Maternal influence on activity rhythms and reproductive development in Djungarian hamster pups

Photoperiodism and entrainment of the circadian rhythm of locomotor activity were investigated in juvenile Djungarian hamsters. Animals were housed in simulated burrows. Activity was measured as the animal's emergence from a dark nest chamber into an outer box exposed to the room illumination. This burrow emergence activity exhibited marked circadian rhythmicity. Interactions between mother hamsters and their offspring were examined in the simulated burrow system. Male reproductive responses were determined by measuring testicular weights at the time of weaning. It was shown that photoperiodic information received between Days 1 and 15 of life failed to alter the rate of testicular development, but that after Day 15 testicular growth was photoperiod-dependent. The mother, when entrained to a long photoperiod, did not influence the photoperiodic responses of her pups when they were confined to a dark nest box. In contrast, the mother did influence the circadian entrainment patterns of her pups. Pups exhibited a well-developed circadian activity rhythm at weaning with a phase angle roughly similar to that of the mother's activity rhythm. When the maternal rhythms were discrepant with photoperiod information received by the pups directly from the environment, the pups' activity rhythms were synchronized with the light/dark cycle rather than with the rhythm of their mother. Thus, it appears that although pups may first become entrained by maternal cues, they rapidly adjust to the environmental light cycle after leaving the nest.     

Depth of artificial Burrowing Owl burrows affects thermal suitability and occupancy

Many organizations have installed artificial burrows to help bolster local Burrowing Owl (Athene cunicularia) populations. However, occupancy probability and reproductive success in artificial burrows varies within and among burrow installations. We evaluated the possibility that depth below ground might explain differences in occupancy probability and reproductive success by affecting the temperature of artificial burrows. We measured burrow temperatures from March to July 2010 in 27 artificial burrows in southern California that were buried 15–76 cm below the surface (measured between the surface and the top of the burrow chamber). Burrow depth was one of several characteristics that affected burrow temperature. Burrow temperature decreased by 0.03°C per cm of soil on top of the burrow. The percentage of time that artificial burrows provided a thermal refuge from above‐ground temperature decreased with burrow depth and ranged between 50% and 58% among burrows. The percentage of time that burrow temperature was optimal for incubating females also decreased with burrow depth and ranged between 27% and 100% among burrows. However, the percentage of time that burrow temperature was optimal for unattended eggs increased with burrow depth and ranged between 11% and 95% among burrows. We found no effect of burrow depth on reproductive success across 21 nesting attempts. However, occupancy probability had a non‐linear relationship with burrow depth. The shallowest burrows (15 cm) had a moderate probability of being occupied (0.46), burrows between 28 and 40 cm had the highest probability of being occupied (>0.80), and burrows >53 cm had the lowest probability of being occupied (<0.43). Burrowing Owls may prefer burrows at moderate depths because these burrows provide a thermal refuge from above‐ground temperatures, and are often cool enough to allow females to leave eggs unattended before the onset of full‐time incubation, but not too cool for incubating females that spend most of their time in the burrow during incubation. Our results suggest that depth is an important consideration when installing artificial burrows for Burrowing Owls. However, additional study is needed to determine the possible effects of burrow depth on reproductive success and on possible tradeoffs between the effects of burrow depth on optimal temperature and other factors, such as minimizing the risk of nest predation.     

Crepuscular activity of adult Sericesthis geminata (Coleoptera: Scarabaeidae): Influence of circadian rhythmicity and light intensity

Subterranean Sericesthis geminata (Boisduval) beetles emerge from the soil daily during the flight season. Emergence and flight are initiated within 15 min after sunset. The beetles are active above the soil surface as the intensity of illumination decreases from 240 lux to 0.7 lux.

If young adult beetles still in their pupal cells in the soil are placed under constant, low‐intensity illumination, they first emerge at any time of day, showing no cyclical diurnal activity pattern. When such beetles are exposed to diurnal fluctuations in illuminance, the first emergence and flight occur at dusk. These beetles subsequently show a diurnal rhythm in their activity, even when exposed to constant environmental conditions. This endogenous activity cycle has a period of about 22 h, and is synchronised with diurnal fluctuations in light intensity. It is reset in response to a change in the photoperiod.

