Genetic divergence in Northamerican freshwater planarians of the Dugesia dorotocephala group (Turbellaria, Tricladida, Paludicola)

The genetic differentiation between the members of the Dugesia (Girardia) dorotocephala group was analyzed by means of multilocus electrophoresis, and comared to that of another planarian secies, D. tahitiensis, also belonging to the subgenus Girardia. The species examined were: D. dorotocephala s.s (2n = 16), D. arizonensis (2n = 8), D. jenkinsae (2n = 8), and the above mentioned D. tahitiensis (2n = 16). The former three species inhabit North America, and show different proportion of fissiparous and sexual individuals; the latter species inhabits Polynesia and is fully asexual. A total of 11 enzyme loci were genetically analyzed: Mdh-1, Mdh-2, Zdh-1, Idh-2, G3pdh, Got-1, Ck, Pgm-2, Ada, Mpi, and Gpi. Low values of observed mean heterozygosity per locus (Ho) were found in the populations studied, ranging from 0 to 0.18 (average 0.08. In asexual populations (except that of D. tahitiensis) fixed heterozygosity was observered in all the individuals for 1 or 2 loci. The genetic divergence between the species examined is very high, with many loci showing discriminating alleles in different taxa (Nei's genetic distance varies from 0.871 to 1.759). The populations of D. dorotocehala s.s., on the contrary, appear to be genetically quite homogenous average D= 0.019), and the genetic distance values are apparently unrelated to their geographic location and to their way of reproduction. The genetic distance between D. tahitiensis, a species not included in the D. dorotocephala group and D. dorotocephala s.s. is 1.314 and hence similar to the D value between two members of;he dorotocephala group: D. dorotocephala and D. jenkinsae (D = 1.303). The genetic relationships among the populations studied were established by UPGMA cluster analysis and multidimensional scaling. The descendence of the North American species with 2n = 8 from a dorotocephala-like ancestor with 2n = 16 is considered. It is suggested that the latter, as well as a tahitiensis-like line, also having 2n = 16, have originated from a common ancestor by geographic isolation.     

Abnormality in the fissioning control of a strain of asexual Dugesia dorotocephala found near Fort Collins,Colorado

Asexual Dugesia dorotocephala, collected from a new site several miles northwest of Fort Collins, Colorado, appeared similar, at the time of collection, to ones collected from other sites in the same general locale. However, these exhibited marked differences in the more crowded conditions of laboratory culture: abnormally long, 30–50 mm specimens, seemingly unable to fission, developed. Since previous studies of asexual D. dorotocephala had revealed an inhibitory effect of cohorts on fissioning (Best et al., 1969, 1974, 1975; Pigon et al., 1974), experiments were conducted with this new strain to ascertain the effect of population density (group size) on fissioning incidence. Results are described which show that this inhibitory effect of cohorts on fissioning is exaggerated in this new strain.     

Host Range of Mycoleptodiscus terrestris, a Microbial Herbicide Candidate for Eurasian Watermilfoil, Myriophyllum spicatum

A native strain of the fungal plant pathogen Mycoleptodiscus terrestris is capable of causing under experimental conditions necrotic shoot lesions and a generalized decline and disintegration of Eurasian watermilfoil (Myriophyllum spicatum), an exotic submerged aquatic weed in North America. The potential of this fungus to cause disease on nontarget plants was evaluated on 33 species and cultivars in 11 families. The nontarget selection, intended as a Tier I group, was biased toward probable suscepts consisting of submerged, floating, and emergent aquatic species and terrestrial crop plants. The plants were exposed to the fungal mycelium formulated in alginate beads. Pathogenicity rather than phytotoxicity was the primary mode of attack by the fungus. Of the 16 nontarget aquatic species tested, the fungus was pathogenic to Hydrilla verticillata (hydrilla), Myriophyllum aquaticum (parrotfeather), and Ceratophyllum demersum (coontail), but only in hydrilla did it cause plant mortality comparable to that in Eurasian watermilfoil. The remaining 13 submerged, floating, and emergent aquatic species were unaffected. Of the 17 terrestrial species screened, none was significantly affected by the fungus in germination studies, but postemergent disease symptoms developed on seedlings of 10 species. Four of the 10, Medicago sativa (alfalfa), Lotus corniculatus (birdsfoot trefoil), Trifolium hybridum (alyce clover), and T. repens (white clover), developed disease affecting 26-50% of their tissues. Thus, this host range testing scheme, based on the concept of screening plants under the maximum hazard potential, helped to identify susceptible species. Nonetheless, it exaggerated the nontarget risk due to the small number of host species tested. Screening a taxonomically diverse and larger selection of plants as well as testing under conditions of less severe exposure to the fungal inoculum are necessary to obtain a more realistic view of the host range than presently indicated.     

