Effects of Nematophagous Fungi on Numbers and Death Rates of Bacterivorous Nematodes in Arable Soil

In a series of microcosm experiments with an arable, sandy loam soil amended with sugarbeet leaf, the short-term (8 weeks) dynamics of numbers of nematodes were measured in untreated soil and in γ-irradiated soil inoculated with either a field population of soil microorganisms and nematodes or a mixed population of laboratory-propagated bacterivorous nematode species. Sugarbeet leaf stimulated an increase in bacterivorous Rhabditidae, Cephalobidae, and a lab-cultivated Panagrolaimus sp. Differences were observed between the growth rates of the nematode population in untreated and γ-irradiated soils, which were caused by two nematophagous fungi, Arthrobotrys oligospora and Dactylaria sp. These fungi lowered the increase in nematode numbers due to the organic enrichment in the untreated soil. We estimated the annually produced bacterivous nematodes to consume 50 kg carbon and 10 kg nitrogen per ha, per year, in the upper, plowed 25 cm of arable soil.     

Influence of bacterivorous nematodes on the decomposition of cordgrass

The influence of bacterivorous nematodes (Diplolaimelloides meyli, Diplolaimelloides oschei, Diplolaimella dievengatensis, Panagrolaimus paetzoldi) on the decomposition of a macrophyte (Spartina anglica) in an aquatic environment was investigated by using laboratory microcosm experiments. Several earlier studies have shown enhancement of the decomposition process in the presence of nematodes, but nematode species-specific effects were never tested. In this study four bacterivorous nematode species were applied separately to microcosms to investigate such species-specific influences.No stimulation of the decomposition process nor of the microbial community was observed in the presence of the nematodes, both were highest in the absence of nematodes. However, clear differences were found between nematode treatments. P. paetzoldi reached much higher numbers than the other species, causing a decrease in microbial activity, probably due to (over)grazing. Remarkably this low microbial activity did not result in a slow-down of the decomposition process compared to the other nematode treatments, raising the question whether P. paetzoldi might be able to directly assimilate detrital compounds. Other nematode species reached much lower densities, but nevertheless an influence on the decomposition process was observed. However, this experiment does not support the view that bacterivorous nematodes enhance decomposition rate.The experimental results show that in nematode communities the use of functional groups is inadequate for biodiversity studies. The four nematode species used in this study belong to the same functional group, but are clearly not functionally redundant since they all have a different influence on the cordgrass decomposition. This suggests that the relationship between nematode species diversity and ecosystem functioning may be idiosyncratic.     

Parasitism of Nematodes by the Fungus Hirsutella rhossiliensis as Affected by Certain Organic Amendments

Experiments were conducted to determine whether the addition of organic matter to soil increased numbers of bacterivorous nematodes and parasitic activity of the nematophagous fungus Hirsutella rhossiliensis. In a peach orchard on loamy sand, parasitism of the plant-parasitic nematode Criconemella xenoplax by H. rhossiliensis was slightly suppressed and numbers of C. xenoplax were not affected by addition of 73 metric tons of composted chicken manure/ha. In the laboratory, numbers of bacterivorous nematodes (especially Acrobeloides spp.) and fungivorous nematodes increased but parasitism of nematodes by H. rhossiliensis usually decreased with addition of wheat straw or composted cow manure to a loamy sand naturally infested with H. rhossiliensis. These results do not support the hypothesis that organic amendments will enhance parasitism of nematodes by H. rhossiliensis.     

Benthic predators and zooplanktonic prey: predation by Crangonyx shoemakeri (Crustacea; Amphipoda) on Daphnia obtusa (Crustacea; Cladocera)

Amphipods and cladocerans are common inhabitants of seasonal ponds throughout North America. Although amphipods are usually considered to be benthic detritivores, Crangonyx shoemakeri was found to capture and consume mosquito larvae and Daphnia obtusa. The rate of capture of Daphnia was independent of the amount of decomposing leaf matter available. However, this rate was dependent on prey density and the presence of light, indicating that these amphipods are visual predators.     