The data suggest that, after initial emergence from the soil, daily crepuscular activity is initiated by an endogenously controlled activity rhythm which causes the beetles to burrow to the soil surface shortly before dusk. At the soil surface they are exposed to fluctuations in the duration and intensity of illumination which may reset the endogenous rhythm, affecting the time of subsequent emergence.     

Circadian Rhythms of Locomotor Activity in Lycosa tarentula (Araneae, Lycosidae) and the Pathways of Ocular Entrainment

Lycosa tarentula is a ground-living spider that inhabits a burrow where it awaits the appearance of prey or conspecifics. In this study, circadian rhythms of locomotor activity were examined as well as the ocular pathway of entrainment. Thirty-three adult virgin females were examined under constant darkness (DD); all of them exhibited robust circadian rhythms of locomotor activity with a period averaging 24.1h. Fourteen of these spiders were studied afterwards under an LD 12:12 cycle; they usually entrained to in the first or second day, even when the light intensity was as low as 1 lx. During the LD cycle, locomotor activity was generally restrained to the darkness phase, although several animals showed a small amount of diurnal activity. Ten males were also examined under LD; they were also nocturnal, but were much more active than the females. Seven females were examined under constant light (LL); under this they became arrhythmic. Except for the anterior median eyes (OMAs), all the eyes were capable of entraining the locomotor activity to an LD cycle. These results demonstrate that under laboratory conditions and low light intensities locomotor activity of Lycosa tarentula is circadian and in accordance with Aschoff's 'rule'. Only OMAs are unable to entrain the rhythm; the possible localization of circadian clock is therefore discussed.     

Circadian Rhythms of Locomotor Activity in Lycosa tarentula (Araneae,Lycosidae) and the Pathways of Ocular Entrainment

Lycosa tarentula is a ground-living spider that inhabits a burrow where it awaits the appearance of prey or conspecifics. In this study, circadian rhythms of locomotor activity were examined as well as the ocular pathway of entrainment. Thirty-three adult virgin females were examined under constant darkness (DD); all of them exhibited robust circadian rhythms of locomotor activity with a period averaging 24.1h. Fourteen of these spiders were studied afterwards under an LD 12:12 cycle; they usually entrained to in the first or second day, even when the light intensity was as low as 1 lx. During the LD cycle, locomotor activity was generally restrained to the darkness phase, although several animals showed a small amount of diurnal activity. Ten males were also examined under LD; they were also nocturnal, but were much more active than the females. Seven females were examined under constant light (LL); under this they became arrhythmic. Except for the anterior median eyes (OMAs), all the eyes were capable of entraining the locomotor activity to an LD cycle. These results demonstrate that under laboratory conditions and low light intensities locomotor activity of Lycosa tarentula is circadian and in accordance with Aschoff's 'rule'. Only OMAs are unable to entrain the rhythm; the possible localization of circadian clock is therefore discussed.     

The distribution and abundance of Helice tridens (De Haan) burrows and substratum conditions in a northeastern Japan salt marsh (Crustacea: Brachyura)

The effects of the physical condition of the substratum on the distribution and abundance of mud-crab burrows were investigated. In the salt-marsh habitats studied, where burrows were abundant, there was a high proportion of silt-clay. In such conditions, the diameters of openings and the depths of the burrows were greater than those when the relative proportion of silt-clay was low.In the laboratory, it was found that with a low proportion of clay, mud-crabs did not dig burrows when the water content was high and thus equivalent to that in the marsh. When the proportion of silt-clay was low, the larger mud-crabs did not make burrows at the depth of the water table in the marsh, because the layer above the water table was too thin to allow construction of the burrow. The field observations could thus be explained by the results of experiments showing that the depth of the burrows was controlled by the depth of the water table and the relative proportion of silt-clay in the substratum.     

