Attraction of mononchoides longicaudatus and M. fortidens (Nematoda: Diplogasterida) towards prey and factors influencing attraction

The attraction of Mononchoides longicaudatus and M. fortidens towards prey and factors influencing their attraction were studied on agar plates. These predators were attracted towards excised and non-excised (live) prey in response to prey secretions, attractants. Predators also responded positively towards agar containing unidentified bacteria. M. longicaudatus and M. fortidens showed preference for the prey nematodes which were tested either alive or by cutting into two pieces (excised). Hirschmanniella oryzae, Tylenchorhynchus mashhoodi and Hoplolaimus indicus attracted predators most while Longidorus SP., and Helicotylenchus indicus elicited least response from the predators. The rest of the prey nematodes attracted predators moderately. Both species of predators were also attracted towards their own individuals. Different factors viz., prey number, temperature, incubation period of prey, starvation of predators and distance of predators from prey affected attraction of the predators towards Hirschmanniella oryzae and the second stage juveniles of Meloidogyne incognita. Both predators were attracted in maximum numbers when 50 prey nematodes were incubated for 12 h in Petri-dishes, at 25°-30°. Starvation of predators increased their attraction towards prey; increase in prey distance decreased attraction

A study of the intestinal contents of some mononchs

The intestinal contents of over one thousand specimens of thirty three species belonging to nine genera of the order Mononchida were analysed to determine their range and preference for prey. The study showed that mononchs feed upon tylenchs, dorylaims, mononchs and free-living saprophagous nematodes besides rotifers. Cuticular remains of al1 types including trophi of rotifers and other unidentifiable objects of prey were of frequent occurrence. Forty five percent of the predators had prey in their intestine. Feeding of different mononchs is polyvalent and predation aleatory. However, more predators 75% had free-living saprophagous nematodes within the intestine rather than tylenchs (45%) or dorylaims (42%). Pratylenchus, Hoplolaimus, Tylenchorhynchus, Tylencholaimus, Aporcelaimus, Thornenema, Iotonchus, Mylonchulus, Rhabditis, Acrobeloides and Chiloplacus were found most frequently in the intestine of different species of mononchs. Parahadronchus shakili appeared to be most active predator as 68 % of its specimens had prey in their intestine while Coomansus indicus was least active with only 21% having prey. Twenty percent predators were cannibals while 27% devoured mononchs belonging to other species/genera. Mylonchulus spp., and Iotonchus baqrii did not contain any prey or its remains in their intestine. None to eight prey could be present in the intestine of a single predator

Chemo-oriented sex attraction in a plant parasitic nematode, Hirschmanniella oryzae

During the present observations on the sex attraction behaviour of H. oryzae it was observed that both the sexes produced attractants which resulted in a mutual response towards each other. Males of H. oryzae were more responsive than females. There was no attraction of males towards male attractants and females towards female attractants. The distance of nematode inoculation and the period of nematode exposure to attractants influenced the degree of attraction. Significant correlations were observed between the attraction (Mean Score) and the period of nematode exposure to attractants

Ovicidal activity of three insect growth regulators against Aedes and Culex mosquitoes

a b s t r a c t Interspecific variations in the susceptibility of freshly and embryonated eggs of Aedes albopictus, Ae. aegypti, Ae. atropalpus and Culex pipiens were tested against three classes of insect growth regulators (IGRs) including ecdysone agonist (azadirachtin), chitin synthesis inhibitor (diflubenzuron) and juvenile hormone analog (pyriproxyfen) at 0.001, 0.01, 0.1 and 1.0 ppm concentrations. Egg hatching inhibition was dose dependent, the highest being at 1.0 ppm concentration for freshly laid eggs of Ae. albopictus (pyriproxyfen: 80.6%, azadirachtin: 42.9% and diflubenzuron: 35.8%). Aedes aegypti showed lower egg hatching inhibition when exposed to pyriproxyfen (47.3%), azadirachtin (15.7%) and diflubenzuron (25.5%). Freshly laid eggs of Cx. pipiens were most susceptible to diflubenzuron. Aedes atropalpus eggs were tolerant to all three classes of IGRs. Embryonated eggs of Ae. albopictus, Ae. aegypti, Ae. atropalpus and Cx. pipiens were resistant to pyriproxyfen, azadirachtin and diflubenzuron than freshly laid eggs. The median desiccation time (DT 50 ) of Ae. atropalpus eggs was maximum (5.1 h) as compared to Ae. aegypti (4.9 h), Ae. albopictus (3.9 h) or Cx. pipiens (1.7 h) eggs. Insignificant relationship between the rates of desiccation and egg hatching inhibition suggests other factors than physical providing eggs the ability to tolerate exposures to various IGRs. Egg hatching inhibition was due to the alteration in embryonic development caused by IGRs. Changes in the egg shell morphology and abnormal egg hatching from the side of the egg wall instead of operculum, was observed at higher concentrations of diflubenzuron. Morphological and physiological variations in eggs may be the key factor to influence the ovicidal efficacy of IGRs. The present data provide a base line for the improvement of the ovicidal efficacy of the insecticide and its formulation

Transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis bacteriophora

Background: The success of a biological control agent depends on key traits, particularly reproductive potential, environmental tolerance, and ability to be cultured. These traits can deteriorate rapidly when the biological control agent is reared in culture. Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora (Hb) but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M) and its original parental line (OHB). We generated transcriptional profiles of two experimental lines of Hb, identified the differentially expressed genes (DEGs) and validated their differential expression in the deteriorated line. Results: An expression profiling study was performed between experimental lines L5M and OHB of Hb with probes for 15,220 ESTs from the Hb transcriptome. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding enzymes involved in metabolism, signal transduction, virulence and longevity. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. Expression of sixteen DEGs in trait deteriorated nematodes was validated by quantitative reverse transcription-PCR (qRT-PCR) which revealed similar expression kinetics for all the genes tested as shown by microarray. Conclusion: As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information could also be used to improve the beneficial traits of biological control agents and better understand fundamental aspects of nematode parasitism and mutualism

A nematode feeding mite: Tyrophagus putrescentiae (sarcoptiformis: Acaridae)

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Effect of chemicals and nematicides on the activity and survival of Dorylaimus stagnalis, a predaceous nematode

Ten concentrations of potassium chloride, sodium chloride, potassium iodide, urea, ammonia and five concentrations of aldicarb and carbofuran were used to determine their effects on the activity and survival of adult and juvenile stages of a predatory nematode, Dorylaimus stagnalis. It was found that high concentrations (0.6-0.8M) of all chemicals were very toxic. In low concentrations the activity decreased with an increase in the period of exposure but the nematodes survived for comparatively longer durations (2880 min). The effectiveness of salts on the activity and survival of nematodes corresponded with their molecular weights and salts with higher molecular weights (e.g., potassium iodide; Mol. Wt-166.01) were more toxic as compared tothe others with lesser molecular weight (Sodium chloride; Mol. Wt = 58.44)

The responses of Mononchus aquaticus to chemicals and pH

Different concentrations of salts and furadan 3-G and pH gradients were used to determine their effects on the activity of the predatory nematode, Mononchus aquaticus. Except urea, the higher concentrations (0.06M) of all the other salts proved highly toxic and except for cupric sulfate and ammonia, the lower concentrations (0.001 M) had stimulating effect. Furadan 3-G proved very toxic, even at low concentration, suppressing activity much below control. pH 5.8 proved optimal for nematode activity. The effectiveness of salts, with some exceptions, was directly proportional to their molecular weight

Interaction between mononcbs in non-sterile agar plates

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