Spatial ecology and habitat use of two-spined blackfish Gadopsis bispinosus in an upland reservoir

The scale and patterns of movement and habitat use are primary considerations in the conservation and management of threatened species. Movement, activity and habitat use of the threatened two-spined blackfish Gadopsis bispinosus were assessed in a small upland reservoir in south-eastern Australia using manual and remote radio-telemetry. Movements and activity of two-spined blackfish (n?=?19) were studied over a 28-day period and exhibited proportionately large directional crepuscular movement and activity with heightened activity continuing throughout the night (although movement was subdued). Two daily movement strategies were observed: movements from diurnal home-shelter habitats (predominantly rock) to macrophytes at night (14 individuals), and occupation of macrophytes during the entire diel period and restricted movement (five individuals). Daily movement strategies were fixed (not plastic) among all individuals, with one exception, for the duration of the study period. Rock, fallen timber and macrophytes were the most commonly used daytime shelter habitat (in order of preference). Although some information exists on movements and habitat use of this species and the congeneric river blackfish G. Marmoratus in lotic environments, we present the first study of movements and habitat use for either species in lentic environments. Given the occupation of lentic environments by this threatened species, the data presented in this study provide insight into the habitat requirements for this species, and offer opportunities for habitat enhancement in existing reservoirs within the species’ geographic range.     

Search tactics of desert lizards: how polarized are they?

The patterns of foraging movements of the teiid species Cnemidophorus tigris (western whiptail) and four iguanid species, Gambelia wislizeni (leopard lizard), Uta stansburiana (side-blotched lizard), Phrynosoma platyrhinos (desert horned lizard), and Callisaurus draconoides (zebra-tailed lizard), were investigated between 1978 and 1981. Rates and frequencies of movement while foraging, based on more than 44 000 minutes of observation of over 500 different lizards, were analysed with respect to temporal variation on yearly, seasonal and daily time scales and compared to expectations froma dichotomous view of foraging modes. The notion of polarized foragiing tactics among lizards was partially supported. Among the iguanid species, only Gambelia exhibited rates of foraging movements that were not always significantly less than those of the active forager, Cnemidophorus. Nevertheless, the analyses also revealed temporal variation in the search tactics of iguanid species. Gambelia exhibited a seasonal decline in foraging movements during three out of four years. Phrynosoma, Callisaurus and Uta all exhibited seasonal declines in their foraging movements in some years, but not in others. The foraging movements of all iguanid species increased during the early-season of 1978, corresponding to a marked increase in late winter/early spring rainfall that year. Uta showed diurnal shifts in foraging movements during most years. Such diurnal variation was also apparent in Callisaurus in some years. Despite consistent differences between Cnemidophorus and most iguanid species, the presence of temporal variability in foraging movements of iguanid lizards indicates a capacity for shifts in tactics in these species. Thus, this variability more realistically reflects a continuum of foraging tactics than it does dichotomous strategies.     

Force–velocity,force–power relationships of bilateral and unilateral leg multi-joint movements in young and elderly women

The present study investigated force–velocity and force–power relationships of bilateral and unilateral knee-hip extension movement in young and elderly women. Twelve healthy young (age, 19–31 yr) and 12 healthy elderly (age, 60–82 yr) women performed bilateral and unilateral knee-hip extension movements on the dynamometer against loads controlled by the servo system. Under the isotonic force condition, force–velocity relationships were measured. The maximum isometric force (F_max), unloaded velocity (V_max) and power output (P_max) of the movements were calculated from extrapolating force–velocity and force–power relationships. F_max and P_max of bilateral and unilateral knee-hip extension movements were 20–30% lower in elderly than in young women. On the other hand, there were no significant differences in V_max between young and elderly women and between bilateral and unilateral movements. Bilateral deficit was larger as the generation of force was larger in both young and elderly women. Also, bilateral deficit of F_max and P_max were not different between young and elderly women. The results were that lower maximum power output of bilateral and unilateral leg multi-joint movements in elderly women did not depend on the intrinsic shortening velocity of muscle action, but largely on reduction in force generating capacity. This suggests the importance of preventing a loss of force generating capacity of muscles during leg multi-joint movements in elderly women.     