Variability of water temperature may influence food-chain length in temperate streams

Nutrient enrichment may alter population dynamics of species in different ways depending on their life strategies. The aim of this study was to test the effect of different nutrient concentrations on the population development of two bacterivorous freshwater nematodes, Bursilla monhystera and Plectus aquatilis. Microcosms with autoclaved natural sand from a pristine stream (Fuirosos, NE of Spain) were enriched with different levels of phosphate, nitrate and ammonia as inorganic nutrients and glucose as a biodegradable dissolved organic carbon source. Although leaching of carbon and nutrients from the detritus fraction in the sediment initially may have overruled differences between treatments, later samplings revealed bottom-up control, with Bursilla monhystera abundances positively correlated to bacterial abundances at high nutrient concentrations. Nevertheless, there were several indications that nematodes in turn affected microbial abundance, most likely through excretion of ammonia and through grazing. In contrast to B. monhystera, Plectus aquatilis at high nutrient concentrations showed a unimodal abundance curve, while not increasing in abundance at low nutrient concentrations. Glucose enrichment did not have any stimulatory effect on either microbial or nematode abundances, probably as a result of unfavourable C:N:P stoichiometry. P enrichment, by contrast, stimulated microbial and Bursilla abundances. Our results indicate that episodic nutrient enrichment may affect populations of bacterial-feeding nematodes in the short term. Their longer-term dynamics may, however, be more dependent on leaching of carbon and nutrients from the pools of sediment-bound detritus.     

Ecological role of <Emphasis Type="Italic">Phyllophora antarctica</Emphasis> drift accumulations in coastal soft-sediment communities of McMurdo Sound,Antarctica

At Cape Evans on Ross Island, Antarctica, the rhodophyte Phyllophora antarctica is the dominant primary producer in terms of biomass from 10 to >30 m depth. The vast majority of Phyllophora occurs as accumulations of unattached plants. Whilst decomposition and incorporation of macroalgal drift material into the food web is rapid in temperate ecosystems, we predicted these processes to be slow in Antarctica. We address the functional role of macroalgal detritus in fuelling the biodiversity of benthic communities at Cape Evans during the summers of 2001 and 2002. Specifically we (a) describe the distribution and biomass of attached and drift algae, (b) assess the photosynthetic capacity and degradation of drift accumulations using in situ fluorometry, (c) assess the effect of patches of drift Phyllophora on underlying macrofaunal communities, and, (d) use stable isotopes to investigate the possible uptake of Phyllophora by macrofauna. We found drift Phyllophora accumulations throughout the depth range investigated (3–31 m), with peak biomasses of 140±30 g dwt m^–2 in the 15–25 m depth strata. At this depth stratum Phyllophora was a conspicuous habitat element with the % cover on the seafloor averaging 30%. While initially the drift algal accumulations appeared in good health we measured significant declines in photosynthetic capacity between years suggesting ongoing, albeit slow, degradation of the drift algal accumulations. Our results demonstrate that Phyllophora drift accumulations have a structuring role on soft-sediment communities, which increases in strength with the gradual degradation of the algae. The longevity of Phyllophora is enhanced by secondary metabolites, which serve as protection against grazers, and their extreme shade adaptation. However, our carbon and nitrogen stable isotope data of polychaetes and amphipods associated with Phyllophora suggest that macroalgal detritus enters the food web, and although this process is slow, Phyllophora accumulations might serve to dampen the seasonality in food supply providing higher trophic levels with a more constant food source.     

Feeding rates of amphipods in boreal lakes: is there a seasonal shift independent of temperature and photoperiod?

