Blastomycosis in wild wolves

Blastomycosis was fatal to a wild wolf in Minnesota, and serologic evidence of blastomycosis was found in a Wisconsin wolf. No unusual movements were detected in the Minnesota animal from October 1983 through October 1985. However, by early December 1985, this wolf was weak and debilitated, and it perished on 14 December after approaching a human residence.     

Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes

A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent. ¹Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA ²Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA     

Adaptive advantages of patterns of growth and asexual reproduction of the sea anemone Metridium senile (L.) in intertidal and submerged populations

Individual size, rate of growth, and mode and frequency of asexual reproduction are life-history traits of primary importance for sea anemones. These traits determine sexual reproductive output, affect an individual's probability of survival, and are crucial in adapting an individual to its environmental surroundings. The sea anemone Metridium senile (L.) is highly variable in ecological distribution and life history, including rate of growth, individual size, and rate of asexual reproduction. Gonad size (measured as cross-sectional area of gonadal tissue) increases with body weight, so individuals should grow as large and as rapidly as possible to maximize individual sexual reproductive output. Cessation of growth and small body size in intertidal populations suggest that growth is constrained by genetic or environmental conditions. The growth of intertidal individuals transplanted to harbor-float panels demonstrated that growth limits are imposed by environmental factors, most probably limited food and feeding time and damage from wave exposure (which stimulates fragmentation). Individuals in harbor-float populations, which are continuously immersed, grow much larger, and large individuals comprise a greater proportion of the population than in the intertidal zone. The highest rate of fragmentation observed was on harbor-float panels. Patterns of growth and asexual reproduction provide adaptive advantages for M. senile. For harborfloat individuals, large individual size increases gamete production and may increase feeding efficiency. For intertidal individuals, asexual reproduction allows growth despite individual size constraints and rapid population growth, with specific advantages resulting from clone formation.