Environmental Influences on Thyroid Function in Teleost Fish

SYNOPSIS. A brief account of some of the influences that environmentalfactors, such as the lunar cycle, daylength and temperature,may have on thyroid activity in certain salmonids and the killifish,Fundulus heteroclitus, is presented. The rapid and immediatecharacterof temperature effects is discussed and a role for central neuroendocrinecontrolin mediating the effects of photoperiod and lunar phenomenainvolvement is suggested.     

The effect of visual input on calling song attractiveness for female Acheta domesticus

ABSTRACT. Of twelve mature phonotactically-responsive female Acheta domesticus L., ten responded phonotactically to a wider range (30 or SO to 100 ms) of model calling song (CS) syllable periods (SP) on the Kramer treadmill in the dark than in a lighted visually structured arena (50–70 ms). When given a choice between the visually attractive target and the invisible loudspeaker, seven of the ten females that tracked a visually attractive target (black square) when presented alone in the light reduced the range of SPs they tracked phonotactically to 50–70 ms. Three of the ten females that were not strongly attracted to the visual target when presented alone, continued to respond to model calling songs with a wide range of SPs (30–100 ms) when given a choice between visual and acoustical targets under the same conditions. Two of the twelve females responded only to model calling songs with a 50–70 ms SP on the Kramer treadmill in the dark. These females did not change their choice for model calling song SPs when presented with the visually attractive target.     

Scototaxis and shape discrimination in the female cricket Acheta domesticus in an arena and on a compensatory treadmill

ABSTRACT. The scototactic responses of adult female Acheta domesticus L. were tested toward various shaped targets in an orientation arena and on a compensatory treadmill. In an arena, crickets oriented toward dark targets (positive scototaxis) if they had horizontal visual angles ≥30, and if the vertical dimensions of the target was ≤ its horizontal dimension. Unattractive targets did not result in negative scototaxis but caused crickets to orient randomly with no net directionality. When complex targets were composed of two or more simple rectangular targets which had been previously defined as attractive or unattractive, intermediate responses were obtained. Crickets oriented less toward complex targets than toward simple attractive targets, but oriented more than toward simple unattractive targets. The responses of a female cricket toward an attractive target can be modified by the presence of a chemical signal emitted by previously tested females. When the signal is present females are less likely to orient toward a target that would otherwise be very attractive. This effect was not as great when the females being tested were taken directly from densely populated colonies.
When running on a compensatory treadmill, female crickets exhibit scototactic tendencies similar to those displayed in the arena. When tested on the treadmill over long periods, the amount of time spent orienting toward an attractive target increased.