Observations on Moulting of Fourth-Stage Larvae of Paratylenchus Nanus

Fisher, J.M.

doi:10.1071/bi9661073

Cited by 23 publications

(6 citation statements)

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“…Rather than group plant parasites into a single functional group, we used the categories of ectoand endoparasites to further identify possible interactions with other soil factors and biota (Freckman 1982). The fourth-stage juvenile of the ectoparasite Paratylenchus, recovered from mesquite, creosote, and grasslands (Yeates 1978), is resistant to desiccation and is triggered to moult by specific plant root exudates (Fisher 1966, Ishibashi et al 1975). Many nematodes in desiccating soils enter a resistant state, anhydrobiosis, while other species have evolved specific survival mechanisms (Freckman 1986).…”

Section: Herbivorymentioning

confidence: 99%

Plant-Feeding Nematodes in Deep-Rooting Desert Ecosystems

Freckman

Virginia

1989

Ecology

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 128.235.Abstract. In the Chihuahuan Desert of southern New Mexico, mesquite (Prosopis glandulosa) occurs in a variety of landscape positions where water may accumulate to varying depths. The structure of Chihuahuan Desert landscapes has changed dramatically in the past 100 yr with mesquite expanding from its original distribution (playa, arroyo) into grassland and dune ecosystems. Our objective was to examine spatial and seasonal distribution of plant-feeding nematodes and the potential importance of herbivory in four mesquite communities (playa, arroyo, dunes, grassland) hypothesized to differ in rooting depth and distribution. These sites were compared to a more shallow-rooted creosote bush (Larrea tridentata) community. Intact soil cores were recovered to depths of 13 m beneath the canopies of mesquite or creosote bush using a continuous sampling tube drilling system in the winter, spring, and fall on the Jorada LTER site, Las Cruces, New Mexico.Nematode density and root mass decreased with depth. Nematodes were found to the maximum depth of recovered roots only at the playa (11-12 m) and occurred as deep as 5-6 m at the arroyo, 2-3 m at the dunes, and 1-2 m at the grassland and creosote bush sites. At the playa, 75% of the nematodes and 90% of the roots were below 0.5 m, whereas, in the creosote bush system 79% of the roots and 99.7% of the nematodes were recovered in the upper 0.5 m of soil. Nematode diversity (seven genera) and endoparasite densities were greatest at the playa. Only ectoparasites (three genera) were found at the creosote bush system. Total nematodes across all sites were highly correlated with total soil N, NH4+, and P04-3, but not NO3-. Nematodes were not positively correlated with soil moisture. Potential herbivory was best described by nematode numbers per gram root or an herbivory index (based on nematode density weighted by an impact factor for each genus), rather than the ratio of endoparasite:ectoparasite numbers. The herbivory index decreased in the order playa > creosote bush > dune > grassland > arroyo.The movement of mesquite into new habitats (grassland, dunes) is associated with shallow rooting, and relative to the playa, a greater allocation of roots to the upper 0.5 m soil layer, a decrease in nematode herbivory and diversity, and, a failure of the nematodes to be distributed throughout the entire rooting zone. The densities ofecto-and endoparasites varied with site, thus, plant-feeding nematodes should not be treated as a single guild since they have different effects on roots. Our study shows that in some ecosystems the majority of herbivory may occur at soil depths rarely studied. Although technically difficult ...

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Section: Herbivorymentioning

confidence: 99%

Plant-Feeding Nematodes in Deep-Rooting Desert Ecosystems

Freckman

Virginia

1989

Ecology

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“…Although loss of motility is a common assay to evaluate effectiveness of nematicidal chemicals, the induction of a reversible quiescence has not been described among most previous studies of seed and root exudate-nematode interactions (e.g., Viglierchio, 1961;Griffin, 1969;Prot, 1980;Perry, 1997;Smant et al, 1997). However, in a study of Paratylenchus nanus exposed to apricot root exudates, a phenomenon similar to EIQ was described (Fisher, 1966). After exposure of fourth-stage juveniles (J4) to exudates for a period of 5-10 days, J4 'became motionless' and this state of quiescence was followed in the next day or two with the onset of moulting.…”

