Influence of food density on respiration rate of two crustacean plankters, Daphnia galeata and Bosmina longirostris

Oecologia ◽  
1990 ◽  
Vol 82 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Jotaro Urabe ◽  
Yasunori Watanabe
Keyword(s):  
Respiration Rate ◽  
Food Density ◽  
Daphnia Galeata ◽  
Bosmina Longirostris ◽  
Influence Of Food

Acid and Aluminum Effects on Sodium Homeostasis and Survival of Acid-Sensitive and Acid-Tolerant Cladocera

1992 ◽  
Vol 49 (11) ◽  
pp. 2392-2398 ◽  
Author(s):  
Karl E. Havens
Keyword(s):  
Acid Stress ◽  
Relative Increase ◽  
Al Toxicity ◽  
Whole Body ◽  
Population Declines ◽  
Daphnia Galeata ◽  
Sodium Homeostasis ◽  
Bosmina Longirostris ◽  
Acid Tolerant ◽  
Daphnia Galeata Mendotae

Acid-sensitive (Daphnia galeata mendotae) and acid-tolerant (Bosmina longirostris) cladocerans were exposed to 0, 100, or 200 μg Al/L at pH 4.5, 6.0, or 7.5. Whole-body Na content and survivals were determined after 12- and 24-h exposures to the nine treatments. Daphnia galeata mendotae experienced significant decreases in body Na content and survival at pH 4.5. Aluminum effects were pH dependent. At pH 7.5 and 6.0, Na content and survival declined with increasing Al; at pH 4.5, the highest Al concentration enhanced Na content and prolonged survival. Bosmina longirostris Na content and survival were only slightly reduced at pH 4.5, and there were no significant Al or pH × Al interaction effects. The results support the view that (1) the extinction of D. galeata mendotae and the relative increase of B. longirostris during lake acidification are largely due to differential impacts of acid stress on osmoregulation and (2) Al toxicity might also be a factor responsible for D. galeata mendotae population declines, which are most pronounced near pH 6.0.

scholarly journals Determinants of seasonal changes in availability of food patches for elephants (Loxodonta africana) in a semi-arid African savanna

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3453 ◽  
Author(s):  
Bruce W. Clegg ◽  
Timothy G. O’Connor
Keyword(s):  
Soil Water ◽  
Loxodonta Africana ◽  
Life Forms ◽  
Food Density ◽  
Regression Equations ◽  
African Savanna ◽  
Plant Life Forms ◽  
Plant Groups ◽  
Influence Of Food ◽  
Semi Arid

Loss of biodiversity caused by impact of elephants (Loxodonta africana) on African woodlands may require a management response, but any action should be based on an understanding of why elephants choose to utilise trees destructively. Comprehension of elephant feeding behaviour requires consideration of the relative value of the plant groups they may potentially consume. Profitability of available food is partly determined by the time to locate a food patch and, therefore, as a foundation for understanding the influence of food availability on diet selection, key controls on the density of grass, forb, and browse patches were investigated across space and time in a semi-arid African savanna. Density of food patches changed seasonally because plant life-forms required different volumes of soil water to produce green forage; and woody plants and forbs responded to long-term changes in soil moisture, while grasses responded to short-term moisture pulses. Soil texture, structure of woody vegetation and fire added further complexity by altering the soil water thresholds required for production of green forage. Interpolating between regularly-timed, ground-based measurements of food density by using modelled soil water as the predictor in regression equations may be a feasible method of quantifying food available to elephants in complex savanna environments.

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