Combined effects of fatigue and temperature manipulation on skeletal muscle electrical and mechanical characteristics during isometric contraction

Peripheral fatigue and muscle cooling induce similar effects on sarcolemmal propagation properties. The aim of the study was to assess the combined effects of muscle temperature (Tm) manipulation and fatigue on skeletal muscle electrical and mechanical characteristics during isometric contraction. After maximum voluntary contraction (MVC) assessment, 16 participants performed brief and sustained isometric tasks of different intensities in low (Tm(L)), high (Tm(H)) and neutral (Tm(N)) temperature conditions, before and after a fatiguing exercise (6s on/4s off at 50% MVC, to the point of fatigue). During contraction, the surface electromyogram (EMG) and force were recorded from the biceps brachii muscle. The root mean square (RMS) and conduction velocity (CV) were calculated off-line. After the fatiguing exercise: (i) MVC decreased similarly in all Tm conditions (P<0.05), while EMG RMS did not change; and (ii) CV decreased to a further extent in Tm(L) compared to Tm(N) and Tm(H) in all brief and sustained contractions (P<0.05). The larger CV drop in Tm(L) after fatigue suggests that Tm(L) and fatigue have a combined and additional effect on sarcolemmal propagation properties. Despite these changes, force generating capacity was not affected by Tm manipulation. A compensatory mechanism has been proposed to explain this phenomenon.     

British Columbia’s Fish Health Regulatory Framework’s Contribution to Sustainability Goals Related to Salmon Aquaculture

Salmon farming is a significant contribution to the global seafood market to which the goal of sustainability is often applied. Diseases related to farms are perhaps the most contentious issues associated with sustainable salmon farming. We reviewed literature and policies in British Columbia, Canada, as well as interviewed key informants to examine how fish health regulations do or could support sustainability goals. We found four main obstacles to the development and application of a sustainability-based health management system. First, salmon farming faced the same challenges as other industries when trying to establish an operational definition of sustainability that captures all stakeholders’ interests. Second, there was no program responsible for integrating the various regulations, responsible departments, and monitoring efforts to develop a comprehensive view of sustainability. Third, there was inadequate research base and social consensus on the criteria that should be used to track health outcomes for sustainability purposes. Fourth, the regulatory and management paradigm for salmon farming has been focused on diseases and pathogens as opposed to embracing a more inclusive health promotion model that includes biotic, abiotic, and social determinants of health. A transparent and inclusive participatory process that effectively links expert views with community and industry concerns should serve as the foundation for the next generation of health management regulations for salmon farming.     

Faunal impact on vegetation structure and ecosystem function in mangrove forests: A review

The last 20 years witnessed a real paradigm shift concerning the impact of biotic factors on ecosystem functions as well as on vegetation structure of mangrove forests. Before this small scientific revolution took place, structural aspects of mangrove forests were viewed to be the result of abiotic processes acting from the bottom-up, while, at ecosystem level, the outwelling hypothesis stated that mangroves primary production was removed via tidal action and carried to adjacent nearshore ecosystems where it fuelled detrital based food-webs. The sesarmid crabs were the first macrofaunal taxon to be considered a main actor in mangrove structuring processes, thanks to a number of studies carried out in the Indo-Pacific forests in the late 1970s and early 1980s. Following these classical papers, a number of studies on Sesarmidae feeding and burrowing ecology were carried out, which leave no doubts about the great importance of these herbivorous crabs in structuring and functioning Old world ecosystems. Although Sesarmidae are still considered very important in shaping mangrove structure and functioning, recent literature emphasizes the significance of other invertebrates. The Ocypodidae have now been shown to have the same role as Sesarmidae in terms of retention of forest products and organic matter processing in New world mangroves. In both New and Old world mangroves, crabs process large amounts of algal primary production, contribute consistently to retention of mangrove production and as ecosystem engineers, change particle size distribution and enhance soil aeration. Our understanding of the strong impact of gastropods, by means of high intake rates of mangrove products and differential consumption of propagules, has changed only recently. The role of insects must also be stressed. It is now clear that older techniques used to assess herbivory rates by insects strongly underestimate their impact, both in case of leaf eating and wood boring species and that herbivorous insects can potentially play a strong role in many aspects of mangrove ecology. Moreover, researchers only recently realized that ant–plant interactions may form an important contribution to our understanding of insect–plant dynamics in these habitats. Ants seem to be able to relieve mangroves from important herbivores such as many insects and sesarmid crabs. It thus seems likely that ants have positive effects on mangrove performance.     

