacum) was used as the host plant and M. persicae as the host insect. In the greenhouse, we collected tobacco seedlings for about 35 days (i.e., until the six-true-leaf stage), transferred them to 7.5-cm diameter pots, and kept these plants in the greenhouse for another 18 days. These pots were then transferred to an insectary-greenhouse, where the tobacco seedlings were inoculated with five to seven wingless adult M. persicae per pot. After 3 days, the infested seedlings were moved to a second greenhouse to allow the aphid population to increase, and after an additional 4 +/- 1 days when 182 +/- 4.25 aphid adults and nymphs were produced per pot, they were inoculated with A. gifuensis. With this rearing system, we were able to produce 256 +/- 8.8 aphid mummies per pot, with an emergence rate of 95.6 +/- 2.45%; 69% were females. The daily cost of parasite production (recurring costs only) was US$ 0.06 per 1000 aphid mummies. With this technique, we released 109 800 parasitoids in 1998, 196 000 in 1999, 780 000 in 2000, and 5 600 000 in 2001 during a 2-month period each year This production method is discussed with respect to countrywide usage in biological control and integrated control of M. persicae.

In vivo dynamics of the internal fibrous structure in smooth adhesive pads of insects.

Many insects with smooth adhesive pads can rapidly enlarge their contact area by centripetal pulls on the legs, allowing them to cope with sudden mechanical perturbations such as gusts of wind or raindrops. The short time scale of this reaction excludes any neuromuscular control; it is thus more likely to be caused by mechanical properties of the pad's specialized cuticle. This soft cuticle contains numerous branched fibrils oriented almost perpendicularly to the surface. Assuming a fixed volume of the water-filled cuticle, we hypothesized that pulls could decrease the fibril angle, thereby helping the contact area to expand laterally and longitudinally. Three-dimensional fluorescence microscopy on the cuticle of smooth stick insect pads confirmed that pulls significantly reduced the fibril angle. However, the fibril angle variation appeared insufficient to explain the observed increase in contact area. Direct strain measurements in the contact zone demonstrated that pulls not only expand the cuticle laterally, but also add new contact area at the pad's outer edge.

Task-level control of the lateral leg spring model of cockroach locomotion

The Lateral Leg Spring model (LLS) was developed by Schmitt and Holmes to model the horizontal-plane dynamics of a running cockroach. The model captures several salient features of real insect locomotion, and demonstrates that horizontal plane locomotion can be passively stabilized by a well-tuned mechanical system, thus requiring minimal neural reflexes. We propose two enhancements to the LLS model. First, we derive the dynamical equations for a more flexible placement of the center of pressure (COP), which enables the model to capture the phase relationship between the body orientation and center-of-mass (COM) heading in a simpler manner than previously possible. Second, we propose a reduced LLS "plant model" and biologically inspired control law that enables the model to follow along a virtual wall, much like antenna-based wall following in cockroaches. © 2006 Springer.

Lift and the leading edge vortex

Leading edge vortices are considered to be important in generating the high lift coefficients observed in insect flight and may therefore be relevant to micro-air vehicles. A potential flow model of an impulsively started flat plate, featuring a leading edge vortex (LEV) and a trailing edge vortex (TEV) is fitted to experimental data in order to provide insight into the mechanisms that influence the convection of the LEV and to study how the LEV contributes to lift. The potential flow model fits the experimental data best with no bound circulation, which is in accordance with Kelvin's circulation theorem. The lift-to-drag ratio is well approximated by the function 'cot α' for α > 15°, which supports the tentative conclusion that shortly after an impulsive start, at post-stall angles of attack, lift is caused non-circulatory forces and by the action of the LEV as opposed to bound circulation. Copyright © 2012 by C. W. Pitt Ford.

Average corotation of line segments near a point and vortex identification

An easy-to-interpret kinematic quantity measuring the average corotation of material line segments near a point is introduced and applied to vortex identification. At a given point, the vector of average corotation of line segments is defined as the average of the instantaneous local rigid-body rotation over "all planar cross sections" passing through the examined point. The vortex-identification method based on average corotation is a one-parameter, region-type local method sensitive to the axial stretching rate as well as to the inner configuration of the velocity gradient tensor. The method is derived from a well-defined interpretation of the local flow kinematics to determine the "plane of swirling" and is also applicable to compressible and variable-density flows. Practical application to direct numerical simulation datasets includes a hairpin vortex of boundary-layer transition, the reconnection process of two Burgers vortices, a flow around an inclined flat plate, and a flow around a revolving insect wing. The results agree well with some popular local methods and perform better in regions of strong shearing. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Functionally different pads on the same foot allow control of attachment: stick insects have load-sensitive "heel" pads for friction and shear-sensitive "toe" pads for adhesion.

Stick insects (Carausius morosus) have two distinct types of attachment pad per leg, tarsal "heel" pads (euplantulae) and a pre-tarsal "toe" pad (arolium). Here we show that these two pad types are specialised for fundamentally different functions. When standing upright, stick insects rested on their proximal euplantulae, while arolia were the only pads in surface contact when hanging upside down. Single-pad force measurements showed that the adhesion of euplantulae was extremely small, but friction forces strongly increased with normal load and coefficients of friction were [Formula: see text] 1. The pre-tarsal arolium, in contrast, generated adhesion that strongly increased with pulling forces, allowing adhesion to be activated and deactivated by shear forces, which can be produced actively, or passively as a result of the insects' sprawled posture. The shear-sensitivity of the arolium was present even when corrected for contact area, and was independent of normal preloads covering nearly an order of magnitude. Attachment of both heel and toe pads is thus activated partly by the forces that arise passively in the situations in which they are used by the insects, ensuring safe attachment. Our results suggest that stick insect euplantulae are specialised "friction pads" that produce traction when pressed against the substrate, while arolia are "true" adhesive pads that stick to the substrate when activated by pulling forces.