Microhabitat and rhythmic behavior of tiger beetle Callytron yuasai okinawense larvae in a mangrove forest in Japan

Mangrove forests are regularly flooded by tides at intervals of approximately 12.4 h (tidal rhythm). Larvae of the tiger beetle Callytron yuasai okinawense in a mangrove forest made shallow burrows in mounds up to 1 m in height constructed by the mud lobster Thalassina anomala. No larval burrows were observed on the forest floor, which was very muddy even during low tide. Some larvae plugged the burrow openings before they were submerged at high tide. The mean interval between consecutive burrow plugging events was 12.37 h, which is similar to the period of tidal cycles. Nine out of 30 larvae plugged the burrow openings even when the burrows did not become submerged. Plugging behavior may be governed by an endogenous biological clock, or may be a response to exogenous information about tidal level (e.g. moisture seeping through the ground).     

Circatidal rhythmic behaviour in the coastal tiger beetle Callytron inspecularis in Japan

Larvae of the coastal tiger beetle Callytron inspecularis (W. Horn) (Coleoptera: Cicindelidae) plug their burrow opening before submergence at high tide. Field observations showed that burrow plugging was a rhythmic behaviour that coincided with the tidal cycle (ca. 12.4 h). On average, larvae plugged their burrows 41.8 min before the tide covered the habitat. The mean interval between consecutive burrow-plugging events in the field was 12.40 h. In the laboratory, in the absence of tidal inundation, the mean interval between consecutive burrow-plugging events was 12.45 h. This suggests that the burrow-plugging rhythm of the coastal tiger beetle is governed by an endogenous circatidal rhythm.     

瑶山鳄蜥洞穴的生态学初步研究

通过对广西昭平鳄蜥的洞穴采用封堵法和坐标法进行研究表明,植被盖度和洞穴之间呈现明显的正相关性.调查中共测量洞穴124个,其深度在18～132cm之间.在鳄蜥活动时间的分配上,洞穴占据了近1/3,故洞穴是其生命活动的一个重要条件.鳄蜥喜欢选择深邃弯曲的石缝、石洞或树洞居住或越冬,洞穴内湿度较大但不被水浸泡,隐蔽程度高、避光,洞口常有较密的植被.     

Intensity-dependent phase-adjustments in the locomotor activity rhythm of the nocturnal field mouse Mus booduga

The locomotor activity rhythm of the nocturnal field mouse Mus booduga was monitored under constant darkness (DD) and free-running periods (tau) were estimated. Following a free-run of about 15 days in DD, the animals were exposed to periodic light pulses (LPs) of various intensities (1 lux, 10 lux, 50 lux, 100 lux, and 1,000 lux) and 15 minutes duration for 65 days at intervals of 24 hours to investigate the influence of intensity of light on the phase-angle-difference (psi) between the onset of locomotor activity and the time of LP administration. The experimentally observed values of psi and tau for a LP of 1,000 lux intensity used for 15 minutes every 24 hr, showed a sigmoid shaped relationship with tau. This relationship was similar to that predicted based on the nonparametric model of entrainment, which uses the tau and the LP phase response curve (PRC) constructed using LP of similar duration and intensity. The functional nature of the relationship between psi and tau was not found to change significantly with increasing intensities of LP used to entrain the locomotor activity rhythm. However, psi was significantly modulated by the intensity of LP. These results suggest that the periodic sensitivity of the circadian pacemaker underlying the locomotor activity rhythm in the nocturnal field mouse M. booduga to LPs plays an important role in maintaining a characteristic psi with the zeitgeber and the psi changes in a light intensity-dependent manner.     

The activity rhythm of Goneplax rhomboides (L.)

Goneplax was found to have a persistent nocturnal rhythm of emergence when maintained in constant conditions in an actograph providing a simulated burrow. The rhythm was synchronized by the light/dark cycle and appeared to be reinforced by contact with the burrow walls. The activity of an animal seemed to be inhibited by the presence of others of the same species. The burrow is seen to play an important role in the life of the crab.     

