[en] The subpopulation of the Irrawaddy dolphin (Orcaella brevirostris) living in the Mekong River, Cambodia, is considered to be critically endangered. The aim of the investigation was to gain information about the genetic variation, health status and exposure to toxic compounds of these dolphins. Tissue samples from 27 Irrawaddy river dolphins found dead along the Mekong River between 2004 and 2009 were analysed with regards to genetics, pathology and ecotoxicology. Genetic maternal lineage detection, based on polymorphisms of the mitochondrial d-loop sequences, was performed. Data indicate a genetic separation of the Mekong dolphins from both the coastal population and the Mahakam dolphins. Pathological investigations revealed acute moderate multifocal suppurative bronchopneumonia, moderate periportal hepatic lipidosis, moderate diffuse hepatic atrophy and acute severe diffuse suppurative leptomeningitis. Residue levels of organochlorines and polybrominated diphenyl ethers in Irrawaddy dolphins from the Mekong River were lower than the concentrations reported for other cetaceans in the coastal and riverine waters of Asia, except for Dichlorodiphenyltrichloroethane. A high percentage of organic mercury compared to the immuno-toxic methylmercury was observed. Due to numerous confounding factors, it is not possible to relate levels of pollutants to observed morphological lesions. However, it is likely that chemical contaminants do adversely impact on the health of the Irrawaddy dolphins at present, and have also affected previous generations.
Research center :
FOCUS - Freshwater and OCeanic science Unit of reSearch - ULiège
Disciplines :
Environmental sciences & ecology Aquatic sciences & oceanology Veterinary medicine & animal health
Author, co-author :
Schnitzler, Joseph G.
Das, Krishna ; Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanographie biologique
Wohlsein, Peter
Kuiken, Thijs
Ludwig, Arne
Lieckfeldt, Dietmar
Phan, Channa
Phay, Somany
Siebert, Ursula
Language :
English
Title :
The Irrawaddy dolphin, Orcaella brevirostris from the Mekong river Cambodia: Preliminary health and toxicological investigations
Bennet, PM, Jepson, PD, Law, RJ, Jones, BR, Kuiken, T, Baker, JR, Rogan, E, Kirkwood, JK, Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales. Environ Pollut 112 (2001), 33–40.
Das, K., Debacker, V., Pillet, S., Bouquegneau, J.-M., Heavy metals in marine mammals. Vos, J.G., Bossart, G., Fournier, M., O'Shea, T., (eds.) Toxicology of Marine Mammals, 2003, Taylor and Francis Publishers, Washington DC, 135–167.
Das, K., De, P.-.G.M.-.C., Dupont, A., Debier, C., Siebert, U., Absence of selenium protection against methylmercury toxicity in harbour seal leucocytes in vitro. Mar. Pollut. Bull. 108 (2016), 70–76.
Das, K., Siebert, U., Gillet, A., Dupont, A., Di-Poï, C., Fonfara, S., Mazzucchelli, G., De, P.E., De, P.-.G.M.-.C., Mercury immune toxicity in harbour seals: links to in vitro toxicity. Environ. Health, 7, 2008, 52.
Dove, V., Mortality investigation of the Mekong Irrawaddy river dolphin (Orcaella brevirostris) in Cambodia based on necropsy sample analysis., 2009, WWF WWF Technical Report.
Jepson, P.D., Bennet, P.M., Deaville, R., Allchin, C.R., Baker, J.R., Law, R.J., Bennett, P.M., Relationships between polychlorinated biphenyls and health status in harbor porpoises (Phocoena phocoena) stranded in the United Kingdom. Environ. Toxicol. Chem. 24 (2005), 238–248.
Kannan, K, Blankenship, AL, Jones, PD, Giesy, JP, Toxicity Reference Values for Toxic Effects of Polychlorinated Biphenyls to Aquatic Mammals. Hum Ecol Risk Assess 6 (2000), 181–201.
