The mechanical properties of fish myotomal muscle

CHAPTER 1 A brief introduction is given to the structure, biochemistry and electrophysiological and mechanical properties of fish muscle. CHAPTER 2 1. The neuromuscular end plates and preterminal axons of cod, Gadus morhua, fast myotomal muscle were stained for cholinesterase activity. 2. The number of end plates per fibre on superficial fast fibres (17.88 ± 2.13, mean ± 1 S.D.) was significantly higher than that of deep fast fibres (14.79 ± 2.48, P<< 0.001). A small degree of multi-terminal innervation was noted. The end plates showed a great variety in structure and size. 3. Fast muscle contains fibres with a wide range of diameters (20-240 µm). However, no correlation was found between the number of end plates per fibre and fibre diameter. CHAPTER 3 1. The force-velocity characteristics of threads of natural actomyosin, and purified component proteins, from dogfish fast and slow muscle, and rabbit fast skeletal and cardiac muscle have been investigated. 2. Maximum isometric tensions were around 30-70 g cm⁻². The time taken to reach full tension after activation with ATP was 2-8 min. 3. Force-velocity curves obtained could be fitted to a linear form of Hill's equation (1938). In common with intact and skinned fibre studies, points below 0.7 P₀ were found to lie on a straight line. 4. Maximum contraction velocities were around 10⁻² Ls⁻¹, 2-3 orders of magnitude lower than those of intact muscle fibres. 5. The relative velocities of the different thread types do not reflect those of the corresponding muscles, on the basis of measurements on intact fibres, and on measurements of actomyosin/myofibrillar ATPase activities. 6. It is concluded that filament formation, geometry and packing, and not differences in cross bridge cycling rates, largely determine the observed properties of actomyosin threads. CHAPTER 4 A description of the apparatus used to study the isometric and isotonic properties of skinned fibres is given, together with the methods and protocol used in Chapters 5-7. CHAPTER 5 1. The pCa-tension relationship of cod, Gadus morhua, and dogfish, Scyliorhinus canicula, fast and slow skinned fibres isolated from the myotomal muscles was investigated. 2. Maximum isometric tensions were 1.9 ± 0.12 (mean ± 1 S.E.) (fast) and 0.85 ± 0.10 (slow) for cod fibres, and 1.87 ± 0.09 (fast) and 0.84 ± 0.04 (slow) for dogfish (All values : kg cm⁻²). 3. Sigmoid pCa-tension curves were obtained for all fibre types. Values for the half maximally activating [Ca²⁺], and n, the minimum number of Ca²⁺ binding sites involved in activation, were calculated: Thus, the minimum number of Ca²⁺ binding sites in cod is two, in dogfish, four. In both fish, greater cooperativity is exhibited by the fast muscle. CHAPTER 6 1. Force-velocity curves were derived from fast and slow skinned fibres isolated from cod and dogfish myotomal muscles. 2. The extrapolated V and the constants a and b were calculated max from a linear form of Hill's equation: 3. These results are discussed with reference to previous studies of the P-V relationship in amphibian and mammalian muscle. The relationship between a/P₀ and efficiency, and its bearing on the present results is discussed.4. Velocity transients showed a small departure from linearity in all experiments, with velocity decreasing continuously during release (usually < 25% over the first 250 ms after release). This is a feature common to many previous experiments on skinned and intact fibres. The decrease in velocity during release was particularly marked in cod slow fibres. Similar results have been reported in amphibian slow muscle. CHAPTER 7 1. Contraction velocity at low loads was studied in dogfish fast fibres during maximal and submaximal activations. 2. The velocity of contraction during the second 50 ms interval after the onset of release was reduced significantly at low [Ca²⁺], The shape of the velocity transient was found to be dependent on [Ca²⁺]. The rate of decrease of velocity was greater in submaximal than in maximal activations. 3. A brief review of previous studies on the dependence of Vmax on max [Ca²⁺] is given. 4. The results are discussed in the light of recent evidence for length dependent changes in the contractile system. Possible mechanisms for a Ca²⁺ and length dependent inactivation process are considered. CHAPTER 8 The major outstanding problems are stated, and suggestions are made for further work which may give a greater insight into the molecular events underlying contraction in fish muscle. (Abstract shortened