Genetic differentiation in the mud crab Scylla serrata (Decapoda: Portunidae) within the Indian Ocean

Scylla serrata (Decapoda: Portunidae) is a swimming crab that is widespread in the Indo-Pacific region and commonly found in estuarine and mangrove waters. An extended planktonic larval phase suggests high dispersal potential and the possibility of extensive gene flow between conspecific populations at least on a geographic mesoscale (tens to hundreds of kilometres).Intraspecific variation of the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) gene was investigated in 77 individuals from four representative mangrove swamps of the African tropics (Kenya and Zanzibar) by means of DNA sequencing. We examined 535 base pairs (bp) and identified 24 different haplotypes. Each population sample is characterised by a single most frequent haplotype, shared among all four populations, and a small number of rare ones, typically present in only one or two individuals and representative of a specific population.Analysis of molecular variance (AMOVA), F_ST statistics and χ² contingency analysis of spatial distribution of mtDNA haplotype frequencies revealed in toto a significant genetic differentiation among populations. These results could indicate that gene flow might be reduced, even between geographically close sites, despite the high potential for dispersal; anyway, at the recorded level of divergence and owing to the abundance of rare haplotypes and singletons in our data set, repeated sampling over time is necessary to establish whether the recorded pattern of genetic differentiation is stable and biologically significant.Finally, integration of our data with those reported by Gopurenko et al. [Mar. Biol. 134 (1999) 227] on S. serrata from South Africa, Red Sea and Mauritius Islands allowed to infer S. serrata population structure within a larger area of the Indian Ocean region.     

Geographic trends in mangrove crab abundance in East Africa

The aim of this work was to determine the abundance of crabs inmangrove communities along a latitudinal gradient along the eastern coastof Africa from 4°S to 32°S. Surveys were made atMombasa (Kenya), Zanzibar (Tanzania), Maputo (Mozambique) and in theTranskei (South Africa). Crabs were estimated at three designated levelsin the mangroves by visual census using a common protocol, and numberswere converted to biomass.Even after standardising the selection of sites and methods of censusthere was still extensive variability in the data, emphasising the complexheterogeneity of mangrove ecosystems. Lunar phase (full versus new moonsprings) did not have a consistent effect on results, but shore height hadseveral effects. Total crab biomass was similar in the two lower shore strataexamined, but about twice as high at the top-Avicennia level. Theratio of grapsid biomass:ocypodid biomass also changed with height: fromnear unity in the lower mangrove, to 0.14 in the middle strata, but to 15at the top.There was no consistent latitudinal trend in total crab numbers, but totalcrab biomass increased from north to south. In addition there was aconsistent and marked change in the grapsid biomass:ocypodid biomassratio: this swung from 0.65 at Mombasa to 6.8 in the Transkei. This hasimplications for the transfer of primary production through the food chain. Grapsids are important macrophagous feeders on the leaves and other partsof mangroves, whereas ocypodids are microphagous deposit feeders.     

Parietal lobe variation in cercopithecid endocasts

In extant primates, the posterior parietal cortex is involved in visuospatial integration, attention, and eye‐hand coordination, which are crucial functions for foraging and feeding behaviors. Paleoneurology studies brain evolution through the analysis of endocasts, that is molds of the inner surface of the braincase. These may preserve imprints of cortical structures, such as sulci, which might be of interest for locating the boundaries of major cortical regions. Old World monkeys (Cercopithecidae) represent an interesting zoological group for evolutionary studies, because of their diverse ecologies and locomotor behaviors. In this study, we quantify parietal lobe variation within the cercopithecid family, in a sample of 30 endocasts including 11 genera and 17 species, by combining landmark‐based and landmark‐free geometric morphometric analyses. More specifically, we quantitatively assess variation of the parietal proportions based on landmarks placed on reliable anatomical references and of parietal lobe surface morphology through deformation‐based methods. The main feature associated with the cercopithecid endocranial variation regards the inverse proportions of parietal and occipital lobes, with colobines, Theropithecus, and Papio displaying relatively larger parietal lobes and smaller occipital lobes compared with cercopithecins. The parietal surface is anteroposteriorly longer and mediolaterally flatter in colobines, while longitudinally shorter but laterally bulging in baboons. Large parietal lobes in colobines and baboons are likely to be independent evolutionary traits, and not necessarily associated with analogous functions or morphogenetic mechanisms.     