In boreal lakes, temperature and photoperiod are important environmental cues affecting reproduction, growth and feeding rates of benthic invertebrates; however, how invertebrates cope with seasonal changes in the availability of their food sources has rarely been addressed. In this study, where temperature and light conditions were controlled, we aimed at assessing whether Hyalella azteca amphipods from the littoral zone of boreal lakes adjust their feeding rates in response to the dynamics of their food sources and their population structure. Using a gravimetric approach, we compared the ingestion and absorption rates of amphipods from a natural population collected periodically during the ice-free season. Amphipods were fed in the laboratory with conditioned leaf detritus. Feeding rates increased regardless of seasonal variations of temperature and photoperiod in the lake. Field data suggest this increase could be linked to seasonal changes in the population structure or in the diet of amphipods. This suggests that H. azteca amphipods adjusted their feeding rates with their energy and nutrient requirements and/or developed a compensatory feeding trade-off to cope with the dynamics of their different food sources in lakes.     

食细菌线虫对土壤微生物量和微生物群落结构的影响

线虫与微生物的相互作用研究往往是在悉生培养体系 (gnotobiotic microcosm)中进行 ,为了研究在自然或开放土壤条件下土壤线虫与微生物的相互作用 ,作者在开放盆栽体系中接种土壤食细菌线虫 (原小杆线虫 ,Protorhabditis sp) ,研究在小麦不同生育期、在有和无根系作用下食细菌线虫对土壤微生物量和微生物群落结构的影响。结果表明 :接种线虫分别使 SMBC、SMBN、SMBP提高了 2 6 .4 %、32 .9%、2 1.8% ,这种促进作用除个别无根系土和非根际土处理外 ,均达到显著性差异。根际土中的 SMBC、SMBN、SMBP>非根际土 >无根系土。从方差解释比例 v来看 ,SMBN受线虫的影响最大 (v=2 4 % )、其次是 SMBC(v=16 % )、然后是 SMBP(v=12 % ) ,线虫对 SMBC的促进作用在根际土中最突出。接种线虫对土壤细菌、真菌和放线菌的数量有明显的影响。在苗期的无根系土和根际土中 ,接种线虫显著降低了细菌的数量、特别在根际土中尤为突出 ,但在其它处理中却增加了细菌的数量。接种线虫对真菌和放线菌数量的促进作用比对细菌更为明显 ,接种线虫后真菌和放线菌数量的总平均值分别比未接种提高了 4 8.5 %和 6 8.2 % ,而细菌数量的总平均值没有变化。细菌数量与微生物量 C相关散点图表明二者相关性在根际土、非根际土和无根系土中均未     

Sunn Hemp Cover Cropping and Organic Fertilizer Effects on the Nematode Community Under Temperate Growing Conditions

Field experiments were conducted in Maryland to investigate the influence of sunn hemp cover cropping in conjunction with organic and synthetic fertilizers on the nematode community in a zucchini cropping system. Two field treatments, zucchini planted into a sunn hemp living and surface mulch (SH) and zucchini planted into bare-ground (BG) were established during three field seasons from 2009 to 2011. In 2009, although SH slightly increased nematode richness compared with BG by the first harvest (P < 0.10), it reduced nematode diversity and enrichment indices (P < 0.01 and P < 0.10, respectively) and increased the channel index (P < 0.01) compared to BG at the final harvest. This suggests a negative impact of SH on nematode community structure. The experiment was modified in 2010 and 2011 where the SH and BG main plots were further split into two subplots to investigate the added influence of an organic vs. synthetic fertilizer. In 2010, when used as a living and surface mulch in a no-till system, SH increased bacterivorous, fungivorous, and total nematodes (P < 0.05) by the final zucchini harvest, but fertilizer type did not influence nematode community structure. In 2011, when incorporated into the soil before zucchini planting, SH increased the abundance of bacterivorous and fungivorous nematodes early in the cropping season. SH increased species richness also at the end of the season (P < 0.05). Fertilizer application did not appear to influence nematodes early in the season. However, in late season, organic fertilizers increased enrichment and structure indices and decreased channel index by the end of the zucchini cropping cycle.     

