Highest Number Of Larvae Research Articles

The First Host Record of Trichinosis in a Red Fox, Vulpes vulpes japonica, from Aomori Prefecture, Northern Honshu, Japan.

A case of wildlife trichinosis was found in a red fox (Vulpes vulpes japonica) captured at Rokkasho, Aomori Prefecture on November 27, 1998. Trichinella larvae were obtained from almost all of the muscle tissues except for the masseter. The highest number of larvae per gram of tissue was found in the muscles of the gluteal region and throat. The lowest number was found in the diaphragm and tongue. Trichina cysts within the muscle fibers had groups of fatty cells at the poles, and minimal tissue reaction was observed around the cyst. No calcification was found in the cyst. These morphological findings suggested that the considerable time had elapsed since the invasion. This is the first case of trichinosis in a red fox in Japan.

Bollworm (Lepidoptera: Noctuidae) Development and Movement on Bacillus thuringiensis-treated Cotton Leaves

Larval mortality, survivorship and movement of the bollworm, Helicoverpa zea (Boddie), on and away from Bacillus thuringiensis-treated cotton leaves were investigated in the laboratory. Bacillus thuringiensis (Costar®, Novartis Crop Protection, Inc; Greensboro, NC) was applied to the upper surface of cotton leaves via a spray table in five concentrations, i.e., 0.0 (control), 0.14, 0.29, 0.58, and 1.15 kg/ha. Three-day-old H. zea larvae were released on treated leaves, kept at 30°C, and transferred to artificial diet after 12, 24, and 48 h. Significantly higher numbers of larvae were found on the lower than upper leaf surface after all three transfer times, but the numbers surviving in all treatments were similar to the control. Larval movement from the leaf to cup surface was significantly higher in B. thuringiensis-treated leaves than in the control. The mortality of larvae that were transferred from leaves to diet at 7 d after treatment was significantly higher in all treatments than in the control and highest at the highest rates (0.58 and 1.15 kg/ha). Data on survival of larvae at different locations suggest that for the first 24 h, the increase in the percentage of larvae on the inner cup surface in B. thuringiensis treatments was not due to larvae that had consumed a lethal dose, but an attempt to avoid the B. thuringiensis on the upper leaf surface. Highest larval weight was recorded in the control for all transfer times. The length of the larval period increased with the B. thuringiensis rate at the 12-h transfer. The pupal weight was reduced at the highest B. thuringiensis rates at the 48-h transfer.

Predators of Mesoplatys ochroptera in sesbania planted-fallows in eastern Zambia

Mesoplatys ochroptera Stal (Coleoptera: Chrysomelidae) is a serious pest of the tropical legume sesbania (Sesbania sesban (L.) Merrill) widely used for soil fertility improvement in southern Africa. Surveys were conducted between October 1997 and June 1999 in order to identify the predators of M. ochroptera in sesbania fallows in eastern Zambia. The Heteroptera Afrius yolofa (Guerin-Meneville), Glypsus conspicuus (Westwood), Macrorhaphis acuta Dallas, Mecosoma mensor (Germar), Rhinocoris segmentarius (Germar), and Deraeocoris ostentans (Stal), the carabid beetle Cyaneodinodes fasciger (Chaudoir), the ants Tetramorium sericeiventre Emery and Pheidole sp., and the lacewing Mallada sp. were recorded as predators of M. ochroptera for the first time. The pentatomid bugs G. conspicuus, M. acuta and M. mensor were the most common predators in sesbania fallows. Adults and the different nymphal stages of the three species preyed on larvae, adults and occasionally on eggs of the beetle. In the insectary, the adults of G. conspicuus, M. acuta and M. mensor consumed a significantly higher number of larvae (p < 0.001) compared to adults of M. ochroptera under both free-choice and no-choice conditions. The voracity of the three species showed a positive response to prey density. The fifth instar nymphs showed variation in daily consumption of larvae, the highest number of prey being consumed two to three days after the fourth molt. These predators also attacked other pests associated with sesbania and crop plants. The potential role of the predators in the natural control of pests in agroforestry systems is discussed, with a review of their prey species.

Feeding behavior of bollworm and tobacco budworm (Lepidoptera: Noctuidae) larvae in mixed stands of nontransgenic and transgenic cotton expressing an insecticidal protein.

