Genetic specificity of a plant-insect food web: Implications for linking genetic variation to network complexity.

Theory predicts that intraspecific genetic variation can increase the complexity of an ecological network. To date, however, we are lacking empirical knowledge of the extent to which genetic variation determines the assembly of ecological networks, as well as how the gain or loss of genetic variation will affect network structure. To address this knowledge gap, we used a common garden experiment to quantify the extent to which heritable trait variation in a host plant determines the assembly of its associated insect food web (network of trophic interactions). We then used a resampling procedure to simulate the additive effects of genetic variation on overall food-web complexity. We found that trait variation among host-plant genotypes was associated with resistance to insect herbivores, which indirectly affected interactions between herbivores and their insect parasitoids. Direct and indirect genetic effects resulted in distinct compositions of trophic interactions associated with each host-plant genotype. Moreover, our simulations suggest that food-web complexity would increase by 20% over the range of genetic variation in the experimental population of host plants. Taken together, our results indicate that intraspecific genetic variation can play a key role in structuring ecological networks, which may in turn affect network persistence.

Effects of zinc acquired through the plant-aphid-ladybug food chain on the growth, development and fertility of Harmonia axyridis.

Heavy metal pollution is an increasingly serious problem in agricultural ecosystems. Zinc accumulation in the food chain may harm the physiological functions of organisms, including herbivorous and predatory insects. Its effects on development and reproduction in Harmonia axyridis are largely unknown. In this study, five Zn solutions (25, 50, 100, and 150 mg/kg) plus control (0 mg/kg) were used to treat broad beans and to water the resulting seedlings. Aphids fed on these seedlings were eaten by H. axyridis ladybugs. Zn accumulation was found at all three trophic levels. Compared with the control group, ladybugs in the 25, 50, and 100 mg/kg groups had significantly reduced weight gain from the 4th instar to adulthood. Pupae and larvae (instars 1-4) in the 150 mg/kg group had the lowest survival of any group; pupal mortality in the 100 mg/kg group was significantly higher than that in the control group. Under Zn stress, female adults had inhibited expression of Vg1, Vg2 and VgR, reducing egg production and hatchability. Zn thus negatively affected their fertility. These results provide a theoretical basis for future exploration of soil heavy metal pollution impacts in ecosystems.

Food-borne parasitic zoonoses in China: perspective for control.

Food-borne parasitic zoonoses (FBPZs) cause death and serious diseases in humans and animals worldwide, and are of both public health significance and socioeconomic importance. The FBPZ problem is severe in mainland China, where approximately 150 million people are suffering from FBPZs and more people are at risk. Here, the current status of the FBPZ problem in mainland China is reviewed and strategies and measures for effective control of FBPZs are proposed. Major parasitic zoonoses transmitted through consumption of infected or contaminated meat, fish, plants and/or water will be discussed.

Conditions under which plants help herbivores and benefit from predators through apparent competition.

Leaf domatia are tiny structures in leaf vein axils that are typically inhabited by predatory and fungivorous mites. A recent article reported plant domatia specifically suited for herbivorous mites, which seems paradoxical, since the plant is thus supporting a natural enemy that can harm itself. The authors claimed that domatia are created to promote herbivorous mites as "fodder" for predatory mites that attack another herbivorous mite damaging the plant, and that the relationship among the plant, the fodder mite, and the predatory mite constitute a multiway mutualism because all three species benefit from the interaction. I formulate this system using two simple mathematical models of apparent competition, which differ in how domatia are modeled, and then assess when it is advantageous for the plant to create such space for a natural enemy. As a necessary condition for mutualism, the product of reproductive efficiency and nutritious value of the fodder prey should exceed that of the pest prey. This condition is also sufficient, if the direct costs for making the structure of domatia are negligible. If there are significant costs, however, the condition is broader for predators with lower reproductive efficiency and higher mortality, and for non-fodder prey with high consumption rate and low predation rate. I suggest that creating domatia is more effective when predators are less prolific and non-fodder prey are more severe as pests. Finally, I discuss how this mathematical model can apply to a wider range of tritrophic mutualistic relationships such as those among plants, aphids, and ants.

