Blubber development in bottlenose dolphins (Tursiops truncatus)

Blubber, the lipid-rich hypodermis of cetaceans, functions in thermoregulation, buoyancy control, streamlining, metabolic energy storage, and locomotion. This study investigated the development of this specialized hypodermis in bottlenose dolphins (Tursiops truncatus) across an ontogenetic series, including fetuses, neonates, juveniles, subadults, and adults. Blubber samples were collected at the level of the mid-thorax, from robust specimens (n = 25) that stranded along the coasts of North Carolina and Virginia. Blubber was dissected from the carcass and its mass, and the depth and lipid content at the sample site, were measured. Samples were prepared using standard histological methods, viewed by light microscopy, and digital images of blubber captured. Images were analyzed through the depth of the blubber for morphological and structural features including adipocyte size, shape, and numbers, and extracellular, structural fiber densities. From fetus to adult, blubber mass and depth increased proportionally with body mass and length. Blubber lipid content increased dramatically with increasing fetal length. Adult and juvenile blubber had significantly higher blubber lipid content than fetuses, and this increase was reflected in mean adipocyte size, which increased significantly across all robust life history categories. In juvenile, subadult, and adult dolphins, this increase in cell size was not uniform across the depth of the blubber, with the largest increases observed in the middle and deep blubber regions. Through-depth counts of adipocytes were similar in all life history categories. These results suggest that blubber depth is increased during postnatal growth by increasing cell size rather than cell number. In emaciated adults (n = 2), lipid mobilization, as evidenced by a decrease in adipocyte size, was localized to the middle and deep blubber region. Thus, in terms of both lipid accumulation and depletion, the middle and deep blubber appear to be the most metabolically dynamic. The superficial blubber likely serves a structural role important in streamlining the animal. This study demonstrates that blubber is not a homogeneous tissue through its depth, and that it displays life history-dependent changes in its morphology and lipid content.     

GROWTH OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U. S. A.

Gompertz growth models were fitted to total lengths and ages from tooth sections of 199 stranded bottlenose dolphins ( Tursiops truncatus ) from the Indian River Lagoon system, eastern Florida. Based on the model, dolphins from this population are estimated to be born at 119 cm and reach asymptotic length at 250 cm. No apparent pubescent growth acceleration was noted for either sex. Males appeared to grow to slightly longer lengths than females. There were small size differences between Indian River dolphins and those in Texas and Sarasota, indicating general size similarities between North Atlantic and Gulf of Mexico bottlenose dolphins stocks.     

Lobomycosis in Bottlenose Dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>) from the Indian River Lagoon,Florida: Estimation of Prevalence,Temporal Trends,and Spatial Distribution

Lobomycosis (lacaziosis) is a chronic fungal disease of the skin that affects only dolphins and humans. Previous studies have shown a high prevalence of lobomycosis in bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon, Florida (IRL). We studied the occurrence and distribution of lobomycosis in the IRL using photo-identification survey data collected between 1996 and 2006. Our objectives were to (1) determine the sensitivity and specificity of photo-identification for diagnosis of lobomycosis in free-ranging dolphins; (2) determine the spatial distribution of lobomycosis in the IRL; and (3) assess temporal patterns of occurrence. Photographs from 704 distinctly marked dolphins were reviewed for skin lesions compatible with lobomycosis. The presumptive diagnosis was validated by comparing the results of photographic analysis with physical examination and histologic examination of lesion biopsies in 102 dolphins captured and released during a health assessment and 3 stranded dolphins. Twelve of 16 confirmed cases were identified previously by photography, a sensitivity of 75%. Among 89 dolphins without disease, all 89 were considered negative, a specificity of 100%. The prevalence of lobomycosis estimated from photographic data was 6.8% (48/704). Spatial distribution was determined by dividing the IRL into six segments based on hydrodynamics and geographic features. The prevalence ranged from <1% in the Mosquito Lagoon to 16.9% in the south Indian River. The incidence of the disease did not increase during the study period, indicating that the disease is endemic, rather than emerging. In summary, photo-identification is a useful tool to monitor the course of individual and population health for this enigmatic disease.     

A MODEL LIFE TABLE FOR BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) FROM THE INDIAN RIVER LAGOON SYSTEM, FLORIDA, U.S.A.