Feeding behavior of third-instar bollworm, Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), was observed in pure and mixed stands of nontransgenic and transgenic cotton (BTK), Gossypium hirsutum L., expressing an insecticidal protein CryIA(c) from a bacterium, Bacillus thuringiensis Berliner subsp. kurstaki. Five plant stands composed of BTK and non-BTK plants were evaluated; two pure stands and three mixed stands. Percentage ratios of BTK to non-BTK plants in the stands were 100:0, 75:25, 50:50, 25:75 and 0:100, respectively. In all stands with BTK plants, fewer bollworm and tobacco budworm larvae were found on BTK plants than non-BTK plants 24 h after infestation with third instars. At 48 h, significantly fewer tobacco budworm larvae, but not fewer bollworm larvae, were found on BTK plants. However, the number of larvae of either insect did not increase on non-BTK plants compared with the initial infestation density of three larvae per plant. The number of obacco budworm injured flower buds, and capsules was lower in all plant stands containing BTK plants compared with the pure stand of non-BTK at 48 h after infestation. Higher numbers of larvae on non-BTK plants were possibly the result of larval intoxication, reduced feeding, and increased plant abandonment and death on BTK plants rather than a classical feeding preference. Unexpectedly, the number of flower buds and capsules injured by bollworm and tobacco budworm when averaged per plant for all plants in a stand, differed little among the 75:25, 50:50 and 25:75 plant mixtures. These data suggest that larvae of both species frequently moved among plants, feeding indiscriminately on BTK and non-BTK plants.

Field tests on managing resistance to Bt-engineered plants.

Several important crops have been engineered to express toxins of Bacillus thuringiensis (Bt) for insect control. In 1999, US farmers planted nearly 8 million hectares (nearly 20 million acres) of transgenic Bt crops approved by the EPA. Bt-transgenic plants can greatly reduce the use of broader spectrum insecticides, but insect resistance may hinder this technology. Present resistance management strategies rely on a "refuge" composed of non-Bt plants to conserve susceptible alleles. We have used Bt-transgenic broccoli plants and the diamondback moth as a model system to examine resistance management strategies. The higher number of larvae on refuge plants in our field tests indicate that a "separate refuge" will be more effective at conserving susceptible larvae than a "mixed refuge" and would thereby reduce the number of homozygous resistant (RR) offspring. Our field tests also examined the strategy of spraying the refuge to prevent economic loss to the crop while maintaining susceptible alleles in the population. Results indicate that great care must be taken to ensure that refuges, particularly those sprayed with efficacious insecticides, produce adequate numbers of susceptible alleles. Each insect/Bt crop system may have unique management requirements because of the biology of the insect, but our studies validate the need for a refuge. As we learn more about how to refine our present resistance management strategies, it is important to also develop the next generation of technology and implementation strategies.

Visceral larva migrans: migratory pattern of Toxocara canis in pigs

The migratory pattern of Toxocara canis was investigated following infection of pigs with 60 000 infective eggs. Groups of six pigs were slaughtered at 7, 14 and 28 days after infection (p.i.), and the number of larvae in selected organs and muscles was determined by digestion. A group of uninfected pigs was used as negative controls for blood parameters and weight gain. Toxocara canis migrated well in the pig, although the relative numbers of larvae recovered decreased significantly during the experiment. On day 7 p.i., high numbers of larvae were recovered from the lymph nodes around the small intestine and to some extent also from the lymph nodes around the large intestine, and from the lungs and the liver. On day 14, the majority of larvae were recovered from the lungs and the lymph nodes around the small intestine, and by day 28 p.i. most larvae were found in the lungs. Larvae were recovered from the brain on days 14 and 21, with a maximum on day 14 p.i. No larvae were found in the eyes. Severe pathological changes were observed in the liver and lungs, especially on day 14 p.i.; also, development of granulomas was observed in the kidneys. Finally, a strong specific antibody response towards T. canis L2/L3 ES products was observed from day 14 p.i. until termination of the experiment, and the maximum eosinophil response was observed 14 days p.i. The pig is a useful non-primate model for human visceral larva migrans, since T. canis migrate well and induce a strong immunological response in the pig. However, the importance of the pig as a paratenic host is probably minor, because of the relatively early death of most of the larvae.

