Circadian Activity Rhythms in the Australian Platypus,Ornithorhynchus anatinus (Monotremata)

The Australian platypus, Ornithorhynchus anatinus, is one of three extant genera of the order monotremata. Given the divergent evolutionary lineage of monotremes in relation to more commonly studied animals, it was of interest to determine first, whether platypuses possess endogenous biological pacemakers and, second, general parameters of aquatic activity rhythms under artificial and natural light–dark (LD) cycles. Using a novel recording device, aquatic activity rhythms were measured in three platypuses: a paired male and female studied together, and a single female studied in isolation from other platypuses. Under a constant photic environment, some evidence was found for persistent and free-running rhythmicity, indicating the presence of an endogenous circadian pacemaker in the platypus. Under artificial LD cycles the paired animals exhibited a nocturnal pattern of entrainment, although in the single female considerable variability in entrained phase-relations was found under natural LD cycles. Evidence for a circadian pacemaker in the hypothalamic region of platypuses is also discussed.     

Nematode parasites from the skin of the platypus Ornithorhynchus anatinus (Monotremata)

The morphology of three nematode taxa found in the skin of the platypus Ornithorhynchus anatinus (Monotremata) in southeastern New South Wales, Australia, is described and illustrated. Fourth-stage larvae belonging to the Rhabditoidea, ?Cylindrocorporidae, occurred primarily in superficial keratin and epidermal layers of the skin and in hair follicles. A nematode recognised by its conspicuous synlophe as a fourth-stage larva of the Trichostrongyloidea, of unknown genus and species but probably belonging to the molineid evolutionary line, was observed in histological section in the hypodermis. A gravid female nematode belonging to the Filarioidea, ?Lemdaninae, occurred in a lymphoid nodule in the hypodermis. O. anatinus is a protected species and these data are presented to draw the attention of parasitologists to skin as an important habitat for nematodes of the platypus.     

A Component of Platypus (Ornithorhynchus anatinus) Venom Forms Slow-Kinetic Cation Channels

The lipid bilayer technique is used to examine the biophysical properties of anion and cation channels frequently formed by platypus (Ornithorhynchus anatinus) venom (OaV). The OaV-formed anion channel in 250/50 mm KCl cis/trans has a maximum conductance of 857 ± 23 pS (n= 5) in 250/50 mm KCl cis/trans. The current-voltage relationship of this channel shows strong inward rectification. The channel activity undergoes time-dependent inactivation that can be removed by depolarizing voltage steps more positive than the reversal potential for chloride, E _Cl , (+40 mV). The reversal potential of the OaV-formed slow current activity in 250/50 mm KCl cis/trans is close to the potassium equilibrium potential (E _K ) of −40 mV. The conductance values for the slow channel are 22.5 ± 2.6 pS and 41.38 ± 4.2 pS in 250/50 and 750/50 mm cis/trans, respectively. The gating kinetics of the slow ion channels are voltage-dependent. The channel open probability (P _o ) is between 0.1 and 0.8 at potentials between 0 and +140 mV. The channel frequency (F _o ) increases with depolarizing voltages between 0 and +140 mV, whereas mean open time (T _o ) and mean closed time (T _c ) decrease. Ion substitution experiments of the cis solution show that the channel has conductance values of 21.47 ± 2.3 and 0.53 ± 0.1 pS in 250 mm KCl and choline Cl, respectively. The amplitude of the single channel current is dependent on [K⁺] _cis and the current reversal potential (E _rev ) responds to increases in [K⁺] _cis by shifting to more negative voltages. The increase in current amplitude as a function of increasing [K⁺] _cis can be best described by a third order polynomial fit. At +140 mV, the values of the maximal single channel conductance (γ _max ) and the concentration for half maximal γ (K _s ) are 38.6 pS and 380 mm and decline to 15.76 pS and 250 mm at 0 mV, respectively. The ion selectivity of the channel to K⁺, Na⁺, Cs⁺ and choline⁺ was determined in ion substitution experiments. The permeability values for P _K+ :P _Na+ :P _Cs+ :P _choline+ were 1:1:0.63:0.089, respectively. On the other hand, the activity of the slow channel was eliminated (Fig. 7B). The slow channel was reversibly inhibited by [TEA⁺] _trans and the half-maximal inhibitory concentration (K _i ) was ∼48 mm. Received: 26 April 1999/Revised: 19 July 1999     

