scholarly journals Biological Invasion of Fish Parasite Neoergasilus japonicus (Harada, 1930) (Copepoda: Ergasilidae) in Lake Grand Laoucien, France: A Field Study on Life Cycle Parameters and Reasons for Unusual High Population Density

Life ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1100
Author(s):  
Victor Alekseev ◽  
Corinne Cuoc ◽  
Dominique Jamet ◽  
Jean-Louis Jamet ◽  
Remi Chappaz
Keyword(s):  
Life Cycle ◽  
Population Density ◽  
Water Levels ◽  
High Population ◽  
Fish Parasite ◽  
High Population Density ◽  
Contributing Factors ◽  
Free Living ◽  
The Amur River ◽  
Neoergasilus Japonicus

The fish parasite, Neoergasilus japonicus (Harada, 1930), native to Eastern Siberia and the Amur River catchment area, invaded European water bodies in the middle of the last century, possibly due to the human-mediated distribution of fish in the Amur complex (i.e., the genera Hypophthalmichthys and Ctenopharyngodon). In the deep karst lake, Grand Laoucien (Marseille area, France), this species had an unusually high population density (from 1000 ind./ m3 in zooplankton to 4000 ind./ m3 in the nearshore area) during the free-living period of its life cycle. The annual cycle of N. japonicus includes a 5-month overwintering of fertilized females attached to fish fins and, following this, a five- to six-generation chain from March to November, when the free-living stages in the population alternate with parasite females which attach to their hosts for breeding. The population density of the parasites in zooplankton increased exponentially from spring to autumn, which positively correlated with temperature. We found a strong correlation between N. japonicus density and the community development of microphytobenthos, but not between N. japonicus and phyto- or zooplankton dynamics. The local contributing factors included a seasonal three-fold decrease in water levels and the development of anoxia in profundal waters, which led to a high ambient fish density and thus susceptibility to the parasite. Although the free-living parasite represented only 1% of zooplankton production, it consumed up to 25% of small invertebrate productivity. The maximum intensity of infection reached 140 parasites per fish, or 4.14 per g of weight. The high infection of fish with this parasite, in our opinion, indicated the danger it poses to the local ichthyofauna, which first encountered this new parasite.

scholarly journals River Mitigation as a Form of Elderly-Nature Interaction in Densely Populated Settlement in Yogyakarta

2021 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Muhammad Aldi Rahmatul Hakim ◽  
Diananta Pramitasari
Keyword(s):  
Population Density ◽  
The Elderly ◽  
Water Levels ◽  
High Population ◽  
High Population Density ◽  
Residential Areas ◽  
Negative Effects ◽  
Dominant Form ◽  
Physical Limitations

High population density has been associated with disease susceptibility. To address this problem many suggest that the negative effects of population density can be reduced by interacting with nature as a restorative activity. This study aims to determine how the elderly in the residential areas on the banks of the Winongo river, Ngampilan District, Yogyakarta City with high population density interact with nature in the riverside environment, and what form of space is needed. This study uses a deductive exploratory method with elderly respondents who are active on the riverbank. The results showed that the riverside space which is used as a space for interaction between the elderly and nature is a room with sitting facilities, walls that are not closed, and shade that is not too tight. Interactions with nature that occur can be in the form of physical restoration, recreation, domestic, and mitigation activities. The activity of seeing water levels as flood mitigation is the most dominant form. Physical limitations make elderly people more aware of disasters along the riverbanks. A space that makes it easier for the elderly to do disaster anticipation activities needs to be prepared for long-term planning.

scholarly journals Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

Aggregations of masked shrews ( Sorex cinereus ): density-related mating behavior? / Agrégation de musaraignes masquées ( Sorex cinereus ): accouplement relatif à la densité de la population?

Mammalia ◽  
2006 ◽  
Vol 70 (1-2) ◽  
Author(s):  
Thomas J. Maier ◽  
Katherine L. Doyle
Keyword(s):  
Population Density ◽  
Mating Behavior ◽  
High Population ◽  
High Population Density ◽  
Genetic Analyses ◽  
Highly Active ◽  
Sorex Cinereus

AbstractLarge aggregations of shrews have been reported and various explanations offered for this seemingly rare behavior; however, there has been little evidence to support any particular interpretation. We observed two small aggregations of highly active vocalizing Sorex cinereus while performing wildlife surveys in forested habitats in central Massachusetts, USA. These observations, in conjunction with a review of other reports, including genetic analyses, strongly suggest that such aggregations of adult Sorex are associated with mating behavior, more readily observed during periods of high population density. Published accounts of such behavior may be rare because primarily large aggregations have been reported; however, smaller breeding aggregations may be common.

Analysis of steroid hormone levels in female mice at high population density

1998 ◽  
Vol 64 (4) ◽  
pp. 529-533 ◽  
Author(s):  
John C Chapman ◽  
John J Christian ◽  
Mary Ann Pawlikowski ◽  
Sandra D Michael
Keyword(s):  
Population Density ◽  
Steroid Hormone ◽  
High Population ◽  
High Population Density ◽  
Hormone Levels ◽  
Female Mice

Environmental Issues Regarding Space Launches over the Black Sea

2013 ◽  
Vol 330 ◽  
pp. 805-810
Author(s):  
Dragos R. Rugescu
Keyword(s):  
Population Density ◽  
Black Sea ◽  
Environmental Issues ◽  
High Population ◽  
The Black Sea ◽  
Western Coast ◽  
High Population Density ◽  
Research Activity ◽  
The West ◽  
Space Project

The Romanian NERVA space project, aimed at building and using a small rocket launcher for injecting nanosatellites into a LEO, requires the establishment of a secure launching area. The first candidate is on the western coast of the Black Sea and the candidate launching and flight corridor is the west-east vector above the sea. A series of ecological and safety challenges appear due to the high population density of the regions close to the sea-shores of the Black Sea; they must be catalogued and securely solved, before any space activity above the Black Sea begins. The main challenges of such an endeavor are analyzed henceforth and several solutions that fall within the scope of a recent research activity of the NERVA team are proposed.

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