Data gathered from 220 stranded bottlenose dolphins ( Tursiops truncatus ) in the Indian River Lagoon system, Florida, were used to derive a life table. Survivorship curves were fit to the data using Siler's competing-risk model and a maximum likelihood approach. Population growth was estimated to be between r = 0.0 and 0.046 based on the observed numbers of stranded dolphins. Variance in survival rates was estimated using an individual-based, age-structured population projection model. We estimate that the overall annual mortality rate for this population was 9.8% per year. Sex-specific differences in survivorship were apparent with females outliving males. The overall mortality curve resembles that of other large mammals, with high calf mortality and an exponentially increasing risk of senescent mortality. The inclusion of live-capture removals of individuals from this population did not significantly affect the estimation of survival parameters for most age classes.     

Hematologic, biochemical, and cytologic findings from apparently healthy atlantic bottlenose dolphins (Tursiops truncatus) inhabiting the Indian River Lagoon, Florida, USA

The objective of this study was to establish reference baseline data for hematologic, biochemical, and cytologic findings in apparently healthy Atlantic bottlenose dolphins (Tursiops truncatus) inhabiting the Indian River Lagoon, Florida, USA. Sixty-two dolphins were captured, examined, and released during June 2003 and June 2004. Mean, standard deviation, and range were calculated for each parameter, and values for which published data were available, were close to or within the ranges previously reported for free-ranging bottlenose dolphins. No pathologic abnormalities were found in fecal and blowhole cytologic specimens. However, 24% (7/29) of the dolphins examined in 2003 had evidence of gastritis, which was graded as severe in 14% (4/29) of the cases. In 2004, only 4% (1/24) of dolphins sampled had evidence of mild or moderate gastritis; no severe inflammation was present. Dolphins with evidence of gastritis were 8 yr of age or older and predominantly male. Several statistically significant differences were found between males and females, between pregnant and nonpregnant animals, and between juveniles (<6 yr) and adults (> or =6 yr). However, the values remained within the established ranges for this species, and the differences were not likely to be of clinical significance.     

Home Ranges of Bottlenose Dolphins (<Emphasis Type="Italic">Tursiops truncatus</Emphasis>) in the Indian River Lagoon,Florida: Environmental Correlates and Implications for Management Strategies

Photo-identification surveys conducted between 2002 and 2005 were used to determine dolphin home ranges and site fidelity within the Indian River Lagoon (IRL), Florida. The IRL was divided into six segments based on hydrodynamics and geographic features for purposes of characterization. Among the 615 dolphins with identifiable dorsal fins, 339 had ≥6 sightings and were used in segment and linear range analyses. The majority (98%) of dolphins were seen in ≤3 consecutive segments (331/339); of these, 44% (144/331) occurred in two segments, and 33% (109/331) in one segment. No dolphins were observed in all six segments. The largest number of dolphins was sighted in segment 1C (North Indian River). However, the highest density of dolphins was found in segment 2 (North-Central Indian River). Re-sighting rates for dolphins with ≥6 sightings ranged from 2.8 to 8.7 times observed. The mean linear home range varied from 22 to 54 km. Distributional analyses indicated that at least three different dolphin communities exist within the IRL: Mosquito Lagoon, and the North and South Indian River. No statistically significant correlations were found between the total number or density per km² of dolphins and surface water area, salinity, or contaminant loads within segments of the lagoon. These results suggest that dolphins do not selectively avoid areas with relatively unfavorable water quality. IRL dolphins should be studied on smaller spatial scales than currently practiced, and potential anthropogenic impacts should be evaluated based on geographic partitioning.     

RESIDENCE PATTERNS OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN THE STONO RIVER ESTUARY, CHARLESTON COUNTY, SOUTH CAROLINA, U.S.A.

