Cytoplasmic Particles in the Killers of Euplotes minuta and their Relationship to the Killer Substance*

SYNOPSIS. The killer strains of Euplotes minuta contain cytoplasmic epsilon particles absent in sensitive strains. The toxic principle of killers is associated with large particles which sediment readily in the centrifuge and may be identical with epsilon. Killing particles are inactivated by heat, certain proteolytic enzymes, and lysis with the French press.     

Predicting population consequences of ocean climate change for an ecosystem sentinel,the seabird Cassin's auklet

Forecasting the ecological effects of climate change on marine species is critical for informing greenhouse gas mitigation targets and developing marine conservation strategies that remain effective and increase species' resilience under changing climate conditions. Highly productive coastal upwelling systems are predicted to experience substantial effects from climate change, making them priorities for ecological forecasting. We used a population modeling approach to examine the consequences of ocean climate change in the California Current upwelling ecosystem on the population growth rate of the planktivorous seabird Cassin's auklet (Ptychoramphus aleuticus), a demographically sensitive indicator of marine climate change. We use future climate projections for sea surface temperature and upwelling intensity from a regional climate model to forecast changes in the population growth rate of the auklet population at the important Farallon Island colony in central California. Our study projected that the auklet population growth rate will experience an absolute decline of 11–45% by the end of the century, placing this population on a trajectory toward extinction. In addition, future changes in upwelling intensity and timing of peak upwelling are likely to vary across auklet foraging regions in the California Current Ecosystem (CCE), producing a mosaic of climate conditions and ecological impacts across the auklet range. Overall, the Farallon Island Cassin's auklet population has been declining during recent decades, and ocean climate change in this century under a mid‐level emissions scenario is projected to accelerate this decline, leading toward population extinction. Because our study species has proven to be a sensitive indicator of oceanographic conditions in the CCE and a powerful predictor of the abundance of other important predators (i.e. salmon), the significant impacts we predicted for the Cassin's auklet provide insights into the consequences that ocean climate change may have for other plankton predators in this system.     

Cross-Reactivity to Mammalian Anti-H-Y Antiserum in Teleostean Fish

Anti-H-Y antiserum, raised in highly inbred rats, is absorbed by gonadal cells of various species of fish. This cross-reactivity proved to be restricted to the male sex in the cyprinodont species Lebistes and Xiphophorus, known to have the XX/XY mechanism of sex determination. In members of the more primitive fish orders Isospondyli and Ostariophysi, cross-reactivity was shown to occur as well, but the amount of antiserum absorbed was very similar in both sexes. An antigen cross-reacting with mammalian anti-H-Y antiserum is assumed to exist in fish similar to that found in higher vertebrates. If this is true, this antigen may have been shared originally by both sexes. However, during evolution, its expression has become restricted to the heterogametic sex.