A New Direction to Athletic Performance: Understanding the Acute and Longitudinal Responses to Backward Running

Backward running (BR) is a form of locomotion that occurs in short bursts during many overground field and court sports. It has also traditionally been used in clinical settings as a method to rehabilitate lower body injuries. Comparisons between BR and forward running (FR) have led to the discovery that both may be generated by the same neural circuitry. Comparisons of the acute responses to FR reveal that BR is characterised by a smaller ratio of braking to propulsive forces, increased step frequency, decreased step length, increased muscle activity and reliance on isometric and concentric muscle actions. These biomechanical differences have been critical in informing recent scientific explorations which have discovered that BR can be used as a method for reducing injury and improving a variety of physical attributes deemed advantageous to sports performance. This includes improved lower body strength and power, decreased injury prevalence and improvements in change of direction performance following BR training. The current findings from research help improve our understanding of BR biomechanics and provide evidence which supports BR as a useful method to improve athlete performance. However, further acute and longitudinal research is needed to better understand the utility of BR in athletic performance programs

Interference and exploitation components in interespecific competition between sympatric, intertidal hermit crabs

This study was designed to evaluate the effect of interference and exploitation competition in shell partitioning between two hermit crab species (Pagurus criniticornis and Clibanarius antillensis). Field samples revealed that shells of the gastropod Cerithium atratum were the main resource used by both hermit crab species and that Pagurus used eroded or damaged shells in higher frequency than Clibanarius. The exploitative ability of each species was compared between species in the laboratory using dead gastropod (Cerithium) baits to simulate predation events and signalize newly available shells to hermit crabs. Pagurus reached the baits more rapidly than Clibanarius, but this higher exploitative ability did not explain shell utilization patterns in nature. Another experiment evaluated the dominance hierarchy between these two hermit crab species and revealed that Clibanarius was able to outcompete Pagurus for higher quality shells in agonistic encounters. This higher interference competitive ability of Clibanarius in relation to Pagurus may explain field observations. Nevertheless, Pagurus may be responsible to enhance shell availability to other hermit crab species that have lower ability to find and use newly available shells. Differently, the poorer condition of shells used by Pagurus, the higher ability of this species to attend gastropod predation events and its higher consumption rate by shell-breaking crabs (Menippe nodifrons) may increase its predation risks, thus revealing the disadvantages of such an exploitative competitive strategy for hermit crabs. (C) 2004 Elsevier B.V. All rights reserved.310218319

A comparative study of intertidal molluscan communities in sandy beaches, Sao Sebastiao Channel, Sao Paulo State, Brazil

The aim of this work was to study the molluscan communities in two intertidal environments and their relationship with selected environmental variables. The study areas are located along Sao Francisco and Engenho d'Agua beaches (Sao Sebastiao Channel, Sao Paulo State, Brazil). These sites are structurally similar with sediments of coarse sand and pebbles that facilitate settlement of molluscan species. The area was subdivided into low, intermediate and high intertidal levels where the samples were taken. Temperature, salinity, grain size, organic matter, and calcium carbonate content were analyzed as environmental variables. The high species diversity recorded in the study sites was due to the occurrence of organisms on consolidated and unconsolidated substrates. However, differences in the specific composition of the two areas were associated with local differences in sediment constituents and the presence of urban waste water in Sao Francisco. In general, few species were common to both sites, with higher richness and number of individuals in Engenho d'Agua. Differences in environmental variables and in species distribution between the two areas were indicated by Canonical Correspondence Analysis, which also revealed that grain size, salinity and calcium carbonate content played a more important role in species distribution than did the organic matter content.6519110

Desiccation tolerance of four sympatric tropical intertidal hermit crabs (Decapoda, Anomura)

This study describes and quantifies the air exposure tolerance of four sympatric hermit crabs (Pagurus criniticornis, Clibanarius antillensis, C. selopetarius, and C. vittatus) in an intertidal area in southeastern Brazil. We report on survivorship, percentage and rate of weight and water loss until death, and overall body water content. The coexisting populations showed similar percentages of overall body water content and weight and water loss until death. Survivorship depended on crab size rather than species, and was positively correlated with crab size within each species (linear relationship) and with the size of all individuals of this hermit crab assemblage (exponential relationship). Each species had a characteristic rate of weight and water loss, indicating the existence of different physiological adaptations to resist desiccation. These differences were directly related to the species' distribution patterns in the intertidal zone.34422723

Predation on gastropods by shell-breaking crabs: effects on shell availability to hermit crabs

This study addressed the effect predation on gastropods by shell-breaking crabs has on shell availability to hermit crabs. (1) Variable rates of predation on the gastropod Cerithium atratum were recorded within and among the crab species Menippe nodifrons, Panopeus occidentalis, Eriphia gonagra, and Callinectes danae. Predation rate was more dependent on crab size than on crab species, and all predators consumed the largest individuals of C. atratum available. Comparison of M. nodifrons and C. danae predation of the rocky shore gastropods Stramonita haemastoma, Morula nodulosa, and Tegula viridula revealed that only M. nodifrons consumed M. nodulosa, while both crabs preyed more heavily upon S. haemastoma than on T. viridula. M. nodifrons crushed larger individuals of Stramonita. (2) Prey subjected to M. nodifrons and C. danae presented different critical sizes (S. haemastoma > T viridula = M. nodulosa. (3) The investment in shell material varied among gastropod species (M. nodulosa > T viridula > S. haemastoma) and was inversely related to their consumption rate by M. nodifrons. (4) M. nodifrons generally crushed its prey, C. danae and E. gonagra used both peeling and crushing, and P. occidentalis generally peeled. Crushing was usually lethal, while peeling attempts resulted in higher prey survival. Predatory strategy was dependent on relative prey size: small shells were crushed, medium-sized were peeled, and large ones were non-destructively preyed upon through the aperture. (5) Most shells used by the hermit crab Pagurus criniticornis (68%) in nature presented damage very similar to that recorded for gastropods preyed upon experimentally, indicating that this kind of predation makes new shells available to hermit crabs. (6) M. nodifrons showed a clear preference for the gastropod C. atratum over the hermit crab P. criniticornis, suggesting differential predation pressures in nature. In conclusion, shell availability to hermit crabs was demonstrated to be dependent on predator species and size, gastropod architectural defenses, and on the relative predator-prey size, which determined the predatory strategy and the damage inflicted on the shells.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.28627929