Seroprevalence of fasciolosis and the difference of fasciolosis between rural area and city center in Isparta, Turkey.

OBJECTIVE: To investigate the seroprevalence of fasciolosis and the possible causes of differences between rural and city center. METHODS: We undertook a multi-stage sampling analysis of data from Isparta, Turkey, between March and June 2004. Four hundred and fifteen individuals participants from Isparta center and 171 from Asagi Gokdere village were included in the study. Fasciola hepatica (F. hepatica) specific antibodies were analyzed using excretory-secretory (ES)-enzyme-linked immunosorbent assay (ELISA) method. RESULTS: Fasciola hepatica antibodies were detected as positive in 10 (2.4%) of 415 people whose sera were collected from the city center and 16 (9.3%) of 171 people from Asagi Gokdere village. The positivity rates between village and city center were found statistically significant. A statistical difference was noted for fasciolosis positivity between individuals who have ingested water cress and who have not. Fasciolosis was not detected in the individuals who used to wash vegetables with water containing vinegar. CONCLUSION: Most of the patients in this region reported consumption of uncooked or unwashed water cress. Watering channel is one of the major risk factors of fasciolosis. Therefore, it is essential to determine the watering systems in this region. Moreover, ES-ELISA would be useful in investigating the laboratory diagnosis of fasciolosis.

Fasciolopsiasis: a first case report from Malaysia.

Fasciolopsiasis is a disease caused by the largest intestinal fluke, Fasciolopsis buski. The disease is endemic in the Far East and Southeast Asia. Human acquires the infection after eating raw freshwater plants contaminated with the infective metacercariae. There has been no report of fasciolopsiasis either in man or in animal in Malaysia. We are reporting the first case of fasciolopsiasis in Malaysia in a 39-year-old female farmer, a native of Sabah (East Malaysia). This patient complained of cough and fever for a duration of two weeks, associated with loss of appetite and loss of weight. She had no history of traveling overseas. Physical examination showed pallor, multiple cervical and inguinal lymph nodes and hepatosplenomegaly. Laboratory investigations showed that she had iron deficiency anemia. There was leukocytosis and a raised ESR. Lymph node biopsy revealed a caseating granuloma. Stool examination was positive for the eggs of Fasciolopsis buski. The eggs measure 140 x 72.5 microm and are operculated. In this case, the patient did not present with symptoms suggestive of any intestinal parasitic infections. Detection of Fasciolopsis buski eggs in the stool was an incidental finding. She was diagnosed as a case of disseminated tuberculosis with fasciolopsiasis and was treated with antituberculosis drugs and praziquantel, respectively.

Intraocular fascioliasis: a case report.

We report the case of a 28-year-old male who had been ill with headache and motor weakness for a month and developed sudden pain and blindness of the right eye. During ophthalmoscopy, a worm was recognized penetrating the iris, occupying the anterior chamber for a brief period, returning back behind the iris, and leaving corneal edema with hyphyema. Enucleation was performed to prevent the worm's escape from the eye. The enucleated eye revealed areas of a focal degeneration of sclera and intraocular hemorrhage. Microscopic findings of an abrupt tissue defect and few inflammatory reactions in the uvea suggested very recent migration of a moving worm. The flatworm detected in the anterior chamber was identified to be a juvenile Fasciola sp. This case is presumed to be the first case of intraocular fascioliasis reported in the literature.

Influence of a short exposure to teflubenzuron residues on the predation of thrips by Iphiseius degenerans (Acari: Phytoseiidae) and Orius laevigatus (Hemiptera: Anthocoridae).

A short duration (24h) leaf-disc bioassay was used to determine the effects of teflubenzuron residues on the predation levels of two predators, Iphiseius degenerans (Berlese) and Orius laevigatus (Fieber), foraging on nymphs of two species of thrips, Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouche), on a range of different species of plant. Teflubenzuron did cause thrips mortality during the 24-h bioassay; it was more active against H haemorrhoidalis than F occidentalis. Teflubenzuron did not cause significant mortality to either species of predator, although on some plants the effectiveness of both predators was reduced in the presence of teflubenzuron.

