Hyperactive and anxiolytic‐like behaviors result from loss of COUP‐TFI/Nr2f1 in the mouse cortex

The nuclear receptor COUP TFI (also known as Nr2f1) plays major roles in specifying distinct neuronal subtypes during patterning of the neocortical motor and somatosensory cortex, as well as in regulating the longitudinal growth of the hippocampus during development. In humans, mutations in the NR2F1 gene lead to a global developmental delay and intellectual disabilities. While more than 30% of patients show behavioral features of autism spectrum disorder, 16% of haploinsufficient children show signs of hyperactivity and impulsivity. Loss of COUP‐TFI in the cortical mouse primordium results in altered area organization and serotonin distribution, abnormal coordination of voluntary movements and learning and memory deficits. Here, we asked whether absence of COUP‐TFI affects locomotor activity, anxiety, as well as depression. Mice mutant for COUP‐TFI have normal motor coordination, but significant traits of hyperactivity, which does not seem to respond to N‐Methyl‐D‐aspartate (NMDA) antagonists. However, no changes in anxiety, despite increased locomotor performances, were observed in the open field task. On the contrary, elevated plus maze and dark‐light test explorations indicate a decreased anxiety‐like behavior in COUP‐TFI mutant mice. Finally, significantly reduced immobility in the forced swim test and no changes in anhedonia in the sucrose preference task suggest no particular depressive behaviors in mutant mice. Taken together, our study shows that loss of COUP‐TFI leads to increased locomotor activity but less anxiety and contributes in further deciphering the pathophysiology of patients haploinsufficient for NR2F1.     

GENETIC BASIS OF ACTIVITY METABOLISM. I. INHERITANCE OF SPEED,STAMINA, AND ANTIPREDATOR DISPLAYS IN THE GARTER SNAKE THAMNOPHIS SIRTALIS

Recent conceptual advances in physiological ecology emphasize the potential selective importance of whole-animal performance. Empirical studies of locomotor performance in reptiles have revealed surprising amounts of individual variation in speed and stamina. The present study is the first in a series examining the genetic basis of variation in locomotor performance, activity metabolism, and associated behaviors in garter snakes. Maximal sprint crawling speed, treadmill endurance, and antipredator displays (Arnold and Bennett, 1984; exhibited as snakes reached exhaustion on the treadmill) were measured for approximately six offspring (presumed to be full siblings) from each of 46 wild-caught gravid garter snakes (Thamnophis sirtalis). Each character was measured on two days; all were individually repeatable. Correlations of these characters with body mass, snout–vent length, age at testing, litter size, dam mass, and dam snout–vent length were removed by computing residuals from multiple-regression equations. These residuals were used in subsequent genetic analyses. Approximate coefficients of variation of residuals were 17% for speed, 48% for endurance, and 31% for antipredator displays. Broad-sense heritabilities were significant for all characters: speed h² = 0.58; stamina h² = 0.70; antipredator display h² = 0.42. All three residual characters showed positive and statistically significant phenotypic correlations (r = 0.19–0.36). Genetic correlations (estimated and tested by restricted maximum likelihood) among residuals were positive and highly significant between speed and endurance (0.58), but nonsignificant between speed and antipredator display (0.43), and between endurance and antipredator display (0.26). All environmental correlations were nonsignificant. These data suggest that, contrary to expectations based on previous physiological studies, there may be no necessary evolutionary trade-off between speed and stamina in these animals. This tentative conclusion will have important implications for future theoretical studies of the evolution of locomotor performance and associated antipredator behaviors.     

Daily and seasonal rhythms of locomotor activity and adrenal function in male hedgehogs(Erinaceus europaeus L.)

Abstract

Male hedgehogs were maintained in outdoor parks, under natural climatic conditions. The general locomotor activity was recorded over one year in five hedgehogs, using an infra‐red producer‐receptor system registering entering or leaving the nest box in relation to time. Simultaneously, thecortico‐adrenal activity was studied monthly by sampling without disturbing, at 4 h intervals over a period of 24 h, in groups of 6 animals with a catheter inserted in the left carotid artery. The corticosteroids were assayed using a competitive protein binding technique.