Residence patterns of inshore bottlenose dolphins ( Tursiops truncatus ) in the Stono River estuary, Charleston County, South Carolina were investigated as part of a larger effort to better understand stock structure of these dolphins along the east coast of the United States. Eighty-seven small-boat surveys for bottlenose dolphins were conducted from October 1994 through January 1996. Dolphins were sighted during all surveys. Approximately 304 h were spent surveying the study area; 64% ( n = 196 h) of this time was spent observing and videotaping dolphins. A catalog, containing 112 individually identified dolphins was compiled. Thirty-two percent ( n = 36) of identified dolphins were sighted once, while 28% ( n = 31) were sighted five or more times. Nineteen percent ( n = 21) of identified dolphins were determined to be year-round residents; eight percent ( n = 9) seasonal residents. The majority (64%, n = 72) of identified dolphins were sighted in the study area during a single season or in two consecutive seasons and were classified as transients. This study documents the northernmost known site of a resident bottlenose dolphin community on the east coast of the United States, suggesting a complex bottlenose dolphin stock structure.     

Lacaziosis and lacaziosis-like prevalence among wild, common bottlenose dolphins Tursiops truncatus from the west coast of Florida, USA

Lacaziosis (lobomycosis; Lacazia loboi) is a fungal skin disease that naturally occurs only in humans and dolphins. The first reported case of lacaziosis in a bottlenose dolphin Tursiops truncatus occurred in 1970 in Sarasota Bay, Florida, USA, and subsequent photo-ID monitoring of the Sarasota Bay dolphin population has revealed persistence of the disease. The objectives of this study were to estimate lacaziosis prevalence (P) in 2 bottlenose dolphin populations on the west coast of Florida (Sarasota Bay and Charlotte Harbor) and compare disease occurrence to other published estimates of lacaziosis in dolphin populations across the globe. Historic photographic records of dolphins captured and released for health assessment purposes (Sarasota Bay) and photo-ID studies (Charlotte Harbor) were screened for evidence of lesions consistent with lacaziosis. Health assessment data revealed a prevalence of lacaziosis in the Sarasota Bay bottlenose dolphin population between 2 and 3%, and analyses of photo-ID data provided a lacaziosis-like prevalence estimate of 2% for Charlotte Harbor dolphins. With the exception of lacaziosis prevalence estimates for dolphins inhabiting the Indian River Lagoon (P = 0.068; P = 0.12), no statistically significant differences were seen among Sarasota Bay, Charlotte Harbor, and other published estimates. Although lacaziosis is a rare disease among these dolphin populations, studies that assess disease burden among different populations can assist with the surveillance of this zoonotic pathogen.     

Investigation of growth phases for bottlenose dolphins using a Bayesian modeling approach

The Gompertz function is the most commonly used growth function for cetacean studies. However, this function cannot represent multiple phases of growth. In this study, we present a Bayesian framework fitting parameters of a triple-logistic growth function to describe multiple phases of growth for bottlenose dolphins ( Tursiops truncatus ), simultaneously fitting and comparing all growth parameters between South Carolina (SC), Mississippi Sound (MSS), and Indian River Lagoon (IRL) cohorts. The fitted functions indicated a preliminary early, rapid growth phase, followed by a second phase of slower growth, and then a moderate growth spurt later in life. Growth parameters between geographic cohorts did not show obvious differences, although asymptotic length for SC dolphins was lower than MSS and IRL dolphins and significantly lower between females from SC and the IRL. Growth rate velocities between the sexes showed females exceed males initially (<1 yr), followed by males gaining an advantage around the ages of 3–4 yr until the age of around 15 yr when growth rates for both sexes approached zero (asymptotic length). This study demonstrates age-related changes in growth rates between bottlenose dolphin sexes and evidence of at least some differences ( i.e. , asymptotic length) across geographic cohorts.     

INTERACTIONS BETWEEN THE INDIAN RIVER LAGOON BLUE CRAB FISHERY AND THE BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS

Anecdotal reports from blue crab fishermen in the Indian River Lagoon (IRL), Florida suggested that bottlenose dolphins ( Tursiops truncatus ) followed their boats, and stole bait fish from crab pots soon after they were deployed. To investigate these reports, we made biweekly observations from IRL commercial crab boats from January 1998 to January 1999 (670 h). Only 2.8% of the 18,891 crab pots surveyed revealed evidence of dolphin/crab pot interaction. Dolphin interactions included: (1) begging at boats, (2) feeding on discarded bait fish, (3) engaging in crab pot tipping behavior, and (4) dolphin mortality from crab pot float line entanglement. Overall, 16.6% of the 1,296 dolphins sighted interacted with fishing boats. Seasonal trends were evident, with fishery interactions peaking in the summer. Crab pot interactions ranged from 0% to 36% of the traps checked daily. Different methods of securing the bait-well door and the role of trap locality were tested using a replicated experimental design. Results showed significant differences in successful bait removal by dolphins, among the degrees of door security ( P < 0.001) and between trap location ( P < 0.01). Thus, increased door security may help to reduce the negative impacts to the fishery and dolphins involved.     