Drifting Algae as a means of Re-Colonizing Defaunated Sediments in the Baltic Sea. A Short-Term Microcosm Study

We conducted a microcosm experiment to evaluate the capability of fauna inhabiting or being transported by drifting filamentous algae to colonize defaunated sediment. We expected meiofauna would perform a quicker and more effective re-colonization of disturbed areas by means of the algal mats than their macrofaunal counterparts. Similarly, within meiofauna, we expected more mobile taxa such as ostracods and harpacticoids to colonize the sediment more readily than other more sedentary ones such as nematodes. Naturally drifting algae were collected from the field and placed in 1 l aquaria on top of 5 cm of defaunated sediment. After 3 and 6 days, one core sample (5 cm deep) was taken from each aquarium; the first 2 cm were sliced into 2 mm layers, and the remaining fraction into 1 cm layers. The sediment remaining in the aquaria was sieved through a 0.5 mm sieve to collect the re-colonizing macrofauna. The dominant macrofaunal taxa inhabiting the algae were juvenile bivalves and gastropods, with Cerastoderma glaucum accounting for the majority of the bivalves and Hydrobia sp. for most of the gastropods. After 3 and 6 days, the most abundant macrofaunal taxa colonizing the sediment were Cerastoderma glaucum, Hydrobia sp. and gammarid amphipods. Higher abundances were found after 6 days than after 3, though differences were not significant for any of the major taxa. Meiofauna inhabiting the algae were dominated by rotifers, nematodes, ostracods, chironomid larvae and harpacticoid copepods. Contrary to our predictions, nematode and harpacticoid species inhabiting the drifting algae were not driven to sediment re-colonization but remained in the algae. Our results indicate that some benthic animals may indeed benefit from drifting algal mats as a means of dispersal and re-colonization of previously defaunated sediments in relatively short periods of time. Also, they may contribute to explain some of the trends found in other studies, regarding species increase under drifting algae and the recovery patterns found in areas often exposed to algal conglomerates.     

The effect of wrack composition and diversity on macrofaunal assemblages in intertidal marine sediments

Wrack (dead, washed-up seaweed and seagrass) buried in soft substrata may increase the organic content and alter the physical structure of sediments. These effects may influence the composition and structure of macrofaunal assemblages in the sediment. Such influences can be expected to vary according to the type and amount of wrack as well as the presence of invasive seaweeds in the wrack. In this study, we deliberately buried different amounts of the invasive species Sargassum muticum in isolation or mixed to the native species Ulva sp. and Fucus vesiculosus, in two intertidal sandflats to test some hypotheses about the response of macrofaunal assemblages. We tested whether (1) diversity of detritus (i.e. different mixtures), and (2) the amount of detritus of S. muticum influenced the composition and the relative abundance of macrofaunal assemblages. We also assessed whether the sediment organic carbon and the biomass of benthic microalgae varied depending on the diversity of detritus and the amount of detritus of S. muticum. Finally, we tested if these effects of wrack were consistent across sites. Results indicated that buried wrack affected the composition and structure of macrofaunal assemblages in short-term (i.e. 4 weeks), but there were no differences depending on detritus diversity or the amount of S. muticum. In addition, sediment organic matter and microalgal biomass were not affected by the addition of wrack. They instead varied greatly among small spatial scales (i.e. plots). Wrack composition or abundance of the invasive species S. muticum played thus a small role in shaping the structure of macrofaunal assemblages or the biomass of benthic microalgae in these intertidal sediments, probably because these sediments are frequently affected by various inputs of organic matter and benthic assemblages are already adapted to organically enriched sediments.     

