A Diurnal Activity Rhythm in Plethodon Cinereus and Its Modification by an Influence Having a Lunar Frequency

Abstract

It has become increasingly clear that many of the physiological processes in organisms do not occur at constant rates, even when the organism is in a constant laboratory environment. These fluctuations in rates are often of regular recurrence and may be designated as rhythms. 2 Various manifestations of these changes taking place within the organisms may be observed. Among them are rhythms of O 2consumption and CO,-production, locomotor activity, chromatophore pigment dispersal and body temperature changes.Judging from the number of contributed works in the field of biological rhythms, locomotor activity has been more often utilized as an index to rhythmic behavior than any other kind of biological process. The simplicity of automatic recording devices needed, the long span of time over which animals may be used for such studies, and the minimal interference with the animals' normal functioning, are some SUMMARY 1. The salamander, Plethodon cincrcus, shows a diurnal rhythm of locomotor activity, both in alternating 12-hour periods of light and darkness, and in continuous darkness.2. The diurnal rhythm is strongly modified by a depressive influence that is apparently associated with the time of lunar zenith.

Better in the dark: two Mediterranean amphibians synchronize reproduction with moonlit nights

“…Moreover, lunar-related activity patterns similar to those observed in this study (lunar phobia) have been described for other amphibians (i.e. Ralph, 1957;Fitzgerald and Bider, 1974) as well as for several nocturnal animals (scorpions - Skutelsky, 1996;snakes -Campbell et al, 2008;mammals -Lockhard, 1978;Wolfe and Tan Summerlin, 1989;Daly et al, 1992;Gannon and Willing, 1997;birds -Clarke, 1983;Mougeot and Bretagnolle, 2000). In all these studies, the observed moonlight avoidance by animals has been related to the increasing risk of predation by visually oriented preda-tors due to bright moonlight (Lima and Dill, 1990).…”

“…Although moon effects on amphibian biology have been recognized (Church, 1960a, b;Byrne, 2002;Grant et al, 2009), the direction of this influence is rather controversial with evidence of both increased (Tuttle and Ryan, 1982;Grant et al, 2009;Yetman and Ferguson, 2011), and decreased activity under the full moon (Ralph, 1956;Church, 1960b;Fitzgerald and Bider, 1974;Duellman and Trueb, 1994). Concerning anurans, it has been observed that they were able to respond directly to changing moonlight (antipredator and/or foraging behaviours; Kotler et al, 1991), or may present an endogenous cycle with lunar periodicity (Ralph, 1957).…”

Vertebrate Behavioral Rhythms

“…; Higginbotham, 1939) and salamanders (Ambystoma tigrinum larvae; Kalmus, 1940) described the "persistence" of 24-hr rhythms rather than freeruns in constant illumination. Several more recent studies have also described persistence of solar-day or 24-hr rhythms in LL or DD (Ralph, 1957;Bennett and Staley, 1960;Cloudsley-Thompson, 1967). These reports should be regarded with great caution since amphibians may share with other poikilotherms (see p. 198) the capacity to entrain to very-small-amplitude temperature cycles that may not have been detected or controlled (cf.…”

“…These include temperature (Fitzgerald and Bider, 1974b); rainfall (Arnold, 1943;Fitzgerald and Bider, 1974b); barometric pressure (Robertson, 1978); and moonlight (Fitzgerald and Bider, 1974b;Robertson, 1978). There are also claims based on scant evidence that lunar cycles exert an influence on animals isolated from moonlight (Ralph, 1957;Bennett and Staley, 1960).…”

Environmental Factors Influencing Local Distribution and Activity of the Salamander, Plethodon Cinereus

“…Hence fully hydrated individuals may move out of the litter when relative humidity is low enough to keep partly desiccated salamanders below the surface. Ralph ( 1957) has suggested that the basis for the activity cycle of P. cinereus is an internal rhythm as captive salamanders maintained an activity pattern corresponding to the day-night cycle although kept in complete darkness for a month. If this conclusion is correct, then the negative reaction to high evaporating power of the air simply tends to suppress the normal rhythm when humidities above ground are low.…”