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Palmae --- palms --- phylogeny --- morphometrics --- neotropics

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At a time when a sixth mass extinction is about to hit our planet, protection and conservation strategies are the best chances of survival of some wildlife populations. But for those strategies to be effective, the use of reliable monitoring techniques is essential to assess the distribution, dynamic and status of the targeted species. Considering the cost of direct observations and that of invasive high-tech tools, such as camera traps and GPS, collars can be, the use of tracks is a low-cost non-invasive alternative to study elusive species such as carnivores. 
In the present study, we evaluate the possibility of identifying the anteroposterior (front or hind) and mediolateral (right or left) position of spotted hyena tracks from their digital models created from field photography. Several combinations of data recording and feature extraction methods were tested so that we could compare the accuracy of prediction of their identification algorithm and determine which combination is the most reliable.
Track sampling, which consisted of photographing encountered tracks, took place in Hluhluwe-iMfolozi Park, in South Africa. 2D and 3D models of 80 tracks (20 from each position) were constructed using ImageJ and Photoscan software respectively. Landmarks were digitized on the models so that different types of measurements could be extracted by conducting either traditional or geometric morphometrics. Using extracted morphological features, Linear Discriminant Analyses (LDA) generated identification algorithms for each combination of methods. In total, the algorithms of 31 different scenarios were compared, each of which involved (i) a type of model (2D or 3D), (ii) a feature extraction method (traditional or geometric morphometrics), (iii) the types of landmarks used to characterize the form of the models (fixed, fixed and curve-sliders, or fixed and curve- and surface-sliders), (iv) a type of object on which statistical analyses were conducted (independent pads or entire track) , and (v) a type of variables taken into account by the algorithms (shape, size, or both).
Nine of the thirty-one scenarios were able to provide algorithms with accuracies of prediction > 95%. It appeared that the relative position of the pads within a track (i.e. the information provided by the “entire track” objects) as well as their sizes are two pieces of information that are essential for the position identification of spotted hyena track. However, before being able to establish which type of model and which type of landmarks provide the most accurate algorithm, the manipulator bias of each method should be quantified and used as a second evaluation criteria. The track modelling process should also be made more effective both in term of time and manipulator bias.

tracks --- digital 2D model --- digital 3D model --- traditional morphometrics --- geometric morphometrics --- position identification of tracks --- ecological monitoring --- spotted hyenas --- Crocuta crocuta --- Sciences du vivant > Sciences de l'environnement & écologie

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Phenotypic variation within populations are essential for biological evolution. Indeed, phenotypic variation can serve as the raw products upon which natural selection acts. Accordingly, we might question if the level of morphological variation (i.e.disparity) might vary over the ontogeny of one species. Here, I test the hypothetical variation of body shape disparity level between post-larval and adult stages in coral reef fishes. Landmark-based geometric morphometrics methods were used to quantify body shapevariation during ontogeny for four species from Moorea Island (French Polynesia) : the surgeonfishes Acanthurus triostegus and Ctenochaetus striatus, the damselfish Chromis viridis, and the cardinalfish Pristiapogon exostigma. First, post-larvae and adults significantly differ in their body shape, and these variations were discussed in a ecomorphological context. Except C.viridis, all the species showed a higher level of morphological disparity at adult stage than at larval stage. This could be explained by a hyper-specialization of C.viridis in the adult stage for habitat use while the other species can use more habitats in the adult stage than in the post-larval stage.

Geometric morphometrics, shape disparity, body shape variation, habitat change, ontogeny, reef fish,, population recruitment. --- Sciences du vivant > Sciences aquatiques & océanologie

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The Phocidae (true seals) is morphologically the most diverse family of the semi-aquatic clade Pinnipedia, extant phocids having a size range from slightly over one meter (genus Pusa) to over six meters (Mirounga leonina, the southern elephant seal). In addition, some phocids have a marked sexual dimorphism. Historically, long bones and primarily the humerus and the femur, have been considered to be diagnostic for phocid identification. As such, humeri and femora have often been used as type specimens for extinct phocid taxa. In total, over twenty extinct taxa of seals are represented by isolated humeri or isolated femora holotypes, whose state of preservation varies largely. Consequently, morphological phylogeny analyses have relied heavily on humeri and femora. However, recent preliminary studies start to question whether the variations in the morphological features of long bones are truly diagnostic; as a result, can isolated long bones be used as type specimens for species identification? Or is interspecific morphological variation obscured by intraspecific variation?