Unusual snail species involved in the transmission of Fasciola hepatica in watercress beds in central France.

Four freshwater pulmonate species (Lymnaea ovata, L. stagnalis, Physa acuta, Planorbis leucostoma) were living in several watercress beds known for their relationships with human cases of fasciolosis, whereas L. truncatula was never found. The aims of these studies were to determine the prevalence of natural infections with Fasciola hepatica in snails and to verify if these species might ensure the full larval development of this trematode (with cercarial shedding) when they were experimentally subjected to F. hepatica only, or to co-infections with an other trematode species. Investigations were so carried out in six snail populations living in watercress beds (including three for P. acuta) and in four others originating from three brooks or a pond (as controls). Snails naturally infected with F. hepatica were found in two watercress beds inhabited by L. ovata (prevalence of infection: 1.4%) and P. leucostoma (0.1%), respectively. The L. ovata from the watercress bed could be infected at a higher size than those from the control population and the prevalence of this infection was greater in the bed population. Similar findings were noted for L. stagnalis. Despite single or dual infections, the results obtained with the four populations of P. acuta were unsuccessful. In contrast, the co-infections of young P. leucostoma with Paramphistomum daubneyi and F. hepatica resulted in the shedding of some F. hepatica cercariae. According to the authors, the occurrence of fasciolosis in these watercress beds would be the consequence of frequent natural encounters between parasite and snails (L. ovata, L. stagnalis), or of co-infections with P. daubneyi and F. hepatica (P. leucostoma). In watercress beds only colonized by P. acuta, a lymnaeid species would have ensured the larval development of F. hepatica but it would have been eliminated by P. acuta, as this last species was known to be invasive and could colonize open drainage ditches on siliceous soil.

Intake of trichostrongylid larvae by goats and sheep grazing together.

Cashmere goats and Merino sheep were grazed together at 7.5 animals per ha on annual rye grass and clover pasture in southern Victoria, a winter rainfall area. Intake of parasitic larvae was measured in oesophageal extrusa samples collected from 2 animals of each species, 4 times in one week, on 7 occasions between mid-March (autumn) and mid-June (winter). Pasture contamination with larvae was measured at the same times. The number of larvae per kg of green grass was lower than on green clover; the most heavily contaminated portion of the pasture was the mat of dead herbage on the ground. The diet selected by goats contained more green grass and dead herbage and less clover that that of sheep (P < 0.01). Goats ingested 643 infective trichostrongylid larvae per kg dry matter intake (DMI) versus 274 per kg DMI for sheep in autumn, increasing to 1892 versus 1143 in early winter. The heavier trichostrongylid burdens of goats compared with sheep, when grazed together, are due in part to greater rates of infection consequent on different grazing patterns as well as greater susceptibility to infection.

[Stomach ache and fever after consumption of watercress in Turkey: fascioliasis]. / Buikpijn en koorts na consumptie van waterkers in Turkije: fascioliasis.

A 52-year-old woman presented several months after returning from a visit to Turkey with stomach-ache and fever. Laboratory results showed leucocytosis with marked eosinophilia. Furthermore, serum liver enzyme activities were slightly elevated. A CT scan of the abdomen showed several spots which, on a later scan, had migrated. Serologic tests confirmed the clinical diagnosis of fascioliasis. The patient was successfully treated with triclabendazole. Infection presumably occurred after eating watercress which the patient had bought on a market in Turkey.

[Massive hepatobiliary fascioliasis]. / Fasciolosis hepatobiliar masiva.