Two monotreme cell lines,derived from female platypuses (Ornithorhynchus anatinus; Monotremata,mammalia)

Summary Two diploid platypus cell lines, designated Oa-1F and Oa-2F, have been derived from the toe webs of two females. The development and growth characteristics of the lines are described and G-banded karyotypes presented (the first reported for the platypus). The availability of these lines will greatly facilitate chromosome and gene mapping studies of the platypus and permit the extension of comparative studies of mammalian chromosome and genome evolution to the monotremes.     

Use of time and space by platypus (Ornithorhynchus anatinus: Monotremata) along a Victorian stream

Radio-tracking and mark recapture methods were used to characterize the spatial organization and temporal activity patterns of free-ranging platypuses in southern Victoria. The study area supported an estimated 1.3-2.1 adult or subadult animals per kilometre of stream in the three summers sampled. The individual home ranges of 15 radio-tagged animals comprised 0.33-2.28 km of stream; animals foraging exclusively in the stream had significantly longer ranges (mean=1.40 km) than animals which also foraged in associated pond habitats (mean=0.64km). Home ranges of grown females overlapped with those of neighbouring grown females, subadult and adult males, and juveniles (相似文献   

Theileria ornithorhynchi Mackerras, 1959 in the platypus, Ornithorhynchus anatinus (Shaw)

Blood smears from 54 platypuses in southeastern Australia were examined by light microscopy. Protozoa were found in erythrocytes in 53 platypuses; all infections were sparse. A few parasites were found in leukocytes. Intraerythrocytic forms examined by electron microscopy contained vacuoles, micronemes, rhoptries and cytostomes with double unit membranes. Merozoites were identified in leukocytes. The parasites were identified as Theileria ornithorhynchi Mackerras, 1959.     

D-Amino acid residue in the C-type natriuretic peptide from the venom of the mammal,Ornithorhynchus anatinus,the Australian platypus

The C-type natriuretic peptide from the platypus venom (OvCNP) exists in two forms, OvCNPa and OvCNPb, whose amino acid sequences are identical. Through the use of nuclear magnetic resonance, mass spectrometry, and peptidase digestion studies, we discovered that OvCNPb incorporates a D-amino acid at position 2 in the primary structure. Peptides containing a D-amino acid have been found in lower forms of organism, but this report is the first for a D-amino acid in a biologically active peptide from a mammal. The result implies the existence of a specific isomerase in the platypus that converts an L-amino acid residue in the protein to the D-configuration.     

Lesions associated with metazoan parasites of wild platypuses (Ornithorhynchus anatinus)

Pathological findings associated with helminth and arthropod parasites of four wild platypuses (Ornithorhynchus anatinus) are described. Fourth-stage larval rhabditoid nematodes (?Cylindrocorporidae) found partially embedded in the stratum corneum were associated with mild acanthosis, orthokeratotic hyperkeratosis and inconstant subacute dermatits. A filarioid nematode (?Lemdaninae) was found in hypodermal lymphoid tissue. A larval trichostrongyloid nematode was found in the dermis, with no evidence of host response. An undescribed species of trombiculid mite ("chigger") was found in the pelage and attached to superficial stratum corneum. Focal inclusions of eosinophilic material within stratum corneum, interpreted as mite gel saliva produced during formation of the "stylostome," were also observed. The tick Ixodes ornithorhynchi punctured the epidermis causing adnexal trauma, dermal haemorrhage and chronic active dermatitis. The digenean Mehlisia ornithorhynchi was present in the small intestine of one animal and was associated with mild catarrhal enteritis.     