Kannan, K., Ramu, K., Kajiwara, N., Sinha, R., Tanabe, S., Organochlorine pesticides, polychlorinated biphenyls, and polybrominated diphenyl ethers in Irrawaddy dolphins from India. Arch. Environ. Contam. Toxicol. 49 (2005), 415–420.
Krützen, M., Beasley, I., Ackermann, C.Y., Lieckfeldt, D., Ludwig, A., Ryan, G.E., Bejder, L., Parra, G.J., Wolfensberger, R., Spencer, P.B.S., Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River. PLoS One, 13(1), 2018, 10.1371/journal.pone.0189200.
Kuiken, T., Garcia Hartmann, M., Dissection techniques and tissue sampling. ECS Newsletter #17 special issue. Proceedings of the first European Cetacean Society workshop on cetacean pathology, 1993, 1–39.
Law, R.J., Fileman, C.F., Hopkins, A.D., Baker, J.R., Harwood, J., Jackson, D.B., Kennedy, S., Martin, A.R., Morris, R.J., Concentrations of trace metals in the livers of marine mammals (seals, porpoises and dolphins) from waters around the British Isles. Mar. Pollut. Bull. 22 (1991), 183–191.
Yamashita, N, Kannan, K, Taniyasu, S, Horii, Y, Petrick, G, Gamo, T, A global survey of perfluorinated acids in oceans. Mar Pollut Bull 51 (2005), 658–668.
Yeung, LWY, Yamashita, N, Taniyasu, S, Lam, PKS, Sinha, RK, Borole, DV, Kannan, K, A survey of perfluorinated compounds in surface water and biota including dolphins from the Ganges River and in other waterbodies in India. Chemosphere 76 (2009), 55–62.
Limsong H, Ath M, Thomas P, Smith B (2017) Report of the International Workshop on the Conservation of Irrawaddy Dolphins in the Mekong. Kratie, Cambodia.
Phan, C., Hang, S., Tan, S., Lor, K. (2015) Population monitoring of the critically endangered Mekong Dolphin Based on Rark-Resight Models.
Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O'Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y., Zhou, K. (2008) Orcaella brevirostris,. IUCN Red List Threat Species e.T15419A4.
Reeves, RR, River dolphins. William, FP, Bernd, W, Thewissen, JGM, (eds.) Encyclopedia of marine mammals., 2002, Academic Press, San Diego.
Ryan, GE, Dove, V, Trujillo, F, Doherty, PF, Irrawaddy dolphin demography in the Mekong River: an application of mark–resight models. Ecosphere 2:5 (2011), 1–15.
Siebert, U., Prenger-Berninghoff, E., Weiss, R., Regional differences in bacterial flora in harbour porpoises from the North Atlantic: environmental effects?. J. Appl. Microbiol. 106 (2009), 329–337.
Siebert, U., Wünschmann, A., Weiss, R., Frank, H., Benke, H., Frese, K., Post-mortem findings in harbour porpoises (Phocoena phocoena) from the German North and Baltic Seas. J. Comp. Pathol. 124 (2001), 102–114.
Smith, B.D., Beasley, I., Orcaella brevirostris (Mekong River subpopulation). The IUCN Red List of Threatened Species, 2004 IUCN Redlist e.T44555A1.
Weijs, L, Dirtu, AC, Das, K, Gheorghe, A, Reijn ders, PJH, Neels, H, Blust, R, Covaci, A, Inter-species differences for polychlorinated biphenyls and polybrominated diphenyl ethers in marine top predators from the Southern North Sea: Part 1. Accumulation patterns in harbour seals and harbour porpoises. Environ Pollut 157 (2009), 437–444.
Wolfe, M.F., Schwarzbach, S., Sulaiman, R.A., Effects of mercury on wildlife: a comprehensive review. Environ. Toxicol. Chem. 17 (1998), 146–160.