Influence of age and environmental factors on burrow-making behavior of the short-tailed cricket,Anurogryllus muticus (De Geer) (Orthoptera: Gryllidae)

For the short-tailed cricket, Anurogryllus muticus, burrow-making behavior is essential. All nymphal instars construct burrows, but in the adult stage the rate of burrowing behavior is age dependent. Increases in photophase and light intensity stimulate burrowing, and the explicit negative phototaxis is correlated with the cricket's inability to exist under dry conditions. Ingestion of substrate during burrow construction may serve to acquire additional moisture. There is no evidence of burrow recognition, and crickets can construct a burrow when needed. The natural distribution of burrows at the plot investigated on Moorea supports the notion thatA. muticus builds burrows where the preferred food plantAlysicarpus vaginalis is most abundant. By minimizing the traveling distance to food sources when foraging they can retreat to their burrow again.     

Issues to Be Considered in Counting Burrows as a Measure of Atlantic Ghost Crab Populations,an Important Bioindicator of Sandy Beaches

The use of indirect estimates of ghost-crab populations to assess beach disturbance has several advantages, including non-destructiveness, ease and low cost, although this strategy may add some degree of noise to estimates of population parameters. Resolution of these shortcomings may allow wider use of these populations as an indicator of differences in quality among beaches. This study analyzed to what extent the number of crab burrows may diverge from the number of animals, considering beach morphology, burrow depth and signs of occupation as contributing factors or indicators of a higher or lower occupation rate. We estimated the occupation rate of crabs in burrows on nine low-use beaches, which were previously categorized as dissipative, intermediate or reflexive. Three random 2-m-wide transects were laid perpendicular to the shoreline, where burrows were counted and excavated to search for crabs. The depth and signs of recent activity around the burrows were also recorded. The occupation rate differed on the different beaches, but morphodynamics was not identified as a grouping factor. A considerable number of burrows that lacked signs of recent activity proved to be occupied, and the proportions of these burrows also differed among beaches. Virtually all burrows less than 10 cm deep were unoccupied; the occupation rate tended to increase gradually to a burrow depth of 20–35 cm. Other methods (water, smoke, and traps) were applied to measure the effectiveness of excavating as a method for burrow counts. Traps and excavation proved to be the best methods. These observations illustrate the possible degree of unreliability of comparisons of beaches based on indirect measures. Combining burrow depth assessment with surrounding signs of occupation proved to be a useful tool to minimize biases.     

Short-term and circadian rhythms in the behaviour of the vole,Microtus agrestis (L.)

Summary The activity behaviour of the vole, Microtus agrestis, has been recorded in order to investigate the relationship between short-term rhythm and circadian rhythm. A simple device was developed, allowing separate monitoring of the time spent in or outside the nest, wheel-running, eating and drinking. Under natural light conditions during summer, a distinct differentiation between a short term rhythm of eating and drinking during the day-time and a circadian rhythm of wheel-running during the night was observed. The short-term rhythm depends closely on metabolic demands (hunger, thirst, excretion). Control of these demands by an endogenous oscillation could not be substantiated. The circadian rhythm of wheel-running activity is, however, controlled by an endogenous oscillation, synchronized by light conditions. It is subjected to seasonal variations. a) The threshold of light intensity below which wheel-running occurs is lowest during summer (<0.5 lx) and is higher during spring and autum (> 5 lx). b) Wheel-running is controlled by a circadian oscillation during summer only whereas it is an integrated part of the short-term rhythm during spring and autumn (experiments during the winter have not yet been performed). Experiments gave evidence that the properties of the cage can deeply influence the amount and pattern of wheel-running activity. It is concluded that wheel-running reflects a certain level of excitation, which may be caused by different behavioural intentions. The seasonal changes of the control of wheel-running activity are discussed with respect to this assumption. The relevancy of locomotor activity patterns as usually recorded in the laboratory to reveal the physiological and ecological significance of endogenously controlled behavioural patterns is discussed.Supported by the Deutsche Forschungsgemeinschaft     

Burrow construction and behavior of tilefish,Lopholatilus chamaeleonticeps,in Hudson Submarine Canyon

