Sometimes Sperm Whales (Physeter macrocephalus) Cannot Find Their Way Back to the High Seas: A Multidisciplinary Study on a Mass Stranding

BACKGROUND: Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Solar cycles and related changes in the geomagnetic field, variations in water temperature and weather conditions, coast geographical features and human activities have been proposed as possible causes. In December 2009, a pod of seven male sperm whales stranded along the Adriatic coast of Southern Italy. This is the sixth instance from 1555 in this basin. METHODOLOGY/PRINCIPAL FINDINGS: Complete necropsies were performed on three whales whose bodies were in good condition, carrying out on sampled tissues histopathology, virology, bacteriology, parasitology, and screening of veins looking for gas emboli. Furthermore, samples for age determination, genetic studies, gastric content evaluation, stable isotopes and toxicology were taken from all the seven specimens. The animals were part of the same group and determined by genetic and photo-identification to be part of the Mediterranean population. Causes of death did not include biological agents, or the "gas and fat embolic syndrome", associated with direct sonar exposure. Environmental pollutant tissue concentrations were relatively high, in particular organochlorinated xenobiotics. Gastric content and morphologic tissue examinations showed a prolonged starvation, which likely caused, at its turn, the mobilization of lipophilic contaminants from the adipose tissue. Chemical compounds subsequently entered the blood circulation and may have impaired immune and nervous functions. CONCLUSIONS/SIGNIFICANCE: A multi-factorial cause underlying this sperm whales' mass stranding is proposed herein based upon the results of postmortem investigations as well as of the detailed analyses of the geographical and historical background. The seven sperm whales took the same "wrong way" into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. Seismic surveys should be also regarded as potential co-factors, even if no evidence of direct impact has been detected

Elemental concentrations in skin and internal tissues of Commerson’s dolphins (Cephalorhynchus commersonii) from subantarctic waters

The skin of cetaceans is the most accessibletissue, and its sampling has been proposed as a noninvasivemethod to evaluate trace element concentrations in free-rangingpopulations. In the present work, concentrations ofessential (Cl, Na, K, Mg, Fe, Zn, Mn and Co), nonessential(As and Ag), and of unknown essentiality (Br, Rb and Cs)elements were determined in the skin from nine by-caughtCommerson´s dolphins (Cephalorhynchus commersonii)from Tierra del Fuego, Argentina. Skin correlations withinternal tissues (lung, liver, kidney and muscle) wereassessed to evaluate how the skin represents internal elementconcentration for monitoring purposes. Elementalcontents were analyzed by instrumental neutron activationanalysis (INAA). Regarding tissue distribution, skin hadthe highest concentration of Zn being two orders of magnitudehigher than internal tissues, while other elementssuch as Co and Rb had similar concentrations among tissues.High mean concentrations of Cl, Na, Mg, Br and Mnwere observed in the lung and liver. Our results support theuse of skin to evaluate Fe, Br and Rb concentrations ininternal tissues for biomonitoring purposes; however, otherelements did not show significant skin-to-tissue correlations.Overall, toxic element levels were far below concentrationsfound to cause harm in marine vertebrates. Thisstudy provided baseline data on elemental concentrationsin tissues of Commerson´s dolphins in subantarctic watersfrom the South Atlantic Ocean.Fil: Cáceres Saez, Iris. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Museo Acatushún de Aves y Mamíferos Marinos Australes; ArgentinaFil: Ribeiro Guevara, Sergio. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Ingeniería Nuclear. Laboratorio de Análisis por Activación Neutróica; ArgentinaFil: Prosser Goodall, Rae Natalie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Museo Acatushún de Aves y Mamíferos Marinos Australes; ArgentinaFil: Dellabianca, Natalia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Museo Acatushún de Aves y Mamíferos Marinos Australes; ArgentinaFil: Cappozzo, Humberto Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentin