Because manipulation of the parasite depends on both acanthocephalan species and developmental stage, only individuals harboring Pomphorhynchus tereticollis (for the phototaxis and refuge use tests) and Polymorphus minutus (for the geotaxis
tests) parasites at the cystacanth stage were retained (hereafter referred as "parasitized" individuals).
a) Locomotor ability of flies was analyzed by negative geotaxis
after seven days of exposure to coconut oil enriched diet (0%, 10%, and 20%).
All of the animals that displayed a consistent sign of geotaxis
during the tilting experiments and were used for analysis of beat frequencies were negatively geotactic.
This interpretation is supported by the work of Rice (1985) and Rice and Salt (1988, 1990) who selected on multifarious habitat selection (phototaxis, geotaxis
, and chemotaxis as well as developmental time) under conditions of maximal gene flow between divergently selected populations, and tested for the development of reproductive isolation as a correlated response.
An important functional question is whether these asymmetries of statolith morphology and orientation with respect to the sagittal and tentacular body planes affect the function of the statocyst during geotaxis
To determine whether descending movements resulted from passive sinking or active swimming due to either negative phototaxis or positive geotaxis
, we compared speed of movement for dark-adapted cercariae with the speed of cercariae that were anesthetized.
Since phyllosoma larvae did not display a negative phototaxis to low light intensities, it is likely that the descent results from either a sinking response or positive geotaxis
Zoeae show a negative geotaxis
in darkness, in which they ascend.
We have observed that larvae in culture exhibit positive geotaxis
, a behavioral tendency that would contribute to their apparently limited dispersal (Reitzel, Darling, Sullivan, and Finnerty, unpubl.
2]-deficient water, the animal displays negative geotaxis
and moves to the water surface to breathe air.
in sea urchin larvae: a possible role of mechanoreception in the late stages of development.
1997) provided experimental evidence that differential weighting, caused by the presence of spicules at the posterior end in some larvae, is correlated with positive geotaxis