In our study, hedgehogs living in Western Central France showed:

(1) from February‐March to August‐September a daily nocturnal locomotor activity well synchronized with sunset and sunrise,

(2) between August‐September and February‐March an alternation of resting and activity periods which constitute the hibernating period. The activity periods occur still during the night, but there are no relationships with sunset or sunrise,

(3) from February to October, a nycthemeral rhythm of plasma corticosteroids wi th an evening maximum and a morning minimum, as in laboratory animals with nocturnal locomotor activity,

(4) after October, during hibernation, significant variations of plasma corticos teroids with an irregular.pattern (shifting of the maximum or biphasic profile),

(5) a clearly annual cycle of the daily plasma corticosteroids levels, with a considerable increase in autumn (maximum in December), a significant decrease in January and a minimum from January to May.

These daily and seasonal variations of locomotor activity and cortico‐adrenal activity are related to the seasonal variations of the environment.     

Brain cell number and motor activity in rats subjected to neonatal undernutrition

Rat pups were undernourished until weaning by raising them in oversized litters. After weaning they were fed $\text{ad lib}$. Control subjects were raised in normal-sized litters and fed $\text{ad lib}$. After weaning. They were all examined between 4 and 5 weeks of age in 3 behavioral tests, measuring various aspects of motor capabilities: orienting locomotor activity, rotarod performance, and activity wheel running. Following the completion of behavioral studies the animals were sacrificed and cerebral and cerebellar DNA (cell number) were assayed. Comparisons between control and undernourished groups revealed significant reduction in body weights in the undernourished subjects, both at weaning and at the time of behavioral testing. Cerebral and cerebellar DNA were reduced in the undernourished rats as compared to controls. No difference was noted between the groups in rotarod performance or activity wheel running. The orienting locomotor activity, however, was greater in controls than in undernourished subjects. When these one-hour activity counts were divided into periods, the early counts did not differ between groups, while the counts late in the hour were significantly less in the undernourished animals. Thus, while the high counts of the initial orienting response were unaffected by the state of nutrition, the decay with habituation occurred at a more rapid rate in the rats that were poorly nourished. Cerebellar levels of DNA were found to correlate with locomotor activity counts, but cerebral DNA levels did not. The findings suggest that cerebellar underdevelopment can influence behavior in subtle ways not clearly associated with deficiencies in control of skeletal muscle tone or coordination.     

Neuroleptic properties of the ion-channel-forming peptaibol zervamicin: locomotor activity and behavioral effects

Zervamicins IIA and IIB are members of the peptaibol family of peptide antibiotics. They are produced by the fungus Emericellopsis salmosynnemata. Peptaibols are known to be of potential usefulness for chemotherapeutic applications, as are other secondary fungal metabolites. Previously, we have found zervamicins to decrease spontaneous locomotor activity in mice, suggesting their neurotropic properties on an equal footing with antimicrobial activity. The current study deals with behavioral effects of zervamicins IIA and IIB in mice. According to our results, both zervamicins induce a reliable decrease in locomotion and exploratory activity measured in the hole-board test. The behavioral effects of zervamicin IIA become apparent at lower dosages (0.05-2.0 mg/kg) as compared with zervamicin IIB (0.5-12.0 mg/kg). The experiments on behavioral effects in the elevated plus maze test showed that both zervamicins caused a reliable decrease in the number of head-dippings, open-arm entries, and rearings. The observed behavioral effects may be rather associated with a decrease in the exploratory activity than with anxiety-related responses in mice. Zervamicins induced depression-like behavior of experimental animals in the forced-swim test. Both peptaibols reduce physical endurance and change motor coordination of experimental animals in the bar-holding test. Taken together, the data obtained clearly indicate that both zervamicins possess neuroleptic activity.     

Tail Autotomy Plays No Important Role in Influencing Locomotor Performance and Anti‐Predator Behavior in a Cursorial Gecko

We used the frog‐eyed sand gecko (Teratoscincus scincus) as a model system to evaluate the locomotor costs of tail loss, and to examine whether tailless geckos use alternative anti‐predator behavior to compensate for the costs of tail loss. Of the 16 field‐captured geckos, eight were used as experimental animals and the remaining ones as controls. Locomotor performance, activity level and anti‐predator behavior were measured for experimental geckos before and after the tail‐removing treatment. Control geckos never undergoing the tail‐removing manipulation were measured to serve as controls for the measurements taken at the same time for experimental geckos. Experimental geckos did not differ from controls in activity level before they underwent the tail‐removing manipulation, but became less active thereafter. The mean locomotor stamina of tailless geckos was reduced by about 30% of the mean value for tailed ones. However, as the maximum stamina predicted from the laboratory trials is seldom required in nature, we expect that the costs associated with the reduced locomotor stamina may be relatively minor in T. scincus. All other examined locomotor (overall speed, maximal speed and stride length) and behavioral (distance to refuge, approach distance and flight distance) traits were not affected by the tail‐removing manipulation. Overall, our results suggest that tail autotomy plays no important role in influencing locomotor performance and anti‐predator behavior in lizards where the tail has no direct role in locomotion but is used to direct predatory strikes away from the torso.     

