The NSS Bulletin - ISSN 1090-6924
Volume 47 Number 2: 147-162 - December 1985
A publication of the National Speleological Society

Time-Keeping Mechanisms and Their Ecological Significance in Cavernicolous Animals
Günther Lamprecht and Friedrich Weber

Abstract

The present paper reviews the "circadian literature" in cavernicolous animals. Distrinct circadian periodicities, which were reported in locomotory patterns of trogloxenic, troglophilic and even troglobitic species, seem to be ecologically significant. Extremely evolved cavernicolous animals, however, lack circadian periodicities of location. Circadian growth rhythms are also unknown to troglobitic species. It is concluded that during the course of regressive evolution under cave conditions the circadian system degenerates without any residue. This conclusion implies the hypothesis that circadian clocks are not necessary for separating incompatible metabolic reactions in eukaryotic organisms.

The spontaneous locomotory patterns of cavernicolous carabids, including extremely evolved trogolbitic species, frequently show structural regularities which can be described as the consequence of control by randomly generated internal signals. Stochastic regularities are also demonstrable in epigean carbids. It is concluded that central random generators, which control behavior, have survived the regressive evolution under cave conditions. A control by stochastic regularities seems to be adaptive. The variable parameters are the probabilities of transition from activity to rest and from rest to activity. A model is proposed to explain the interaction between the circadian clock and the random generators in animals which possess both controlling systems.

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