First description of Rhodococcus equi infection in common bottlenose dolphin (Tursiops truncatus)

Rhodococcus equi is a terrestrial bacterium and a common pathogen in foals (Equus caballus), in which causes pneumonia. This report describes for the first time the infection caused by R. equi in a common bottlenose dolphin (Tursiops truncatus) stranded in the Calabrian coast, Italy. The post mortem examination of the animal revealed lesions in lung and colon. The animal was also positive to dolphin morbillivirus. The histological study showed lesions attributable to R. equi infection, such as pyogranulomatous bacterial pneumonia and chronic granulomatous colitis. Whole genome sequencing of the isolated strain confirmed its identification as R. equi.

Determination of water balance maintenance in Orcinus orca and Tursiops truncatus using oxygen isotopes

The secondary adaptation of Cetacea to a fully marine lifestyle raises the question of their ability to maintain their water balance in a hyperosmotic environment. Cetacea have access to four potential sources of water: surrounding salt oceanic water, dietary free water, metabolic water and inhaled water vapour to a lesser degree. Here, we measured the 18O/16O oxygen isotope ratio of blood plasma from 13 specimens belonging to two species of Cetacea raised under human care (four killer whales Orcinus orca, nine common bottlenose dolphins Tursiops truncatus) to investigate and quantify the contribution of preformed water (dietary free water, surrounding salt oceanic water) and metabolic water to Cetacea body water using a box-modelling approach. The oxygen isotope composition of Cetacea blood plasma indicates that dietary free water and metabolic water contribute to more than 90% of the total water input in weight for cetaceans, with the remaining 10% consisting of inhaled water vapour and surrounding water accidentally ingested or absorbed through the skin. Moreover, the contribution of metabolic water appears to be more important in organisms with a more lipid-rich diet. Beyond these physiological and conservation biology implications, this study opens up questions that need to be addressed, such as the applicability of the oxygen isotope composition of cetacean body fluids and skeletal elements as an environmental proxy of the oxygen isotope composition of present and past marine waters.

The impact of anthropogenic pollutants on the distribution of a marine top predator within a coastal estuarine system

Due to anthropogenic pressures, estuarine systems are among the most broadly impacted areas for marine top predator species. Given this, it is crucial to study the interaction between the vulnerable marine species that inhabit these regions with environmental and anthropogenic variables. This study aims to determine whether nutrient pollution is related to the presence of bottlenose dolphins in a coastal environment. Using a multi-year dataset and GAMs, we studied the relationship between marine pollutants and the presence of bottlenose dolphins in this highly impacted coastal marine environment. We observed that urban fertilizers were linked to the spatial distribution of bottlenose dolphins. There was a higher presence of bottlenose dolphins in areas with high levels of phosphoric acid. In contrast, at higher concentrations of nitrate, the presence of bottlenose dolphins decreased.

Bottlenose dolphin distribution in a Mediterranean area exposed to intensive trawling

The Adriatic Sea is one of the areas most exposed to trawling, worldwide. We used four years (2018-2021) and 19,887 km of survey data to investigate factors influencing daylight dolphin distribution in its north-western sector, where common bottlenose dolphins Tursiops truncatus routinely follow fishing trawlers. We validated Automatic Identification System information on the position, type and activity of three types of trawlers based on observations from boats, and incorporated this information in a GAM-GEE modelling framework, together with physiographic, biological and anthropogenic variables. Along with bottom depth, trawlers (particularly otter and midwater trawlers) appeared to be important drivers of dolphin distribution, with dolphins foraging and scavenging behind trawlers during 39.3% of total observation time in trawling days. The spatial dimension of dolphin adaptations to intensive trawling, including distribution shifts between days with and without trawling, sheds light on the magnitude of ecological change driven by the trawl fishery.

Yawn-like behavior in captive common bottlenose dolphins (Tursiops truncatus)

Yawning is an involuntary action that begins with a slow opening of the mouth with inhalation, followed by a maximum gaping phase, and ends with a short exhalation and the closing of the mouth. A wide variety of vertebrate species, including humans, yawn. Here, we report underwater yawn-like behavior in three captive common bottlenose dolphins, inferred from 119-h of observations. Five cases of yawn-like behavior were selected out of 2045 open-mouth behaviors, after removing intentional open-mouth behaviors. Yawn-like behaviors were chosen that had a mouth open-close duration ratio of ≤ 1 (duration of Phase 3, the period of mouth closing after maximum opening, divided by the duration of Phase 1, the period of mouth opening from start to maximum opening). Naïve human evaluators selected "yawn-like" behaviors. All five cases of yawn-like behavior occurred during inactive periods, similar to human yawns. In three of the five cases, inactivity levels significantly decreased within 4 min after the yawn-like behavior; therefore, yawn-like behavior in dolphins may increase their arousal level in drowsy states. Thus, the yawn-like behavior of dolphins, without breathing, is similar to yawning in terrestrial animals, including humans.

