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Rosati, L.; Caputo, I.; Lionetti, L.; Fontes, M.K.; Pereira, C.D.S.; Capaldo, A. European Eel. Encyclopedia. Available online: https://encyclopedia.pub/entry/42714 (accessed on 18 November 2024).
Rosati L, Caputo I, Lionetti L, Fontes MK, Pereira CDS, Capaldo A. European Eel. Encyclopedia. Available at: https://encyclopedia.pub/entry/42714. Accessed November 18, 2024.
Rosati, Luigi, Ivana Caputo, Lillà Lionetti, Mayana Karoline Fontes, Camilo Dias Seabra Pereira, Anna Capaldo. "European Eel" Encyclopedia, https://encyclopedia.pub/entry/42714 (accessed November 18, 2024).
Rosati, L., Caputo, I., Lionetti, L., Fontes, M.K., Pereira, C.D.S., & Capaldo, A. (2023, April 01). European Eel. In Encyclopedia. https://encyclopedia.pub/entry/42714
Rosati, Luigi, et al. "European Eel." Encyclopedia. Web. 01 April, 2023.
European Eel
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This entry is adapted from the peer-reviewed paper 10.3390/fishes8030166

The European eel (Anguilla anguilla) is a migratory, catadromous fish species, consisting of a single stock, distributed throughout the European continent as well as in the Mediterranean basin, which reproduces in the Atlantic Ocean and for which the panmixia hypothesis is currently accepted. 

Anguilla anguilla cocaine endocrine system histopathological changes

1. Introduction

Illicit drug use is a growing phenomenon, which, as numerous studies have shown, poses a threat not only to human health but also to the environment. In 2020, an estimated 284 million people worldwide, aged 15–64, had used a drug of abuse within the last 12 months; of these users, approximately 13.6 per cent are estimated to suffer from drug use disorders [1]. At the same time, the environmental impact of the drugs of abuse appears increasingly evident; cultivation and production of plant-based and synthetic drugs, and drug use, have many consequences like energy use, deforestation, soil and water pollution and depletion, air pollution, food chain effects and biodiversity loss. Although the global effects of the activities related to the cultivation and production of illicit drugs are less significant than those of the pharmaceutical industry and agriculture, they can be important at local or community level [2].
Cocaine, for example, is estimated to have been consumed at least once by about 21.5 million people (0.4 percent of the global population aged 15–64) in 2020 [1]. It is estimated that 1982 tons of pure cocaine were produced in 2020, an increase of 11% over the previous year. The carbon footprint (a measure that expresses the total emissions of greenhouse gases, represented as carbon equivalents) of cocaine, related to cultivation of coca plants, processing of cocaine, disposal of waste generated in the manufacturing process and land-use change, is 4500 kg CO2e per kg of cocaine produced. Therefore, referring to the 2020 data, researchers obtain a mean value of the total emissions per year of 1.9 million tons of CO2e, a value significantly higher than that of other crops, as sugar cane or cocoa beans [2].
Another important environmental effect of drugs of abuse, as well as human and veterinary medicines, is their ability to contaminate the aquatic environment and influence the organisms living there [3][4][5][6][7]. Indeed, the intake of drugs of abuse is followed by their metabolization, usually partial, and the excretion of the parent drug and its metabolites especially by the renal way, that is the primary way in which these substances are removed from the body, though they can also be excreted through stool, sweat, tears and saliva [8]. Moreover, another possible source of contamination is the occasional discharge of drugs of abuse by clandestine laboratory wastes into sewage systems [3]. Therefore, illicit drugs and their metabolites reach treatment plants that do not always remove these substances, mainly because they are not always designed to do so. As a result, both drugs of abuse and their metabolites can be found in treated wastewater effluents and surface water, groundwater and drinking water [9][10][11][12][13][14]. Although the concentrations of drugs of abuse and their metabolites, found in surface waters around the world, are rather low (between ng⋅L−1 and μg⋅L−1), the continuous exposure and the remarkable pharmacological properties of drugs of abuse and their metabolites, sometimes greater than the parent drug, raise concerns about the fate of aquatic species living in contaminated sites. Indeed, scientific evidence is increasingly showing that different animal and plant aquatic organisms can bioaccumulate the different drugs of abuse and their metabolites, often suffering toxic effects [4][5][6][7].