Effects of leaf litter addition on meiofaunal colonization of azoic sediments in a subtropical mangrove in Hong Kong

The responses of major meiofaunal taxa and nematode species assemblage to the decaying leaf litter of the mangrove Kandelia candel were investigated through a field colonization experiment in subtropical Hong Kong. Sixty-four replicate azoic and organic-free sediment cores were treated with leaf litter additions of 0x, 0.5x, 1x and 2x natural sediment organic concentration, respectively, and retrieved 1, 10, 30 and 60 days post-placement. Replicate cores of ambient sediment were also taken at each sampling date to provide baseline information. Results of ANOVAs suggested that either different meiofaunal taxa responded to the leaf litter in different ways or the response of the same taxon changed over decomposition time. Multivariate ordination performed on nematodes revealed an alteration in community structure after 10, 30 and 60 days between controls and treatments. This alteration was attributed to some deposit feeding nematodes, particularly a bacterivorous species, Diplolaimella sp., which bloomed in all the cores treated with leaf litter, testifying to the important role such meiofauna plays in the process of detritus decomposition.     

Effects of two acanthocephalan species on the reproduction of Hyalella patagonica (Amphipoda, Hyalellidae) in an Andean Patagonian Lake (Argentina)

The aim of the present study was to evaluate alterations in the reproduction induced by acanthellae and cystacanths of the acanthocephalans Acanthocephalus tumescens and Corynosoma sp. in the amphipod Hyalella patagonica from Lake Mascardi. Specimens of H. patagonica were separated in two categories: paired amphipods (joined specimens during precopulatory mate guarding period until fertilization) and unpaired amphipods (alone specimens). Different analyses were performed: first with paired (n = 406) and unpaired (n = 375) amphipods, and second only with female amphipods (n = 1949), that were classified into three categories (without internal oocytes and eggs, only with internal oocytes, and with eggs). Also, carotenoid extraction was performed of amphipods uninfected (n = 75) and infected (n = 105) by cystacanths of Corynosoma sp. Unpaired amphipods had significantly higher prevalence of cystacanths of both acanthocephalan species than paired ones; but such differences were not found in prevalence of acanthellae. Female amphipods without internal oocytes and eggs showed significantly higher prevalence of cystacanths of both acanthocephalan species than the two other female categories; while females with eggs had significantly higher prevalence of A. tumescens acanthellae. Amphipods infected by Corynosoma sp. showed lower carotenoid concentration than uninfected ones. In Lake Mascardi, there is indirect evidence of both reduced mating success and female fecundity of H. patagonica provoked by both cystacanths species (A. tumescens and Corynosoma sp.). However, infections by acanthellae seem to have no effects.     

The effects of macroalgal cover on the spatial distribution of macrobenthic invertebrates: the effect of macroalgal morphology

The growth of green macro-algae in response to nutrient inputs is a common phenomenon in marine estuaries and sheltered bays. While the ecological effects of the growth of the most commonly occurring macroalgal taxa (Enteromorpha, Chaetomorpha, Ulva, Cladophora) have been well studied, the effects of a morphologically very different species, Vaucheria subsimplex, have not been investigated. This study investigated the ecological effects of the establishment of V. subsimplex on a relatively exposed intertidal sandflat, Drum Sands, Firth of Forth, Scotland. Because of the spatially heterogeneous development of the weed, the short term (4 weeks) and long term (20 weeks) effects of the weed could be studied using a survey approach in which the weed-affected and weed-free plots were interspersed. After 4 weeks, V. subsimplex significantly increased the mean number of individuals and diversity of the macrofauna, eight of the ten most abundant species showed significant increases in abundance compared to weed-free areas. After 20 weeks, mean number of species and individuals were significantly higher under weed patches, while species diversity was reduced due to the numerical dominance of Pygospio elegans (Claparède). The weed, therefore, had an enriching effect on the macrofaunal communities on Drum Sands. The increased numbers of P. elegans, the numerical dominant infaunal species on Drum Sands, resulted mainly from enhanced larval recruitment to weed-affected areas. The effects of V. subsimplex on sediment characteristics were similar to those reported for other macroalgal taxa, i.e., increased water, organic and silt/clay contents, medium particle size and sorting coefficients, and reduced redox potentials. The results from this study are compared to those for other, morphologically different macroalgal species, with particular reference to an Enteromorpha-implanted experiment on the same sandflat. Since the general effect of such macroalgal taxa on macrofaunal communities is a detrimental one, the present study supports the contention that macroalgal morphology is an important feature in algal–faunal interactions.     