Anisakis spp. in toothed and baleen whales from Japanese waters with notes on their potential role as biological tags

In this study, Anisakis nematodes isolated from toothed and baleen whales from localities around Japan were molecularly (PCR-RFLP) identified. In Wakayama, common bottlenose dolphins (Tursiops truncatus) were infected with A. simplex sensu stricto (s.s.), A. typica and A. pegreffii, while A. typica was the only species found in pantropical spotted dolphin (Stenella attenuata) and striped dolphin (S. coeruleoalba). Offshore common minke whales (Balaenoptera acutorostrata) and sei whales (B. borealis) were almost exclusively infected with A. simplex s.s.. However, in common minke whales from two Hokkaido localities, mature worms mostly consisted of A. simplex s.s. in some individuals and of A. pegreffii in others, but immature worms were mainly A. simplex s.s.. Gross and histopathological examination on gastric mucosa attached by anisakids resulted in mild and superficial reactions by the two baleen whale species in contrast to severe inflammatory reaction associated with ulcer formations by common bottlenose dolphin. Host specificity and adaptability of Anisakis spp. in these baleen and toothed whales were discussed from the points of view of adult worm size, worm population and pathological reactions by hosts. Interestingly, most of the common minke whales predominantly harboring mature A. pegreffii adults belonged to the Yellow Sea - East China Sea stock (J stock), which migrates through the Sea of Japan, whereas most of those mainly parasitized by mature A. simplex s.s. adults were from the Okhotsk Sea - West Pacific stock (O stock), mostly inhabiting the Pacific side, suggesting that these sibling species may have utility as biological tags to differentiate whale stocks. These results represent the first definitive host records for A. pegreffi in the Northwestern Pacific Ocean.

Pregnancy profiles in the common bottlenose dolphin (Tursiops truncatus): Clinical biochemical and hematological variations during healthy gestation and a successful outcome

The physiological demands of pregnancy inevitably result in changes of both biochemical and hematological parameters as the fetus develops. Alterations in blood parameters have been observed to shift according to both trimester and species, to support fetal physiological needs and maternal basal requirements. Establishing normal reference ranges for each stage in gestation is important to facilitate diagnosis of underlying health concerns and prevent over-diagnosing abnormalities. Despite bottlenose dolphins (Tursiops truncatus) being one of the most highly studied cetaceans, the blood profile changes occurring as a result of pregnancy have not been previously described. A retrospective analysis was performed from blood samples obtained from 42 successful pregnancies from 20 bottlenose dolphins in a managed population over 30 years. Samples were compared to non-pregnant states and among trimesters of pregnancy. Blood profile fluctuations occurred throughout gestation, however significant alterations predominantly occurred between the 2nd and 3rd trimester. Hematological changes from the 2nd to the 3rd trimester included a decrease in lymphocytes, decrease in platelet count, and hemoconcentration with increased hematocrit and hemoglobin. Biochemical changes in the 3rd trimester included significant reductions in ALKP (alkaline phosphatase), ALT (alanine aminotransferase) and AST (aspartate aminotransferase) with significant increases observed in albumin, globulins, total protein, cholesterol, triglycerides and CO₂. It's important to note that despite significant shifts occurring between the 2nd and 3rd trimester, there was no significant change in platelets, hematocrit, hemoglobin, lymphocytes or CO₂ between non-pregnant and 3rd trimester blood samples. The normal reference ranges for each trimester established herein, will enable future identification of abnormalities occurring during pregnancy and help improve our understanding of factors potentially influencing a failed or successful pregnancy outcome.

