Iron Indices in Bottlenose Dolphins (Tursiops truncatus)

Bottlenose dolphins can have iron overload (that is, hemochromatosis), and managed populations of dolphins may be more susceptible to this disease than are wild dolphins. Serum iron, total iron-binding capacity (TIBC), transferrin saturation, and ferritin were measured in 181 samples from 141 dolphins in 2 managed collections and 2 free-ranging populations. Although no iron indices increased with age among free-ranging dolphins, ferritin increased with age in managed collections. Dolphins from managed collections had higher iron, ferritin, and transferrin saturation values than did free-ranging dolphins. Dolphins with high serum iron (exceeding 300 μg/dL) were more likely to have elevated ferritin but not ceruloplasmin or haptoglobin, demonstrating that high serum levels of iron are due to a true increase in total body iron. A time-series study of 4 dolphins with hemochromatosis that were treated with phlebotomy demonstrated significant decreases in serum ferritin, iron, and TIBC between pre- and posttreatment samples; transferrin saturation initially fell but returned to prephlebotomy levels by 6 mo after treatment. Compared with those in managed collections, wild dolphins were 15 times more likely to have low serum iron (100 μg/dL or less), and this measure was associated with lower haptoglobin. In conclusion, bottlenose dolphins in managed collections are more likely to have greater iron stores than are free-ranging dolphins. Determining why this situation occurs among some dolphin populations and not others may improve the treatment of hemochromatosis in dolphins and provide clues to causes of nonhereditary hemochromatosis in humans.Abbreviations: TIBC, total iron-binding capacityBottlenose dolphins (Tursiops truncatus) are susceptible to iron overload (that is, hemochromatosis).^19,32,33,35 Dolphins with hemochromatosis have high serum iron levels that progress over years, have high transferrin saturation (85% and greater), and are responsive to phlebotomy therapy.¹⁹ Left untreated, dolphins with hemochromatosis are more likely to have increased liver aminotransferases, chronic inflammation, and hyperlipidemia than are healthy controls.³⁵ A 25-y retrospective study of one population demonstrated that 67% of dolphins had excessive hepatic hemosiderin deposition at time of death, 92% of which had hemosiderin deposition in Kupffer cells; hemolytic anemia, anemia of chronic disease, and viral infections were not associated with hemosiderin deposition, and the primary hypothesis is that dolphins in managed collections may be susceptible to iron storage disease.³²The etiology of dolphin iron overload is unknown. The most common cause in humans is hereditary hemochromatosis, which is most often attributed to a point mutation of the HFE gene.¹² Other causes of iron overload include primary liver disease, excessive iron intake, and insulin resistance.^3,36 Comparisons of the HFE gene among dolphins with and without hemochromatosis showed no significant differences (unpublished data), and iron deposition in Kupffer cells (compared with hepatocytes) is not supportive of a hereditary cause.^3,32 Liver enzymes decrease in response to the removal of body iron through phlebotomy; this effect indicates that iron overload leads to liver disease rather than that primary liver disease causes iron overload.¹⁹ At least one dolphin population from which cases of hemochromatosis have been reported have not received iron supplementation for more than 10 y, although the iron content in their frozen–thawed fish diet has not been assessed fully.¹⁹ Dolphins with hemochromatosis have significantly higher 2-h postprandial insulin levels than do controls, suggesting that insulin resistance plays a role in this disease, as occurs in humans.³³In addition to dolphins and humans, iron overload occurs in diverse captive birds, callitrichids, black rhinos, Egyptian fruit bats, lemurs, northern fur seals, California sea lions, tapirs, and Saler cattle.^{5,11,15,18,20,21,23,29,31} Similar to that in other exotic species, iron overload in dolphins is thought to be a disease that is associated with managed care, but comparisons of iron levels among managed collections and free-ranging dolphin populations have been lacking.¹⁹ Further, measurements of serum ferritin, ceruloplasmin, and haptoglobin have not typically been included in iron overload evaluations in dolphins. Although serum ferritin levels can be an indicator of total iron body stores, ferritin also increases in response to inflammation or hemolytic anemia.⁴ In humans, ceruloplasmin is a plasma protein that increases with acute and chronic inflammation and plays a role in iron metabolism. Haptoglobin is a protein that, in humans, decreases with intravascular hemolytic anemia, among other conditions.² As such, concurrent measurements of iron, ferritin, ceruloplasmin, and haptoglobin provide insight into the true cause of changing iron and ferritin levels.Low serum iron is used as a general indicator of inflammation in marine mammals, and return of serum iron to normal levels during illness is seen as a positive indicator for recovery.^13,24 The dynamics of iron, erythrocyte sedimentation rate, and fibrinogen in inflammation have remained important as indicators of dolphin health for decades, yet little has been published about dolphin iron stores and associated acute-phase proteins in the past 30 y.²⁴ One barrier to the use of acute-phase proteins, including C-reactive protein, has been the need for species-specific assays; development of tests that better detect early phases of inflammation and infection could lead to earlier treatment and better outcomes. Other barriers include the need for consecutive samples from dolphins with known health status to validate indicators for inflammation, including ceruloplasmin.To better understand the prevalence of high serum iron and potential risks for hemochromatosis among various dolphin populations, indices of serum iron, ferritin, total iron-binding capacity (TIBC), percentage transferrin saturation, ceruloplasmin, and haptoglobin concentrations were measured in 2 populations of free-ranging dolphins and 2 managed collections, including the cohort of Navy dolphins. These variables were compared by age, sex, and population. Serum ferritin was measured by using a newly developed dolphin-specific assay.     