Clinicoimmunopathologic findings in Atlantic bottlenose dolphins Tursiops truncatus with positive cetacean morbillivirus antibody titers

Sera from free-ranging Atlantic bottlenose dolphins Tursiops truncatus inhabiting the Indian River Lagoon (IRL), Florida were tested for antibodies to cetacean morbilliviruses from 2003 to 2007 as part of a multidisciplinary study of individual and population health. A suite of clinicoimmunopathologic variables were evaluated in morbillivirus-seropositive dolphins (n = 14) and seronegative healthy dolphins (n = 49). Several important differences were found. Serum alkaline phosphatase, creatine phosphokinase, chloride, albumin and albumin/globulin ratios were significantly lower in seropositive dolphins. Innate immunity appeared to be upregulated with significant increases in lysozyme concentration and marginally significant increases in monocytic phagocytosis. Adaptive immunity was also impacted in dolphins with positive morbillivirus antibody titers. Mitogen-induced T lymphocyte proliferation responses were significantly reduced in dolphins with positive morbillivirus antibody titers, and marginally significant decreases were found for absolute numbers of CD4+ lymphocytes. The findings suggest impairment of cell-mediated adaptive immunity, similar to the immunologic pattern reported with acute morbillivirus infection in other species. In contrast, dolphins with positive morbillivirus antibody titers appeared to have at least a partially upregulated humoral immune response with significantly higher levels of gamma globulins than healthy dolphins, which may represent an antibody response to morbillivirus infection or other pathogens. These data suggest that subclinical dolphin morbillivirus infection in IRL dolphins may produce clinicoimmunopathologic perturbations that impact overall health.     

Lacaziosis in bottlenose dolphins Tursiops truncatus along the coastal Atlantic Ocean, Florida, USA

This study represents the first systematic study of lacaziosis (lobomycosis) in bottlenose dolphins Tursiops truncatus in the Atlantic Ocean along the east-central coast of Florida, USA. Lacaziosis is a chronic infection of the skin caused by the fungus Lacazia loboi, which affects only dolphins and humans. Previous studies have shown a high prevalence (6.8 to 12.0%) of lacaziosis in resident dolphins from the adjacent Indian River Lagoon Estuary (IRL), where the disease is endemic. We examined the prevalence of lacaziosis in this coastal area using photo-identification data collected between 2002 and 2008 to determine the prevalence of lacaziosis in coastal dolphins using photographic methodology shown to have high sensitivity and specificity in prior research. The prevalence of skin lesions compatible with lacaziosis estimated from photographic data was 2.1% (6/284), approximately 3 times lower than that described for the estuarine population using similar methods. To exclude potential bias introduced by differences in study duration and survey effort among areas, an 18 mo period when effort was most equal (January 2006 to June 2007) was chosen for statistical comparison. The prevalence of lacaziosis estimated from photographic data was significantly lower (3.8%: n = 6/160) in the Atlantic Ocean compared to the IRL (12.0%: n = 20/167) (risk ratio = 3.19, 95% CI 1.32 to 7.75, p < 0.01 by chi-square analysis). The lower prevalence of lacaziosis in dolphins found in the Atlantic Ocean and the overall lack of movement of dolphins between these habitats suggests that environmental conditions within the estuary may favor viability of L. loboi, and/or that immune compromise in resident estuarine dolphins is a precursor to the disease.     

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.     