Synopsis During 22 daylight submersible dives in August 1979 numerous juvenile and adult tilefish, Lopholatilus chamaeleonticeps, were observed in and around vertical burrows in the clay substrate of portions of Hudson submarine canyon in depths from 110–230 m. The size and shape of the burrows varied considerably with the smallest juveniles occupying simple vertical shafts in the substrate. Larger fish were found in much larger burrows (up to 4–5 m in diameter and at least 2–3 m deep) that were funnel shaped in cross-section with the upper conical portions containing numerous smaller burrows of associated crabs. The range of burrow sizes observed suggests a regular sequence of burrow construction by tilefish and the associated crabs. Both juvenile and adult tilefish swam into the burrows head first and exited tail first. This behavior, which would preclude the possibility of ambushing prey, and evidence of predation by sharks and other tilefish, suggests that the burrow is a refuge from predators.Tilefish burrows appear to serve as a focus for biological activity. Species associated with the burrows included galatheid crabs, Cancer sp., Acanthocarpus alexandri, Homarus americanus, Heliocolenus dactylopterus and Conger oceanicus. Tilefish may play an important role in structuring outer continental shelf communities. They physically shape their environment and probably have significant biological interactions with the species that associate with their burrows.     

Effects of psi-mutations on the Oviposition Rhythm of Drosophila rajasekari

The psi -mutations affected the circadian rhythm of locomotor activity in the early and late strains of Drosophila rajasekari (Joshi, 1999a). The present study was designed to determine the effects of psi -mutations on the oviposition rhythm of the early and late strains. Oviposition rhythms were studied in light-dark cycles of 12 :12 h in which the light intensity of photophase was 0.001, 0.01, 0.1, 1, 10, 100 or 1000 lux. The oviposition rhythm of wild type was unimodal at or above 10 lux with a peak before lights-off, while it was bimodal at lower light intensities. The early strain was unimodal at all light intensities with a peak after lights-on at or above 10 lux, and around the mid-day at or below 1lux. The late strain was rhythmic at 100 and 1000 lux with a peak after the lights-off, weakly rhythmic at 10 lux and arrhythmic at or below 1 lux. Free running period in constant darkness was shortest in the early and longest in the late strain. Threshold light intensity of constant light to generate arrhythmicity was lowest in the early and highest in the late strain, apparently the photic sensitivity of the clock photoreceptors was differentially altered by these mutations. Thus the psi -mutations for locomotor rhythmicity affected the oviposition rhythm too, suggesting that the same circadian oscillator might be controlling these both rhythms.     

Effects of psi-mutations on the Oviposition Rhythm of Drosophila rajasekari

The psi -mutations affected the circadian rhythm of locomotor activity in the early and late strains of Drosophila rajasekari (Joshi, 1999a). The present study was designed to determine the effects of psi -mutations on the oviposition rhythm of the early and late strains. Oviposition rhythms were studied in light-dark cycles of 12 :12 h in which the light intensity of photophase was 0.001, 0.01, 0.1, 1, 10, 100 or 1000 lux. The oviposition rhythm of wild type was unimodal at or above 10 lux with a peak before lights-off, while it was bimodal at lower light intensities. The early strain was unimodal at all light intensities with a peak after lights-on at or above 10 lux, and around the mid-day at or below 1lux. The late strain was rhythmic at 100 and 1000 lux with a peak after the lights-off, weakly rhythmic at 10 lux and arrhythmic at or below 1 lux. Free running period in constant darkness was shortest in the early and longest in the late strain. Threshold light intensity of constant light to generate arrhythmicity was lowest in the early and highest in the late strain, apparently the photic sensitivity of the clock photoreceptors was differentially altered by these mutations. Thus the psi -mutations for locomotor rhythmicity affected the oviposition rhythm too, suggesting that the same circadian oscillator might be controlling these both rhythms.     

