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    Phased activity in Heterorhabditis megidis infective juveniles


    Dempsey, Catherine M. and Griffin, Christine (2002) Phased activity in Heterorhabditis megidis infective juveniles. Parasitology, 124. pp. 605-613. ISSN 0031-1820

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    Abstract

    The infectivity of Heterorhabditis megidis infective juveniles (IJs) increases during storage in water. We investigated whether this change can be related to other features of the IJs' behaviour. IJs were stored in water for 4 weeks at 20 degrees C, and the following parameters were assessed at intervals: infectivity for Galleria mellonella, dispersal in sand, host-finding on agar, and the percentage of IJs active in water. In addition, the behaviour of the IJs in water was described using 7 categories. Immediately after emerging from the host cadaver, IJs were highly active (99% of IJs in water were active and 65% displayed 'waving', the normal method of forward movement). Maximum responsiveness to host volatiles in an agar plate assay was recorded on day 2 (69% of IJs moved from the point of application and 44% of all IJs in the agar arena moved towards a host) and maximum dispersal in sand (5.8 cm) on day 0. These tendencies declined gradually with age, while infectivity underwent a significant increase from 11 nematodes per insect on day 0 to 38 nematodes per insect on day 9. Three phases could be distinguished in the behaviour of H. megidis IJs: an initial dispersal phase, during which infectivity was low; an infective phase, during which dispersal tendency was declining, and a third phase during which all behaviours (dispersal, infectivity and activity) were declining. Over the 4-week storage period, infectivity of H. megidis IJs was correlated (R2 = 0.83) with the percentage time IJs engaged in 'head thrusting' (a behaviour that resembles penetration). There is no evidence that the observed increase in infectivity of H. megidis strain UK211 could be accounted for by a generally greater level of motor activity, nor by an increase in responsiveness to volatile host cues, and it is suggested that it is due to an increased tendency to attempt penetration.

    Item Type: Article
    Keywords: behaviour; ageing; entomopathogenic nematodes; Heterorhabditis megidis; infectivity; foraging;
    Academic Unit: Faculty of Science and Engineering > Biology
    Item ID: 7537
    Identification Number: https://doi.org/10.1017/S0031182002001609
    Depositing User: Dr. Christine Griffin
    Date Deposited: 19 Oct 2016 14:46
    Journal or Publication Title: Parasitology
    Publisher: Cambridge University Press
    Refereed: Yes
    URI:

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