A method to estimate body mass and relative age of exotic lagomorphs in the southern Neotropics

Exotic prey species can dramatically alter trophic interactions by functionally replacing native prey species. This pattern has been observed in the southern Neotropics, where introduced haresLepus europaeus Pallas, 1778 and rabbitsOryctolagus cuniculus (Linnaeus, 1758) have become the staple prey for native predators. Despite their importance as prey, no data are available on the mass and relative age of the lagomorphs on which native predators feed. We used linear regression models to predict the mass of lagomorphs from their hind-foot length, and investigated the influence of sex, season, and collection site on this relationship. Hind-foot length was a good predictor of body mass for both species and accounted for 58.4 and 71.6% of the variability in body mass for hares and rabbits, respectively. Sex and season significantly influenced the relationship, whereas the effect of collection site was negligible. Hind-foot length was also a good predictor of age class for hares and rabbits, allowing the discrimination between nonreproductive and reproductive classes for both species. Future research can use this method to determine the biomass and age class of exotic lagomorphs consumed by predators.     

Molecular phylogeny and host-plant use (Lamiaceae) of the Thymogethes pollen beetles (Coleoptera)

The 24 members of the Euro-Asiatic genus Thymogethes are highly specialized pollen beetles associated as larvae with flowers of Lamiaceae Nepetoideae. All members of the genus were analysed in within the framework of an integrative taxonomy approach, which was aimed to reconstruct the phylogenetic relationships, as well as the possible pattern of evolution of their larval-host-plant association. Evidence from multiple molecular markers [COI; 16S; H3], combined with an estimation of divergence times using an average rate of 0.0177 substitutions/site/My among branches, placed the origin of the genus at a minimum of 9–10 Mya. This date of origin approximates the known evolution of the host plants in Euro-Mediterranean areas. Evidence from combined molecular and cladistic morphological analyses resulted in suitable agreement with the previously established morphology-based systematics of the genus, although members of the exilis species-group were split into three clades. The only disagreement between results of this new combined phylogeny and previous classification is in the exclusion of “Thymogethes” grenieri. This species is herein positioned outside the genus, based on molecular evidence. Our analysis depicts several Thymogethes species differentiating in the last few Mys, specifically those included in the T. lugubris species-group. Combined evidence from DNA, morphology and ancestral state parsimony reconstruction of larval-host-plant associations suggests that subtribe Menthinae likely represents the ancestral host plants, with a series of independent host shifts during the radiation of the clade, in association first with Menthinae and subsequently with Lavandulinae and Nepetinae. Steno-oligophagy is the most frequent (86%) condition, while strictly monophagous species are less numerous (14%).     

The Ca2+-dependent incorporation of nitrogenous bases into brain microsomal phospholipid subspecies in vitro.

The specificity of the Ca2+-stimulated choline and ethanolamine incorporation into the molecular subspecies of the correspondent choline and ethanolamine phosphoglycerides has been investigated in vitro in rat brain microsomes. In the presence of 5.0 mM Ca2+-ions and at pH 8.1, choline was incorporated 6 times faster into the tetraenoic diacyl-glycero-3-phosphorylcholines (diacyl-GPCs or lecithins) than into the saturated subspecies. The specific activities of the other species were intermediary, and decreased with increasing saturation. Hexaenoic species of lecithins were however weakly labelled. The rate of labelling of diacyl-GPC molecular subspecies was affected noticeably by changing the pH and the Ca2+-ion concentration of the incubation medium. Ethanolamine was incorporated in the presence of 2.5 mM Ca2+-ions and at pH 8.1 preferentially into the monoenoic species of total ethanolamine phosphoglycerides of rat brain microsomes. The rate of incorporation into the monoenoic species was twice that into the trienoic, tetraenoic and hexaenoic and 4 times faster that into the dienoic species. When the pattern of labelling was determined specifically for the molecular subspecies of diacyl-glycero-3-phosphorylethanolamines (diacyl-GPEs or phosphatidylethanolamines), the rate of incorporation of ethanolamine into the hexaenoic species resulted three times faster that into the saturated and monoenoic species and about twice that into the trienoic and tetraenoic species, in accordance with data for liver microsomes. The pattern of labelling of the molecular subspecies of ethanolamine phosphoglycerides and of diacyl-GPEs was not influenced by changing the pH and the Ca2+-ion concentration of the incubation medium.