Drivers of Population Structure of the Bottlenose Dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea

Evolutionary Biology - The drivers of population differentiation in oceanic high dispersal organisms, have been crucial for research in evolutionary biology. Adaptation to different environments is...     

The Orexin System in the Enteric Nervous System of the Bottlenose Dolphin (Tursiops truncatus)

This study provides a general approach to the presence and possible role of orexins and their receptors in the gut (three gastric chambers and intestine) of confined environment bottlenose dolphin. The expression of prepro-orexin, orexin A and B and orexin 1 and 2 receptors were investigated by single immunostaining and western blot analysis. The co-localization of vasoactive intestinal peptide and orexin 1 receptor in the enteric nervous system was examined by double immunostaining. Also, orexin A concentration were measured in plasma samples to assess the possible diurnal variation of the plasma level of peptide in this species. Our results showed that the orexin system is widely distributed in bottlenose dolphin enteric nervous system of the all gastrointestinal tract examined. They are very peculiar and partially differs from that of terrestrial mammals. Orexin peptides and prepro-orexin were expressed in the main stomach, pyloric stomach and proximal intestine; while orexin receptors were expressed in the all examined tracts, with the exception of main stomach where found no evidence of orexin 2 receptor. Co-localization of vasoactive intestinal peptide and orexin 1 receptor were more evident in the pyloric stomach and proximal intestine. These data could suggest a possible role of orexin system on the contractility of bottlenose dolphin gastrointestinal districts. Finally, in agreement with several reports, bottlenose dolphin orexin A plasma level was higher in the morning during fasting. Our results emphasize some common features between bottlenose dolphin and terrestrial mammals. Certainly, further functional investigations may help to better explain the role of the orexin system in the energy balance of bottlenose dolphin and the complex interaction between feeding and digestive physiology.     

Spontaneous Ejaculation in a Wild Indo-Pacific Bottlenose Dolphin (Tursiops aduncus)

Spontaneous ejaculation, which is defined as the release of seminal fluids without apparent sexual stimulation, has been documented in boreoeutherian mammals. Here we report spontaneous ejaculation in a wild Indo-Pacific bottlenose dolphin (Tursiops aduncus), and present a video of this rare behavior. This is the first report of spontaneous ejaculation by an aquatic mammal, and the first video of this behavior in animals to be published in a scientific journal.     

Gonadal activity in some Bottlenose dolphins (Tursiops truncatus)

Details are given of the characteristics of the ovaries and testes of young and adult dolphins, Tursiops truncatus , all of which had been caught off Florida or Mississippi. Most had been in captivity for periods varying from a few days to ten years. Birth takes place most commonly during February to May and September to November. Length of neonates is between 98 and 126 cm. The state of activity of the gonads suggests that sexual maturity is reached in females at a length of over 220 cm and probably in their fifth year. Males do not become sexually active until about 260 cm in length and at an estimated age of at least ten years. Plasma testosterone levels are highest in a captive fertile male during April and May and October and November. The corpus luteum persists throughout the 12-month gestation period and also appears to persist as a corpus albicans for the dolphin's life span. The left ovary is usually larger than the right and twice as many corpora are found in the left as in the right ovary. No evidence of regular, cyclic ovulation is detected and it is concluded that ovulation is induced in Tursiops.     