Predilection sites of Trichinella spiralis larvae in naturally infected horses.

A total of 120 muscle tissues from three horses naturally infected with Trichinella spiralis were examined. The head was the most infected site. In particular, the muscles harbouring the highest number of larvae were: musculus buccinator (12, 411 and 1183 larvae g-1), the tongue (11, 615 and 1749 larvae g-1), m. levator labii maxillaris (17,582 and 1676 larvae g-1), and the masseter (4.9, 289 and 821 larvae g-1). Compared with the diaphragm, the number of larvae per gram was from 3.5 to 6.8 times higher in the tongue, from 3.5 to 6.5 higher in m. levator labii maxillaris, and from 2.5 to 4.6 higher in m. buccinator. Of the examined muscles, the diaphragm had from the 6th to the 15th highest level of infection (3.1, 166 and 256 larvae g-1). Published data from experimentally infected horses confirm these results, suggesting that efforts to detect predilection sites should focus on the head muscles.

Trichinella spiralis: the infectivity of synchronous newborn larvae of different ages inoculated intraocularly.

Trichinella spiralis infection results in the transformation of muscle cells into a new, non-muscular cell called the nurse cell, and the nurse cell-muscle larva complex is finally created. To investigate whether T. spiralis infectivity is NBL age-dependent, five groups of synchronous newborn larvae (sNBL) were obtained at 1, 9, 24, 48, and 72 h of age and were inoculated into mice by intravenous injection into the retro-orbital venous plexus. When both "young" groups of sNBL (1 and 9 h old) were injected, the highest number of larvae were capable of infecting the muscle cells. The highest infectivity of 80.0 % was observed for 9-h-old sNBL. In older sNBL the infectivity gradually decreased; thus, for 72-h-old sNBL the lowest level - 0.1% - was detected. Therefore, an "age limit" for NBL infectivity in the present study was precisely determined.

COMPETITION AND GENOTYPE-BY-ENVIRONMENT INTERACTION IN NATURAL BREEDING SUBSTRATES OF DROSOPHILA.

Although empirical studies frequently suggest that genotype-by-environment (G X E) interaction can maintain genetic variation, very few data are available to test for the specific conditions necessary for the existence of a protected polymorphism (i.e., the property of persistence of an allele even when initially rare). Drosophila species live in patchy environments and their local population structure may be characterized to some extent by Levene's migration pattern, namely by a single pool of individuals that presumably mate at random and breed on discrete and ephemeral resources. We present here a field experiment that links Drosophila ecology and population genetics, which used the alcohol dehydrogenase (Adh) and α-glycerophosphate dehydrogenase (αGpdh) polymorphic loci in D. melanogaster flies raised from Opuntia ficus-indica fruits (prickly pears). The results show that there is density-dependent mortality in those fruits with a relatively high number of larvae (i.e., selection is "soft") and suggest that there is differential viability for αGpdh genotypes. Additionally, a pattern of G X E interaction for fitness values, which is fully compatible with the theoretical conditions required for the existence of a protected polymorphism, was found after weighting the fitness estimates by the relative contribution that each fruit makes to the total adult population. The strong association between AdhS and αGpdhF alleles suggests that the occurrence of the common cosmopolitan inversion In(2L)t in the population might be responsible for the negative frequency-dependent selection predicted by Levene's model when genetic variation persists in heterogeneous environments.

Vertical migration of nematodes and soil-borne fungi to developing roots of Ammophila arenaria (L.) link after sand accretion

Ammophila arenaria benefits from regular burial of windblown beach sand as it allows escape from soil-borne pathogens (nematodes and fungi). The present study was done to obtain more insight into the timing and order of migration of the soil organisms towards the newly formed roots. Accordingly, plants were grown in non-sterilized root zone soil, buried by 20 cm of beach sand and harvested periodically during one growing season. Plants were buried in November. After 17 weeks, the internodes of the planted seedlings elongated and again 10 weeks later, in May, new roots began to develop. The majority of plant parasitic nematodes remained in the original core until root formation started in the deposited layer. Juveniles of Heterodera spp. successfully infected the roots, formed cysts and produced an offspring in October, resulting in high numbers of larvae at the end of the experiment. In February, at the first harvest of plants, fungi were isolated from soil and buried shoots in the whole deposited layer, although it was still winter. During the growing season a shift in the community of fungi in soil and buried shoots occurred in both the original core and the deposited layer. In both layers, the plant pathogenic fungi were gradually replaced by saprophytes. As all fungal and nematode species were able to colonize the deposited sand layer within one year, we conclude that both fungi and nematodes in the root zone of A. arenaria are very well adapted to sand deposition. Because of the fast migration rate of both pathogenic fungi and parasitic nematodes, the window for A. Arenaria to escape in time from its soil-borne pathogens seems to be narrow.