Invertebrate Assemblages Associated with Root Masses of <Emphasis Type="Italic">Eichhornia crassipes</Emphasis> (Mart.) Solms-Laubach 1883 in the Alvarado Lagoonal System,Veracruz, Mexico

This paper describes the spatial and temporal variation of aquatic invertebrate assemblages associated with root masses of Eichhornia crassipes collected at 12 sites between July 2000 and June 2002 in the Alvarado Lagoonal System (ALS), Veracruz, Mexico. A total of 96 taxa were registered; acari showed the highest species richness with 15 taxa followed by decapods (14), mollusks (12), amphipods (9), and isopods (7). Freshwater organisms represented 44% of the total taxa, 53% belonged to estuarine taxa, and marine taxa 3%. The isopod Munna sp. was the dominant taxon throughout the entire study period, followed by Ephemeroptera, Hyalella azteca, Chydorus sp., Physella sp., Podura aquatica, and Fossaria sp. during the low salinity period (July–September 2001, 1.6–3.8 psu), and Neritina virginea, Cassidinidea ovalis, Macrobrachium acanthurus and Melita longisetosa during the high salinity period (March–May 2001 9.7–12.7 psu and April–May 2002, 8.2–8.9 psu). A spatial gradient of species richness and diversity was registered for the freshwater organisms. Additionally, the spatial and temporal patterns of invertebrate densities could be explained due to the movements of Eichhornia crassipes mats through the system, and the temporal variation of environmental variables such as salinity, dissolved oxygen, and turbidity.     

The effects of group size on per capita ingestion in flatworms

1. We evaluated the effect of group size on the per capita ingestion rates of three species of flatworm, two of which actively group with conspecifics (Dugesia tigrina, D, dorotocephala) and employ mucus to capture prey, and a third species (Mesostoma ehrenbergii) that does not actively group but does use mucus to capture prey. 2. As flatworm group size increased, daily per capita ingestion first increased and then decreased for D. tigrina and D. dorotocephala. In the case of D. tigrina this pattern was observed even at low predator densities. Ingestion rates of M. ehrenbergii were largely unaffected by group size. 3. Results suggest that the observed changes in per capita ingestion rates with changes in group size previously reported for D. tigrina are related to their tendency for active grouping and are not directly a consequence of prey capture technique or experimental design. 4. We argue that freshwater triclads in general, and D. tigrina in particular, represent an ideal model system for the development and testing of group foraging theory.     

Aquatic amphipods (Crustacea: Amphipoda: Crangonyctidae) in three pieces of Baltic amber

Three amber pieces containing crangonyctid aquatic amphipods are examined. One of the specimens appears to have the urosome unsegmented, and uropods 3 shortened, resembling extant Synurella sp. In another amber piece there are eight specimens of Palaeogammarus sp. which look as if they had been dry prior to becoming embedded in the resin.     

The feeding behaviour of New Zealand Dolomedes species (Araneae: Pisauridae)

Abstract

The prey spectrum and predatory behaviour of Dolomedes sp. (‘D. III’), D. aquaticus, and D. minor are described from a series of field and laboratory investigations, the former made around Nelson and on Banks Peninsula, Canterbury, during summer months. All species are large, robust spiders that capture prey by directly seizing it in their mouthparts, not using silk at any stage of predation. Adult aquatic insects are their main prey, but these are available only irregularly during their activity period (night-time), and the spiders are opportunistic in their feeding habits. They will eat virtually any available small animal, and at least the largest species, D. III, is able to capture and ingest small fishes. Dead as well as live organisms are taken. Furthermore, the spiders are capable of feeding infrequently; when feeding on small prey organisms they may capture several sequentially, to increase the size of the meal. Live prey is caught while it is in flight, or on the ground, or at the water surface (rarely submerged), and is detected primarily by touch and airborne sound; vision is unnecessary for normal predation. Prey is captured very rapidly, even though this may initially involve a dash of up to 40 cm across the water surface to locate the organism. Stages in the behaviour of an active spider, from waiting for prey to grooming after ingestion, are described.     

