25 research outputs found
Uterine adenocarcinoma with generalised metastasis in a bottlenose dolphin <i>Tursiops truncatus</i> from northern Patagonia, Argentina
An endometrial adenocarcinoma with areas of squamous differentiation and generalised metastasis was observed in a bottlenose dolphin Tursiops truncatus stranded in northern Patagonia in July 1997. This is the second report of a uterine adenocarcinoma in a free-living cetacean and the first in a Delphinidae. This neoplasm likely compromised reproduction for several years. In addition, the dolphin presented tattoo-like skin lesions and its digestive tract was infested by Anisakis simplex, Pseudoterranova sp., Braunina cordiform-is and Corynosoma australe
Ray dynamics in a long-range acoustic propagation experiment
A ray-based wavefield description is employed in the interpretation of
measurements made during the November 1994 Acoustic Engineering Test (the AET
experiment). In this experiment phase-coded pulse-like signals with 75 Hz
center frequency and 37.5 Hz bandwidth were transmitted near the sound channel
axis in the eastern North Pacific Ocean. The resulting acoustic signals were
recorded on a moored vertical receiving array at a range of 3252 km. In our
analysis both mesoscale and internal-wave-induced sound speed perturbations are
taken into account. Much of this analysis exploits results that relate to the
subject of ray chaos; these results follow from the Hamiltonian structure of
the ray equations. We present evidence that all of the important features of
the measured AET wavefields, including their stability, are consistent with a
ray-based wavefield description in which ray trajectories are predominantly
chaotic
Drifter motion in the Gulf of Mexico constrained by altimetric Lagrangian coherent structures
Application of recent geometric tools for Lagrangian coherent structures (LCS) shows that material attraction in geostrophic velocities derived from altimetry data imposed an important constraint to the motion of drifters from the Grand Lagrangian Deployment (GLAD) in the Gulf of Mexico. This material attraction is largely transparent to traditional Eulerian analysis. Attracting LCS acted as approximate centerpieces for mesoscale patterns formed by the drifters. Persistently attracting LCS cores emerged 1âweek before the development of a filament resembling the âtiger tailâ of the Deepwater Horizon oil slick, thereby anticipating its formation. Our results suggest that the mesoscale circulation plays a significant role in shaping nearâsurface transport in the Gulf of Mexico.
Key Points
Altimetric LCS constrain drifter motion
Altimetric LCS form centerpieces of drifter distributions
Altimetric LCS cores predate shape changes in drifter distribution
Flow Coherence: Distinguishing Cause from Effect
The geodesic transport theory unveils the especial fluid trajectory sets, referred to as Lagrangian Coherent Structures (LCS), that cause a flow to organize into ordered patterns. This is illustrated through the analysis of an oceanic flow dataset and contrasted with the tendency of a widely used flow diagnostic to carry coherence imprints as an effect of the influence of LCS on neighboring fluid trajectories
Molecular systematics of pinniped hookworms (Nematoda: Uncinaria): species delimitation, host associations and host-induced morphometric variation
Hookworms of the genus Uncinaria have been widely reported from juvenile pinnipeds, however investigations of their systematics has been limited, with only two species described, Uncinaria lucasi from northern fur seals (Callorhinus ursinus) and Uncinaria hamiltoni from South American sea lions (Otaria flavescens). Hookworms were sampled from these hosts and seven additional species including Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), South American fur seals (Arctocephalus australis), Australian fur seals (Arctocephalus pusillus), New Zealand sea lions (Phocarctos hookeri), southern elephant seals (Mirounga leonina), and the Mediterranean monk seal (Monachus monachus). One hundred and thirteen individual hookworms, including an outgroup species, were sequenced for four genes representing two loci (nuclear ribosomal DNA and mitochondrial DNA). Phylogenetic analyses of these sequences recovered seven independent evolutionary lineages or species, including the described species and five undescribed species. The molecular evidence shows that U. lucasi parasitises both C. ursinus and E. jubatus, whereas U. hamiltoni parasitises O. flavescens and A. australis. The five undescribed hookworm species were each associated with single host species (Z. californianus, A. pusillus, P. hookeri, M. leonina and M. monachus). For parasites of otarids, patterns of Uncinaria host-sharing and phylogenetic relationships had a strong biogeographic component with separate clades of parasites from northern versus southern hemisphere hosts. Comparison of phylogenies for these hookworms and their hosts suggests that the association of U. lucasi with northern fur seals results from a host-switch from Steller sea lions. Morphometric data for U. lucasi shows marked host-associated size differences for both sexes, with U. lucasi individuals from E. jubatus significantly larger. This result suggests that adult growth of U. lucasi is reduced within the host species representing the more recent host parasite association. Intraspecific host-induced size differences are inconsistent with the exclusive use of morphometrics to delimit and diagnose species of Uncinaria from pinnipeds. (C) 2013 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved
A surface âsuper-convergenceâ pathway connecting the South Indian Ocean to the subtropical South Pacific gyre
We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at Ρ resolution and refreshed daily over the 1985-2013 period. Results confirm and document the five known sites of surface convergence at the scale of individual oceanic basins, but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea and the southwest Pacific Ocean. This âsuper-convergentâ pathway at the ocean surface is robust and permanent over a distance longer than 8000 km. The currents variability is crucial to sustain this pathway