Anticonvulsant Activity of Pterostilbene in Zebrafish and Mouse Acute Seizure Tests

Pterostilbene (PTE), a natural dimethylated analog of resveratrol, possesses numerous health-beneficial properties. The ability of PTE to cross the blood–brain barrier raised the possibility that this compound may modulate central nervous system functions, including seizure activity. The aim of our study was to investigate the activity of PTE in the larval zebrafish pentylenetetrazole (PTZ) seizure assay and three acute seizure tests in mice, i.e., in the maximal electroshock seizure threshold (MEST), 6 Hz-induced psychomotor seizure threshold and intravenous (iv) PTZ tests. Additionally, potential antidepressant activity of PTE was estimated in the forced swim test in mice. The chimney test was used to determine the influence of PTE on motor coordination in mice, while its influence on neuromuscular strength was assessed in the grip strength test in mice. Locomotor activity was determined to verify the results from the forced swim test. PTE revealed an evident anticonvulsant effect both in zebrafish larvae (10 µM; 2 h-incubation) and mice (at doses of 100 and 200 mg/kg, intraperitoneally) but it did not exhibit antidepressant potential in the forced swim test. Furthermore, it did not cause any statistically significant changes in motor coordination, neuromuscular strength and locomotor activity in mice. In conclusion, our present findings demonstrate for the first time the anticonvulsant potential of PTE. The aforementioned results suggest that it might be employed in epilepsy treatment, however, further precise studies are required to verify its activity in other experimental seizure and epilepsy models and its precise mechanism of action should be determined.

     

Insights into post-fledging dispersal of Bearded Vultures Gypaetus barbatus in southern Africa from GPS satellite telemetry

Capsule: Fledglings progressively increase their home range size and ranging behaviour as they age.

Aims: To examine the home range size and ranging behaviour of Bearded Vulture fledglings during the post-fledging dependence period and determine the onset of natal dispersal.

Methods: Post-fledging movements of three individuals were investigated in southern Africa using global positioning system (GPS) satellite telemetry which enabled home range sizes and distances travelled from the nest to be calculated.

Results: Fledglings increased their home range size from an average of 0.4–10 999?km² (100% Minimum Convex Polygons) and 9.13–11 466?km² (fixed 95% kernels) within the first six months post fledging. They also increased home range use as they aged with maximum daily distances travelled from the nest occurring between 98 and 136 days post fledging (when fledglings were aged between 222 and 262 days), after which time they dispersed from their natal area. Distances between fixes were highest during the dispersal period.

Conclusion: GPS satellite telemetry allows us to accurately demonstrate how fledglings progressively increase and use their home ranges as they age and undertake pre-dispersive exploratory flights. Results confirm the notion that juveniles disperse at the onset of the following breeding season and suggest that dispersal occurs earlier in the southern hemisphere.     

Antinociceptive activity of a 3(2H)-pyridazinone derivative in mice.

The antinociceptive activity of a 3(2H)-pyridazinone derivative (18a) was investigated in mice. 18a administered at doses which did not change either motor coordination or locomotor activity was able to induce antinociceptive effects in four nociceptive tests, the hot plate test, the tail flick test, the writhing test, and the formalin test. In the hot plate and tail flick test, 18a-induced antinociception was observed both after intraperitoneal administration and after intracerebroventricular injection thus indicating 18a has a central site of action. The pretreatment with the opioid antagonist naloxone, the alpha2-antagonist yohimbine or the GABA(B) antagonist CGP 35348 did not change 18a-induced antinociception in the hot plate test and in the tail flick test. Pretreatment with nicotinic antagonist mecamylamine did not change 18a effects either. A reversion of the 18a effects was observed after pretreatment with the muscarinic antagonists atropine and pirenzepine. Binding experiments revealed that 18a binds to muscarinic receptors, suggesting that 18a antinociception is mediated by central muscarinic receptors. The above findings together with the lack of parasympathomimetic cholinergic side effects indicate useful clinical application for this compound.     