2. European Eel

The European eel (Anguilla anguilla) is a migratory, catadromous fish species, consisting of a single stock, distributed throughout the European continent as well as in the Mediterranean basin, which reproduces in the Atlantic Ocean and for which the panmixia hypothesis is currently accepted. Eel fishing is carried out throughout the distribution area of the species and concerns the juvenile and preadult stages, but the conservation of the stock depends on the recruitment and emigration of breeding animals at sea. Eel farming is practiced in many countries, for a European level of around 8000 tons; the production completely depends on the wild seed, since the reproduction artificial, although implemented experimentally, does not go beyond the larval stage, at least in the European eel. Adult eels can survive in both air and water thanks to the fact that respiratory exchanges can occur both through the gills and through the skin. Eels are present in a wide range of aquatic habitats (rivers, canals, estuaries, lakes, ponds, and lagoons), in relation to their great adaptability to different environmental conditions; moreover, being a euryhaline species, eels can adapt to both fresh and sea water, and well tolerate variations in oxygen concentrations. As a primarily bottom-dwelling fish, the eels rely in their feeding on the prey population that is present there and prefer to eat at night [15][16].
The biological cycle of the eel is considered unique in relation to the nature and extent of reproductive migration. This life cycle takes place mainly in continental fresh waters, for most of the life of the eel, and in open ocean during the reproductive phase. Moreover, the life cycle involves a succession of metamorphic stages: leptocephalus larvae, hatching from eggs in the Sargasso Sea and heading for continental waters; glass eels that move into continental waters; yellow eels that remain in continental waters until sexual maturity is reached; silver eels that migrate back to reproductive areas [15][16].
This complex life cycle exposes the eels to different and numerous stressors, and many studies have shown that overfishing, habitat loss, pest attack and water contamination pose a serious threat to eel survival. In particular, the presence of fat in the eels, their long stay in the same area and their ability to accumulate contaminants especially lipophilic, make this species particularly susceptible to aquatic contamination. Indeed, to date, the European eel is included, according to IUCN, among the endangered species and considered at risk of extinction [15][17][18][19]. In addition to the different types of contaminants present in the water, illicit drugs are proving to be a new, widespread class of contaminants with remarkable pharmacological properties, that are likely to have effects on aquatic fauna [3][4][5][6][7].
Therefore, researchers' research group has begun to study the effects of one of these illicit drugs, cocaine, on European eel, to understand how this substance could affect the physiology and reproductive capacity of this species. The experiments were carried out on silver eels, which, after a month’s acclimatization, were exposed to an environmental concentration of cocaine (20 ng/L−1), among those measured in surface water. The eels were housed in aquariums with a capacity of 300 L, in dechlorinated and well-aerated tap water, exposed to natural photoperiod and not fed, as in the silver stage eels do not normally feed. Moreover, the following parameters of the water were established and monitored: dissolved oxygen 8.1 ± 0.5 mg/L; salinity 0, temperature 15 ± 1 °C, pH 7.3 ± 0.2, ammonia < 0.1 mg/L. For the exposure, a stock solution of 3 mg/500 mL of cocaine free-base in ethanol was prepared and kept in the refrigerator. During the exposure, 1 mL of the stock solution was administered every day, after the change of the water, directly in each aquarium for 30–50 days. At the same time control groups, exposed to tap water only, and carrier groups, exposed to ethanol only, in the same concentrations as eels receiving cocaine, were set up. At the end of exposure, some of the exposed eels were deprived of cocaine and exposed to tap water only, for 3–10 days, to verify their recovery ability. At the end of the exposure, or the recovery period, histological, histochemical, biochemical, and molecular biology analyses were performed [20]. All these studies were carried out in accordance with EU Directive 2010/63/EU for animal experimentation and institutional guidelines for care and use of laboratory animals and were authorized by the Italian Ministry of Health’s General Directorate of Animal Health and Veterinary Drugs.

