Feeding and grazing in Lake George, Uganda

1973 ◽  
Vol 184 (1076) ◽  
pp. 299-319 ◽  
Keyword(s):  
Food Preference ◽  
Food Selection ◽  
Trophic Levels ◽  
Food Sources ◽  
Cyclopoid Copepod ◽  
Blue Green Algae ◽  
Tilapia Nilotica ◽  
Daily Ingestion ◽  
Herbivorous Species ◽  
Lake George

The fauna of Lake George is dominated by herbivores, in particular the fish Tilapia nilotica and Haplochromis nigripinnis , and the cyclopoid copepod Thermocyclops hyalinus . Digestion, and the assimilation of carbon from algae, by these herbivores were studied in detail. It was found that, contrary to previous observations reported in the literature, both fish and zooplankton were able to digest and assimilate blue-green algae. The diurnal feeding patterns of the herbivores were examined, and methods devised for assessing, in terms of carbon, the daily ingestion of algae. Hence, using biomass data, the total amount grazed by the herbivores was calculated. Estimates of carbon requirements at other trophic levels were made, as was an assessment of the required level of net production by the algae for comparison with figures for standing crop and net algal production measured by other means. Food selection by secondary and tertiary producers is discussed, and in several species age correlated changes in selectivity were examined. Both the major herbivorous species of fish adopt phytoplankton feeding after a period of carnivorous or omnivorous feeding as fry. Thermocyclops hyalinus is herbivorous all its life, but the size of particle taken changes with age. There are more species of carnivorous than herbivorous fish and these exploit a wider variety of food sources; the few species studied also show changes in food preference with age.

scholarly journals What Is the Carcass-Usage Mode of the Collembola? A Case Study of Entomobrya proxima in the Laboratory

Insects ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 67 ◽  
Author(s):  
Lichao Feng ◽  
Liang Chang ◽  
Shaoqing Zhang ◽  
Xinyu Zhu ◽  
Sina Adl ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Food Preference ◽  
Feeding Habits ◽  
Food Resource ◽  
Food Preferences ◽  
Trophic Levels ◽  
Food Sources ◽  
Body Parts ◽  
Animal Food ◽  
Rhizopus Sp

Collembola display a variety of feeding habits, and prey on many types of food at different trophic levels in the soil. In most cases, their feeding selections are widely varied. In the interest of the food preferences of E. proxima, we attempted to confirm how the Collembola utilize food when feeding on carrion (unusual sources). Four different soil animals (with different stable isotope values and increasing trophic levels) were used to examine whether collembolans can use dead insects as a food resource in specific manners, depending on food preference. Our results demonstrated that the food preference of a collembolan changed significantly after feeding on insects with different feeding habits for 60 days. We found that stable isotope values (δ13C) of Entomobrya proxima approached those of the food sources. A large proportion of the diet (more than 50%) should directly consist of insect body parts, with the remainder consisting of indirectly used, mixed microorganisms naturally growing on animal food, such as fungi (Rhizopus sp., Alternaria sp., Penicillium sp., and Aspergillus sp.) and bacteria (Bacillus sp1. and Bacillus sp2.). Based on this research, the food preference of collembolans is more focused on carcasses (dead insect bodies) than microorganisms during the animal-food decomposition process.

The biomass and distribution of organisms in Lake George, Uganda

1973 ◽  
Vol 184 (1076) ◽  
pp. 271-298 ◽  
Keyword(s):  
Aquatic Vegetation ◽  
Open Water ◽  
Cyclopoid Copepod ◽  
Lake Basin ◽  
Total Biomass ◽  
Lake Area ◽  
Blue Green Algae ◽  
Animal Populations ◽  
Water Community ◽  
Lake George

Ninety-five per cent of the total biomass in the open water of Lake George, a shallow equatorial lake, is phytoplankton. The biomass of this and the other major groups of organisms are given and compared with some figures from other lakes. Apart from the phytoplankton, standing crop levels in Lake George are not high and may be exceeded, although only for short periods, by organisms in temperate waters. Levels in Lake George, in contrast, fluctuate little throughout the year. The specific composition of the open water community is described and shown to be dominated by blue-green algae and three herbivores which utilize them as a food source: one cyclopoid copepod and two fish. The reasons why these and other species make up the open water community in Lake George are discussed and also possible factors which may limit some of the animal populations to the levels observed. Both the phytoplankton and the zooplankton exhibit a concentric pattern of distribution across the lake. Concentrations are highest in the centre and this may be attributable to the circular movements of the water mass which result from the shape of the basin and the wind régime. It might also be correlated with grazing effects since the fish population, which also shows a concentric distribution of biomass, has its highest concentrations in the inshore regions and its lowest in the centre. The distribution and species composition of the benthos is determined primarily by the nature of the substrate. In the open water area the bottom consists of soft, unstable, de-oxygenated mud which contains few species. Inshore the substrate is firmer and more varied and carries a greater density and variety of animals. These are preyed upon by a greater variety of fish, particularly species of the cichlid genus Haplochromis , than are found in the mid-lake area. The inshore region is short, due to the regular shape of the lake basin, and narrow, but provides a variety of habitats in contrast to the homogeneity of the mid-lake area. The lake is fringed in many places by papyrus swamp, the Nile cabbage floats on the surface of the water but there is no submerged aquatic vegetation.