Effect of GABA receptor agonist phenibut on behavior and respiration of rabbits in the negative emotional situation

The influence of systemic injection of GABA-receptor agonist--phenibut (40 mg/kg, s/c) on open field behavior, behavioral reactivity and changes in respiratory parameters after exposure of negative emotional stimuli was studied in three rabbit groups differentiated by locomotor activity in open field (active, passive and medium-active animals). The injection of phenibut results in decrease of rabbits horizontal locomotor activity and some components of research behavior in open field and also decrease of behavioral reactivity on emotional stimuli. At the same time the probability of both an active orienting exploratory or defensive reactions and passive reactions (freezing) were decreased. The influence of phenibut depended on typological features of rabbits: the most potent effect occurred upon behavior of active rabbits, less on passive animals and practically none on medium-active rabbits. The phenibut injection results in increase of duration of inhalation during exposure to emotional stimuli, whereas it decreased in normal.     

Determinants of musculoskeletal frailty and the risk of falls in old age

Neuromuscular parameters that describe locomotion are indispensable variables for the diagnosis and treatment of frailty, fall risk and osteoporosis. A scientifically-based standardized locomotor assessment should be an essential part of medical examinations in research and clinical practice. There has been no previous consensus regarding which test procedures should be included in a locomotor assessment. The goal of this article is to provide a rationale for the selection of appropriate locomotor tests in a comprehensive locomotor assessment for elderly patients. We propose that a locomotor assessment should comprise the parameters that have been proven predictive for both falls and impending disability. The parameters should be measured in the standard units of physics. Therefore, we propose the following tests for a standardized locomotor assessment: (1) Self-selected gait velocity as the single best measure of general locomotor status and a good predictor of age-related adverse events; (2) Chair rise test (timed 5 chair rises) which measures power on vertical movement and the hip surrounding muscles as the most important neuromuscular risk factor for falls and fall-related fractures; (3) Tandem standing and tandem walking to measure postural capacity (balance) to the side; (4) Timed up and go test as a global screening procedure; (5) Clinical gait analysis with special focus on regularity; and (6) At least on a research level, movement must be measured referring to the terms of physics by mechanography. Mechanography (Leonardo force plate system, Novotec Pforzheim, Germany) records the time course of ground reaction forces, velocity of the vertical movements of the center of mass and power during unrestricted physiological movements. In the mechanogram the eccentric and concentric phases of movements can be differentiated and the storage of energy in the elastic elements of the body can be examined. The kinetics of human movement is explained by mechanograms of a two-legged jump. The ground reaction forces resulting from a jump down from a height of 0,46 m are demonstrated as a performance that is representative for human coordination. One goal of this text is to underline the insights that arise if the rules of physics are applied to human movement. A deeper understanding enables us to create more effective treatments for disorders of the muscle-bone unit. Bringing physics and cybernetics into the field of osteoporosis is a great heritage of Harold Frost.     

Comparison of the effects of TRH and D-Ala2-metenkephalinamide on hippocampal electrical activity and behavior in the unanesthetized rat

Administration of TRH into the lateral ventricle of unanesthetized rats produced increases in the incidence of hippocampal theta (5.9–9.1 Hz) rhythm, locomotor activity and shaking behavior. The increase in theta rhythm produced by TRH was brief (<5 min) and was coincident with a brief, large increase in locomotor activity. Intracerebroventricular injection of either TRH or D-Ala²-metenkephalinamide (D-Ala²-ME) also induced episodes of shaking behavior. Shakes induced by D-Ala²-ME were associated with the occurrence of hippocampal epileptiform activity whereas those caused by TRH occurred in the absence of any recorded abnormalities in hippocampal activity. These results suggest that the increase in hippocampal theta rhythm after TRH is secondary to the increase in locomotor activity and, that in contrast to enkephalins, shaking behavior caused by TRH may not be related to an action on the electrographic activity of the hippocampus.     

Eine Methode zur Registrierung der Laufaktivität von kleinen Insekten

Summary The method described in this paper enables the locomotor activity of small insects to be recorded. It is based on variations in capacitance within a bridge circuit, the variations being due to movements of the animals. The method is adapted to the use of multi-channel action recorders, thus allowing a greater number of sensor units to be employed simultaneously.As an example of application, a comparison is made between the diurnal rhythmicity patterns of locomotor activity inDrosophila melanogaster andDrosophila azteca. Both species show maximal activity in the morning and in the evening.D. melanogaster is active throughout the middle of the day as well, butD. azteca, being adapted to an arid climate, shows a resting period during this time of day.