The gastrointestinal tract of the rock hyrax (Procavia habessinica). 1. Morphology and motility patterns of the tract

The stomach of the rock hyrax (Procavia habessinica) is divided into a non glandular part with very slow movements, and a glandular part which rapidly mix the digesta. The large intestine has two fermentation chambers, the caecum, which rapidly mixes the digesta, and the colonie sac, which efficiently, but slowly, mixes digesta. Between these chambers runs the connecting colon. No retrograde transport is observed in any part of the large intestine.     

The pattern and influential factors of aquatic pharyngeal movements of Trionyx sinensis

• 1.1. The pharyngeal movements of Trionyx sinensis during submersion where recorded with physiological instruments.
• 2.2. Anoxia or hypercapnia caused a marked increase in breathing rate of tested turtles during voluntary diving, and in anoxia there was a significant increase in the frequency of aquatic pharyngeal movements while hypercapnia had a slight or no effect on the frequency of these movements.
• 3.3. During voluntary diving when turtles could easily extend their heads out of water to breathe air, the frequency of rhythmic pharyngeal movements was lower; but during forced submersion, the frequency was higher and the movements were continuous.
• 4.4. The frequency increased more rapidly and greatly when turtles were in forced submersion than when they dived freely and could easily surface to breathe in N₂.
• 5.5. The frequency of pharyngeal movements of T. sinensis during diving in an aquarium with water depth of 30 or 45 cm was markedly higher than that at a water depth of 15 cm. Disturbing stimuli also influenced the aquatic rhythmic pharyngeal movements of T. sinensis.

     

On the habits and nature of association of the copepod Pseudomyicola spinosus with the rock oyster Crassostrea glomerata in New Zealand

Both adults and early stages of Pseudomyicola spinosus (Cyclopoidea, Myicolidae) occur on the labial palps as well as in the gut of the rock oyster Crassostrea glomerata. There is evidence to suggest movements of the copepod to and from the gut. Clear evidence of damage to the epithelial walls of the gut is seen in several regions, particularly in confined portions of the stomach near the openings of the ducts of the digestive diverticula. In addition to mechanical injuries, changes from a columnar to a low squamous epithelium have been observed in one instance; an increase of leucocytes has also been observed in another specimen. The evidence suggests that the myicolid copepod is a parasite in the gut of the oyster.     

Is slow walking more stable?

Several efforts have been made to study gait stability using measures derived from nonlinear time-series analysis. The maximum finite time Lyapunov exponent (λ_max) quantifies how a system responds to an infinitesimally small perturbation. Recent studies suggested that slow walking leads to lower λ_max values, and thus is more stable than fast walking, but these studies suffer from methodological limitations. We studied the effects of walking speed on the amount of kinematic variability and stability in human walking. Trunk motions of 15 healthy volunteers were recorded in 3D during 2 min of treadmill walking at different speeds. From those time series, maximum Lyapunov exponents, indicating short-term and long-term divergence (λ_S-stride and λ_L-stride), and mean standard deviation (MeanSD) were calculated. λ_S-stride showed a linear decrease with increasing speed for forward–backward (AP) movements and quadratic effects (inverted U-shaped) for medio-lateral (ML) and up–down (VT) movements. λ_L-stride showed a quadratic effect (inverted U-shaped) of walking speed for AP movements, a linear decrease for ML movements, and a linear increase for VT movements. Moreover, positive correlations between λ_S and MeanSD were found for all directions, while λ_L-stride and MeanSD were correlated negatively in the AP direction. The different effects of walking speed on λ_S-stride and λ_L-stride for the different planes suggest that slow walking is not necessarily more stable than fast walking. The absence of a consistent pattern of correlations between λ_L-stride and MeanSD over the three directions suggests that variability and stability reflect, at least to a degree, different properties of the dynamics of walking.     

An electromagnetic tracking system for use in shallow water

Modifications to an electromagnetic method of tracking juvenile western rock lobsters Panulirus cygnus George are documented. The receiving aerials were made more robust to increase their useful life, and an automated tracking system was developed. The system continuously collects data on the movements of up to 14 tagged lobsters simultaneously. The feasibility of the method and its problems are discussed and suggestions are made for its improvement. The susceptibility to wave action of the aerials and the main communication cable that brings the signals to shore suggest that electromagnetic tracking is feasible only in calm and shallow environments.     