The biological activities of prothioconazole enantiomers and their toxicity assessment on aquatic organisms

Chiral fungicide prothioconazole has a wide range of antifungal spectrum; however, little research has been conducted to evaluate prothioconazole on an enantiomeric level. Five target pathogens and three common aquatic organisms were tested for the enantioselective bioactivity and toxicity of prothioconazole in this work. The antifungal activity of the enantiomers against wheat phytoalexin, rice blast fungus, exserohilum turcicum, Alternaria triticina, and Fusarium avenaceum was determined, and it was found that (?)‐prothioconazole were 85 to 2768 times more active than (+)‐prothioconazole toward these target organisms. In order to reflect the risk to aquatic ecosystem, the acute toxicity of the enantiomers to Daphnia magna, Chlorella pyrenoidosa, and Lemna minor L. was assessed. It was observed that the toxicity of (?)‐prothioconazole to D. magna was 2.2 times higher than (+)‐prothioconazole, but it was lower to C. pyrenoidosa and L. minor L. The toxicities of (+)‐enantiomer and (?)‐enantiomer to D. magna and C. pyrenoidosa were synergy, indicating that the racemate had higher threat to the organisms. It could be concluded that the effects of prothioconazole on target organisms and the acute toxicity to nontarget species were enantioselective with (?)‐enantiomer possessing higher efficiency and lower toxicity. Such enantiomeric differences should be taken into consideration when assessing the performance of prothioconazole.     

Marine Glutathione <Emphasis Type="Italic">S</Emphasis>-Transferases

The aquatic environment is generally affected by the presence of environmental xenobiotic compounds. One of the major xenobiotic detoxifying enzymes is glutathione S-transferase (GST), which belongs to a family of multifunctional enzymes involved in catalyzing nucleophilic attack of the sulfur atom of glutathione (γ-glutamyl-cysteinylglycine) to an electrophilic group on metabolic products or xenobiotic compounds. Because of the unique nature of the aquatic environment and the possible pollution therein, the biochemical evolution in terms of the nature of GSTs could by uniquely expressed. The full complement of GSTs has not been studied in marine organisms, as very few aquatic GSTs have been fully characterized. The focus of this article is to present an overview of the GST superfamily and their critical role in the survival of organisms in the marine environment, emphasizing the critical roles of GSTs in the detoxification of marine organisms and the unique characteristics of their GSTs compared to those from non-marine organisms.     

Analysis of Initial Fouling Process in Coastal Environment: Effects of Settlement, Attachment, and Metamorphosis Promoters

Effects of lumichrome, l-tryptophan, and curcumin on fouling organisms were examined on panels immersed in a near-shore aquatic environment. These products showed effective action in aquariums in preliminary screening tests for promoting different steps of fouling. Lumichrome showed metamorphosis-inducing activity for ascidian larvae (Halocynthia), l-tryptophan was a settlement-inducer for larvae of barnacles (Balanus), and curcumin showed attachment-promoting activity on the blue mussel (Mytilus). In order to establish that these tests are helpful in screening actual fouling or antifouling compounds, we examined the action of these three compounds in a coastal environment by following the first steps of biofouling, that is, by studying the quantity of chlorophyll, the number of bacterial cells, and the larvae settled. These experiments on the seashore indicated that these compounds did not act as promoters for the target organisms; however, they did show promoting effects on some nontarget organisms. Received September 30, 1998; accepted September 28, 1999     

Environmental stimulants to asexual reproduction in the planarian,Dugesia dorotocephala

Studies of environmental factors that stimulate asexual reproduction in the planarian,Dugesia dorotocephala (Woodworth), feeding onCulex pipiens quinquefasciatus Say revealed that unchlorinated well and irrigation waters were superior to buffered aqueous media for fission. Constant darkness also was superior to constant light; although, a 12/12-hr photoperiod also allowed good asexual reproduction. Fluctuating dissolved oxygen levels between 3 and 8 ppm apparently stimulated fission. A coarse gravel substrate was superior to smooth plastic. Daily temperature increases of 0.8°C/day between 22.5° and 28.9°C also stimulated fission. Fission rates decreased with increased densities ofD. dorotocephala in unfiltered aquaria, contrary to earlier results obtained in filtered aquaria. The addition of the ostracods,Cypridopsis vidua (Müller) andPhysocypria pustulosa Sharpe, to a diet of mosquito larvae increased fission. Brine shrimp (Artemia sp.) and red tubifex worms (Tubifex sp.) were not as suitable as mosquito larvae for food, apparently because the planaria had difficulty capturing these prey.D. dorotocephala was tolerant of salinities between 250–1,000 ppm, but feeding activity was impaired above and below this range. Mechanical sectioning of individuals was not a practical method for mass production; although if sectioning were coupled with media filtration, some reproductive acceleration might result.