UNLABELLED: Massive hepatobiliary fascioliasis. Report of two cases. INTRODUCTION: Liver fascioliasis is the most frequent parasitic disease of the biliary tract in Mexico. Massive infestation is common in sheep and bovines and rarely occurs in humans. Only two previous cases of massive fascioliasis has been reported and we present here in two additional cases. Case reports. Both cases presented in alcohol-related liver disease patients who had eaten watercress Nasturium officinalis. Upper abdominal pain, obstructive jaundice, and choledochal dilatation were the salient manifestations. Diagnosis was made by surgical exploration and adult fluke identification. One patient died due to progressive liver failure and the other, is alive and received praziquantel treatment. CONCLUSIONS: Since 1935, approximately fifty cases of massive hepatobiliary fascioliasis have been reported in Mexico, most misdiagnosed as cholelithiasis; however, a history of watercress ingestion has been recorded in most of these cases.

Fascioliasis: 3 cases with three different clinical presentations.

Fascioliasis, which is a zoonotic infestation caused by the trematode Fasciola hepatica (liver fluke), is primarily a disease of herbivorous animals such as sheep and cattle. Humans become accidental hosts through ingesting uncooked aquatic plants such as watercress. It presents a wide spectrum of clinical pictures ranging from fever, eosinophilia and vague gastrointestinal symptoms in the acute phase to cholangitis, cholecystitis, biliary obstruction, extrahepatic infestation, or asymptomatic eosinophilia in the chronic phase. However, it may often be overlooked, especially in the acute phase, because of vague symptoms. As a result of newly introduced serological assays facilitating the diagnosis, there has been an increase in the number of reported cases. Here, we report the clinical and laboratory assessment and therapeutic approach of a series of three cases diagnosed (in order of) one week, three months and one and a half years after presentation of the first symptoms of the disease.

Crystallization of α- and ß-carotene in the foregut of Spodoptera larvae feeding on a toxic food plant.

In the animal kingdom, carotenoids are usually absorbed from dietary sources and transported to target tissues. Despite their general importance, the uptake mechanism is still poorly understood. Here we report the "red crop" phenomenon, an accumulation of α- and ß-carotene in crystalline inclusions in the enlarged foregut of the polyphagous Spodoptera larvae feeding on some potentially toxic plant leaves. The carotene crystals give the insect foregut a distinctive orange-red color. The crystals are embedded in a homogenous lawn of the bacterium Enterococcus casseliflavus, but the carotene seems to be selectively taken from the food plant. Caterpillars which fail to develop these carotene crystals exhibit a high mortality or fail to develop to adulthood. The crystallization of carotene and the enlargement of the foregut thus appears to manifest a multiple-step physiological adaptation of the insects to toxic food plants.

Farmers' perception on the importance of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon.

BACKGROUND: Zonocerus variegatus (Linnaeus, 1758) (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in West and Central Africa. However, its importance in the agricultural production system in Cameroon has not been investigated. The study assesses farmers' perception on the importance of Z. variegatus in the agricultural production systems of the humid forest zone of Southern Cameroon. METHODS: Research was carried out in 5 villages of each of three Agro-Ecological, Cultural and Demographic Blocks (AECD-Blocks) of the Forest Margin Benchmark Area (FMBA). In each village, a semi-structured survey was used; male and female groups of farmers were interviewed separately. RESULTS: Z. variegatus is present throughout the humid forest zone of Southern Cameroon, where it is ranked as the third most economically important insect pest of agriculture. In the farmers' opinion, Z. variegatus is a polyphagous insect with little impact on young perennial crops. The length of the pre-farming fallow does not affect Z. variegatus pest pressure in the following crops. The increased impact of the grasshopper observed today in the fields, compared to what existed 10 years ago is as a result of deforestation and increase in surface of herbaceous fallow. The damage caused by Z. variegatus is higher in fields adjacent to C. odorata and herbaceous fallows than in those adjacent to forests and shrubby fallows. The fight against this grasshopper is often done through physical methods carried out by hand, for human consumption. The farmers highlight low usage of the chemical methods and a total absence of biological and ecological methods. CONCLUSION: Farmers' perception have contributed to understanding the status of Z. variegatus in the humid forest zone of Southern Cameroon. The results are in general similar to those obtained in other countries.

Management of agricultural insects with physical control methods.