Hot-water spraying is a sensitive test for signs of life before dressing and scalding in pig abattoirs with carbon dioxide (CO2) stunning

This study investigated the benefits of hot-water spraying (HWS) as a diagnostic test to verify the absence of signs of life (SOL) before scalding in pigs slaughtered with carbon dioxide (CO₂) stunning. A total of 37 108 finishing pigs from five German abattoirs (A to E) operating at 55 to 571 pigs per hour were assessed. Suspended pigs were sprayed onto the muzzle, head and front legs (143 to 258 s post sticking for 4 to 10 s, 57°C to 72°C). Any active movements during HWS were rated as positive test outcomes. In comparison, SOL were considered to be absent if a subsequent manual examination was negative and no active movements were observed following HWS. The incidence of pigs with activity during hot-water spraying (PWA) was restricted to two abattoirs (B: 0.25%; D: 0.02%; A, C, E: 0.00%). PWA showed movements of facial muscles (88%), mouth opening (78%), righting reflex (63%), isolated leg movements (35%) and vocalization (4%). The manual examination was positive in 71% of PWA (corneal/dazzle reflex: 67%/53%, nasal septum pinch: 33%), whereas all inactive pigs tested negative (P<0.001). The sensitivity for HWS as a test for SOL was calculated as 100%, dropping to 75% when only obvious and strong movements were taken into account. The specificity was >99.9% in either case. Any positive manual findings as well as any respiratory activity were instantly terminated using a penetrating captive bolt. Active movements triggered by the shot were shown to be an indicator for SOL (P<0.001). Video analyses revealed that spontaneous movements (SM) following sticking were present in 100% of PWA as opposed to 3.1% in pigs without such activity (controls). Results for different categories of SM in PWA v. controls were as follows: 100% v. 2.6% for mouth opening, 16.0% v. 0.1% for righting reflex and 22.0% v. 0.9% for isolated leg movements (all P<0.001). First mouth opening after sticking was observed later in PWA (28±24 v. 10±7 s), but mouth openings were observed for a longer period of time (141±44 v. 27±25 s) (both P<0.001). PWA with shorter mouth-opening intervals showed higher movement intensities during HWS and more positive manual findings (P<0.05). We conclude that HWS is a promising test for SOL. SM and sustained mouth opening in particular are indicators for compromised animal welfare and affected pigs should be shot by captive bolt.     

RPTPα and PTPε signaling via Fyn/Yes and RhoA is essential for zebrafish convergence and extension cell movements during gastrulation

Convergence and extension (C&E) cell movements are essential to shape the body axis during vertebrate gastrulation. We have used the zebrafish to assess the role of the receptor protein-tyrosine phosphatases, RPTPα and PTPε, in gastrulation cell movements. Both RPTPα and PTPε knockdown and ptpra^−/− embryos show defects in C&E movements. A method was developed to track gastrulation cell movements using confocal microscopy in a quantitative manner and ptpra^−/− embryos displayed reduced convergence as well as extension speeds. RPTPα and PTPε knockdowns cooperated with knockdown of a well known factor in C&E cell movement, non-canonical Wnt11. RPTPα and PTPε dephosphorylate and activate Src family kinases in various cell types in vitro and in vivo. We found that Src family kinase phosphorylation was enhanced in ptpra^−/− embryos, consistent with reduced Src family kinase activity. Importantly, both ptpra^−/− and RPTPα and PTPε knockdown induced C&E defects were rescued by active Fyn and Yes. Moreover, active RhoA rescued the RPTPα and PTPε knockdown and ptpra^−/− induced gastrulation cell movement defects as well. Our results demonstrate that RPTPα and PTPε are essential for C&E movements in a signaling pathway parallel to non-canonical Wnts and upstream of Fyn, Yes and RhoA.     

Growth and posture control strategies in Fagus sylvatica and Acer pseudoplatanus saplings in response to canopy disturbance

Background and Aims

Forest tree saplings that grow in the understorey undergo frequent changes in their light environment to which they must adapt to ensure their survival and growth. Crown architecture, which plays a critical role in light capture and mechanical stability, is a major component of sapling adaptation to canopy disturbance. Shade-adapted saplings typically have plagiotropic stems and branches. After canopy opening, they need to develop more erect shoots in order to exploit the new light conditions. The objective of this study was to test whether changes in sapling stem inclination occur after canopy opening, and to analyse the morphological changes associated with stem reorientation.