Light and dark rations and the photic entrainment of circadian locomotor activity patterns in the South American Silver Catfish (Rhamdia quelen,Quoy & Gaimard, 1824)

The aim of this study was to evaluate the daily rhythm of locomotor activity in Rhamdia quelen (R. quelen). A total of 30 fish were enrolled in the study and were equally divided in 10 groups and maintained in 100 liters tanks. The locomotor activity was measured in fish maintained under the LD 12:12 photoperiod regime; thereafter, the LD cycle was reversed to DL in order to study the resynchronization and to explore the endogenous pacemaker. Subsequently, the fish were subjected to constant conditions of light to test whether or not locomotor rhythms are regulated by the endogenous circadian clock. The effect of increasing light length and intensity was studied on daily rhythm of locomotor activity of fish. Our results showed that the R. quelen is a strictly diurnal species, the rhythm of locomotory activity resynchronized quickly after inverting the LD cycle and persist under free course LL, suggesting a circadian origin. The light showed a significant masking effect often blocking the expression of the biological rhythm. The strictly diurnal behavior is controlled directly by the photoperiod and maintained even under very dim light (30 lux).     

Locomotor activity rhythm in four wrasse species under varying light conditions

Under controlled laboratory conditions, the locomotor activity rhythms of four species of wrasses (Suezichthys gracilis, Thalassoma cupido, Labroides dimidiatus andCirrhilabrus temminckii) were individually examined using an actograph with infra-red photo-electric switches in a dark room at temperatures of 21.3–24.3°C, for 7 to 14 days. The locomotor activity ofS. gracilis occurred mostly during the light period under a light-dark cycle regimen (LD 12:12; 06:00-18:00 light, 18:00-06:00 dark). The locomotor activity commenced at the beginning of the light period and continued until a little before the beginning of dark period. The diel activity rhythm of this species synchronizes with LD. Under constant illumination (LL) this species shows distinct free-running activity rhythms varying in length from 23 hrs. 39 min. to 23 hrs. 47 min. Therefore,S. gracilis appears to have a circadian rhythm under LL. However, in constant darkness (DD), the activity of this species was greatly suppressed. All the fish showed no activity rhythms in DD conditions. After DD, the fish showed the diel activity rhythm with the resumption of LD, but this activity began shortly after the beginning of light period. The fish required several days to synchronize with the activity in the light period. Therefore,S. gracilis appeared to continue the circadian rhythm under DD. InT. cupido, the locomotor activity commenced somewhat earlier than the beginning of the light period and continued until the beginning of the dark period under LD. The diel activity rhythm of this species synchronizes with LD. Under LL, four of the five specimens of this species tested showed free-running activity rhythms for the first 5 days or longer varying in length from 22 hrs. 54 min. to 23 hrs. 39 min. Although the activity of this species was suppressed under DD, two of five fish showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 38 min. to 23 hrs. 50 min. under DD. Therefore, it was ascertained thatT. cupido has a circadian rhythm. InL. dimidiatus, the locomotor activity rhythm under LD resembled that observed inT. cupido. The diel activity rhythm of this species synchronizes with LD. Under LL, four of seven of this species showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 07 min. to 25 hrs. 48 min. Although the activity of this species was suppressed under DD, three of five fish showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 36 min. to 23 hrs. 41 min. under DD. Therefore, it was ascertained thatL. dimidiatus has a circadian rhythm. Almost all locomotor activity of C.temminckii occurred during the light period under LD. The diel activity rhythm of this species coincides with LD. Under LL, two of four of this species showed free-running activity rhythms throughout the experimental period. The lengths of such free-running periods were from 23 hrs. 32 min. to 23 hrs. 45 min. Although the activity of this species was suppressed under DD, one of the four fish showed free-running activity rhythms throughout the experimental period. The length of the free-running period was 23 hrs. 21 min. under DD. Therefore,C. temminckii appeared to have a circadian rhythm. According to field observations,S. gracilis burrows and lies in the sandy bottom whileT. cupido, L. dimidiatus, andC. temminckii hide and rest in spaces among piles of boulders or in crevices of rocks during the night. It seems that the differences in nocturnal behavior among the four species of wrasses mentioned above are closely related to the intensity of endogenous factors in their locomotor activity rhythms.