Circadian Rhythms of Self-feeding and Locomotor Activity in Zebrafish (Danio Rerio)

To investigate daily feeding rhythms in zebrafish, the authors have developed a new self-feeding system with an infrared photocell acting as a food-demand sensor, which lets small-size fish such as zebrafish trigger a self-feeder. In this paper, the authors used eight groups of 20 fish. Locomotor activity rhythms were also investigated by means of infrared sensors. Under a 12?h:12?h light (L)-dark (D) cycle, zebrafish showed a clear nocturnal feeding pattern (88.0% of the total daily food-demands occurring in the dark phase), concentrated during the last 4?h of the dark phase. In contrast, locomotor activity was mostly diurnal (88.2% of total daily activity occurring in the light phase). Moreover, both feeding and locomotor rhythms were endogenously driven, as they persisted under free-running conditions. The average period length (τ) of the locomotor and feeding rhythms was shorter (τ?=?22.9?h) and longer (τ?=?24.6?h) than 24?h, respectively. During the time that food availability was restricted, fish could only feed during ZT0–ZT12 or ZT12–ZT16. This resulted in feeding activity being significantly modified according to feeding time, whereas the locomotor activity pattern remained synchronized to the LD cycle and did not change during this trial. These findings revealed an independent phasing between locomotor and feeding activities (which were mostly nocturnal or diurnal, respectively), thus supporting the concept of multioscillatory control of circadian rhythmicity in zebrafish. (Author correspondence: javisan@um.es)     

Entrainment to Light of Circadian Activity Rhythms in Tench (Tinca tinca)

The present article analyzes locomotor activity rhythms in Tinca tinca. To that end, three different experiments were conducted on 24 animals (20 g body weight) kept in pairs in 60‐liter aquaria fitted with infrared sensors connected to a computer to continuously record fish movements. The first experiment was designed to study the endogenous circadian clock under free‐running conditions [ultradian 40:40 min LD pulses and constant dark (DD)] and after shifting the LD cycle. Our results demonstrate that tench has a strictly nocturnal activity pattern, an endogenous rhythm being evident in 45.8% of the fish analyzed. The second experiment was conducted to test the influence of different photoperiods (LD 6:18, 12:12, 18:6, and 22:2) on locomotor activity, the results showing that even under an extremely long photoperiod, tench activity is restricted to dark hours. The third experiment examined the effect of light intensity on locomotor activity rhythms. When fish were exposed to decreasing light intensities (from 300:0 lux to 30:0, 3:0, and 0.3:0 lux) while maintaining a constant photoperiod (LD 12:12), the highest percentage of locomotor activity was in all cases associated with the hours of complete darkness (0 lux). In short, our results clearly show that (a) tench is a species with a strictly nocturnal behavior, and (b) daily activity rhythms gradually entrain after shifting the LD cycle and persist under free‐running conditions, pointing to their circadian nature. However, light strongly influences activity rhythms, since (c) the length of the active phase is directly controlled by the photophase, and (d) strictly nocturnal behavior persists even under very dim light conditions (0.3 lux). The above findings deepen our knowledge of tench behavior, which may help to optimize the aquacultural management of this species, for example, by adjusting feeding strategies to their nocturnal behavior.     

Ten polymorphic microsatellite DNA markers for the platypus, Ornithorhynchus anatinus

We identified and optimized 10 microsatellite loci for the platypus, Ornithorhynchus anatinus (Monotremata: Ornithorhynchidae), and screened 21 individuals from the southern tablelands area of New South Wales, Australia. Each polymorphic locus possessed between two and 12 alleles with observed heterozygosities between 0.118 and 0.950. The intent of this effort was to provide informative loci for studies on the population genetics of this species.     