Methods

A 4-year canopy-opening field experiment with naturally regenerated Fagus sylvatica and Acer pseudoplatanus saplings was conducted. The appearance of new stem axes, stem basal diameter and inclination along the stem were recorded every year after canopy opening.

Key Results

Both species showed considerable stem reorientation resulting primarily from uprighting (more erect) shoot movements in Fagus, and from uprighting movements, shoot elongation and formation of relay shoots in Acer. In both species, the magnitude of shoot uprighting movements was primarily related to initial stem inclination. Both the basal part and the apical part of the stem contributed to uprighting movements. Stem movements did not appear to be limited by stem size or by stem growth.

Conclusions

Stem uprighting movements in shade-adapted Fagus and Acer saplings following canopy disturbance were considerable and rapid, suggesting that stem reorientation processes play a significant role in the growth strategy of the species.     

<Emphasis Type="Italic">Arabidopsis</Emphasis> petiole torsions induced by lateral light or externally supplied auxin require microtubule-associated TORTIFOLIA1/SPIRAL2

Although rather inconspicuous, movements are an important adaptive trait of plants. Consequently, light- or gravity-induced movements leading to organ bending have been studied intensively. In the field, however, plant movements often result in organ twisting rather than bending. This study investigates the mechanism of light- or gravity-induced twisting movements, coined “helical tropisms.” Because certain Arabidopsis cell expansion mutants show organ twisting under standard growth conditions, we here investigated how the right-handed helical growth mutant tortifolia1/spiral2 (tor1) responds when stimulated to perform helical tropisms. When leaves were illuminated from the left, tor1 was capable of producing left-handed petiole torsions, but these occurred at a reduced rate. When light was applied from right, tor1 plants rotated their petioles much faster than the wild-type. Applying auxin to the lateral-distal side of wild-type petioles produced petiole torsions in which the auxinated flank was consistently turned upwards. This kind of movement was not observed in tor1 mutants when auxinated to produce left-handed movements. Investigating auxin transport in twisting petioles based on the DR5-marker suggested that auxin flow was apical-basal rather than helical. While cortical microtubules of excised wild-type petioles oriented transversely when stimulated with auxin, those of tor1 were largely incapable of reorientation. Together, our results show that tor1 is a tropism mutant and suggest a mechanism in which auxin and microtubules both contribute to helical tropisms.     

Vacuolar remodelling mediates touch-induced androgynophore movement in Passiflora (Subg. Decaloba, Sect. Xerogona) flowers

Some species of the genus Passiflora (sect. Xerogona) have flowers that exhibit a mechanically-induced movement of the androgynophore that is probably involved in pollination. Despite the many reports of touch-induced movements of floral parts, the studies concerning anatomical, ultrastructural and molecular aspects of the plant movements are restricted to the vegetative parts. Rapid plant movements are highly dependent on turgor changes of a particular flexible tissue formed by specialized cells capable of losing and gaining water rapidly. Thigmotropic androgynophores of four species of Passiflora from section Xerogona were analyzed at cellular and subcellular levels. Our results show that the movement is due to a vacuolar remodelling in a group of parenchymatous cells at the base of the androgynophore. After the movement, plasmolyzed and multivacuolated cells are present at the stimulated side and turgid and univacuolated cells at the opposite side. The results suggest that the mechanisms leading to the androgynophore movement in Passiflora are, in general, analogous to those reported for the movements of legume pulvinus, motile stamen filaments and guard cells of stomata, pointing to conserved cellular mechanisms of plant movement.     

Movements of individual BKCa channels in live cell membrane monitored by site-specific labeling using quantum dots

The movements of BK_Ca channels were investigated in live cells using quantum dots (QDs). The extracellular N-terminus was metabolically tagged with biotin, labeled with streptavidin-conjugated QDs and then monitored using real-time time-lapse imaging in COS-7 cells and cultured neurons. By tracking hundreds of channels, we were able to determine the characteristics of channel movements quantitatively. Channels in COS-7 cells exhibited a confined diffusion in an area of 1.915 μm², with an initial diffusion coefficient of 0.033 μm²/s. In neurons, the channel movements were more heterogeneous and highly dependent on subcellular location. While the channels in soma diffused slowly without clear confinement, axodendritic channels showed more rapid and pseudo-one-dimensional movements. Intriguingly, the channel movement in somata was drastically increased by the neuronal β4 subunit, in contrast to the channels in the axodendritic area where the mobility were significantly decreased. Thus, our results demonstrate that the membrane mobility of BK_Ca channels can be greatly influenced by the expression system used, subunit composition, and subcellular location. This QD-based, single-molecule tracking technique can be utilized to investigate the cellular mechanisms that determine the mobility as well as the localization of various membrane proteins in live cells.     