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Herrn Prof. Dr. Georg Birukow zum 60. Geburtstag gewidmet.     

Behavioural characterisation of young adult transgenic mice overexpressing galanin under the PDGF-B promoter

The behavioural phenotype of transgenic mice (3- to 5-months old) overexpressing galanin (GalOE) under the platelet-derived growth factor B (PDGF-B) promoter was evaluated in a battery of tests, including open field, locomotor cages, light-dark exploration test, elevated plus-maze and the Porsolt forced swim test. Learning and memory were assessed in the passive avoidance and the Morris water maze tasks. No difference between genotypes was found in exploratory activity in the open field. GalOE mice showed a slight increase in spontaneous locomotor activity assessed in the locomotor cages, but the amphetamine-induced increase in locomotor activity was somewhat lower in GalOE mice. Anxiety-like behaviour in the three different tests including open field, light-dark exploration and elevated plus-maze did not differ between genotypes. In the Porsolt forced swim test, GalOE mice displayed an increased time of immobility, indicative of increased learned helplessness possibly reflecting increased stress-susceptibility and/or depression-like behaviour. GalOE mice showed normal learning and memory retention in the passive avoidance and the Morris water maze tasks. These data support the hypothesis that galanin may have a role in functions related to mood states including affective disorders.     

Age‐depending effects of narcosis and transmitter implantation on circadian body temperature and activity rhythms in mice

Summary

The effects of narcosis and of telemetry transmitter implantation on core temperature and locomotor activity were investigated in female laboratory mice of various age (3, 15 and 52 weeks old). Following surgery a transient hypothermia was observed. The body temperatures measured 30 min after beginning of narcosis were lower in juvenile and in presenile mice (29.6° ±0.8°C resp. 30.0° ±0.2°C) than in adult animals (31.9° ±0.3°C). The following temperature increase was fastest in juvenile mice. Normal body temperature was reached after 6h 20’ already. Adult and presenile mice needed 8h 30’ resp. 7h 30’. The temperature increase seemed to be independent from activity behaviour of the animals. No substantial differences could be obtained whether the transmitters had room or body temperature before implantation and whether the animals were warmed after surgery by an infrared bulb or not. Probably, the temperature increase depended mainly on the elimination rate of the drug.

Normal circadian core temperature and activity rhythms reappeared on average within 5–6 days in juvenile mice and a little faster in adult (4–5 days) as well as in presenile ones (3–4 days). However, interindividual differences in recovery time were more pronounced than age‐dependent variations.

Circadian core temperature and activity patterns were quite similar in all three age classes investigated. Ontogenetic differences concern, besides changes in daily mean values, mainly a temperature amplitude increasing with age, as well as a high percentage of ultradian components in the activity pattern of juvenile mice compared to older ones.

Telemetry systems are widely used for long‐term measurements of core temperature in laboratory animals (Clement et al., 1989; Refinetti and Menaker, 1992). In our investigations of ontogenetic changes of the circadian temperature and activity rhythms in mice we used an integrated telemetry and data acquisition system (Dataquest, Data Sciences Inc., USA). It comprises implantable wireless transmitters, telemetry receivers, a consolidation matrix and a data acquisition system. The aim of a preliminary study was to analyse the effects of narcosis and transmitter implantation. The time required to recover normal values of body temperature and of locomotor activity as well as normal circadian rhythms was determined, considering also ontogenetic variations.     

Short-day photoperiod disrupts daily activity and facilitates anxiety–depressive behaviours in gerbil Meriones unguiculatus

Seasonal photoperiod has impact on the physiology of many plants and animals. Short days related with the winter are often associated with changes in activity patterns and, in humans, with some mood disorders. Natural changes related with seasonality occur gradually and such approach has to be considered when studying animal models in laboratory conditions. In the present work, we studied if gradual changes from light–dark cycles 12:12 h to short (08:16) or long days (16:08) have a significant effect upon the locomotor activity profile and some anxiety- and depression-like behaviours in the gerbil Meriones unguiculatus. Locomotor activity was recorded by means of infrared light beams. Once adapted to experimental photoperiod, gerbils were used for elevated plus maze (EPM) or forced swim test (FST). Our results indicate that in 12:12, a clear bimodal pattern associated with light transitions was present. When exposed to long days, gerbils increased their total locomotor activity and the bimodal profile persisted. When in short days, locomotor activity decreased and no rhythm was noted. Behavioural assays on EPM and FST indicated that exposition to short days induce in the gerbils an anxiety and depressive-like behaviour, reducing the time spent in open arms and increasing the time of immobilizations. We conclude that short photoperiod affects negatively the locomotor activity daily patterns and mood behaviour in anxiety and depressive way in the Mongolian gerbil.     

