Degradation of marine ecosystems is an increasing problem and extends beyond nearshore coastal waters with significant human development. However, measuring ecosystem damage and decreased ecosystem ...function can be difficult. Marine mammals have often been recommended as indicators for evaluating ecosystem health. Between March 2010 and July 2014, a significant cetacean unusual mortality event occurred across the northern Gulf of Mexico, where multiple demographically independent populations of common bottlenose dolphins Tursiops truncatus occur adjacent to one another. Some populations are fairly small and restricted to small habitat areas, while other populations have higher abundances and cover broader geographic ranges. An integral component to determining the impact of this event on these populations is identifying what percentage of each population the stranded animals comprise. We applied genetic assignment test methods to stranded dolphins from southeastern Louisiana to determine the proportion of dead dolphins that came from the local estuarine population versus the population found in adjacent coastal waters. Forty-one microsatellite loci were genotyped in 156 live dolphins sampled to represent the 2 potential stocks of origin and in 131 dead stranded dolphins of unknown origin. Both classical assignment tests and genetic stock identification methods indicated that approximately 6 to 7% of the sampled stranded dolphins originated from the Western Coastal Stock and the remainder from the smaller, estuarine stock in Barataria Bay, Louisiana.
Coastal and offshore ecotypes of common bottlenose dolphins have been recognized in the western South Atlantic, and it is possible that trophic niche divergence associated with social interactions is ...leading them to genetic and phenotypic differentiation. The significant morphological differentiation observed between these ecotypes suggests they represent two different subspecies. However, there is still a need to investigate whether there is congruence between morphological and genetic data to rule out the possibility of ecophenotypic variation accompanied by gene flow. Mitochondrial DNA (mtDNA) control region sequence data and 10 microsatellite loci collected from stranded and biopsied dolphins sampled in coastal and offshore waters of Brazil as well as 106 skulls for morphological analyses were used to determine whether the morphological differentiation was supported by genetic differentiation. There was congruence among the data sets, reinforcing the presence of two distinct ecotypes. The divergence may be relatively recent, however, given the moderate values of mtDNA nucleotide divergence (dA = 0.008), presence of one shared mtDNA haplotype and possibly low levels of gene flow (around 1% of migrants per generation). Results suggest the ecotypes may be in the process of speciation and reinforce they are best described as two different subspecies until the degree of nuclear genetic divergence is thoroughly evaluated: Tursiops truncatus gephyreus (coastal ecotype) and T. t. truncatus (offshore ecotype). The endemic distribution of T. t. gephyreus in the western South Atlantic and number of anthropogenic threats in the area reinforces the importance of protecting this ecotype and its habitat.
Genetic and morphological results indicate the coastal and offshore bottlenose dolphins of the western South Atlantic are in process of speciation due to ecological divergence.
Attempts to measure the propulsive forces produced by swimming dolphins have been limited. Previous uses of computational hydrodynamic models and gliding experiments have provided estimates of thrust ...production by dolphins, but these were indirect tests that relied on various assumptions. The thrust produced by two actively swimming bottlenose dolphins (Tursiops truncatus) was directly measured using digital particle image velocimetry (DPIV). For dolphins swimming in a large outdoor pool, the DPIV method used illuminated microbubbles that were generated in a narrow sheet from a finely porous hose and a compressed air source. The movement of the bubbles was tracked with a high-speed video camera. Dolphins swam at speeds of 0.7 to 3.4 m s(-1) within the bubble sheet oriented along the midsagittal plane of the animal. The wake of the dolphin was visualized as the microbubbles were displaced because of the action of the propulsive flukes and jet flow. The oscillations of the dolphin flukes were shown to generate strong vortices in the wake. Thrust production was measured from the vortex strength through the Kutta-Joukowski theorem of aerodynamics. The dolphins generated up to 700 N during small amplitude swimming and up to 1468 N during large amplitude starts. The results of this study demonstrated that bubble DPIV can be used effectively to measure the thrust produced by large-bodied dolphins.