Circadian Rhythm of Leaves of Phaseolus angularis Plants Grown in a Controlled Carbon Dioxide and Humidity Environment

Leaf movements of primary leaves of Phaseolus angularis Wight. were studied in an environment with controlled levels of CO₂, relative humidity, temperature, light, nutrient concentrations, and water tension. Rhythmic circadian movements and irregular short period movements were evident as the leaves unfolded and persisted during development of the leaves. The mean period in rhythmic circadian movement was 27.3 hours with no significant differences in period between plants of the same or different experiments. The leaf movements of separate plants were not closely synchronized.     

Characteristics of Gait Ataxia in δ2 Glutamate Receptor Mutant Mice,ho15J

The cerebellum plays a fundamental, but as yet poorly understood, role in the control of locomotion. Recently, mice with gene mutations or knockouts have been used to investigate various aspects of cerebellar function with regard to locomotion. Although many of the mutant mice exhibit severe gait ataxia, kinematic analyses of limb movements have been performed in only a few cases. Here, we investigated locomotion in ho15J mice that have a mutation of the δ2 glutamate receptor. The cerebellum of ho15J mice shows a severe reduction in the number of parallel fiber-Purkinje synapses compared with wild-type mice. Analysis of hindlimb kinematics during treadmill locomotion showed abnormal hindlimb movements characterized by excessive toe elevation during the swing phase, and by severe hyperflexion of the ankles in ho15J mice. The great trochanter heights in ho15J mice were lower than in wild-type mice throughout the step cycle. However, there were no significant differences in various temporal parameters between ho15J and wild-type mice. We suggest that dysfunction of the cerebellar neuronal circuits underlies the observed characteristic kinematic abnormality of hindlimb movements during locomotion of ho15J mice.     

Subunit-specific effect of the voltage sensor domain on Ca2+ sensitivity of BK channels

Large conductance Ca²⁺- and voltage-activated K⁺ (BK) channels, composed of pore-forming α-subunits and auxiliary β-subunits, play important roles in diverse physiological processes. The differences in BK channel phenotypes are primarily due to the tissue-specific expression of β-subunits (β1-β4) that modulate channel function differently. Yet, the molecular basis of the subunit-specific regulation is not clear. In our study, we demonstrate that perturbation of the voltage sensor in BK channels by mutations selectively disrupts the ability of the β1-subunit—but not that of the β2-subunit—to enhance apparent Ca²⁺ sensitivity. These mutations change the number of equivalent gating charges, the voltage dependence of voltage sensor movements, the open-close equilibrium of the channel, and the allosteric coupling between voltage sensor movements and channel opening to various degrees, indicating that they alter the conformation and movements of the voltage sensor and the activation gate. Similarly, the ability of the β1-subunit to enhance apparent Ca²⁺ sensitivity is diminished to various degrees, correlating quantitatively with the shift of voltage dependence of voltage sensor movements. In contrast, none of these mutations significantly reduces the ability of the β2-subunit to enhance Ca²⁺ sensitivity. These results suggest that the β1-subunit enhances Ca²⁺ sensitivity by altering the conformation and movements of the voltage sensor, whereas the similar function of the β2-subunit is governed by a distinct mechanism.     

Predatory behaviour of juvenile shore crab Carcinus maenas (L.)

Juvenile shore crabs Carcinus maenas (L.) were observed feeding on rock barnacles Semibalanus balanoides (L.) on a Bay of Fundy rocky shore. This previously unreported predatory behaviour was further investigated in the laboratory. When given a choice of three common and abundant gastropods, Nucella lapillus (L.), Littorina littorea (L.), and Littorina obtusata (L.), and the rock barnacle Semibalanus balanoides, juvenile shore crabs of both sexes ate mainly barnacles and consumed proportionately more barnacles than gastropods compared with adults, which ate mainly gastropods. The rock barnacle is an abundant and readily available food source which may be important in sustaining the juvenile crab through periods of moults and rapid growth. As the shore crab attains a certain age (size), it must forage lower on the shore as gastropods become more important in its diet.