Quantification of sexual reproduction in the marine benthic hydroid Campanularia everta

Campanularia everta is an epiphytic hydroid that may form dense populations on the macroalga Halimeda tuna. The main objects of this study were to quantify sexual reporduction and estimate sexual reproductive output of this hydroid. Sexual reproduction occurred from mid-October to mid-December 1991 along the Spanish Mediterranean coast. During this period, male and female colonies formed gonangia. Four oocytes mature in each female gonangium, and embryonic development starts probably after internal fertilization occurs. Planulae complete their development within a mucus sheath attached to the top of the gonotheca (acrocyst). Eight successive gonangia with a life-span of ≈1 wk each were formed over a 2 mo period. The fertile period was characterized by high initial production of gonangia followed by a progressive decline resulting from a decrease both in the number of fertile colonies and in the gonangia density of fertile colonies. Annual production was estimated at ≈42000 gonangia m-2, representing 83000 oocytes m-2. The high fertilization rates observed (77 to 100%) yielded a minimum production of 64000 planulae m-2. Reproduction in C. everta is characterized by: (1) a high number of larvae produced m-2; (2) formation and gradual release of larvae throughout the sexual reproduction period; (3) direct formation of planulae with no intermediate medusa stage; (4) low dispersive ability of the planula. All these mechanisms are part of a reproductive strategy designed to ensure the permanence of the population in its habitat.

Trichinella infections in arctic foxes from Greenland: studies and reflections on predilection sites of muscle larvae.

Studies were carried out to determine the predilection sites of Trichinella nativa muscle larvae in arctic foxes (Alopex lagopus) caught in Greenland. The highest number of larvae per gram of tissue was found in the muscles of the eyes and the legs. With regard to predilection sites no significant differences were demonstrated either between age groups or between foxes with high and low total parasite burdens. Predilection sites were comparable with those recorded earlier in experimentally infected caged foxes and in other carnivorous species. Hypotheses on predilection sites of Trichinella muscle larvae are discussed.

Ticks (Acari: Ixodidae) Infesting Wild Birds (Aves) and White-Footed Mice in Lyme, CT

Birds were captured and recaptured (20.8% of 5,297) with Japanese mist nets, and white-footed mice, Peromyscus leucopus (Rafinesque), were caught and recaught (69.1% of 355) with Sherman box traps during the late spring, summer, and early fall from July 1989 through October 1991 to study tick-host relationships in Lyme, CT. Ixodes scapularis Say, a vector of Lyme disease spirochetes, Borrelia burgdorferi sensu stricto Johnson, Schmid, Hye, Steigerwalt & Brenner, infested 803 birds (15.2%) in 36 species and 148 (40.3%) of the mice. This tick dominated both birds (94.4% of 4,065 ticks) and mice (82.6% of 529 ticks). Other ticks that were recovered from birds were Haemaphysalis leporispaustris (Packard) (23 birds in seven species), I. dentatus Marx (34 birds in 14 species), and Dermacentor variabilis (Say) (two birds in two species). The latter was also collected from 12.7% of the 355 mice (n = 92 ticks). Infestations of I. scapularis were high for worm-eating warblers (30.6% of 111), ovenbirds (44.4% of 286), common yellowthroats (27.1% of 188), hooded warblers (35% of 80), Carolina wrens (50.9% of 110), house wrens (21.6% of 102), wood thrushes (23.0% of 867), veeries (32.5% of 246), and American robins (36.2% of 69). Coinfestation by larvae and nymphs of I. scapularis was significantly high for Carolina wrens (35.7% of 56 infested individuals), veeries (27.2% of 80), American robins (29.4% of 25), and common grackle (19.0% of 5), possibly enhancing transmission of B. burgdorferi. Mean crowding on larvae by nymphs, measured by Lloyd's index (1967), was highest for these four species (range 1.19-5.76). Seasonal patterns of infestation for each species of bird can account for much of the differences in degree of coinfestation. High infection rates by B. burgdorferi in larvae removed from some of these birds (14.9-20.0%) were found on those birds with both high numbers of larvae and nymphs. Spirochetemia in most avian hosts may be short and only certain species with concurrent infestations of nymphs and larvae may function effectively as reservoirs.