Lake George, Uganda

1976 ◽  
Vol 274 (934) ◽  
pp. 375-391 ◽  
Keyword(s):  
Green Algae ◽  
Aquatic Environment ◽  
Open Water ◽  
Blue Green Algae ◽  
Plankton Biomass ◽  
Herbivorous Species ◽  
Animal Community ◽  
Lake George

This small (250 km 2 ), shallow (mean depth 2.4 m) equatorial lake has an exceptionally constant physicochemical aquatic environment. Two outstanding features are the high relative biomass of the blue-green algae (ca. 95 % of the total), and the lake’s 24 h rather than seasonal physiological cycle. In open water areas the animal community is dominated by three herbivorous species feeding on the blue-green algae. Various factors interact to produce a concentric and centripetal pattern of distribution for the plankton biomass, but a centrifugal one for fishes and benthos.

scholarly journals Effect of Different Salinity Levels on Population Dynamics and Growth of the Cyclopoid Copepod Oithona nana

Diversity ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 190
Author(s):  
Fawzy I. Magouz ◽  
Mohamed A. Essa ◽  
Mustafa Matter ◽  
Abdallah Tageldein Mansour ◽  
Ahmed Gaber ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Transition Period ◽  
Salinity Level ◽  
Food Sources ◽  
Cyclopoid Copepod ◽  
Population Composition ◽  
Optimal Salinity ◽  
Marine Copepod ◽  
Salinity Levels

Copepods are one of the most abundant and diverse live food sources for mesopelagic and bathypelagic fishes and crustaceans. They could contribute to the overlap of the transition period from live feed to an artificial weaning diet in marine larvae production. However, the culture conditions still need optimization to provide sufficient production to cover the increasing demand for marine hatcheries. Therefore, the present study investigated the effects of different salinity levels (5, 10, 15, 20, 25, and 30 ppt) on the population growth, growth rate, and population composition (males, females, copepodite, and nauplii ratio) of the marine copepod, Oithona nana. The experiment continued for 15 days, under laboratory-controlled conditions of temperature (27 ± 1 °C), pH (7.7 ± 0.15), and continuous gentle aeration in 30 L glass aquaria. The copepod culture aquaria were supplemented with a mixture of soybean and yeast (0.5 g 10−6 individual−1 24-h−1) as a feed source. The highest significant population growth and population growth rate of O. nana were achieved with a salinity level of 20 ppt. Regarding population composition, O. nana cultured at the salinity level of 20 ppt recorded the highest significant percentages of copepodite and nauplii. The results concluded that copepod, O. nana, is capable of withstanding abrupt changes in the salinity, but there are limits to their tolerance, with an optimal salinity level of 20 ppt. This salinity level achieved the highest population growth and the highest percentages of copepodite and nauplii of marine Copepoda, O. nana.

Food Selection by Grey-headed Flying Foxes (Pteropus poliocephalus) Occupying a Summer Colony Site near Gosford, New South Wales

1991 ◽  
Vol 18 (1) ◽  
pp. 111 ◽  
Author(s):  
K Parry-Jones ◽  
ML Augee
Keyword(s):  
Food Selection ◽  
Food Sources ◽  
Flying Foxes ◽  
Food Items ◽  
South Wales ◽  
The Family ◽  
Pteropus Poliocephalus ◽  
Marked Preference ◽  
Colony Site

A colony site occupied by grey-headed flying-foxes (Pteropus poliocephalus) from October to May on the central coast of N.S.W. was monitored over a 48 month period (1986-1990). Faecal and spat-out material was collected for microscopic determination of contents. Comparison of food items in the droppings with the array of possible food sources present in the vicinity of the colony at the same time showed a marked preference for certain foods, in particular blossoms of the family Myrtaceae and of the genus Banksia. Cultivated orchard fruits were not a preferred food and were only taken at times when preferred food items were scarce.

scholarly journals Low and reduced carbohydrate diets: challenges and opportunities for type 2 diabetes management and prevention

2020 ◽  
Vol 79 (4) ◽  
pp. 498-513 ◽  
Author(s):  
Chaitong Churuangsuk ◽  
Michael E. J. Lean ◽  
Emilie Combet
Keyword(s):  
Type 2 Diabetes ◽  
Weight Loss ◽  
Weight Control ◽  
Diabetes Management ◽  
Food Selection ◽  
Food Sources ◽  
Micronutrient Deficiencies ◽  
Clinical Endpoints

