Mirror self-recognition in the bottlenose dolphin: a case of cognitive convergence.
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The ability to recognize oneself in a mirror is an exceedingly rare capacity in the animal kingdom. To date, only humans and great apes have shown convincing evidence of mirror self-recognition. Two dolphins were exposed to reflective surfaces, and both demonstrated responses consistent with the use of the mirror to investigate marked parts of the body. This ability to use a mirror to inspect parts of the body is a striking example of evolutionary convergence with great apes and humans. (+info)
Gastrointestinal parasites and prey items from a mass stranding of false killer whales, Pseudorca crassidens, in Rio Grande do Sul, Southern Brazil.
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The gastrointestinal tract of 14 false killer whales, 6 males and 8 females, stranded in June 1995 in southern Brazil, with total standard lengths from 338 to 507 cm, were analysed for endoparasites and food items. A pregnant female had a male foetus of 77.5 cm. Parasites were found in all 14 false killer whales. The nematode Anisakis simplex (Rudolphi, 1809) was found in the stomach of 57% of the animals and the acanthocephalan Bolbosoma capitatum (Linstow, 1889) Porta, 1908 was present in the intestine of all specimens and showed densities up to 600 m-1. An unidentified cestode (Tethrabothridae) was found also in the intestines of 14% of the individuals. The high infections of B. capitatum and A. simplex were not directly related with the cause of death. In the stomachs of four females, beaks of at least eight specimens of the oceanic and epipelagic species Ommastrephes bartramii (Lesueur, 1821) were found, with mantle lengths ranging from 189.8 to 360.9 mm. The distribution of O. bartramii in the coast of Rio Grande do Sul is consistent with false killer whales feeding in continental shelf waters. (+info)
Retroposon analysis of major cetacean lineages: the monophyly of toothed whales and the paraphyly of river dolphins.
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SINE (short interspersed element) insertion analysis elucidates contentious aspects in the phylogeny of toothed whales and dolphins (Odontoceti), especially river dolphins. Here, we characterize 25 informative SINEs inserted into unique genomic loci during evolution of odontocetes to construct a cladogram, and determine a total of 2.8 kb per taxon of the flanking sequences of these SINE loci to estimate divergence times among lineages. We demonstrate that: (i) Odontocetes are monophyletic; (ii) Ganges River dolphins, beaked whales, and ocean dolphins diverged (in this order) after sperm whales; (iii) three other river dolphin taxa, namely the Amazon, La Plata, and Yangtze river dolphins, form a monophyletic group with Yangtze River dolphins being the most basal; and (iv) the rapid radiation of extant cetacean lineages occurred some 28-33 million years B.P., in strong accord with the fossil record. The combination of SINE and flanking sequence analysis suggests a topology and set of divergence times for odontocete relationships, offering alternative explanations for several long-standing problems in cetacean evolution. (+info)
Osmoregulation in marine mammals.
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Osmoregulation in marine mammals has been investigated for over a century; however, a review of recent advances in our understanding of water and electrolyte balance and of renal function in marine mammals is warranted. The following topics are discussed: (i) kidney structure and urine concentrating ability, (ii) sources of water, (iii) the effects of feeding, fasting and diving, (iv) the renal responses to infusions of varying salinity and (v) hormonal regulation. The kidneys of pinnipeds and cetaceans are reniculate in structure, unlike those of terrestrial mammals (except bears), but this difference does not confer any greater concentrating ability. Pinnipeds, cetaceans, manatees and sea otters can concentrate their urine above the concentration of sea water, but only pinnipeds and otters have been shown to produce urine concentrations of Na+ and Cl- that are similar to those in sea water. This could afford them the capacity to drink sea water and not lose fresh water. However, with few exceptions, drinking is not a common behavior in pinnipeds and cetaceans. Water balance is maintained in these animals via metabolic and dietary water, while incidental ingestion and dietary salt may help maintain electrolyte homeostasis. Unlike most other aquatic mammals, sea otters commonly drink sea water and manatees frequently drink fresh water. Among the various taxonomic groups of marine mammals, the sensitivity of the renin-angiotensin-aldosterone system appears to be influenced by the availability of Na+. The antidiuretic role of vasopressin remains inconclusive in marine mammals, while the natriuretic function of atrial natriuretic peptide has yet to be examined. Ideas on the direction of future studies are presented. (+info)
Alpha 1,3 galactosyltransferase: new sequences and characterization of conserved cysteine residues.