Common bottlenose dolphin (Tursiops truncatus) social structure and distribution changes following the 2008 Unusual Mortality Event in the Indian River Lagoon,Florida

In animal societies with fission-fusion dynamics, demographic disturbances can influence the social and spatial structure of the population. Within the Indian River Lagoon (IRL), Florida, common bottlenose dolphins (Tursiops truncatus) have experienced recurrent unusual mortality events (UMEs) providing an opportunity to examine postdisturbance population and social cluster restructuring. This study investigates the impact of the potentially nonepizootic 2008 UME on the IRL dolphin population. Photo-identification surveys conducted from August 2006 to May 2010 were stratified into pre- (August 2006–April 2008) and post-UME (September 2008–May 2010) time periods. Social network and spatial (univariate kernel density) analyses were limited to individuals sighted 5+ times per period (pre-UME = 183, post-UME = 134), and indicated a change from 11 to ten social clusters, although individuals did not always reassociate with pre-UME cluster associates. Despite the social and spatial disconnect between IRL proper and Mosquito Lagoon clusters, both network density and core area spatial overlap increased post-UME allowing for increased intercluster interactions. However, intracluster associations increased as well, allowing the population to maintain multiple social clusters within a loosely connected network. This study shows the important role sociality may play in the adaptability of cetaceans to environmental and demographic changes.     

Blood mercury concentrations in common bottlenose dolphins from the Indian River Lagoon,Florida: Patterns of social distribution

Social network analysis has been shown to be effective in studying the social structure of cetacean populations. Common bottlenose dolphins (Tursiops truncatus) inhabiting the Indian River Lagoon (IRL), Florida, have among the highest concentrations of total mercury (THg) in blood reported worldwide. The purpose of this study was to examine the relationship between THg concentrations in IRL dolphins and their social affiliations. Whole blood samples from 98 dolphins with photo‐identification sighting histories were collected between 2003–2007 and 2010–2012. Dolphins were categorized into approximate tertiles of low (mean 199.7 μg/L), medium (mean 366.8 μg/L), and high (mean 990.5 μg/L) THg exposure. Social associations between individual dolphins were defined by the proportion of sightings documented with another known individual. Social network measures of individuals and associations between dyads were examined to determine differences among THg categories. Strong social affiliations of individuals within the highest category of THg were found (P = 0.04), suggesting shared exposures among dolphins foraging in specific areas of the estuary. Network measures of strength and affinity were significantly higher in the highest exposure category. This report used social network analysis as a novel way to examine patterns of exposure to an environmental contaminant in a cetacean population.     

Linear skin markings in common bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon,Florida

A previously undescribed skin abnormality, referred to as “linear skin markings” (LSM), has been identified in free-ranging common bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida (IRL). The lesions were identified during photo-identification surveys conducted from 2002 and 2015. LSM presented as distinct, parallel lines running dorso-ventrally on the torso and varied in length and width. The goals of this study were to determine (1) prevalence of the condition in IRL dolphins, (2) age and sex distribution of affected animals, (3) spatial and temporal distribution patterns, (4) duration of the condition, and (5) development of hypotheses regarding the etiology of the condition. Among 1,357 individual dolphins identified during the study period, 96 (7.0%) showed evidence of LSM. Nearly all (98.8%) cases with an established home range occurred in the northern and central regions of the IRL. The majority of cases of known sex were female (85%), of which 100% had given birth to one or more calves. The mean age of animals with LSM when first observed was 7.3 with a range of 1–20 years. The maximum observed duration of LSM was 15 years. Once observed, the condition persisted indefinitely. The etiology of LSM has not been established.     

Antibiotic-Resistant Organisms Cultured from Atlantic Bottlenose Dolphins (Tursiops truncatus) Inhabiting Estuarine Waters of Charleston, SC and Indian River Lagoon, FL

Bottlenose dolphins (Tursiops truncatus) from estuarine waters of Indian River Lagoon, FL (IRL) and Charleston, SC (CHS) were cultured to screen for microorganism colonization and to assess antibiotic sensitivity. Swabs (n = 909) were collected from the blowhole, gastric fluid, and feces of 171 individual dolphins The most frequently cultured organisms were Plesiomonas shigelloides (n = 161), Aeromonas hydrophila (n = 144), Escherichia coli (n = 85), and Pseudomonas fluorescens (n = 82). In descending frequency, organisms demonstrated resistance to erythromycin, ampicillin, and cephalothin. Human and animal pathogens resistant to antibiotics used in human and veterinary medicine were cultured. Escherichia coli (E. coli) more often was resistant in IRL dolphins. Three cases of methicillin-resistant Staphylococcus aureus (MRSA) were found at CHS. Emergence of antibiotic resistance is not confined to humans. Bottlenose dolphins may serve as sentinels for transfer of resistance from humans and animals or indicate that antibiotics are reaching the marine environment and causing resistance to emerge through selective pressure and genetic adaptation.     

