=========================+=============+==============+===================
| | |
| | Number of | Per cent of
| | nematodes | nematodes that
| Per cent of | per host | were immature
| salamanders +-------+------+-------+-----------
| infected | | | |
| | range | mean | July | Aug.-Sept.
-------------------------+-------------+-------+------+-------+-----------
| | | | |
_Oswaldocruzia_ sp. | 83 | 2-15 | 3.6 | 100 | 20
| | | | |
_Thelandros_ sp. | 90 | 1-17 | 3.3 | 64.6 | 5.7
-------------------------+-------------+-------+------+-------+-----------
The numerical and temporal occurrence of the nematodes is summarized in
Table 2. It should be noted that of the 17 worms constituting the
maximum infection by _Thelandros_, only one was an adult worm; the
maximum number of adult _Thelandros_ in any one host was five.
Similarly, the heaviest _Oswaldocruzia_ infection, 15 worms, consisted
of immature individuals; the maximum number of adult worms in any one
host was ten.
The monthly variation in the relative occurrence of young stages
_versus_ adult in both nematodes (Table 2) suggests that the parasites
are eliminated from hosts sometime in the long period, late September
to early June, when _A. hardii_ exists subterraneously; the worms thus
would be reacquired annually when the salamanders resumed living on the
"surface" or near the surface. Table 2 shows that the majority of the
worms are immature (100 per cent, in _Oswaldocruzia_) in samples taken
in July. Additionally, all but one individual of those constituting the
20 per cent occurring as immature _Oswaldocruzia_ in the period August
to September were actually collected in early August. These were found
in one salamander, and this constituted the heaviest infection for the
period; crowding effects may have led to retardation of development of
the worms.
If it is true that parasites are reacquired each spring--we assume that
no temperature factors or immune reactions are delaying development of
the worms, and no unusually long external ovic or free-living phase is a
necessary part of their life-history--then the host-parasite data can
be used as a basis for hypothesizing about the winter life of the
salamander. During "surface" life the incidence of parasitism is high
(90 per cent and 83 per cent: see Table 2), indicating that salamanders
are readily invaded in times of activity. Salamanders examined in
September were all parasitized and probably carried nematodes with
them into their winter retreats. This part of their habitat should thus
be contaminated with infective stages of both parasites. Yet the
salamanders seem to become re-infected when the period of summer
activity starts (note the high incidence of immature parasites in
salamanders taken in July); therefore, the salamanders lose their worms
in winter. This suggests that during their subterranean life salamanders
are inactive, and avoid ingestion of infective stages of the parasites.
A fairly complete hibernation such as we suppose they undergo has been
reported by Szymanski (1914) for _Salamandra_ on the basis of
kymographic records of movement.