Ideally, integrated pest management should rely on an array of tactics. In reality, the main technologies in use are synthetic pesticides. Because of well-documented problems with reliance on synthetic pesticides, viable alternatives are sorely needed. Physical controls can be classified as passive (e.g., trenches, fences, organic mulch, particle films, inert dusts, and oils), active (e.g., mechanical, polishing, pneumatic, impact, and thermal), and miscellaneous (e.g., cold storage, heated air, flaming, hot-water immersion). Some physical methods such as oils have been used successfully for preharvest treatments for decades. Another recently developed method for preharvest situations is particle films. As we move from production to the consumer, legal constraints restrict the number of options available. Consequently, several physical control methods are used in postharvest situations. Two noteworthy examples are the entoleter, an impacting machine used to crush all insect stages in flour, and hot-water immersion of mangoes, used to kill tephritid fruit fly immatures in fruit. The future of physical control methods will be influenced by sociolegal issues and by new developments in basic and applied research.

Do earthworms help to sustain the slug predator Pterostichus melanarius (Coleoptera: carabidae) within crops? Investigations using monoclonal antibodies.

Earthworms provide a major potential source of alternative food for polyphagous predators, such as carabid beetles, that are natural enemies of slugs, aphids and other agricultural pests. Non-pest prey may foster larger numbers of natural enemies, which then help to control pests, or alternatively may help to divert the predators away from pest control. An earthworm-specific monoclonal antibody was developed to study carabid-earthworm interactions in the field and assess the role of earthworms as alternative prey. The antibody could identify as little at 7 ng of earthworm protein in an ELISA, and could detect earthworm remains in the foregut of the carabid beetle Pterostichus melanarius for 64 h after consumption. Thirty-six per cent of field-collected beetles contained earthworm remains. Quantities of earthworm proteins in the beetle foreguts were negatively related to total foregut biomass, suggesting that earthworm consumption increased as total prey availability declined. There was also a negative relationship between foregut biomass and beetle numbers, but both quantities and concentrations of earthworm proteins in beetle foreguts were positively related to beetle numbers. This suggests that as beetle activity-density increased, total prey availability declined, or, as prey availability declined, beetles spent more time searching. In these circumstances, beetles fed to a greater extent on earthworms, an acceptable but nonpreferred food item. Earthworms may, therefore, provide an ideal alternative prey for P. melanarius, helping to sustain it when pest numbers are low but allowing it to perform a 'lying-in-wait' strategy, ready to switch back to feeding on pests when they become available.

[The water-cress pools in connection with cases of human fasciolasis in Limousin, France. Experimental studies of Trematode snails and their biological control (author's transl)]. / Les cressonnières à l'origine de cas de distomatose humaine en Limousin. Etude des Mollusques vecteurs et leur contrôle biologique.

Experimental studies on 16 water-cress pools with cases of human fasciolasis in Limousin were undertaken. Two species of snails, Lymnaea glabra and L. truncatula are here trematode hosts. L. glabra alone lives in 5 pools. The introduction of Zonitoides nitidus -- predatory snail -- without vegetation modification produces a progressive elimination of Lymnaea in 3 years. The author insists on the use of determine the trematode host-aptitude of L. glabra and its limits when the two species -- L. glabra and L. truncatula -- live in the same habitats.

[Fasciola hepatica infestation. Biopathology and new diagnostic and therapeutic aspects]. / Infestación por Fasciola hepatica. Biopatología y nuevos aspectos diagnósticos y terapéuticos.

We present here 6 patients with Fasciola hepatica infection, all from rural origin, and with the risk factors of eating wild watercress. The more common symptoms were: fever (83%), abdominal pain (100%), weight loss (83%) and generalized myalgia and joint pain (67%). All patients presented with an absolute eosinophil count above 1,000 cell/mm3. The diagnosis was established in five cases by means of serologic techniques (haemagglutination) and with direct visualization of adult worms while surgery in one case. A CT abdominal scan was performed in five patients, revealing specific lesions of tissue infiltration in four of them. Praziquantel was used in four patients, achieving clinical cure in three cases. In two patients, bithionol was used, with clinical cure in both cases. We review also some newer diagnostic and therapeutic approaches to this parasitic disease.