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Nucleotide sequences were determined for alpha1,3 galactosyltransferases (alpha1,3 GalTs) from several species (bat, mink, dog, sheep, and dolphin) and compared with those previously determined for this enzyme and members of the alpha1,3 galactosyl/N-acetylgalactosyltransferase (alpha1,3 Gal(NAc)Ts) family of enzymes. Sequence comparison of the newly characterized alpha1,3 GalT nucleotide and predicted amino acid sequences with those previously characterized for other alpha1,3GalT enzymes demonstrated a remarkable level of sequence identity at the nucleotide and amino acid level. The identity of each sequence as an alpha1,3 GalT was confirmed by expressing the encoded protein and characterizing the resulting enzyme. The alpha1,3 GalTs have a significant degree of sequence homology with A and B transferases, the alpha1,3 GalNAcT that catalyzes the synthesis of Forssman antigen, and the recently cloned iso-globotriaosylceramide synthase. Among the conserved residues, there are two Cys residues. To determine if these conserved residues are free or involved in the formation of a disulfide bond, bovine alpha1,3 GalT was characterized by chemical modification and mass spectrometry. Each peptide containing a Cys residue was chemically labeled with an alkylating reagent demonstrating that these enzymes do not contain disulfide bonds. Similar results have recently been reported for A and B transferases (Yen et al., 2000, J. Mass. Spectrom., 35, 990-1002). Thus, the highly conserved Cys residues found in these members of the alpha1,3 Gal(NAc)Ts family of enzymes are likely involved in other important aspects of enzyme structure/function within this enzyme family. (+info)
Trawling and bottlenose dolphins' social structure.
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Human activities can affect the behaviour of mammals through the modification of habitats, changes in predation pressure or alterations in food distribution and availability. We analysed the association and ranging patterns of 242 individually identified bottlenose dolphins (Tursiops aduncus) in eastern Moreton Bay, Queensland, Australia, and distinguished two separate communities of dolphins. Unlike bottlenose dolphins elsewhere, the communities' core areas overlapped substantially. There was a correlation between the dolphins' responses to fishing activities and community membership-members of one community feed in association with trawlers and members of the other do not. Apart from feeding mode, the communities differed in habitat preference and group sizes. Inadvertent anthropogenic impacts on animals' societies are likely to be far more widespread than just this study and can increase conservation challenges. In this instance, managers need to consider the two communities' differing habitat requirements and their behavioural traditions in conservation planning. (+info)
Alliance membership and kinship in wild male bottlenose dolphins (Tursiops aduncus) of southeastern Australia.
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Bottlenose dolphins are one of only a few mammalian taxa where the males are known to cooperate within their social group in order to maintain mating access to single females against other males. Male bonds in bottlenose dolphins have been hypothesized as evolving through kinship and associated inclusive fitness effects. In this study we tested whether individually identified male bottlenose dolphins preferentially associate and form alliances with kin in a small coastal resident population of southeastern Australia using a combination of behavioural data, genetic sexing, sequences of the mitochondrial DNA control region and nuclear microsatellite markers. Males generally associated significantly more often than expected with one to three other males, with whom they jointly herded females for mating. Associations and alliance membership were not associated with either maternal kinship or genetic relatedness. The majority of male pairs within alliances were randomly related, although high relatedness values were found between males of different alliances in the resident population. These findings indicate that mechanisms other than kin selection may be foremost in the development and maintenance of cooperation between male bottlenose dolphins. (+info)
The influence of parental relatedness on reproductive success.
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The relationship between fitness and parental similarity has been dominated by studies of how inbreeding depression lowers fecundity in incestuous matings. A widespread implicit assumption is that adult fitness (reproduction) of individuals born to parents who are not unusually closely related is more or less equal. Examination of three long-lived vertebrates, the long-finned pilot whale, the grey seal and the wandering albatross reveals significant negative relationships between parental similarity and genetic estimates of reproductive success. This effect could, in principle, be driven by a small number of low quality, inbred individuals. However, when the data are partitioned into individuals with above average and below average parental similarity, we find no evidence that the slopes differ, suggesting that the effect is more or less similar across the full range of parental similarity values. Our results thus uncover a selective pressure that favours not only inbreeding avoidance, but also the selection of maximally dissimilar mates. (+info)