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Song recorded near a super-group of humpback whales on a mid-latitude feeding ground off South Africa
Get PDFHumpback whales (Megaptera novaeangliae) are well known for their complex song which is culturally transmitted and produced by males. However, the function of singing behavior remains poorly understood. Song was observed from 57 min of acoustic recording in the presence of feeding humpback whales aggregated in the near-shore waters on the west coast of South Africa. The structural organization of the song components, lack of overlap between song units, and consistency in relative received level suggest the song was produced by one "singer." The unusual timing and location of song production adds further evidence of plasticity in song production
The dinoflagellate cyst genera <i>Achomosphaera</i> Evitt 1963 and <i>Spiniferites</i> Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions
Get PDFWe present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al. 1973) Londeix et al. 2009, Spiniferites rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes & 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail
Looking for the key to preservation of fossil marine vertebrates in the Pisco Formation of Peru: new insights from a small dolphin skeleton
No full textThe upper Neogene Pisco Formation of Peru is known worldwide as one of the most significant Cenozoic marine vertebrate Konservatt-Lagerstatten, even featuring cetacean specimens that retain remains of soft tissues or stomach contents. Previous works showed that biomediated precipitation of dolomite concretions around large-sized decaying carcasses was one of the most relevant processes responsible for exceptional fossil preservation. In turn, little is known about the modes of fossilization of well-preserved small-sized vertebrates, which arc rather common in the Pisco Formation ; but mostly do not exhibit dolomite concretions. We report on a cetacean specimen, identified as belonging to the extinct short-snouted, small dolphin species Brachydelphis mazeasi (Pontoporiidae), preserved within a late Miocene sandy deposit at the site of Pampa Cone Viento. This specimen consists of a moderately disarticulated partial skeleton exhibiting well-mineralized bones; it is not enclosed within a dolomite concretion, being however delimited by an evident dark boundary in the host sediment. Scanning electron microscopy and microanalytical investigations identify Mn-oxides and apatite as early diagenetic minerals around the skeleton. We argue that a rapid burial of the specimen was pivotal for the preservation of the bones, and allowed the early establishment of anoxic processes for degradation of organic matter. Coupled with availability of P in porewater, the reducing conditions and the lowered pH allowed precipitation of Ca-phosphate while increasing Mn solubility close to the pontoporiid carcass. Mn-oxides precipitated at the redox boundary, the latter defining the outer edge of the volume of sediment affected by altered chemical conditions due to the decaying processes. The permeability of the sediment and the small size of the carcass were possible factors unfavorable to extensive sulfate reduction, thus preventing the formation of a dolomite concretion and allowing bone phosphatization. This record emphasizes the role of conditions favorable to bone mineralization in absence of an isolating carbonate concretion, in cases of high quality preservation of small-sized vertebrates observed in the Pisco Formation. The observation of patterns in the distribution of diagenetic minerals in the sediment enclosing vertebrate remains without, or with limited carbonate concretions provides insights into early taphonomic processes
The Weeks Formation Konservat-Lagerstatte and the evolutionary transition of Cambrian marine life
No full textThe Weeks Formation in Utah is the youngest (c. 499 Ma) and least studied Cambrian Lagerstatte of the western USA. It preserves a diverse, exceptionally preserved fauna that inhabited a relatively deep water environment at the offshore margin of a carbonate platform, resembling the setting of the underlying Wheeler and Marjum formations. However, the Weeks fauna differs significantly in composition from the other remarkable biotas of the Cambrian Series 3 of Utah, suggesting a significant Guzhangian faunal restructuring. This bioevent is regarded as the onset of a transitional episode in the history of life, separating the two primary diversifications of the Early Paleozoic. The Weeks fossils have been strongly affected by late diagenetic processes, but some specimens still preserve exquisite anatomical details
The paradigm shift in Antarctic ice sheet modelling
Get PDFThe Antarctic ice sheet is one of the largest potential contributors to future sea level rise. Predicting its future behaviour using physically-based ice sheet models has been a bottleneck for the past decades, but major advances are ongoing
Sea surface currents and geographic isolation shape the genetic population structure of a coral reef fish in the Indian Ocean
Get PDFIn this contribution, we determine the genetic population structure in the Skunk Clownfish (Amphiprion akallopsisos) across the Indian Ocean, and on a smaller geographic scale in the Western Indian Ocean (WIO). Highly restricted gene flow was discovered between populations on either side of the Indian Ocean using the control region as a mitochondrial marker (mtDNA). We verify this conclusion using 13 microsatellite markers and infer fine scale genetic structuring within the WIO. In total 387 samples from 21 sites were analysed using mtDNA and 13 microsatellite loci. Analysis included estimation of genetic diversity and population differentiation. A haplotype network was inferred using mtDNA. Nuclear markers were used in Bayesian clustering and a principal component analysis. Both markers confirmed strong genetic differentiation between WIO and Eastern Indian Ocean (EIO) populations, and a shallower population structure among Malagasy and East African mainland populations. Limited gene flow across the Mozambique Channel may be explained by its complex oceanography, which could cause local retention of larvae, limiting dispersal between Madagascar and the East African coast. Two other potential current-mediated barriers to larval dispersal suggested in the WIO, the split of the SEC at approximately 10°S and the convergence of the Somali Current with the East African Coast Current at approximately 3°S, were not found to form a barrier to gene flow in this species
A 3D quantitative method for analyzing bone mineral densities: a case study on skeletal deformities in the gilthead sea bream, <i>Sparus aurata</i> (Linnaeus, 1758)
Get PDFSkeletal deformities, one of the major threats for aquaculture, have been studied extensively. These include opercular malformations in gilthead sea bream (Sparus aurata), a key fish species for Mediterranean aquaculture. What is causing it and at what morphogenetic level it arises, however, is still unclear. Here we focus on bone formation, at the level of bone mineralization. Several methods have been used to study bone mineralization density (BMD), however, these are frequently limited when targeting a high-resolution, three-dimensional mapping of BMD. We used micro-computed tomography (micro-CT) data to perform such a 3D quantification of BMD levels in gilthead sea bream that showed different levels of opercular bone deformations. This approach has the advantage of not having to rely on calibration phantoms, as long as relative BMD values are needed. The results show an increased BMD in deformed opercles compared to normal ones, especially in a bilaterally-deformed specimen. Furthermore, we show that opercular deformations are not necessarily associated with similar mineralization patterns in other mineralized cranial elements, except for the otoliths. Also, mineralization seems to occur left-right independently, matching earlier observations of such an independency of the opercular phenotype as a whole. This study confirms that a quantitative characterization of BMD patterns in 3D is feasible, even in smaller specimens, and that it has several advantages over other commonly used approaches