A Study on the Predilection Sites of Trichinella spiralis Muscle Larvae in Experimentally Infected Foxes (Alopex lagopus, Vulpes vulpes)

Studies were carried out on the predilection sites of Trichinella spiralis muscle larvae in experimentally infected arctic foxes (Alopex lagopus) and silver foxes (Vulpes vulpes) reared in cages. The highest number of larvae per gram tissue was found in the muscles of the legs, eyes, diaphragm, and tongue. The 2 fox species showed no significant differences with regard to predilection sites.

Infestation and pod damage byHelicoverpa armigera(Hubner) on Chickpea(Cicer arietinumL.) in Uganda

Abstract Eight early and five medium maturing chickpea cultivars were evaluated for infestation and pod damage by the podborer, Helicoverpa armigera (Hubner), at Kabanyolo, Uganda, during the short and long rainy seasons of 1990/91. Larvae were found feeding on leaves 2–3 weeks after crop emergence, and three distinct generations were recognized 2–5, 6–11 and 12–15 weeks after emergence. Infestation was higher during the long rainy seasons and on short duration cultivars; the highest number of larvae was on the cultivar Annigeri (1.34/plant) and the lowest on ICC 506 (0.22/plant). On average, the most susceptible cultivars were Annigeri, the Local Check, K 850 (Desai) and ICC 5264‐E10 (Kabuli), while ICC × 790197–25PLB‐12PLB‐3PLB‐BPLB, ICC × 780286–5PLB‐2PLB‐2EB, ICC × 790197–23PLB‐11PLB‐2EB and ICC 506 were the least infested. On most cultivars, fewer larvae were found but highest pod damage was recorded during the short rains. Pod damage ranged from 8.0% to 44.1 %, with Annigeri, ICC 4935‐E2793 and ICC 5264‐E10 having least damage, and the Local Check, ICC × 73008–8 and ICC 506 having the most damage. The significant cultivar‐season interaction explains the observed difference in relative pod damage among cultivars in this study compared with that reported from ICRISAT.

Comparing the Applicability of Weight-Length Relationships, the Relative Condition Index and Morphometric Criteria to Assess Larval Condition: A Test Case with Striped Bass

We compared the applicability of using a weight-length relationship, the relative condition index (Kn) and morphometric criteria to provide insight on the nutritional condition and recruitment potential of larvae of the striped bass Morone saxatilis collected in the Potomac River, MD in 1980-1982 and 1986. Morphometric data indicate that relatively high numbers of larvae In poor condition were present In samples taken prior to mid-May In all years except 1986, but especially In 1980 and 1981. Results of ANCOVA on a subset of data from the first 2 weeks of May In each of the 4 years Indicated significant differences in weight-length regression equations. Larvae In the 1980 and 1981 samples were in poorer condition than in 1982 and 1986, based on regressions coefficients. Estimates of relative condition (Kn) were high in all years except 1986. The morphometric criteria and the regression parameter estimates concurred with an Index of striped bass year class strength, but only after a careful consideration of the assumptions of those condition indices, requiring a reduction in sample size that excluded larger larvae (> 12 mm, morphometric criteria) or averaging data over several larval cohorts (regression parameters).

Effects of stone topography on abundance of net-building caddisfly larvae and arthropod diversity in an upland stream