Polychlorinated biphenyls (PCBs), chlorinated pesticides (i.e., dichlorodiphenyltrichloroethane (DDT) and its metabolites, chlordanes (CHLs), dieldrin, hexachlorobenzene (HCB), and mirex), ...polybrominated diphenyl ethers (PBDEs), perfluorinated chemicals (PFCs), and polyaromatic hydrocarbons (PAHs) were measured in blubber biopsy samples collected from 139 wild bottlenose dolphins (
Tursiops truncatus) during 2003–2005 in Charleston (CHS), SC and the Indian River Lagoon (IRL), FL. Dolphins accumulated a similar suite of contaminants with ∑
PCB dominating (CHS 64%, IRL 72%), followed by ∑
DDT (CHS 20%, IRL 17%), ∑
CHLs (CHS 7%; IRL 7%), ∑
PBDE (CHS 4%, IRL 2%), PAH at 2%, and dieldrin, PFCs and mirex each 1% or less. Together ∑
PCB and ∑
DDT concentrations contributed ∼
87% of the total POCs measured in blubber of adult males. ∑
PCBs in adult male dolphins exceed the established PCB threshold of 17
mg/kg by a 5-fold order of magnitude with a 15-fold increase for many animals; 88% of the dolphins exceed this threshold. For male dolphins, CHS (93,980
ng/g lipid) had a higher ∑
PCBs geomean compared to the IRL (79,752
ng/g lipid) although not statistically different. In adult males, the PBDE geometric mean concentration was significantly higher in CHS (5920
ng/g lipid) than the IRL (1487
ng/g). Blubber ∑
PFCs concentrations were significantly higher in CHS dolphins. In addition to differences in concentration of PCB congeners, ∑
PBDE, TEQ, ∑
CHLs, mirex, dieldrin, and the ratios ∑
DDE/∑DDT and trans-nonachlor/cis-nonachlor were the most informative for discriminating contaminant loads in these two dolphin populations. Collectively, the current ∑
PCB, ∑
DDT, and ∑
PBDEs blubber concentrations found in CHS dolphins are among the highest reported values in marine mammals. Both dolphin populations, particularly those in CHS, carry a suite of organic chemicals at or above the level where adverse effects have been reported in wildlife, humans, and laboratory animals warranting further examination of the potential adverse effects of these exposures.
Two subspecies of bottlenose dolphins are observed, not simultaneously, in a narrow coastal area of the western South Atlantic Ocean. However, their trophic interaction is unknown. Such information ...can be explored using stable isotope composition in teeth, warranting time series data. We analyzed carbon and nitrogen isotopic values (δ
13
C and δ
15
N) of dentin growth layer groups in teeth of
Tursiops truncatus truncatus
and
Tursiops truncatus gephyreus
stranded along this area of potential co-occurrence in order to investigate the trophic, spatial and temporal dimensions of their isotopic niches. For each subspecies, we calculated isotopic niche width and the possible overlap in resource use between them. We modeled δ
13
C and δ
15
N according to age to verify ontogenetic variations in resources use. We also measured the ratio of individual variation by that of the population to estimate the degree of individual specialization within each subspecies. Mean isotopic values differed only for carbon values (δ
13
C
Ttg
= − 12.7‰; δ
13
C
Ttt
= − 14.3‰), and a small overlap in resource use between subspecies was observed. Individual specialization was evident in both subspecies suggesting temporal consistency in resource use and indicating they forage upon various preys. Although weaning age and feeding habit seem similar, subspecies diverge especially in habitat use, indicating they adapted for feeding in different environments. These results show a clear habitat partitioning between subspecies and only a small overlap on resource use within the area, reinforcing the hypothesis of a parapatric distribution with very occasional contacts in this region of the western South Atlantic Ocean.
Telomere shortening rate predicts species life span Whittemore, Kurt; Vera, Elsa; Martínez-Nevado, Eva ...