2. Bat Conservation

Expert assessors John Altringham, University of Leeds, UK James Aegerter, Animal and Plant Health Agency, UK Kate Barlow, Bat Conservation Trust, UK Anna Berthinussen, University of Leeds, UK Fabio Bontadina, SWILD — Urban Ecology & Wildlife Research, Switzerland David Bullock, National Trust, UK Paul Cryan, Fort Collins Science Center, US Geological Survey Brock Fenton, University of Western Ontario, Canada Anita Glover, University of Leeds, UK Joanne Hodgkins, National Trust, UK David Jacob..

Bats in the Ghats: Agricultural intensification reduces functional diversity and increases trait filtering in a biodiversity hotspot in India

The responses of bats to land-use change have been extensively studied in temperate zones and the neotropics, but little is known from the palaeotropics. Effective conservation in heavily-populated palaeotropical hotspots requires a better understanding of which bats can and cannot survive in human-modified landscapes. We used catching and acoustic transects to examine bat assemblages in the Western Ghats of India, and identify the species most sensitive to agricultural change. We quantified functional diversity and trait filtering of assemblages in forest fragments, tea and coffee plantations, and along rivers in tea plantations with and without forested corridors, compared to protected forests. Functional diversity in forest fragments and shade-grown coffee was similar to that in protected forests, but was far lower in tea plantations. Trait filtering was also strongest in tea plantations. Forested river corridors in tea plantations mitigated much of the loss of functional diversity and the trait filtering seen on rivers in tea plantations without forested corridors. The bats most vulnerable to intensive agriculture were frugivorous, large, had short broad wings, or made constant frequency echolocation calls. The last three features are characteristic of forest animal-eating species that typically take large prey, often by gleaning. Ongoing conservation work to restore forest fragments and retain native trees in coffee plantations should be highly beneficial for bats in this landscape. The maintenance of a mosaic landscape with sufficient patches of forest, shade-grown coffee and riparian corridors will help to maintain landscape wide functional diversity in an area dominated by tea plantations

Do Bat Gantries and Underpasses Help Bats Cross Roads Safely?

Major roads can reduce bat abundance and diversity over considerable distances. To mitigate against these effects and comply with environmental law, many European countries install bridges, gantries or underpasses to make roads permeable and safer to cross. However, through lack of appropriate monitoring, there is little evidence to support their effectiveness. Three underpasses and four bat gantries were investigated in northern England. Echolocation call recordings and observations were used to determine the number of bats using underpasses in preference to crossing the road above, and the height at which bats crossed. At gantries, proximity to the gantry and height of crossing bats were measured. Data were compared to those from adjacent, severed commuting routes that had no crossing structure. At one underpass 96% of bats flew through it in preference to crossing the road. This underpass was located on a pre-construction commuting route that allowed bats to pass without changing flight height or direction. At two underpasses attempts to divert bats from their original commuting routes were unsuccessful and bats crossed the road at the height of passing vehicles. Underpasses have the potential to allow bats to cross roads safely if built on pre-construction commuting routes. Bat gantries were ineffective and used by a very small proportion of bats, even up to nine years after construction. Most bats near gantries crossed roads along severed, pre-construction commuting routes at heights that put them in the path of vehicles. Crossing height was strongly correlated with verge height, suggesting that elevated verges may have some value in mitigation, but increased flight height may be at the cost of reduced permeability. Green bridges should be explored as an alternative form of mitigation. Robust monitoring is essential to assess objectively the case for mitigation and to ensure effective mitigation