References

  1. UNODC. Book 2: Drug use and health consequences. In World Drug Report; (United Nations Publication, sales, No. E.22.XI.8); UNODC: Vienna, Austria, 2022.
  2. UNODC. Book 5: Drug and the environment. In World Drug Report; (United Nations Publication, sales, No. E.22.XI.8); UNODC: Vienna, Austria, 2022.
  3. Pal, R.; Megharaj, M.; Kirkbride, K.P.; Naidu, R. Illicit drugs and the environment—A review. Sci. Total Environ. 2013, 463–464, 1079–1092.
  4. Fontes, M.K.; Maranho, L.; Pereira, C.D.S. Review on the occurrence and biological effects of illicit drugs in aquatic ecosystems. Environ. Sci. Pollut. Res. 2020, 27, 30998–31034.
  5. Fontes, M.K.; Dourado, P.L.R.; de Campos, B.G.; Maranho, L.A.; de Almeida, E.A.; de Souza Abessa, D.M.; Pereira, C.D.S. Environmentally realistic concentrations of cocaine in seawater disturbed neuroendocrine parameters and energy status in the marine mussel Perna perna. Comp. Biochem. Physiol. C 2022, 251, 109198.
  6. Chen, L.; Guo, C.; Sun, Z.; Xu, J. Occurrence, bioaccumulation and toxicological effect of drugs of abuse in aquatic ecosystem: A review. Environ. Res. 2021, 200, 111362.
  7. Yedhu Krishnan, R.; Manikandan, S.; Subbaiya, R.; Biruntha, M.; Balachandar, R.; Karmegam, N. Origin, transport and ecological risk assessment of illicit drugs in the environment A review. Chemosphere 2023, 311, 137091.
  8. Grilly, M.G.; Salamone, J.D. Drugs, Brain and Behavior, 6th ed.; Pearson: Boston, MA, USA, 2012; pp. 132–178.
  9. Kasprzyk-Hordern, B.; Dinsdale, R.M.; Guwy, A.J. The removal of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs during wastewater treatment and its impact on the quality of receiving waters. Water Res. 2009, 43, 363–380.
  10. Seabra-Pereira, C.D.; Maranho, L.A.; Cortez, F.S.; Pusceddu, F.H.; Santos, A.R.; Ribeiro, D.A.; Cesar, A.; Guimarães, L.L. Occurrence of pharmaceuticals and cocaine in a Brazilian coastal zone. Sci. Total Environ. 2016, 548, 148–154.
  11. Davoli, E.; Zuccato, E.; Castiglioni, S. Illicit drugs in drinking water. Curr. Opin. Environ. Sci. Health 2019, 7, 92–97.
  12. Deng, Y.; Guo, C.; Zhang, H.; Yin, X.; Chen, L.; Wu, D.; Xu, J. Occurrence and removal of illicit drugs in different wastewater treatment plants with different treatment techniques. Environ. Sci. Eur. 2020, 32, 28.
  13. Davey, C.J.E.; Kraak, M.H.S.; Pratorius, A.; ter Laak, T.L.; van Wezel, A.P. Occurrence, hazard, and risk of psychopharmaceuticals and illicit drugs in European surface waters. Water Res. 2022, 222, 118878.
  14. Pisetta, A.M.; Roveri, V.; Lopes Guimarães, L.; de Oliveira, T.M.N.; Correia, A.T. First report on the occurrence of pharmaceuticals and cocaine in the coastal waters of Santa Catarina, Brazil, and its related ecological risk assessment. Environ. Sci. Pollut. Res. 2022, 29, 63099–63111.
  15. Bevacqua, D.; Melià, P.; Gatto, M.; De Leo, G. A global viability assessment of the European eel. Glob. Change Biol. 2015, 21, 3323–3335.
  16. Tesch, S.W. The Eel, 3rd ed.; Blackwell Science, Ltd.: Oxford, UK, 2003; pp. 1–117.
  17. Belpaire, C.; Goemans, G. The European eel Anguilla anguilla, a rapporteur of the chemical status for the water framework directive? Vie et Milieu/Life Environ. 2007, 57, 235–252.
  18. Van Ginneken, V.; Palstra, A.; Leonards, P.; Nieveen, M.; van den Berg, H.; Flik, G.; Spanings, T.; Niemantsverdriet, P.; van der Thillart, G.; Murk, A. PCBs and the energy cost of migration in the European eel (Anguilla anguilla L.). Aquat. Toxicol. 2009, 92, 213–220.
  19. Bettinetti, R.; Galassi, S.; Quadroni, S.; Volta, P.; Capoccioni, F.; Ciccotti, E.; De Leo, G.A. Use of Anguilla anguilla for biomonitoring persisten organic pollutants (POPs) in brackish and riverine waters in central and southern Italy. Water Air Soil Pollut. 2011, 217, 321–331.
  20. Capaldo, A.; Gay, F.; Lepretti, M.; Paolella, G.; Martucciello, S.; Lionetti, L.; Caputo, I.; Laforgia, V. Effects of environmental cocaine concentrations on the skeletal muscle of the European eel (Anguilla anguilla). Sci. Total Environ. 2018, 640–641, 862–873.
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Subjects: Biology
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Luigi Rosati
,
Ivana Caputo
,
Lillà Lionetti
,
Mayana Karoline Fontes
,
Camilo Dias Seabra Pereira
,
Anna Capaldo
View Times: 411
Revisions: 2 times (View History)
Update Date: 03 Apr 2023
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