Proceedings of the National Academy of Sciences - PNAS,
07/2019, Letnik:
116, Številka:
30
Journal Article
Recenzirano
Odprti dostop
Telomere shortening to a critical length can trigger aging and shorter life spans in mice and humans by a mechanism that involves induction of a persistent DNA damage response at chromosome ends and ...loss of cellular viability. However, whether telomere length is a universal determinant of species longevity is not known. To determine whether telomere shortening can be a single parameter to predict species longevities, here we measured in parallel the telomere length of a wide variety of species (birds and mammals) with very different life spans and body sizes, including mouse (Mus musculus), goat (Capra hircus), Audouin’s gull (Larus audouinii), reindeer (Rangifer tarandus), griffon vulture (Gyps fulvus), bottlenose dolphin (Tursiops truncatus), American flamingo (Phoenicopterus ruber), and Sumatran elephant (Elephas maximus sumatranus). We found that the telomere shortening rate, but not the initial telomere length alone, is a powerful predictor of species life span. These results support the notion that critical telomere shortening and the consequent onset of telomeric DNA damage and cellular senescence are a general determinant of species life span.
Entre junio del 2002 y agosto del 2003 se evaluó la abundancia y distribución de delfines toninas (Tursiops truncatus) en la costa norte de la provincia de Matanzas. Fue empleada la técnica de ...muestreo a distancia durante seis salidas, en las cuales se recorrieron 1 553,3 Km en 164 horas de esfuerzo. Se analizaron las diferencias en abundancia de delfines por zonas (Costa Norte, Bahía de Cárdenas, Cinco Leguas), estaciones y horario del día y su relación con la temperatura del agua y el estado de la marea. Se observaron 253 delfines en 34 avistamientos. El tamaño de grupo más frecuente fue de ocho individuos. El mayor número de avistamientos realizados ocurrió en la en la parte norte del área de estudio. No se detectaron diferencias estadísticas en la abundancia entre estaciones de lluvia y seca (U=105, p=0,77). En la Bahía de Cárdenas la abundancia relativa de delfines fue menor que en la Costa Norte (U=45,7, p=0,04). No existieron diferencias asociadas con la marea, horario del día, temperatura ni salinidad. La densidad de delfines estimada para el área de estudio fue de 1,28 delfines/km2 , la cual se encuentra dentro del rango reportado para la especie.
Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous environmental contaminants in aquatic ecosystems worldwide. Marine mammals, as top predators, are constantly exposed to several PFAS ...compounds that accumulate in different tissues. As a proxy to assess cytotoxicity of PFAS in the bottlenose dolphin (Tursiops truncatus), we generated a new immortalized cell line derived from skin samples of bottlenose dolphin. Using high content imaging, we assessed the effects of increasing concentrations of PFOS, PFOA, PFBS, PFBA and C6O4 on cell viability and cell cycle phases. In particular, we classified all cells based on multiple morphometric differences of the nucleus in three populations, named respectively “Normal” (nuclei in G0, S and M phase); “Large” (nuclei showing characteristics of senescence) and “Small” (nuclei with fragmentation and condensed chromatin). Combining this approach with cell cycle analysis we determined which phases of the cell cycle were influenced by PFAS. The results revealed that the presence of PFOS, PFBS and PFBA could increase the number of cells in G0+G1 phase and decrease the number of those in the S phase. Moreover, PFOS and PFBS lowered the fraction of cells in the M phase. Interestingly PFOS, PFBS and PFBA reduced the prevalence of the senescence phenotype (“large” nuclei), suggesting a potential tumorigenic effect. Besides, the presence of PFOS and PFBS correlated also with a significant decrease in the number of “small” nuclei. The C6O4 exposure did not highlighted morphometric alteration or cell cycle modification bottlenose dolphin skin cell nuclei. While the effects of PFAS on cell cycle was clear, no significant change was detected either in term of cell proliferation or of viability. This study fosters the overall knowledge on the cellular effects of perfluoroalkyl substances in marine mammals.
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Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the ...diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom single trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.
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