Anatomy of the Cranial Endocast of the Bottlenose Dolphin, Tursiops truncatus, Based on HRXCT

Endocranial surfaces, volumes, and interconnectivities of extant and fossil odontocetes potentially offer information on the general architecture of the brain and on the structure of the specialized cetacean circulatory system. Although conventional methods for acquiring such data have generally involved invasive preparation of the specimen, particularly in the case of fossils, new tomographic technologies afford nondestructive access to these internal morphologies. In this study we used high-resolution X-ray computed tomography (HRXCT) to scan a skull of the extant Tursiops truncatus (Cetacea: Odontoceti). We processed the data to reveal the cranial endocast and details of internal skeletal architecture (data at www.digimorph.org). Major features that can be discerned include aspects of the specimen's hypertrophied retia mirabilia, the major canals and openings of the cranial cavity, and the relationship of the brain and endocranial circulatory structures to the surrounding skeleton. CT data also provide information on the shape of the brain that may be lost in conventional anatomical preparations, and readily provide volumetric and linear measurements of the endocast and its individual segments. These results demonstrate the utility of HRXCT for interpreting the internal cranial anatomy of both extant and fossil cetaceans.     

Comparative Analysis of Three Brevetoxin-Associated Bottlenose Dolphin (Tursiops truncatus) Mortality Events in the Florida Panhandle Region (USA)

In the Florida Panhandle region, bottlenose dolphins (Tursiops truncatus) have been highly susceptible to large-scale unusual mortality events (UMEs) that may have been the result of exposure to blooms of the dinoflagellate Karenia brevis and its neurotoxin, brevetoxin (PbTx). Between 1999 and 2006, three bottlenose dolphin UMEs occurred in the Florida Panhandle region. The primary objective of this study was to determine if these mortality events were due to brevetoxicosis. Analysis of over 850 samples from 105 bottlenose dolphins and associated prey items were analyzed for algal toxins and have provided details on tissue distribution, pathways of trophic transfer, and spatial-temporal trends for each mortality event. In 1999/2000, 152 dolphins died following extensive K. brevis blooms and brevetoxin was detected in 52% of animals tested at concentrations up to 500 ng/g. In 2004, 105 bottlenose dolphins died in the absence of an identifiable K. brevis bloom; however, 100% of the tested animals were positive for brevetoxin at concentrations up to 29,126 ng/mL. Dolphin stomach contents frequently consisted of brevetoxin-contaminated menhaden. In addition, another potentially toxigenic algal species, Pseudo-nitzschia, was present and low levels of the neurotoxin domoic acid (DA) were detected in nearly all tested animals (89%). In 2005/2006, 90 bottlenose dolphins died that were initially coincident with high densities of K. brevis. Most (93%) of the tested animals were positive for brevetoxin at concentrations up to 2,724 ng/mL. No DA was detected in these animals despite the presence of an intense DA-producing Pseudo-nitzschia bloom. In contrast to the absence or very low levels of brevetoxins measured in live dolphins, and those stranding in the absence of a K. brevis bloom, these data, taken together with the absence of any other obvious pathology, provide strong evidence that brevetoxin was the causative agent involved in these bottlenose dolphin mortality events.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin ( Tursiops Truncatus )

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin (Tursiops Truncatus)

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Fatal Asphyxiation in Bottlenose Dolphins (Tursiops truncatus) from the Indian River Lagoon

Multiple single case reports of asphyxiation in dolphins caused by fish lodged in the esophagus exist. However, the significance of this cause of mortality in a single population has not been documented. We performed a retrospective evaluation of pathology records from stranded bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon to evaluate the impact of this cause of death on this population. From 1997 to 2011, asphyxiation due to choking was identified as the cause of death in 14 of 350 cases (4%). Sampling of an unrelated but adjacent population over this same period yielded 186 necropsy cases of bottlenose dolphins with no cases of asphyxiation. Asphyxiated animals presented with a fish lodged in the cranial esophagus associated with a dislocated and obstructed or compressed larynx. There was no clear sex predilection. Affected animals included 12 adults and two juveniles. The fish species involved included sheepshead, black chin tilapia and striped mojarra. In five cases, recreational fishing gear was also present. Cetacean choking is related to selection of prey fish species with strong dorsal spines and may be secondarily associated with fish attached to fishing gear. Prey abundance and dolphin behavior may influence these selections. Environmental alterations leading to changes in prey availability or increased interactions with fishing gear may change the significance of fatal choking in dolphin populations.     