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Résumé Les études sur les facteurs de l'environnement qui stimulent la reproduction asexuée chez la planaire,Dugesia dorotocephala (Woodworth), se nourrissant deCulex pipiens quinquefasciatus Say ont mis en évidence que les puits d'eau ordinaires et les eaux d'irrigation sont supérieurs à d'autres milieux aqueux pour la division; et que le noir total est supérieur à la lumière totale bien qu'une photopériode de 12/12 soit aussi un optimum. Des niveaux variables d'oxygène dissous entre 3 et 8 ppm semblent stimuler la reproduction. Un substrat de gros gravier est supérieur à une surface de plastique lisse et des augmentations quotidiennes de température de 0,8°C/jour entre 22,5° et 28,9°C ont stimulé la partition. La fréquence de multiplication a été diminuée par l'augmentation de la densité enDugesia dans les aquariums non-filtrés, contrairement aux résultats antérieurs dans les aquariums filtrés. L'addition des ostracodes,Cypridopsis vidua (Müller) etPhysocypria pustulosa Sharpe à un régime alimentaire à base de larves de moustiques a augmenté la reproduction. Les crevettes de saumure,Artemia sp., et les vers rougesTubifex sp., ne conviennent pas autant que les larves de moustiques comme aliment, à cause des difficultés, semble-t-il, de capture de ces proies.D. dorotocephala a supporté des salinités entre 250–1,000 ppm, mais l'activité alimentaire a été diminuée au-dessus et audessous de ces extrêmes. Le sectionnement mécanique des individus n'est pas une méthode pratique pour une production massive, bien que, associé à une filtration, il soit possible d'obtenir une accélération de la reproduction.

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Research partially supported by funds from a special appropriation for mosquito research authorized by the California State Legislature during 1975.     

A two-phase open-field test to evaluate the host-specificity of candidate biological control agents for Heliotropium amplexicaule

This paper describes an open-field host-specificity test conducted to make a preliminary evaluation of the safety of four candidate agents for the biological control of Heliotropium amplexicaule, an invasive weed of South American origin. These agents were a leaf-eating beetle, Deuterocampta quadrijuga, a flea-beetle, Longitarsus sp., that feeds on leaves as an adult and roots as a larva, a shoot-feeding thrips, Haplothrips heliotropica, and a cell-sucking bug, Dictyla sp. During the first phase of the experiment, the four agents were given a choice between the target weed and six species of nontarget plant of varying degrees of phylogenetic relatedness. All four species were found to feed and reproduce on only H. amplexicaule and the closely related H. nicotianaefolium (a member of the same section of the genus Heliotropium). No plants outside this genus were attacked. For the second “no-choice” phase, the host-plants used in Phase 1 were cut, forcing the insects to use either other plant species within the plots, emigrate, or die of starvation. Heliothrips heliotropica disappeared rapidly from the plot, while D. quadrijuga persisted for several days on Heliotropium arborescens with some exploratory nibbling and then disappeared. Host-choice behavior of these species therefore remained unchanged, even in the absence of the primary host-plants. In contrast, adults of Longitarsus sp. rapidly colonized and fed on H. arborescens when the preferred hosts were removed. It therefore demonstrated a wider host-range under these more extreme conditions. In fact, on some plots, feeding commenced on H. arborescens before the “no-choice” phase, once the two preferred Heliotropium species were heavily damaged by these insects. The two-phase test is shown here to be a useful way of measuring host-choice behavior under “normal” conditions of choice and under more extreme conditions, such as it might occur were an agent to locally destroy the target weed following its release. It therefore provides a more refined assessment of the risk that would be posed to nontarget plants by the release of weed biological control agents.     