Section: Discussionmentioning

confidence: 89%

“…As in EIQ, Fisher (1966) reported induction of a relatively prolonged but reversible state of immobilisation in response to root exudates. Both states of transient quiescence appear to represent a behavioural response triggered by a specific signal from root exudates rather than a toxin-induced state of metabolic distress.…”

Section: Discussionmentioning

confidence: 94%

“…After exposure of fourth-stage juveniles (J4) to exudates for a period of 5-10 days, J4 'became motionless' and this state of quiescence was followed in the next day or two with the onset of moulting. From the onset of quiescence to completion of the moult took approximately 3 days and restoration of motility ensued after moulting was complete (Fisher, 1966).…”

Section: Discussionmentioning

confidence: 99%

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Increased penetration of host roots by nematodes after recovery from quiescence induced by root cap exudate

Hubbard¹,

Flores-Lara²,

Schmitt³

et al. 2005

Nematol

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Fourteen of 20 plant species surveyed produced root cap exudates that induced a state of reversible quiescence in Meloidogyne incognita and Caenorhabditis elegans. Exudate from six species failed to induce quiescence in either nematode species. Root cap exudates from pea were found to trigger quiescence in populations of plant-parasitic, animal-parasitic, insect-pathogenic, and free-living nematode species. One animal parasite was resistant. Caenorhabditis elegans strains with defects in known metabolic pathways also were screened to explore the potential for using this model system to examine the genetic basis for exudates-induced quiescence (EIQ). All 62 lines tested exhibited wild type sensitivity to root cap exudates and preliminary efforts to obtain viable EIQresistant strains by ethyl methanesulphonate (EMS) mutagenesis were unsuccessful. After recovery from EIQ, penetration of alfalfa roots by second-stage juveniles of M. incognita more than doubled within 24 h, compared with controls, and the number of nematodes per root remained high for a week but long-term development and maturation was similar to that of untreated control inoculum. In cucumber, penetration after recovery from EIQ increased by several fold but returned to control levels within 4 days post-inoculation.

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“…exsheathment (Rogers and Sommerville 1968), which is under endocrine control in some animal-parasitic nematodes (Davey and Kan 1968). This information has led to the development of an hypothesis for moulting-stimulus, elaboration of materials (under neurosecretory control), ecdysis (Rogers 1962)-and this has been partly confirmed in the fourth· stage larvae of the plant parasite, Paratylenchus nanus (Fisher 1966). Most experiments on moulting have been done with larvae terminating a survival stage and there is no evidence that the hypothesis can be applied to freeliving nematodes in which moults are separated by regular periods of feeding.…”

Section: Introductionmentioning

confidence: 95%

Growth and Development of Aphelenchus Avenae Bastian

Fisher¹

1970

Aust. Jnl. Of Bio. Sci.

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SummaryIncreases in length and breadth of larvae of A. avenae followed a roughly sigmoid pattern with plateaux representing the motionless phases of moulting. During these phases length decreased slightly, resulting in withdrawal of the head and tail from the old cuticle, and increased again as motility was resumed after the moult.It was not always necessary for larvae to feed (and hence grow) before moulting would take place. The crucial time in a stage was the point when moulting was able to occur without further feeding. The time before this was variable and depended on the previous feeding of the larvae. The time spent in a stage after this was constant. Growth of the gonad was related to this point and occurred without feeding, though more rapidly if the larva had fed. Size of adults depended partly on the amount of feeding which had occurred between the time when moulting was first able to occur and the onset of the motionless phase.

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Observations on Moulting of Fourth-Stage Larvae of Paratylenchus Nanus

Cited by 23 publications

References 7 publications

Plant-Feeding Nematodes in Deep-Rooting Desert Ecosystems

Plant-Feeding Nematodes in Deep-Rooting Desert Ecosystems

Increased penetration of host roots by nematodes after recovery from quiescence induced by root cap exudate

Growth and Development of Aphelenchus Avenae Bastian

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