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21.
Nini Johanna Cadena Camilo Rey Marcela Hernández-Hoyos J. Darío Sánchez Stanislas Teillaud Nestor Ardila Juan A. Sánchez 《Marine Biology》2010,157(5):1003-1010
Branching growth is present both in plants and animals, either marine or terrestrial. Although cellular and other modular
levels of organization in plants and animals have evolved through different molecular and physiological mechanisms, several
aspects of their branching modular system and morphology are similar. We studied vessel organization and colony integration,
in order to comprehend underlying relationships between different structural components in a gorgonian coral network. The
theoretical formalism was validated in the gorgonian coral Eunicea mammosa (Plexauridae, Octocorallia) in Belize. As in vascular plants, these colonial animals create a complex network of connections
among modular branches integrated in stem canals downstream toward the base. A new formalism is proposed for describing gorgonian
branching. A global property of a colony is for instance the size of its base or its weight whereas a local property is the
size of branch in a particular place of the colony. However, a global property is not the simple addition of local modular
properties, as the case of stem canals in the colony base. Theoretically, the process of branching is tightly intertwined
with the internal network organization. The colony network centralization is driven by a linear relationship between the total
number of branches and the stem canals at the base of the colony. If stem canals play important roles in the transport of
nutrients throughout the colony and the biomechanical support from the base up to the tips, we can assume that there is an
underlying association between the number of stem canals at the base and the number of for example, terminal branches. These
associations may provide new findings that extend our understanding of the functional organization of tree-like networks in
octocorals and their vascular systems. The idea that the external components of a tree-like plant network are directly correlated
and connected down to the main trunk seems to be analogous in an animal system. 相似文献
22.
Benayas JM Montaña Ede L Belliure J Eekhout XR 《Journal of environmental management》2006,79(3):279-289
A major task related to conservation is to predict if planned infrastructure projects are likely to threaten biodiversity. In this study we investigated the potential impact of planned infrastructure in Spain on amphibian and reptile species, two highly vulnerable groups given their limited dispersal and current situation of population decline. We used distribution data of both groups to identify areas of high herpetofauna diversity, and compared the locations of these areas with the locations of the planned road, high-speed train railway and water reservoir network. Four criteria were used for this identification: species richness, rarity, vulnerability, and a combined index of the three criteria. From a total of 1441 cells of 20 x 20 km, areas of high diversity were defined as those cells whose ranked values for the different criteria included either all species or all threatened species. The combined index provided the smallest number of cells needed to retain all threatened species (1.7 and 2.6% of the cells for amphibian and reptile species, respectively). Coincidences between these high diversity areas and cells including planned infrastructures-denominated 'alert planning units'-were 35.4% for amphibians and 31.2% for reptiles. Mitigation of the potential impacts would include actions such as barriers to animal access to roads and railways and ecoducts under these constructions. Our approach provides conservation authorities information that can be used to make decisions on habitat protection. A technique that identifies threats to herpetofauna before they occur is also likely to improve the chance of herpetofauna being protected. 相似文献
23.
Rey Gutierrez Rutilio Ortiz Salvador Vega Beatriz Schettino Maria L. Ramirez Jose J. Perez 《Journal of environmental science and health. Part. B》2013,48(11):935-940
A survey was carried out from 2008 to 2010 to determine the concentrations of 16 organochlorine pesticide residues (OPRs) from Tizayuca, Hidalgo, Mexico. Organochlorine residue determinations were made from milk fat, using chromatographic cleanup and analysis by gas chromatography with an electron capture detector. The OPR concentrations found were from below the detection limit (DL) to 0.91 ng g?1 in 2008, DL to 0.38 ng g?1 in 2009 and DL to 0.59 ng g?1 in 2010. In general concentrations of organochlorine pesticides were higher in the wet season (3.37 ng g?1 and 4.79 ng g?1) than the dry season (1.92 ng g?1 and 2.71 ng g?1) for 2009 and 2010, due to control of pests in the pasture and sheds. According to Codex Alimentarius regulations, individual pesticides did not exceed the permissible limits, which for example were 10 μg kg?1 for alpha hexachlorocyclohexane (HCH) and endosulfan I, 20 μg kg?1 for p,p’-DDT, and 6 μg kg?1 for dieldrin, endrin and heptachlor. A reduction of organochlorine pesticide concentrations in cow's milk was noted, indicating that the Mexican government has achieved reduction or elimination of some organochlorine pesticides in response to global agreements on persistent organic pollutants. 相似文献
24.
The coasts of the Gulf of Mexico are zones exposed to the exploration and exploitation of petroleum sources, and the products generated in agricultural zones may become contaminated by persistent organic pollutants (POPs). The objective of the present study was to evaluate the presence of polychlorinated biphenyl compounds (PCBs) in milk from dairy production units near sources of environmental pollutants. It was confirmed that the seven congeners of nondioxin-like PCBs (NDL-PCBs) are present in milk where compounds PCB101, PCB118, PCB153 and PCB180 appear in 100% of the samples analyzed, the rank of concentration for the sum of the seven congeners fluctuating between 2.6 and 26 ng g−1 with a median of 6 ng g−1. None of the samples surpassed the provisional value established by the EU of 40 ng g−1 of milk fat for the sum of the seven congeners, indicator that was not affected by the season of the year (p < 0.05), whose median of 8.6 ng g−1 and 6.3 ng g−1 for rain and drought respectively. The concentrations of NDL-PCBs found in milk do not represent a problem for human health; however, they alert the existence of spontaneously generated, uncontrolled sources that may represent a potential danger for human and animal health. 相似文献
25.
Importance of food quantity to structural growth rate and neutral lipid reserves accumulated in Calanus finmarchicus 总被引:1,自引:0,他引:1
Growth and developmental rates were determined for copepodids of Calanus finmarchicus (Gunnerus) from experimental seawater mesocosms in a western Norwegian fjord. The instantaneous growth rates (g) from copepodid stage I (CI) to adult ranged from 0.08 to 0.10 d−1. Daily per capita mortality rate of the cohorts was as low as 0.012 d−1 (1.2% d−1). At local increasing temperatures (5.1 to 8.3 °C), development was equiproportional, and the cumulative median development
time from egg to CV was approximately 65 d. CV moulted to males and females, and egg production was initiated. Enhancement
of food resources by nutrient addition caused a 23.4% increase in growth rates from CI to adult. Additionally, copepodid stages
showed a generally larger body size, carbon and nitrogen content and total storage lipid content (wax esters + triacylglycerols)
in response to enhanced resources. Our data support an elsewhere proposed exponential-growth hypothesis; growth of the structural
compartments and store lipids (mostly wax esters) was exponential during the copepodid stages. However, a sigmoidal pattern
of growth best described growth of adult stages if reared at high resources, and depot lipid accumulation in late CVs and
adults at high resources. Body nitrogen growth increased exponentially, however, no significant changes in nitrogen specific
growth rates were found between individuals from low and high resources. CV and adults seem to have reached near-maximal weights
at high resources, whereas structural weight continued to increase at low resources. Despite the differences in structural
growth dynamics, cohort development was similar until the end of CV. During the onset of sexual differentiation, the male:female
ratio and the adult:CV ratio were highest at high food resources, suggesting that the time used for the final moult depends
on the feeding history of the copepods in relation to food quality and quantity. It appears that relatively small changes
in food availability strongly influence the biochemical composition of C. finmarchicus copepodids.
Received: 28 May 1999 / Accepted: 10 February 2000 相似文献