Field assessment of the risk posed by Diorhabda elongata, a biocontrol agent for control of saltcedar (Tamarix spp.), to a nontarget plant, Frankenia salina

The biological control program for saltcedar (Tamarix spp.) has led to open releases of a specialist beetle (Chrysomelidae: Diorhabda elongata) in several research locations, but the controversy over potential impacts to native, nontarget plants of the genus Frankenia remains unresolved. To assess the potential for nontarget impacts under field conditions, we installed cultivated Frankenia spp. (primarily two forms of Frankenia salina but also including Frankenia jamesii) at locations in Nevada and Wyoming where D. elongata densities and saltcedar defoliation were expected to be very high, so insects would be near starvation with high probability of attacking nontargets if these were suitable hosts. Subsequent insect abundance was high, and only minor impact (<4% foliar damage) was observed on both forms of F. salina under these ‘worst case’ conditions; there was no impact to F. jamesii. No oviposition nor larval development were observed on any plants, there was no dieback of damaged F. salina stems, and plants continued growing once insect populations subsided. These results under ‘natural’ field conditions contrast with caged host-range tests in which feeding, development and minor oviposition occurred on the nontarget plant. Other ecological factors, such as distance from target plants to natural Frankenia spp. populations, inhospitable conditions for agent survival in such sites, and intrinsic insect behavior that makes colonization and/or genetic adaptation highly unlikely, lead us to conclude that nontarget impacts following program implementation will be insignificant or absent. Host range testing of new agents, while necessary to ensure safety, must put greater attention on assessing the ecological context where agents will be establishing, and on balancing speculated risks against potential benefits of biological control.     

Impedance conversion as a method of research for assessing behavioural responses of aquatic invertebrates

The concept of non-invasive, remote monitoring of the behaviour of aquatic organisms has been a long-sought research goal. In an effort to overcome the induction of artefacts and the generation of unnatural behaviour, a system of quantification of organism activity was developed based upon the theory of impedance conversion. The system is described in detail, and application was made to assess the respiratory behaviour of three aquatic invertebrates,Daphnia magna, Chironomus sp., andTanytarsus sp. in response to declining oxygen tensions. The system shows broad applicability for quantifying organism behaviour over four orders of magnitude in size range.     

Six new species of the genus Diplopeltula (Nematoda: Diplopeltidae) with remarks on the heterogeneity of the taxon

Six new Diplopeltula species are described: D. pulchra sp.n., D. belgica sp.n., D. striolata sp.n. and D. curta sp.n. (Southern Bight of the North Sea), D. nellyae sp.n. and S. pumila sp.n. (New Caledonia). Diplopeltula indica Gerlach, 1962 is redescribed from Guadeloupe (FWI). Based on the examination of these seven Diplopeltula species, the genus has been reappraised. The systematic position of the other genera of the Diplopeltidae Filipjev, 1918 is also discussed. Diplopeltoides Gerlach, 1962 is moved from the Aegialoalaimidae Lorenzen, 1981 to the Diplopeltidae.     

Tolerance of the planarianDugesia dorotocephala to high concentrations of pesticides and growth regulators

In laboratory tests, the planarianDugesia dorotocephala (Woodworth) was exposed to temephos (0.001 ppm), fenthion (0.003, 0.0035 and 0.004 ppm), malathion (0.1 ppm), chlorpyrifos (0.001 and 0.004 ppm), methoprene (0.005 ppm) and Dimilin ® (0.005 ppm) for 24 h without producing recognizable immediate or delayed effects to the viability, behavior, and asexual reproductive capacity of this planarian.D. dorotocephala tolerated relatively high concentrations of the pesticides and growth regulators suggesting their potential for integrated mosquito control. Post-exposure observations concerning the asexual reproductive capacity ofD. dorotocephala that were initially reared in water with a chloride content of 1200–1500 ppm (type 1 planaria) and 780–870 ppm (type 2 planaria) before experimentation indicated that the degree of asexual reproduction of type I planaria was significantly greater than was observed with type 2 planaria. These results would indicate the possibility of artificially stimulating asexual reproduction, hence mass production by stressingD. dorotocephala in some pesticides and growth regulators and/or by subjecting them to changes in chloride or salinity levels.     

Pathway,inhibition and regulation of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether oxidation in a filamentous fungus, <Emphasis Type="Italic">Graphium</Emphasis> sp.