We investigated whether small pits on the surfaces of stream stones affected abundances of net-spinning, hydropsychid larvae (Trichoptera) and species diversity in the Acheron River, southeastern Australia. On stream stones, nets occurred more often in small (at least 5 mm width) pits than expected by chance. However, proportionately high numbers of pits were not associated with high abundances of either of two species of hydropsychid larvae (both Asmicridea spp). A colonization experiment, using bricks with 0, 4, 12 or 30 small (diam. 5.5 mm) and large (13 mm) pits drilled into the top surfaces, showed that numbers of nets were related to numbers of pits. Small pits were preferred over large ones and the pits, as a group, were occupied almost entirely by late instars of both species. However, only Asmicridea sp. 1 was more abundant on pitted bricks; Asmicridea sp. 2 showed no response. The differences between the species, and between the stone and brick results, can be explained by different proportions of late instars in the samples. Many I instars probably did not make nets. Hence, higher numbers of larvae on pitted surfaces is expected only when late instars are relatively frequent, as was true for Asmicridea sp. 1 on bricks. There were no effects of pits per se or increased numbers of hydropsychid nets on species diversity or the abundances of other common species. These results contrast with those of other studies, which found stone topography or hydropsychid nets to increase species diversity on stones.

Colonization of Perspex Strips by Larvae of Austrosimulium-Bancrofti (Taylor) Near Willawarin, Nsw

A total of 14 113 larvae of the taxon Austrosimulium bancrofti (Taylor) was collected from perspex strips placed in the MacLeay River. The method of multiple mixture modelling separated larvae into seven instars. Highest numbers of instar III and fewest of instar VII were collected. Significant effects influencing colonisation of the perspex strips were incorporated into a statistical model. This permitted generation of fitted estimates of the number of larvae colonising strips under defined conditions. Fitted captures indicated that higher numbers of larvae colonised strips with increasing water depths (7 less-than-or-equal-to X less-than-or-equal-to 46 cm) and when there was no vegetation beneath the strips. Strip texture, quadratic terms for distance from one river bank and their interaction significantly influenced numbers collected. Fitted estimates demonstrated fewest larvae colonised strips in midstream but this decline was most distinct for the smooth strips. Quadratic terms for water velocity and their interaction with strip thickness also influenced larval colonisation. Fitted estimates were highest when water velocity was in the range 1.05-1.25 m s-1 for each strip thickness.

Experimental infection of mice with Toxocara canis larvae obtained from Japanese quails

The migration and distribution of Toxocara canis larvae in the tissues of Japanese quails, infected orally with 5 × 10 3 infective eggs, were studied, as well as the re-infectivity of these larvae in mice, inoculated with 50 larvae obtained from the liver of these quails. Post-infection, the highest concentrations of larvae were found to be present in the liver of quails while only a few migrated to other tissues like lungs, heart, muscle and brain. The migration and distribution of the larvae in the tissues of mice were studied by necropsy on days 6 and 12 postinfection. On both days the highest number of larvae, 11 and 10, were recovered from the carcase followed by six and seven from the leg muscles and four and eight from the brain, respectively. A few larvae were recovered from the liver, lungs and viscera. This implies that the larvae had a special affinity for the muscle and brain tissue of mice, unlike in the quails. The role of these larvae in relation to paratenism is discussed.

The effect of the bont tick (Amblyomma hebraeum) on the weight gain of Africander steers.

The effects of the bont tick Amblyomma hebraeum on the productivity of cattle need to be quantified in order to design economically optimal control programs. Liveweight gains (LWGs) of three groups of Africander steers, maintained in the same pasture and exposed to zero, medium or high numbers of larvae, nymphs and adults of the tick, were measured. Larvae and nymphs had no significant effect on LWG but adults had a large, statistically significant effect (P less than 0.05). The tick-free group had an average LWG of 20 kg more than the heavily infested group after 3.5 months. No mortality was recorded from ticks or tick-borne diseases during the experiment. There was no relationship between the number of engorging adult female ticks counted and loss of LWG of individual animals. The latter suggests that exposure to ticks as well as engorgement by female ticks causes losses. The loss per adult female that completed engorgement was estimated, by relating the LWGs of individual animals to their tick infestations, to be 4 +/- 2 g per adult female tick. An alternative estimate, made by comparing the average LWG and tick infestations of each treatment group, was equal to 10 +/- 4 g. This latter estimate includes the effect of challenge (and rejection) as well as tick feeding and so was accepted as giving the best estimate. Screw-worm fly (Chrysomya bezziana) struck an average of 7.5% of the cattle infested with ticks in any week but the effects on the productivity of the cattle were minimized by immediate treatment. There was a significant, positive correlation between the incidence of screw-worm fly strike and the numbers of adult ticks counted on the experimental animals. The results provide data for calculating losses caused by A. hebraeum in different parts of its geographical range.