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

• Published in: Parasitology 2004-12, Vol.129 (6), p.753-759
• Main Authors: NOLAN, T. J., BRENES, M., ASHTON, F. T., ZHU, X., FORBES, W. M., BOSTON, R., SCHAD, G. A.
• Format: Article
• Language: English
• Subjects: Adults; ambient temperature; amphidial neurons; Animals; Biological and medical sciences; biological development; Body temperature; Critical period; Dogs; duration; Fundamental and applied biological sciences. Psychology; gastrointestinal nematodes; General aspects; General aspects and techniques. Study of several systematic groups. Models; Infectivity; Invertebrates; Larva - cytology; Larva - growth & development; Larvae; Molting; nematode biology; nematode development; nematode larvae; Nematodes; neuronal control; Neurons; Neurons - physiology; Parasitic diseases; pathogenicity; physiological response; Primates; sensory neurons; sensory receptors; Signal Transduction; Strongyloides stercoralis; Strongyloides stercoralis - cytology; Strongyloides stercoralis - growth & development; Temperature; Temperature effects; temperature-sensitive development; thermosensitive neurons; Thermotaxis; Veterinary colleges; Worms
• ISSN: 0031-1820; 1469-8161
• DOI: 10.1017/S0031182004006092

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.