The filamentous fungus Graphium sp. (ATCC 58400) co-metabolically oxidizes the gasoline oxygenate methyl tertiary butyl ether (MTBE) after growth on gaseous n-alkanes. In this study, the enzymology and regulation of MTBE oxidation by propane-grown mycelia of Graphium sp. were further investigated and defined. The trends observed during MTBE oxidation closely resembled those described for propane-grown cells of the bacterium Mycobacterium vaccae JOB5. Propane-grown mycelia initially oxidized the majority (∼95%) of MTBE to tertiary butyl formate (TBF), and this ester was biotically hydrolyzed to tertiary butyl alcohol (TBA). However, unlike M. vaccae JOB5, our results collectively suggest that propane-grown mycelia only have a limited capacity to degrade TBA. None of the products of MTBE exerted a physiologically relevant regulatory effect on the rate of MTBE or propane oxidation, and no significant effect of TBA was observed on the rate of TBF hydrolysis. Together, these results suggest that the regulatory effects of MTBE oxidation intermediates proposed for MTBE-degrading organisms such as Mycobacterium austroafricanum are not universally relevant mechanisms for MTBE-degrading organisms. The results of this study are discussed in terms of their impact on our understanding of the diversity of aerobic MTBE-degrading organisms and pathways and enzymes involved in these processes.     

SOME FACTORS IN THE COMPETITION OR ANTAGONISM AMONG BACTERIA, ALGAE, AND AQUATIC WEEDS

Field observations of changes in the populations of aquatic weeds and phytoplankton have confirmed that aquatic weeds have antagonistic activity toward phytoplankton. Nutritional studies in the laboratory indicate that cultures of the aquatic weeds, Myriophyllum sp., Ceratophyllum sp., and duckweed (Lemma minor L.); liquid cultures of barley (Hordeum vulgare L., Dickson variety); and cultures of the filamentous green algae, Cladophora sp. and Pithophora oedogonium (Mont.) Withrock, will remain relatively free of epiphytes or competing phytoplankton if the cultures are nitrogen-limited. Field observations of Cladophora sp. have confirmed that the growth of epiphytes on the Cladophora is related to conditions of surplus available nitrogen compounds. It is proposed that this antagonistic activity may be due to a “nitrogen sink” effect in which the aquatic weeds or filamentous green algae prevent the growth of contaminating algae by competition for the limited nitrogen compounds available. However, the presence of bacteria-sized organisms which have selective toxicity to certain algae indicates that perhaps multiple factors exist. Discussed are the ecological implications of associations of certain algae with bacteria that have selective toxicities for other species of algae under certain environmental conditions such as nitrogen-limited growth.     

Effects of Recombinant Baculoviruses on Three Nontarget Heliothine Predators

Genetically engineered baculoviruses, relative to their wild-type progenitors, have successfully improved the time-to-kill of these arthropod-specific biopesticides. Beneficial arthropods that prey on targeted pest insects are likely the first nontarget organisms to be adversely affected by the applications of such biopesticides. The goals of this project were to assess potential risks of the recombinant baculoviruses on Solenopsis invicta, Geocoris punctipes, and Hippodamia convergens, all of which are common predators of heliothines in Texas cotton. Four recombinant Autographa californica nuclear polyhedrosis viruses (AcNPV), one Helicoverpa zea nuclear polyhedrosis virus (HzNPV), and two corresponding wild-type NPVs were used in this risk assessment study. Risks associated with these baculoviruses were determined by possible shifts in predator life history traits (rate of food consumption, travel speed, fecundity, and survival) when fed prey infected with recombinant viruses compared to prey infected with wild-type viruses or to healthy prey. We also tested for possible transmission of these viruses by predators using the polymerase chain reaction (PCR). No significant shifts in life history characteristics were detected in predators fed Heliothis virescens larvae infected with any of the seven viruses. Viral DNA was discovered using PCR in 2.3% of fire ant workers, but not from any of the queens or eggs. In G. punctipes, 13.4% of adults and 0.5% of eggs scored positive for viruses. Twelve percent of H. convergens adults were found PCR positive. Residency in all three predators tested provides a pathway which could increase the persistence of recombinant viral particles in the environment and thus may produce an indeterminable amount of risk associated with their inadvertent movement.     

Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica

Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects on other Aleyrodidae or their natural enemies. Handling Editor: Dirk Babendreier.