Environmental drivers of habitat use by common bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon,Florida, USA

Anthropogenic impacts in estuarine systems can influence marine mammal habitat use, population dynamics, fitness, and mortality events. The objective was to examine habitat use among the resident common bottlenose dolphin (Tursiops truncatus) population inhabiting the Indian River Lagoon, Florida, and the influences of variation in environmental factors and prey availability in 2003–2015. We utilized photo-identification surveys, stratified random samples of prey, and environmental variables collected monthly. Kernel density estimation was used to determine the magnitude-per-unit area of dolphins across the IRL by wet and dry seasons each year, the values were used as a response variable in classification and regression tree analyses with fish community and environmental variables as predictors. Spatial patterns in dolphin density in the IRL were associated with salinity and dissolved oxygen levels, which are in part associated with freshwater discharges of nutrient and algae laden waters from the region's storm water management system. These findings isolate locations of concern for management of dolphin habitat, and anthropogenic drivers of dolphin distributions requiring further research.     

Reproductive seasonality of a recently designated bottlenose dolphin stock near Charleston,South Carolina,U.S.A

Reproductive seasonality of common bottlenose dolphins (Tursiops truncatus) can be affected by numerous ecological and behavioral factors. In 2009, stock boundaries were revised to recognize a Charleston Estuarine System Stock (CESS) of bottlenose dolphins in Charleston, South Carolina. The CESS is a well‐studied population with long‐term data collected from photo‐identification and stranding studies. From 2004 to 2008, a systematic mark‐recapture photo‐identification study was conducted in the Charleston Estuary to estimate population size of the CESS. Sightings data from this photo‐identification study coupled with strandings data (1993–2008) were analyzed to determine the reproductive seasonality of this local population. Both neonate sightings and strandings depicted a primary season of reproduction in the spring into early summer with a small peak in neonate sightings in early autumn, and were significantly different from circular uniform and Von Mises distributions (strandings: P < 0.01, V = 2.8644; sightings: P < 0.01, V = 3.2302). This study increases the knowledge of seasonal reproductive patterns of estuarine stocks of bottlenose dolphin stocks in the southeastern United States. The results will also help wildlife managers detect unusual neonate mortality events, and provide information about critical habitat relevant for evaluating and mitigating coastal development projects.     

Importance of spontaneous micronucleated erythrocytes in bottlenose dolphin (Tursiops truncatus) to marine toxicology studies

The objective of the work was to characterize the presence of spontaneous micronucleated erythrocytes (MNES) from peripheral blood of bottlenose dolphins (Tursiops truncatus) to evaluate the possibility to use this species as potential bioindicator of genotoxic compounds. Forty-eight blood samples from 12 bottlenose dolphins were obtain from three Mexican dolphinariums, and from 10 dolphins was possible to obtain more than one sample at different sampling times. Smears were processed and observed with an epifluorescence microscope. The average of MNES and polychromatic erythrocytes (PCE) from the 48 samples was 24.3 +/- 6.1 MNES/10,000 total erythrocytes (TE), and 9.1 +/- 5.5 PCE/1,000 TE. MNES and PCE number did not show differences between gender and age. No variations in the MNES values of the bottlenose dolphins that were sampled more than one occasion were found. Comparisons among dolphinariums revealed differences in MNES frequency, with the highest significant frequency observed in dolphins from dolphinarium "A" (26.0 +/- 5.9 MNES/10,000 TE) than dolphinarium "B" (19.5 +/- 3.1 MNES/10,000 TE) (p < 0.05) and dolphinarium "C" (18.6 +/- 3.5 MNES/10,000 TE) (p < 0.007). The presence of MNES and PCE in the bottlenose dolphin may provide a useful marine mammal model to detect DNA damage by means of micronuclei test in peripheral blood erythrocytes to evaluate genotoxicity and cytotoxicity expositions.