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The amphidial neuron pair ALD controls the temperature-sensitive choice of alternative developmental pathways in the parasitic nematode, Strongyloides stercoralis

Published online by Cambridge University Press:  18 November 2004

T. J. NOLAN ,
M. BRENES ,
F. T. ASHTON ,
X. ZHU ,
W. M. FORBES ,
R. BOSTON  and
G. A. SCHAD
T. J. NOLAN
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
M. BRENES
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
F. T. ASHTON
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
X. ZHU
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
W. M. FORBES
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
R. BOSTON
Affiliation:
Section of Animal Production Systems, University of Pennsylvania School of Veterinary Medicine, 382 West Street Road, Kennett Square, PA 19348, USA
G. A. SCHAD
Affiliation:
Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine, 3800 Spruce St, Philadelphia, PA 19104, USA
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Abstract

The parasitic nematode Strongyloides stercoralis, has several alternative developmental pathways. Upon exiting the host (humans, other primates and dogs) in faeces, 1st-stage larvae (L1) can enter the direct pathway, in which they moult twice to reach the infective 3rd-stage. Alternatively, if they enter the indirect pathway, they moult 4 times and become free-living adults. The choice of route depends, in part, on environmental cues. In this investigation it was shown that at temperatures below 34 °C the larvae enter the indirect pathway and develop to free-living adulthood. Conversely, at temperatures approaching body temperature (34 °C and above), that are unfavorable for the survival of free-living stages, larvae develop directly to infectivity. The time-period within the L1's development during which temperature influenced the choice of the pathway depended on the temperature, but, at any given temperature, occurred approximately in the middle of the time-span spent in the L1 stage, which varied inversely with temperature. This critical period was associated with the time-interval in which the number of cells in the genital primordium began to increase, thus providing a morphological marker for the pathway decision in individual worms. Sensing the environment is the function of the amphidial neurons, and therefore we examined the role of individual amphidial neurons in controlling entry into the direct pathway to infectivity. The temperature-sensitive developmental switch is controlled by the neuron pair ALD (which also controls thermotaxis), as seen by the loss of control when these neurons are ablated. Thus, in S. stercoralis a single amphidial neuron pair controls both developmental and behavioural functions.

Keywords

amphidial neuronsnematode developmenttemperature
Type
Research Article
Information
Parasitology , Volume 129 , Issue 6 , December 2004 , pp. 753 - 759
Copyright
© 2004 Cambridge University Press

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