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.

scholarly journals Population Dynamics, Fecundity and Fatty Acid Composition of Oithona nana (Cyclopoida, Copepoda), Fed on Different Diets

Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1188
Author(s):  
Fawzy I. Magouz ◽  
Mohamed A. Essa ◽  
Mustafa Matter ◽  
Abdallah Tageldein Mansour ◽  
Mohamed Alkafafy ◽  
...  
Keyword(s):  
Growth Rate ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Population Growth ◽  
Acid Composition ◽  
Rice Bran ◽  
Nutritional Value ◽  
Corn Starch ◽  
Copepod Species ◽  
Marine Copepod

The marine copepod species Oithona nana is considered as one of the most successfully mass cultured Cyclopoida species in marine hatcheries. This study investigated the effects of four feed diets (soybean, yeast, rice bran, and corn starch) on the population growth, growth rate, population composition, fecundity, and fatty acid composition of native isolated Cyclopoida copepod species O. nana. The experiment was continued for 15 days and the copepods were fed on one of the four diets with a concentration of 1 g 10−6 individual day−1. The results revealed that corn starch was found to be the most supportive diet for population growth and population growth rate. For nutritional value, copepods fed on rice bran were detected to have the highest content of MUFA, PUFA, and the lowest SFA and SFA/UFA ratio; more importantly, the rice bran diet was the only treatment that showed C20:5ω3. Moreover, copepods fed on rice bran showed the highest significant female fecundity, copepodite, and nauplii percent. Finally, the protocols described in the current study concluded that the dry feeds, especially corn starch, are very useful and applicable in hatcheries for maximizing the fecundity and density of Cyclopoida copepod species, O. nana.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

Lessons from a century of conservation translocations

2021 ◽  
Author(s):  
Shane D Morris ◽  
Katherine E. Moseby ◽  
Barry W. Brook ◽  
Christopher N. Johnson
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Historical Context ◽  
Extrinsic Factors ◽  
Global Database ◽  
Terrestrial Vertebrates ◽  
Failure Classification ◽  
High Population Growth ◽  
Number Of Individuals

Translocation—moving individuals for release in different locations—is among the most important conservation interventions for increasing or re-establishing populations of threatened species. However, translocations often fail. To improve their effectiveness, we need to understand the features that distinguish successful from failed translocations. Here, we assembled and analysed a global database of translocations of terrestrial vertebrates (n=514) to assess the effects of various design features and extrinsic factors on success. We analysed outcomes using standardized metrics i.e. a categorical success/failure classification, and population growth rate. Probability of categorical success and population growth rate increased with the total number of individuals released but with diminishing returns above about 20-50 individuals. There has been no increase in numbers released per translocation over time. Positive outcomes—reported success and high population growth—were less likely for translocation in Oceania, possibly because invasive species are a major threat in this region and are difficult to control at translocation sites. Increased rates of categorical reported success and population growth were found for Europe and North America, suggesting the key role of historical context in positive translocation outcomes. Categorical success has increased throughout the 20th century, but that increase may have plateaued at about 75% since about 1990. Our results suggest there is potential for further increase in the success of conservation translocations. This could be best achieved by greater investment in individual projects, as indicated by total number of animals released.

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