Plankton reach new heights in effort to avoid predators

The marine environment associated with the air-water interface (neuston) provides an important food source to pelagic organisms where subsurface prey is limited. However, studies on predator-prey interactions within this environment are lacking. Copepods are known to produce strong escape jumps in response to predators, but must contend with a low-Reynolds-number environment where viscous forces limit escape distance. All previous work on copepod interaction with predators has focused on a liquid environment. Here, we describe a novel anti-predator behaviour in two neustonic copepod species, where individuals frequently exit the water surface and travel many times their own body length through air to avoid predators. Using both field recordings with natural predators and high-speed laboratory recordings, we obtain detailed kinematics of this behaviour, and estimate energetic cost associated with this behaviour. We demonstrate that despite losing up to 88 per cent of their initial kinetic energy, copepods that break the water surface travel significantly further than those escaping underwater and successfully exit the perceptive field of the predator. This behaviour provides an effective defence mechanism against subsurface-feeding visual predators and the results provide insight into trophic interactions within the neustonic environment.     

Lagrangian description of zooplankton swimming trajectories

Three-dimensional swimming, in 20 trajectories of Daphnia pulex,was characterized in terms of its kinematic properties. Resultsshow that the random component was stronger than the deterministiccomponent at time scales >1–2 s. Such random movementsmay have evolved to outwit potential predators and prey.     

Chorioallantoic placentation in Galea spixii (Rodentia,Caviomorpha, Caviidae)

Background  

Placentas of guinea pig-related rodents are appropriate animal models for human placentation because of their striking similarities to those of humans. To optimize the pool of potential models in this context, it is essential to identify the occurrence of characters in close relatives.     

Procathepsin and acid phosphatase are stored in Musca domestica yolk spheres

Yolk spheres present in mature invertebrate oocytes are composed of yolk proteins and proteolytic enzymes. In the fly Musca domestica, yolk proteins are degraded during embryogenesis by a cathepsin-like proteinase that is stored as a zymogen. An acid phosphatase is also active in the yolk spheres during Musca embryogenesis. In this paper we show that procathepsin and acid phosphatase are initially stored by a different pathway from the one followed by yolk protein precursors. Both enzymes are taken up by the oocytes and transitorily stored into small vesicles (lysosomes) surrounding the early yolk spheres. Fusion of both structures, the early yolk spheres and lysosomes, creates the mature yolk spheres.     

To see or not to see: evolution of eye degeneration in mexican blind cavefish

The evolutionary mechanisms responsible for the loss of eyesin cave animals are still unresolved. Hypotheses invoking naturalselection or neutral mutation have been advanced to explaineye regression. Here we describe comparative molecular and developmentalstudies in the teleost Astyanax mexicanus that shed new lighton this problem. A. mexicanus is a single species consistingof a sighted surface-dwelling form (surface fish) and many blindcave-dwelling forms (cavefish) from different caves. We firstreview the evolutionary relationships of Astyanax cavefish populationsand conclude that eye degeneration may have evolved multipletimes. We then compare the mechanisms of eye degeneration indifferent cavefish populations. We describe the results of experimentsshowing that programmed cell death of the lens plays a key rolein controlling eye degeneration in these cavefish populations.We also show that Pax6 gene expression and fate determinationin the optic primordia are modified similarly in different cavefishpopulations, probably due to hyperactive midline signaling.We discuss the contributions of the comparative developmentalapproach toward resolving the evolutionary mechanisms of eyedegeneration. A new hypothesis is presented in which both naturalselection and neutral mutation are proposed to have roles incavefish eye degeneration.     

What can we hope to gain for trypanosomiasis control from molecular studies on tsetse biology ?

At times of crisis when epidemics rage and begin to take their toll on affected populations, as we have been witnessing with African trypanosomiasis in subSahara, the dichotomy of basic versus applied research deepens. While undoubtedly the treatment of thousands of infected people is the top priority, without continued research and development on the biology of disease agents and on ecological and evolutionary forces impacting these epidemics, little progress can be gained in the long run for the eventual control of these diseases. Here, we argue the need for additional research in one under-investigated area, that is the biology of the tsetse vector. Lacking are studies aimed to understand the genetic and cellular basis of tsetse interactions with trypanosomes as well as the genetic and biochemical basis of its ability to transmit these parasites. We discuss how this knowledge has the potential to contribute to the development of new vector control strategies as well as to improve the efficacy and affordability of the existing control approaches.