Identification and Characteristics of Signature Whistles in Wild Bottlenose Dolphins (Tursiops truncatus) from Namibia

A signature whistle type is a learned, individually distinctive whistle type in a dolphin''s acoustic repertoire that broadcasts the identity of the whistle owner. The acquisition and use of signature whistles indicates complex cognitive functioning that requires wider investigation in wild dolphin populations. Here we identify signature whistle types from a population of approximately 100 wild common bottlenose dolphins (Tursiops truncatus) inhabiting Walvis Bay, and describe signature whistle occurrence, acoustic parameters and temporal production. A catalogue of 43 repeatedly emitted whistle types (REWTs) was generated by analysing 79 hrs of acoustic recordings. From this, 28 signature whistle types were identified using a method based on the temporal patterns in whistle sequences. A visual classification task conducted by 5 naïve judges showed high levels of agreement in classification of whistles (Fleiss-Kappa statistic, κ = 0.848, Z = 55.3, P<0.001) and supported our categorisation. Signature whistle structure remained stable over time and location, with most types (82%) recorded in 2 or more years, and 4 identified at Walvis Bay and a second field site approximately 450 km away. Whistle acoustic parameters were consistent with those of signature whistles documented in Sarasota Bay (Florida, USA). We provide evidence of possible two-voice signature whistle production by a common bottlenose dolphin. Although signature whistle types have potential use as a marker for studying individual habitat use, we only identified approximately 28% of those from the Walvis Bay population, despite considerable recording effort. We found that signature whistle type diversity was higher in larger dolphin groups and groups with calves present. This is the first study describing signature whistles in a wild free-ranging T. truncatus population inhabiting African waters and it provides a baseline on which more in depth behavioural studies can be based.     

Seasonal and Diurnal Patterns of Behavior Exhibited by Atlantic Bottlenose Dolphins (Tursiops truncatus) in the Mississippi Sound

Many of the threats to bottlenose dolphins are anthropogenic factors including overfishing, high‐speed boats, chemical runoff, and noise pollution. Having a thorough understanding of the behavior and behavioral patterns of these animals can help with conservation plans to protect this species. This study examined the behavioral states and behavioral events of Atlantic bottlenose dolphins (Tursiops truncatus) in the Mississippi Sound. The behavioral states exhibited by dolphins within the Sound were found to vary by both season and time of day. Dolphins socialized more during the spring and spent more time feeding in the fall. Feeding was highest early in the morning and decreased throughout the day, while socializing occurred at low levels in the morning and increased in the early afternoon. Two distinct forms of social behavior and multiple feeding strategies were exhibited by dolphins within the Sound. Results suggest that certain percussive behavioral events may be used to communicate motivation during transitional behavioral states. These results demonstrate the need for a more complete understanding of dolphin behavior that will facilitate the conservation of this species.     

Adrenal Hormones in Common Bottlenose Dolphins (Tursiops truncatus): Influential Factors and Reference Intervals

Inshore common bottlenose dolphins (Tursiops truncatus) are exposed to a broad spectrum of natural and anthropogenic stressors. In response to these stressors, the mammalian adrenal gland releases hormones such as cortisol and aldosterone to maintain physiological and biochemical homeostasis. Consequently, adrenal gland dysfunction results in disruption of hormone secretion and an inappropriate stress response. Our objective herein was to develop diagnostic reference intervals (RIs) for adrenal hormones commonly associated with the stress response (i.e., cortisol, aldosterone) that account for the influence of intrinsic (e.g., age, sex) and extrinsic (e.g., time) factors. Ultimately, these reference intervals will be used to gauge an individual’s response to chase-capture stress and could indicate adrenal abnormalities. Linear mixed models (LMMs) were used to evaluate demographic and sampling factors contributing to differences in serum cortisol and aldosterone concentrations among bottlenose dolphins sampled in Sarasota Bay, Florida, USA (2000–2012). Serum cortisol concentrations were significantly associated with elapsed time from initial stimulation to sample collection (p<0.05), and RIs were constructed using nonparametric methods based on elapsed sampling time for dolphins sampled in less than 30 minutes following net deployment (95% RI: 0.91–4.21 µg/dL) and following biological sampling aboard a research vessel (95% RI: 2.32–6.68 µg/dL). To examine the applicability of the pre-sampling cortisol RI across multiple estuarine stocks, data from three additional southeast U.S. sites were compared, revealing that all of the dolphins sampled from the other sites (N = 34) had cortisol concentrations within the 95th percentile RI. Significant associations between serum concentrations of aldosterone and variables reported in previous studies (i.e., age, elapsed sampling time) were not observed in the current project (p<0.05). Also, approximately 16% of Sarasota Bay bottlenose dolphin aldosterone concentrations were below the assay’s detection limit (11 pg/mL), thus hindering the ability to derive 95th percentile RIs. Serum aldosterone concentrations from animals sampled at the three additional sites were compared to the detection limit, and the proportion of animals with low aldosterone concentrations was not significantly different than an expected prevalence of 16%. Although this study relied upon long-term, free-ranging bottlenose dolphin health data from a single site, the objective RIs can be used for future evaluation of adrenal function among individuals sampled during capture-release health assessments.     