Whereas the limited number of previous studies either used few, simple measurements and/or 2D data of small datasets, a large and comprehensive study capturing intraspecific and interspecific morphological variation in three dimensions has been lacking. Thus, this study aims to quantitatively analyse the importance of morphological variations of long bones on phocid’s systematics, using 3D morphometry. To do so, a 3D Procrustes morphometric analysis followed by a Principal Component Analysis (PCA) and a Linear Discriminant Function Analysis (LDFA) has been performed on 94 humeri and 75 femora 3D models sampling respectively from 20 and 16 phocid taxa. In all, this biological sample includes 25 taxa from 22 phocid genera. To capture the 3D morphology of the long bones, 17 fixed landmarks and 25 sliding landmarks (134 semi landmarks) have been selected on the humeri as well as 14 fixed landmarks and 25 sliding landmarks (106 semi landmarks) for the femora. The resulting PCAs’ morphospaces and LDFAs seem to sort rather well at the subfamily (Phocinae and Monachinae) level for both humeri and femora. However, while some species are isolated in the morphospaces, peculiarly for humerus and the monachine subfamily, the LDFAs show poor abilities to sort the species, the best having a 60.7% success rate. Thus, the morphological variation of long bones in phocids suggests that humeri and femora might be diagnostic enough only to differentiate between subfamilies and maybe some genera. As such, isolated long bones perhaps should not be used as type specimens based only on their morphology. However, the fact that some genera can still be separated with PCAs indicates that the existing fossil record of Phocidae with isolated long bones as type specimens cannot be disregarded altogether and special care is needed when reassessing these records on a species-by-species base. Phocidae est la famille la plus diversifiée morphologiquement du clade semi-aquatique Pinnipedia, les phocidés actuels pouvant mesurer d’à peine plus d’un mètre (genus Pusa) à plus de six mètres de long (Mirounga leonina, l’éléphant de mer du sud). De plus, certains phocidés montrent un dimorphisme sexuel très marqué. Historiquement, les os longs, principalement l’humérus et le fémur, sont considérés diagnostiques quant à l’identification des phocidés. Ainsi, l’humérus et le fémur ont souvent été utilisés comme holotypes pour les taxons fossiles. En tout, plus d’une vingtaine de taxons fossiles ont été basés sur des humérus isolés ou des fémurs isolés, dont l’état de conservation est très variable. En conséquence, les analyses de phylogénie morphologiques se sont basés très largement sur ces fémurs et humérus isolés. Cependant, des études préliminaires récentes commencent à questionner si les variations de caractères morphologiques des os longs sont vraiment diagnostiques ; en conséquence, est-ce que les os longs peuvent être utilisés comme holotypes pour l’identification d’espèces? Ou est-ce que les variations morphologiques interspécifiques sont masquées par celles intraspécifiques? Malgré cela, actuellement, seules peu d’études publiées se concentrent sur une évaluation quantitative de la morphologie des os longs intra- et interspécifique.

Alors que ces rares études utilisent soit un nombre limité de mesures simples et/ou des données 2Ds sur des petits échantillons, une étude vaste et complète montrant les variations morphologiques intraspécifiques et interspécifiques en trois dimensions fait défaut. Ainsi, cette étude vise à analyser quantitativement l’importance des variations morphologiques des os longs sur le classement systématique des phocidés, en utilisant la morphométrie 3D. Pour ce faire, une analyse morphométrique 3D de Procrustes suivi par une Analyse de Composante Principale (ACP) et une Analyse Linéaire à Fonction Discriminante (ALFD) ont été réalisées sur respectivement 94 et 75 modèles 3Ds d’humérus et de fémurs provenant respectivement de 20 et 16 taxons de phocidés. En tout, cet échantillon biologique comprend 25 taxons provenant de 22 genres de phocidés. Afin de capturer la morphologie 3D de ces os longs, 17 landmarks fixes et 25 landmarks glissants (134 semis-landmarks) ont été marqués sur les humérus ainsi que 14 landmarks fixes et 25 landmarks glissants (106 semis-landmarks) sur les fémurs. Les morphoespaces résultant des ACPs et les ALDFs semblent trier les os longs au niveau des sous-familles (Phocinae et Monachinae) assez efficacement. Cependant, bien que certaines espèces soient isolées dans les morphoespaces, particulièrement la sous-famille des monachines dans celui de l’humérus, les ALDFs n’obtiennent qu’un succès mitigé pour trier par espèces, le meilleur taux de réussite étant de 60,7%. Ainsi, l’étude des variations morphologiques des os longs chez les phocidés suggère que la morphologie des humérus et fémurs des phocidés est seulement diagnostique pour différencier les sous-familles et certains genres. Par conséquent, les os longs isolés ne devraient peut-être pas être utilisés comme holotypes. Par contre, le fait que certains genres ont pu être isolés par les ACPs indique que l’enregistrement fossile actuel de phocidés avec des os longs isolés comme holotypes ne peut pas être complètement ignoré et une attention particulière doit être apportée lors d’une réévaluation espèce par espèce de cet enregistrement.

femur --- humerus --- geometric morphometrics --- taxonomy --- intraspecific --- fémur --- humérus --- morphométriques géométrique --- taxonomie --- intraspécifique --- Physique, chimie, mathématiques & sciences de la terre > Sciences de la terre & géographie physique --- Sciences du vivant > Multidisciplinaire, généralités & autres

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Spermatogenesis requires radical restructuring of germline chromatin at multiple stages, involving coordinated waves of DNA methylation/demethylation, histone modification, and the replacement and removal that occurs before, during, and after meiosis. This Special Issue will draw together papers that address all aspects of chromatin organization and dynamics in the male germ line, in humans, and in model organisms. In particular, we will invite authors to discuss novel methods for studying germline chromatin structure, the interplay between chromatin structure and susceptibility to DNA damage and mutation, chromatin modifications associated with epigenetic inheritance in the early embryo, and the impact this work has for understanding natural fertility and improving assisted reproduction techniques.

mouse sperm chromatin --- chromosome organization --- nuclear-3D-parameters --- spermiogenesis --- chromatin remodeling --- DNA double-strand breaks --- genetic instability --- mutations --- sperm DNA damage --- DNA fragmentation --- infertility --- assisted reproduction --- miscarriage --- implantation --- nuclear organization --- sperm --- morphometrics --- chromosome painting --- nucleoli --- NOR --- chromosome associations --- meiotic prophase --- spermatocytes --- Mus m. domesticus --- Robertsonian chromosomes --- chromosome translocation --- Y chromosome --- testis --- spermatogenesis --- SLY --- mouse --- oxidative stress --- reactive oxygen species --- chromatin --- DNA oxidation --- male infertility --- spermatozoa --- chromosomes --- chromosome territories --- centromeres --- male germ cells --- telomeres --- reproductive aging --- nuclear organisation --- epigenetic inheritance --- histone retention --- in vitro fertilisation