Secondary Metabolites of <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> CHA0 Drive Complex Non-Trophic Interactions with Bacterivorous Nematodes

Non-trophic interactions are increasingly recognised as a key parameter of predator–prey interactions. In soil, predation by bacterivorous nematodes is a major selective pressure shaping soil bacterial communities, and many bacteria have evolved defence mechanisms such as toxicity. In this study, we show that extracellular secondary metabolites produced by the model soil bacterium Pseudomonas fluorescens CHA0 function as a complex defence strategy against bacterivorous nematodes. Using a collection of functional mutants lacking genes for the biosynthesis of one or several extracellular metabolites, we evaluated the impact of bacterial secondary metabolites on the survival and chemotactic behaviour of the nematode Caenorhabditis elegans. Additionally, we followed up the stress status of the nematodes by measuring the activation of the abnormal DAuer Formation (DAF) stress cascade. All studied secondary metabolites contributed to the toxicity of the bacteria, with hydrogen cyanide efficiently repelling the nematodes, and both hydrogen cyanide and 2,4-DAPG functioning as nematicides. Moreover, these metabolites elicited the DAF stress response cascade of C. elegans, showing that they affect nematode physiology already at sublethal concentrations. The results suggest that bacterial secondary metabolites responsible for the suppression of plant pathogens strongly inhibit bacterivorous nematodes and thus likely contribute to the resistance of bacteria against predators in soil.     

Effect of Crotalaria juncea Amendment on Nematode Communities in Soil with Different Agricultural Histories

Effect of sunn hemp (Crotalaria juncea) hay amendment on nematode community structure in the soil surrounding roots of yellow squash (Cucurbita pepo) infected with root-knot nematodes was examined in two greenhouse experiments. Soils were from field plots treated long-term (LT) with yard-waste compost or no yard-waste compost in LT experiment, and from a short-term (ST) agricultural site in ST experiment. Soils collected were either amended or not amended with C. juncea hay. Nematode communities were examined 2 months after squash was inoculated with Meloidogyne incognita. Amendment increased (P < 0.05) omnivorous nematodes in both experiments but increased only bacterivorous nematodes in ST experiment (P < 0.05), where the soil had relatively low organic matter (<2%). This effect of C. juncea amendment did not occur in LT experiment, in which bacterivores were already abundant. Fungivorous nematodes were not increased by C. juncea amendment in either experiment, but predatory nematodes were increased when present. Although most nematode faunal indices, including enrichment index, structure index, and channel index, were not affected by C. juncea amendment, structure index values were affected by previous soil organic matter content. Results illustrate the importance of considering soil history (organic matter, nutrient level, free-living nematode number) in anticipating changes following amendment with C. juncea hay.     

Patterns of macroinvertebrate abundance in inland saline wetlands: a trophic analysis