Platelet-Rich Plasma and Adipose-Derived Mesenchymal Stem Cells for Regenerative Medicine-Associated Treatments in Bottlenose Dolphins (Tursiops truncatus)

Dolphins exhibit an extraordinary capacity to heal deep soft tissue injuries. Nevertheless, accelerated wound healing in wild or captive dolphins would minimize infection and other side effects associated with open wounds in marine animals. Here, we propose the use of a biological-based therapy for wound healing in dolphins by the application of platelet-rich plasma (PRP). Blood samples were collected from 9 different dolphins and a specific and simple protocol which concentrates platelets greater than two times that of whole blood was developed. As opposed to a commonly employed human protocol for PRP preparation, a single centrifugation for 3 minutes at 900 rpm resulted in the best condition for the concentration of dolphin platelets. By FACS analysis, dolphin platelets showed reactivity to platelet cell-surface marker CD41. Analysis by electron microscopy revealed that dolphin platelets were larger in size than human platelets. These findings may explain the need to reduce the duration and speed of centrifugation of whole blood from dolphins to obtain a 2-fold increase and maintain proper morphology of the platelets. For the first time, levels of several growth factors from activated dolphin platelets were quantified. Compared to humans, concentrations of PDGF-BB were not different, while TGFβ and VEGF-A were significantly lower in dolphins. Additionally, adipose tissue was obtained from cadaveric dolphins found along the Spanish Mediterranean coast, and adipose-derived mesenchymal stem cells (ASCs) were successfully isolated, amplified, and characterized. When dolphin ASCs were treated with 2.5 or 5% dolphin PRP they exhibited significant increased proliferation and improved phagocytotic activity, indicating that in culture, PRP may improve the regenerative capacity of ASCs. Taken together, we show an effective and well-defined protocol for efficient PRP isolation. This protocol alone or in combination with ASCs, may constitute the basis of a biological treatment for wound-healing and tissue regeneration in dolphins.     

Complex Social Structure of an Endangered Population of Bottlenose Dolphins (Tursiops truncatus) in the Aeolian Archipelago (Italy)

We investigated social structure and association patterns for a small population of Mediterranean bottlenose dolphins, Tursiops truncatus, inhabiting the Aeolian Archipelago (southern Italy). Specifically we evaluate the role of sex and age composition, residency patterns and interaction with trammel nets on this social organization. Association data for 23 regularly sighted individuals were obtained from summer photoidentification surveys collected from 2005–2012. Using a combined cluster and social network analysis approach, we found associations between dolphins were hierarchically structured, where two mixed-sex social units were subdivided into smaller temporarily dynamic groups. We found non-random and long-term preferred associations in the population; however, the degree of social cohesion, residence pattern and interaction with trammel nets differed considerably between the two social units. Six of eight females occurred in the more resident social unit-1; in addition, social unit-1 individuals had significantly stronger associations, higher preferred associates, lived in larger groups and occurred less frequently with trammel nets. Nine of eleven males were clustered in social unit-2 and five of these males, interacting with trammel nets, formed small groups and preferred associations. We propose that female and male groups associate in the study area during the breeding season and that some males choose to interact with reproductive females forming a distinct but interrelated social unit. Other males may be associating in a larger fission-fusion network, which consists of dolphins that appear to temporarily join the network from the coastal population. We cannot exclude that some males specialized in trammel net foraging, suggesting that this foraging technique may favor a solitary lifestyle. Large group sizes and high degree of social cohesion for females could be an indication of greater protection and more efficiency in detecting, deterring or repelling anthropogenic pressures. Most likely dolphins'' social organization depends on a combination of socio-ecological, demographic and anthropogenic factors.