De novo transcriptome assembly and RNA-Seq expression analysis in blood from beluga whales of Bristol Bay, AK

Assessing the health of marine mammal sentinel species is crucial to understanding the impacts of environmental perturbations on marine ecosystems and human health. In Arctic regions, beluga whales, Delphinapterus leucas, are upper level predators that may serve as a sentinel species, potentially forecasting impacts on human health. While gene expression profiling from blood transcriptomes has widely been used to assess health status and environmental exposures in human and veterinary medicine, its use in wildlife has been limited due to the lack of available genomes and baseline data. To this end we constructed the first beluga whale blood transcriptome de novo from samples collected during annual health assessments of the healthy Bristol Bay, AK stock during 2012-2014 to establish baseline information on the content and variation of the beluga whale blood transcriptome. The Trinity transcriptome assembly from beluga was comprised of 91,325 transcripts that represented a wide array of cellular functions and processes and was extremely similar in content to the blood transcriptome of another cetacean, the bottlenose dolphin. Expression of hemoglobin transcripts was much lower in beluga (25.6% of TPM, transcripts per million) than has been observed in many other mammals. A T12A amino acid substitution in the HBB sequence of beluga whales, but not bottlenose dolphins, was identified and may play a role in low temperature adaptation. The beluga blood transcriptome was extremely stable between sex and year, with no apparent clustering of samples by principle components analysis and <4% of genes differentially expressed (EBseq, FDR<0.05). While the impacts of season, sexual maturity, disease, and geography on the beluga blood transcriptome must be established, the presence of transcripts involved in stress, detoxification, and immune functions indicate that blood gene expression analyses may provide information on health status and exposure. This study provides a wealth of transcriptomic data on beluga whales and provides a sizeable pool of preliminary data for comparison with other studies in beluga whale.

The Gulf of Ambracia's Common Bottlenose Dolphins, Tursiops truncatus: A Highly Dense and yet Threatened Population

The common bottlenose dolphin (Tursiops truncatus) is the only cetacean present in the semiclosed waters of the Gulf of Ambracia, Western Greece. This increasingly degraded coastal ecosystem hosts one of the highest observed densities in the Mediterranean Sea for this species. Photo-identification data and tissue samples collected through skin-swabbing and remote biopsy sampling techniques during boat-based surveys conducted between 2006 and 2015 in the Gulf, were used to examine bottlenose dolphin abundance, population trends, site fidelity, genetic differentiation and toxicological status. Bottlenose dolphins showed high levels of year-round site fidelity throughout the 10-year study period. Dolphin population estimates mostly fell between 130 and 170 with CVs averaging about 10%; a trend in population size over the 10 years was a decline of 1.6% per year (but this was not significant). Genetic differentiation between the bottlenose dolphins of the Gulf and their conspecifics from neighbouring populations was detected, and low genetic diversity was found among individuals sampled. In addition, pesticides where identified as factors posing a real toxicological problem for local bottlenose dolphins. Therefore, in the Gulf of Ambracia, high dolphin density does not seem to be indicative of favourable conservation status or pristine habitat.

Persistent organic pollutants (POPs) in blubber of common bottlenose dolphins (Tursiops truncatus) along the northern Gulf of Mexico coast, USA

A number of studies were initiated in response to the Deepwater Horizon (DWH) oil spill to understand potential injuries to bottlenose dolphins (Tursiops truncatus) that inhabit the northern Gulf of Mexico (NGoM) estuarine waters. As part of these studies, remote biopsy skin and blubber samples were collected from dolphins at six field sites that received varying degrees of oiling: Barataria Bay (BB), Chandeleur Sound West (CSW), Chandeleur Sound East (CSE), Mississippi Sound South (MSS), Mississippi Sound North (MSN), and St. Joseph Bay (SJ). Blubber samples from 108 male dolphins were analyzed for persistent organic pollutant (POP) concentrations, as high levels of POPs have been previously reported in other southeastern U.S. dolphins and the potential contribution of these compounds to adverse health effects in NGoM dolphins must be considered. Dolphin blubber levels of summed POPs (ΣPOPs) did not differ significantly across sites (F-test, P=0.9119) [μg/g lipid; geometric mean and 95% CI]; CSW [65.9 (51.4-84.6)], SJ [74.1 (53.0-104)], MSN [74.3 (58.7-93.9)], BB [75.3 (56.4-101)], CSE [80.5 (57.8-112)], and MSS [82.5 (65.9-103)]. Overall, POP concentrations were in the lower half of the range compared to previously reported concentrations from other southeastern U.S. sites. Increased dolphin mortalities have been ongoing in the NGoM and have been suggested to be linked with the DWH oil spill. In addition, lung disease, impaired adrenal function, and serum biochemical abnormalities have been reported in dolphins from BB, an area that was heavily oiled. The results of this study suggest that POPs are likely not a primary contributor to the poor health conditions and increased mortality observed in some populations of NGoM dolphins following the DWH oil spill.