Low-carbohydrate diets (LCD) have been promoted for weight control and type 2 diabetes (T2D) management, based on an emerging body of evidence, including meta-analyses with an indication of publication bias. Proposed definitions vary between 50 and 130 g/d, or <10 and <40 % of energy from carbohydrate, with no consensus on LCD compositional criteria. LCD are usually followed with limited consideration for other macronutrients in the overall diet composition, introducing variance in the constituent foods and in metabolic responses. For weight management, extensive evidence supports LCD as a valid weight loss treatment, up to 1–2 years. Solely lowering carbohydrate intake does not, in the medium/long term, reduce HbA1c for T2D prevention or treatment, as many mechanisms interplay. Under controlled feeding conditions, LCD are not physiologically or clinically superior to diets with higher carbohydrates for weight-loss, fat loss, energy expenditure or glycaemic outcomes; indeed, all metabolic improvements require weight loss. Long-term evidence also links the LCD pattern to increased CVD risks and mortality. LCD can lead to micronutrient deficiencies and increased LDL-cholesterol, depending on food selection to replace carbohydrates. Evidence is limited but promising regarding food choices/sources to replace high-carbohydrate foods that may alleviate the negative effects of LCD, demanding further insight into the dietary practice of medium to long term LCD followers. Long-term, high-quality studies of LCD with different food sources (animal and/or plant origins) are needed, aiming for clinical endpoints (T2D incidence and remission, cardiovascular events, mortality). Ensuring micronutrient adequacy by food selection or supplementation should be considered for people who wish to pursue long-term LCD.

scholarly journals Effect of demonstrator reliability and recency of last demonstration on acquisition of a socially transmitted food preference

2018 ◽  
Vol 5 (6) ◽  
pp. 172391 ◽  
Author(s):  
Laura A. Agee ◽  
Marie-H. Monfils
Keyword(s):  
Social Interaction ◽  
Food Preference ◽  
Safety Information ◽  
Food Sources ◽  
Novel Food ◽  
Food Research ◽  
Naive Observer ◽  
The Social ◽  
Direct Competition ◽  
State Of The Environment

In the social transmission of food preference paradigm, naive observer rats acquire safety information about novel food sources in the environment through social interaction with a demonstrator rat that has recently eaten said food. Research into the behavioural mechanisms governing this form of learning has found that observers show increased reliance on socially acquired information when the state of the environment makes personal examination of their surroundings risky. We aimed to (1) determine whether reliance on social information would decrease if previous reliance on social learning was unsuccessful, and (2) whether reliance on the specific demonstrator that had transmitted poor information would similarly decrease. By inducing illness in observers following consumption of a socially demonstrated food, we created an environmental situation in which reliance on socially acquired information was maladaptive. We found that under these conditions, observers showed no change in their reliance on a specific demonstrator or socially learned information in general. Our experiment also unexpectedly produced results showing that recent demonstrators were more influential in later transmissions than demonstrators that had been learned from less recently. Notably, this effect only emerged when the observer simultaneously interacted with both demonstrators, indicating that demonstrators must be in direct competition for this effect to manifest.

Lipids that contain arsenic in the Mediterranean mussel, Mytilus galloprovincialis

2020 ◽  
Vol 17 (3) ◽  
pp. 289 ◽  
Author(s):  
Fabiana P. Freitas ◽  
Georg Raber ◽  
Kenneth B. Jensen ◽  
António J. A. Nogueira ◽  
Kevin A. Francesconi
Keyword(s):  
High Performance ◽  
Mytilus Galloprovincialis ◽  
Trophic Levels ◽  
Food Sources ◽  
Tissue Type ◽  
Unicellular Algae ◽  
Molecular Mass Spectrometry ◽  
Mediterranean Mussel ◽  
The Mediterranean ◽  
First Time

Environmental contextAlthough arsenic-containing lipids are widespread in marine environments, their origin remains unknown. We show that the arsenolipids in a filter-feeding bivalve mollusc closely match those found in marine food sources, including unicellular algae and bacteria. The results demonstrate the role of lower trophic levels in determining the forms of arsenic found in higher organisms. AbstractArsenic-containing lipids, arsenolipids, are widely found among marine organisms, but their origin and possible biochemical roles remain unknown This work describes the diversity and abundance of arsenolipids in the digestive gland and mantle of nine specimens of the Mediterranean mussel, Mytilus galloprovincialis. By using high performance liquid chromatography (HPLC) coupled to both elemental and high-resolution molecular mass spectrometry, we identified 36 arsenolipids including arsenic derivatives of fatty acids, hydrocarbons, sugar-phospholipids and sugar-phytol; 21 of these arsenolipids were identified for the first time and included a new group comprising ether-phospholipids. The arsenic compounds in the mussels show distinct profiles depending on the tissue type, which provide insight into the arsenolipid origin. The results suggest that the presence of some arsenolipids in the mussels is from direct uptake of the compounds, presumably from food, rather than biogenesis within the mussels.

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