We used stable isotopes and gut-content analysis to compare trophic relations of macroinvertebrates between two types of saline wetlands in the Laramie Basin, Wyoming, USA. Amphipods (Hyallela azteca), chironomid larvae, and predatory insects (mainly Zygopteran larvae) occurred in both wetland types. However, in oligosaline wetlands (0.5–5‰ total dissolved solids) amphipods were dominant, whereas in mesosaline wetlands (5–18‰) amphipods were scarce and chironomid larvae and predatory insects were much more abundant. Salinity alone seemed inadequate to explain these differences, so we examined trophic interactions to address three main questions: (1) why are predatory insects more abundant in mesosaline wetlands, (2) why are chironomid larvae less abundant in oligosaline wetlands, and (3) why are amphipods uncommon in mesosaline wetlands? Zygopteran larvae ate mainly chironomid larvae and zooplankton, and did not eat amphipods; chironomid larvae were an average 93 dry mass of zygopteran intake. Guts of amphipods contained no animal parts and little vascular plant tissue, but rather mainly amorphous detritus. Chironomid larvae ate amorphous detritus as well as diatoms. There is potential for competition between amphipods and chironomids, but the nature of amorphous detritus in these wetlands needs further study. Because amphipods appear unavailable as prey for predatory insects, top-down impacts on chironomid larvae may be greater in oligosaline than in mesosaline wetlands. Our results suggest that (1) predatory zygopteran larvae and hemipterans are more abundant in mesosaline wetlands due to more abundant chironomid prey, (2) chironomids are less common in oligosaline wetlands because of both competition with amphipods and greater per capita consumption by predatory insects, and (3) amphipods are scarce in mesosaline wetlands because, lacking a resting stage and mode of direct dispersal, they do not cope well with extremes created by hydrologic instability in mesosaline wetlands. These mechanisms may apply to wetlands in other regions where similar patterns of invertebrate community structure have been reported.     

Relationship Between Paratrichadorus sp. Density, and Growth of Wheat in Pots

The effect of a Paratrichodorus sp. (close to P. tunisiensis) on the growth of wheat (Triticum durum Desf.) was investigated in pots containing different nematode densities and maintained in a growth chamber at 20 C for 40 days. The relation between fresh weight of tops and initial nematode density was according to the equation y = m + (1 - m)z^P⁻T. This suggests a tolerance limit of 1.4 nematodes/cm³ of soil under the conditions of the experiment; taking into account the effect of the great nematode mortality, it is estimated to be between 0.15 and 0.35 nematodes/cm³ soil. Models of the growth of the plants and the multiplication of the nematodes (assuming a constant mortality of the nematodes in the absence of roots) which explain the relation between initial and tinal nematodes densities at initial densities greater than 1 nematode/cm³ soil are described in an appendix. Sections of nematode infested roots showed disorganization of root structure clue to abnormal proliferation of lateral roots. Nematode feeding on the root cap and apical meristem caused cessation of root elongation and induced abnormal production of lateral root primordia.     

Association of the Red Ring Nematode and Other Nematode Species with the Palm Weevil,Rhynchophorus palmarum

The palm weevil, Rhynchophorus palmarum (L.), was collected in cocoons from red ring-diseased coconut palms (Cocos nucifera L.) in Trinidad and Tobago. Juveniles of five species of nematodes were extracted from the genitalia and macerated bodies of newly emerged adults of the palm weevil: Rhadinaphelenchus cocophilus (Cobb) Goodey (the red ring nematode), Teratorhabditis sp., Diplogasteritus sp., Mononchoides sp., and Bursaphelenchus sp. Over 90% of newly emerged weevil females and males were infested internally with red ring nematode juveniles, and over 47% of the weevils contained more than 1,000 red ring nematodes each. There was no significant correlation between weevil body length and the number of red ring nematodes carried internally by each weevil. Teratorhabditis sp. and Diplogasteritus sp. were extracted from over 50% of the palm weevils, and Monochoides sp. and Bursaphelenchus sp. were found in a small proportion of the weevils. Field-collected adult weevils were also internally and externally infested with a Rhabditis sp., which was not observed in or on weevils allowed to emerge from field-collected cocoons.     

A Free-living Panagrolaimus sp. from Armenia Can Survive in Anhydrobiosis for 8.7 Years

Although the ability of plant-parasitic nematodes to survive in a dehydrated or anhydrobiotic state for long periods of time has been well documented, the ability of free-living nematodes has not. Here we report on the survival of a free-living nematode, Panagrolaimus sp., from Armenia in the anhydrobiotic state for 8.7 years. This Panagrolaimus sp. can be cultured and maintained readily and may provide a good system for studying anhydrobiosis in nematodes.