Lack of variation in voltage-gated sodium channels of common bottlenose dolphins (Tursiops truncatus) exposed to neurotoxic algal blooms

In coastal marine ecosystems, neurotoxins produced by harmful algal blooms (HABs) often result in large-scale mortality events of many marine species. Historical and frequent exposure to HABs therefore may provide a strong selective pressure for adaptations that result in toxin resistance. Neurotoxin resistance has independently evolved in a variety of terrestrial and marine species via mutations in genes encoding the toxin binding sites within the voltage-gated sodium channel gene complex. Accordingly, we tested the hypothesis that genetic variation in the putative binding site of brevetoxins in common bottlenose dolphins (Tursiops truncatus) explains differences among individuals or populations in resistance to harmful Karenia brevis blooms in the Gulf of Mexico. We found very little variation in the sodium channel exons encoding the putative brevetoxin binding site among bottlenose dolphins from central-west Florida and the Florida Panhandle. Our study included samples from several bottlenose dolphin mortality events associated with HABs, but we found no association between genetic variation and survival. We observed a significant effect of geographic region on genetic variation for some sodium channel isoforms, but this can be primarily explained by rare private alleles and is more likely a reflection of regional genetic differentiation than the cause of different levels of HAB resistance between regions. In contrast to many other previously studied neurotoxin-resistant species, we conclude that bottlenose dolphins have not evolved resistance to HABs via mutations in genes encoding the brevetoxin binding site on the voltage-gated sodium channels.

Organochlorine contaminants in tissues of common bottlenose dolphins Tursiops truncatus from the northeastern part of the Adriatic Sea

Levels of 24 organochlorine compounds, including toxic mono-ortho PCB congeners, were determined in the organs and tissues (blubber, kidney, lung, muscle, liver, heart) of 13 common bottlenose dolphins (Tursiops truncatus) stranded between 2000 and 2005 in the northern part of the Croatian territorial waters of the Adriatic Sea. Polychlorinated biphenyls (PCBs) were found at higher concentrations in comparison with organochlorine pesticides (OCPs) in all of the analyzed tissues. Sums of six indicator congeners (Σ6PCB) constituted around 50% of the total PCB amount, while PCB-153 and PCB-138 were found to have the highest concentrations. Among the seven investigated OCPs, p,p'-DDE was found at the highest concentrations. In blubber, mean values of 22,048 and 11,310ngg(-1) wet weight were determined for ΣPCB and ΣDDT, respectively. Much lower concentrations were found in muscle samples, followed by similar concentrations in kidneys, liver and heart, while the lowest levels of organochlorine contaminants were found in lungs. The results indicate that p,p'-DDT is still being introduced in the Mediterranean region. PCB concentrations are among the highest found in this region and toxicological assessments indicate that the health of this specie is at high risk.

Abundance and distribution of Tursiops truncatus in the Western Mediterranean Sea: an assessment towards the Marine Strategy Framework Directive requirements

The Mediterranean Sea common bottlenose dolphin population has been assessed as Vulnerable according to the IUCN Red List Criteria. The species is also included in several International Agreements, European Union Regulations and Directives. Amongst them, a strict protection and identification of special conservation areas are requested by the EU Habitats Directive. Despite direct takes, by-catch, chemical and acoustic pollution, and prey depletion, general habitat degradation and fragmentation have been indicated as detrimental for the species, the degree to which these threats pose population risk is still largely unknown. At present it is thus not possible to depict the actual status of the population and to assess prospective trends. To address this gap in the current knowledge, line transect distance sampling aerial surveys were conducted in a wide portion of the Western Mediterranean Sea between the summer of 2010 and winter 2011. A total of 165 parallel transects equally spaced at 15 km were designed providing homogeneous coverage probability. Overall, 21,090 km were flown on effort and 16 bottlenose dolphin sightings were recorded and used for the analysis. The surface abundance and density estimates resulted in 1676 animals (CV = 38.25; 95% CI = 804-3492) with a density of 0.005 (CV = 38.25%). These results represent the first ever estimates for the common bottlenose dolphin over a wide portion of the Western Mediterranean Sea Subregion, with the potential to be useful baseline data to inform conservation. Specifically, they could be used as indicators under the Marine Strategy Framework Directive requirements, in conjunction with other study methods.