Immunoglobulin genetics of Ornithorhynchus anatinus (platypus) and Tachyglossus aculeatus (short-beaked echidna)

In this paper, we review data on the monotreme immune system focusing on the characterisation of lymphoid tissue and of antibody responses, as well the recent cloning of immunoglobulin genes. It is now known that monotremes utilise immunoglobulin isotypes that are structurally identical to those found in marsupials and eutherians, but which differ to those found in birds and reptiles. Monotremes utilise IgM, IgG, IgA and IgE. They do not use IgY. Their IgG and IgA constant regions contain three domains plus a hinge region. Preliminary analysis of monotreme heavy chain variable region diversity suggests that the platypus primarily uses a single VH clan, while the short-beaked echidna utilises at least 4 distinct VH families which segregate into all three mammalian VH clans. Phylogenetic analysis of the immunoglobulin heavy chain constant region gene sequences provides strong support for the Theria hypothesis. The constant region of IgM has proven to be a useful marker for estimating the time of divergence of mammalian lineages.     

Iron(III) binding proteins of echidna (Tachyglossus aculeatus) and platypus (Ornithorhynchus anatinus)

Iron (III) binding proteins are isolated from echidna (Tachyglossus aculeatus multiaculeatus) and platypus (Ornithorhynchus anatinus) milk and blood. On the basis of several criteria it is shown that the milk proteins are not lactoferrins, but are transferrins similar to the corresponding transferrins from the blood. The heterogeneity of the proteins, particularly the echidna milk transferrin, is, at least in part, due to different levels of sialic acid. Their N-terminal sequences (30 residues) are determined and compared with those of other transferrins and lactoferrins. The role of the proteins is discussed.     

Energetics of foraging and locomotion in the platypus Ornithorhynchus anatinus

We measured the energy requirements of platypuses foraging, diving and resting in a swim tank using flow-through respirometry. Also, walking metabolic rates were obtained from platypuses walking on a conventional treadmill. Energy requirements while foraging were found to depend on water temperature, body weight and dive duration and averaged 8.48 W kg(-1). Rates for subsurface swimming averaged 6.71 W kg(-1). Minimal cost of transport for subsurface swimming platypuses was 1.85 J N(-1)m(-1) at a speed of 0.4 m s(-1). Aerobic dive limit of the platypus amounted to 59 s. Metabolic rate of platypuses resting on the water surface was minimal with 3.91 W kg(-1) while minimal RMR on land was 2.08 W kg(-1). The metabolic rate for walking was 8.80 W kg(-1) and 10.56 W kg(-1) at speeds of 0.2 m s(-1) and 0.3 m s(-1), respectively. A formula was derived, which allows prediction of power requirements of platypuses in the wild from measurements of body weight, dive duration and water temperature. Platypuses were found to expend energy at only half the rate of semiaquatic eutherians of comparable body sizes during both walking and diving. However, costs of transport at optimal speed were in line with findings for eutherians. These patterns suggest that underwater locomotion of semiaquatic mammals have converged on very similar efficiencies despite differences in phylogeny and locomotor mode.     

Circadian Rhythms and time Measurement in Locomotor Activity of the Scorpion Leiurus Quinquestriatus (Buthidae)

The circadian rhythms of locomotor activity of the scorpion Leiurus quinqueslriatus were examined under different light-dark cycles and in free-running conditions. The circadian rhythm is bimodal in LD 12:12 with alternating cycles of temperature (35°-25°C) with high intensity (1300 lux) or in LD 12: 12 with constant temperature 35° C with 300 lux. In LD 12:12 (1300 lux), in long or in short light spans with constant temperature, the bimodal pattern is slightly changed with the appearance of a third minor peak of activity. In free-running conditions, the bimodal rhythm of locomotor activity persists in DD with T about 24 hr, but in LL the rhythm becomes unimodal with T about 24 hr. Cosinor and power spectrum analysis showed the presence of more than one periodic component. It seems that there is a correlation between the range of light regimens, temperature, light intensity and the coincidence of these components. These components are independently entrained by the environmental light cycle. The mechanism of entrainment of components is 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.