Is the whole more than the sum of its parts? Evolutionary trade-offs between burst and sustained locomotion in lacertid lizards

Trade-offs arise when two functional traits impose conflicting demands on the same design trait. Consequently, excellence in one comes at the cost of performance in the other. One of the most widely studied performance trade-offs is the one between sprint speed and endurance. Although biochemical, physiological and (bio)mechanical correlates of either locomotor trait conflict with each other, results at the whole-organism level are mixed. Here, we test whether burst (speed, acceleration) and sustained locomotion (stamina) trade off at both the isolated muscle and whole-organism level among 17 species of lacertid lizards. In addition, we test for a mechanical link between the organismal and muscular (power output, fatigue resistance) performance traits. We find weak evidence for a trade-off between burst and sustained locomotion at the whole-organism level; however, there is a significant trade-off between muscle power output and fatigue resistance in the isolated muscle level. Variation in whole-animal sprint speed can be convincingly explained by variation in muscular power output. The variation in locomotor stamina at the whole-organism level does not relate to the variation in muscle fatigue resistance, suggesting that whole-organism stamina depends not only on muscle contractile performance but probably also on the performance of the circulatory and respiratory systems.     

Behavioral responses of hatchling painted turtles (Chrysemys picta) and snapping turtles (Chelydra serpentina) at subzero temperatures

We monitored behavioral responses of cold-acclimated hatchling painted turtles (Chrysemys picta) indigenous to Nebraska and hatchling snapping turtles (Chelydra serpentina) indigenous to Nebraska and Arkansas during cooling (0.1°C/min) to temperatures as low as −19°C. All turtles made exploratory movements during cooling and locomotion occurred at temperatures as low as −2 to −4°C, but C. picta maintained relatively higher levels of locomotor activity than C. serpentina, and no differences in motility occurred between northern and southern groups of C. serpentina. Slow movements of the head and limbs were observed in supercooled hatchling C. picta at temperatures as low as −10°C, whereas at about −5°C, C. serpentina exhibited an increase in spontaneous motor activity followed by muscle contracture, immobility, and spontaneous freezing. C. picta spontaneously froze at about −16°C without exhibiting cold contracture, suggesting that they are better adapted to survive exposure to extreme cold.     

The relationship between locomotor activity rhythm and burying behavior in the wrasse,Suezichthys gracilis

The wrasse,Suezichthys gracilis, is a diurnal fish which buries itself in sand during the night-time. The present paper deals with the locomotor activity rhythms ofS. gracilis, examined by using an actograph with infra-red photo-electric switches in a dark room. The fish were kept in eight experimental tanks (each 30l in capacity), with three different bottom conditions: sand (grain size about 1 mm in diameter and 5 cm deep); 1 or 2 stones (about 10cm in diameter) without sand; and transparent acrylic pellets (2 × 2 × 3 mm in size, 5 cm deep). The light intensities were 550–700 lux just above the water surface, decreasing to 21.3% under the acrylic pellets at a water depth of 20cm. The water temperatures were kept at 22.0–25.0°C during the experiments for 7 to 14 days. In the aquarium with bottom sand, diel activity rhythms ofS. gracilis were mostly synchronized to LD (LD12:12; 06:00–18:00 light, 18:00–06:00 dark), free-running activity rhythms continued distinctly under LL (constant illumination), and locomotor activity was greatly suppressed, with disappearance of the activity rhythm, under DD (constant darkness). In the aquarium without sand, locomotor activity ofS. gracilis could be summarized as follows. The fish moved throughout almost the entire period under LD, though more frequent movements were observed in light conditions than in dark ones. Under LL they showed continuous locomotor activity during the experiment, with no obvious periodicity. Under DD the activity of the species was somewhat suppressed, but irregular movement or indistinct periodicity was observed. In the aquarium with transparent acrylic pellets, locomotor activity under LD and DD, respectively, bore a close resemblance to activity patterns under the same light conditions with sand, whilst activity under LL was identical to that under LL without sand. Accordingly, it seems that maintenance of normal activity rhythms in the wrasse was due not only to the darkness, but also to the presence of bottom sand. It therefore seems that the biological clock inS. gracilis is not related to locomotor activity, but to burying behavior.