Sexual Segregation and Flexible Mating Patterns in Temperate Bats

Social structure evolves from a trade-off between the costs and benefits of group-living, which are in turn dependent upon the distribution of key resources such as food and shelter. Males and females, or juveniles and adults, may have different priorities when selecting habitat due to differences in physiological or behavioural imperatives, leading to complex patterns in group composition. We studied social structure and mating behaviour in the insectivorous bat Myotis daubentonii along an altitudinal gradient, combining field studies with molecular genetics. With increasing altitude the proportion of males in summer roosts increased and only males were present in the highest roosts. With increasing altitude environmental temperature decreased, nightly variation in temperature increased, and bat foraging activity decreased, supporting the hypothesis that the harsher, high elevation sites cannot support breeding females. We found that offspring in female-dominated lowland roosts had a very high probability of being fathered by bats caught during autumn swarming at hibernation sites, in contrast to those in intermediate roosts, which had a high probability of being fathered by males sharing the nursery roost with the females. Whilst females normally appear to exclude males from nursery colonies, for those in marginal habitats, one explanation for the presence of males is that the thermoregulatory benefits to the females may outweigh disadvantages, such as competition for food, and give some males an opportunity to increase their breeding success. We suggest that the environment, and its effects on resource distribution, thus determine social structure, which in turn determines the mating pattern that has evolved

What Works in Conservation 2018

This book provides an assessment of the effectiveness of 1277 conservation interventions based on summarized scientific evidence. The 2018 edition contains new chapters covering practical global conservation of primates, peatlands, shrublands and heathlands, management of captive animals as well as an extended chapter on control of freshwater invasive species. Other chapters cover global conservation of amphibians, bats, birds and forests, conservation of European farmland biodiversity and some aspects of enhancing natural pest control, enhancing soil fertility and control of freshwater invasive species. It contains key results from the summarized evidence for each conservation intervention and an assessment of the effectiveness of each by international expert panels. The accompanying website www.conservationevidence.com describes each of the studies individually, and provides full references

Heard but not seen: Comparing bat assemblages and study methods in a mosaic landscape in the Western Ghats of India.

We used capture (mist-netting) and acoustic methods to compare the species richness, abundance, and composition of a bat assemblage in different habitats in the Western Ghats of India. In the tropics, catching bats has been more commonly used as a survey method than acoustic recordings. In our study, acoustic methods based on recording echolocation calls detected greater bat activity and more species than mist-netting. However, some species were detected more frequently or exclusively by capture. Ideally, the two methods should be used together to compensate for the biases in each. Using combined capture and acoustic data, we found that protected forests, forest fragments, and shade coffee plantations hosted similar and diverse species assemblages, although some species were recorded more frequently in protected forests. Tea plantations contained very few species from the overall bat assemblage. In riparian habitats, a strip of forested habitat on the river bank improved the habitat for bats compared to rivers with tea planted up to each bank. Our results show that shade coffee plantations are better bat habitat than tea plantations in biodiversity hotspots. However, if tea is to be the dominant land use, forest fragments and riparian corridors can improve the landscape considerably for bats. We encourage coffee growers to retain traditional plantations with mature native trees, rather than reverting to sun grown coffee or coffee shaded by a few species of timber trees

Boxplots of the number of bats crossing per survey at each underpass.

<p>Boxplots (median with upper and lower quartiles) for the number of bats crossing per survey (n = 10) at each underpass (numbers crossing using underpass, over the road above and at safe and unsafe heights over the road), and at the unmitigated commuting route on the A590 which was diverted to underpass A (numbers crossing over the road and at safe and unsafe heights).</p

Representative MaxEnt response curves.

<p>These graphs show the probability of a species’ presence at a location for a range of parameters. These graphs are based on univariate models to prevent interacting or collinear variables from affecting the relationships modelled. Variables found to have poor predictive power for a species (AUC ≤ 0.5 or test gain < 0.01) are not shown.</p