100,537 research outputs found
Applications of Self-Organizing Maps for Ecomorphological Investigations through Early Ontogeny of Fish
No full textWe propose a new graphical approach to the analysis of multi-temporal morphological and ecological data concerning the life history of fish, which can typically serves models in ecomorphological investigations because they often undergo significant ontogenetic changes. These changes can be very complex and difficult to describe, so that visualization, abstraction and interpretation of the underlying relationships are often impeded. Therefore, classic ecomorphological analyses of covariation between morphology and ecology, performed by means of multivariate techniques, may result in non-exhaustive models. The Self Organizing map (SOM) is a new, effective approach for pursuing this aim. In this paper, lateral outlines of larval stages of gilthead sea bream (Sparus aurata) and dusky grouper (Epinephelus marginatus) were recorded and broken down using by means of Elliptic Fourier Analysis (EFA). Gut contents of the same specimens were also collected and analyzed. Then, shape and trophic habits data were examined by SOM, which allows both a powerful visualization of shape changes and an easy comparison with trophic habit data, via their superimposition onto the trained SOM. Thus, the SOM provides a direct visual approach for matching morphological and ecological changes during fish ontogenesis. This method could be used as a tool to extract and investigate relationships between shape and other sinecological or environmental variables, which cannot be taken into account simultaneously using conventional statistical methods
Neural Stem and progenitor cells: choosing the right Shc" in: NGF and Related Molecules in Health and Disease
No full textSeptal grafts restore cognitive abilities and amyloid precursor protein metabolism
No full textCortical cholinergic loss and amyloidogenic processing of the -amyloid precursor protein (APP), may functionally interact in Alzheimer’s disease. However, it is still unknown whether biological restoration of regulatory cholinergic inputs affects APP metabolism in vivo.
Rats immunolesioned with 192 IgG-saporin exhibited severe acquisition deficits in place navigation that were paralleled by a dramatic loss of terminal cholinergic innervation and by marked changes in the regional expression of APP-like immunoreactivity. Moreover, in these animals, we observed a drastic reduction of soluble APP (sAPP) and a concomitant increase of the unsoluble, membrane-bound fraction (mAPP).
Notably, at about 6 months post-surgery, lesioned animals implanted with reinnervating cholinergic-rich septal tissue grafts exhibited fairly normal spatial navigation abilities, as well as cortical and hippocampal APP levels that were restored up to normal or near-normal values. APP levels correlated significantly with lesion- or graft-induced changes in cholinergic innervation density, and both these measures correlated with performance in the spatial navigation task.
Thus, integrity of ascending cholinergic inputs may be required to prevent amyloidogenic processing of APP in vivo and to modulate cognitive performance
Neural Stem Cells: A Pharmacological Tool For Brain Diseases
No full textStem cells are believed to provide a tool by which new cells and tissues can be made and by which damaged ones can be replaced or repaired. Over the past few years, the existence of a subset of stem cells has been documented in the fetal brain, therefore named neural stem cells (NSCs). To this regard, the more recent demonstration that similar cells are present in the adult mammalian brain and retain the capability to produce new neurons, has undermined the dogma that neurons are only generated during the fetal life and has stimulated investigations into the regulation and role of adult neurogenesis. Here, we will review the recent advancements on the biology of brain stem cells and discuss the mechanisms and drugs regulating adult neurogenesis, aiming at better estimating the possible future applications of NSCs for brain repair
New insights in interpolating fishing tracks from VMS data for different métiers
No full textThe Vessel Monitoring by satellite System (VMS) is a powerful tool in fishery management, since it allows for high resolution analyses of fishing activity and quantitative evaluations of fishing effort at both spatial and temporal scale. Given that the main VMS limit is represented by the temporal resolution (generally 2 h) of signals, a series of approach has been developed to interpolate vessels positions. The newest and most powerful method in this framework is based on cubic Hermite splines (cHs), which have been efficiently tested against the conventional straight line interpolation over a dataset representing fishing activity by beam trawl. However, this method has never been applied on other different gears and/or metiers. Here we propose a new approach (CRm), which is a modification of the Catmull-Rom algorithm (CR). This new method takes into account for the different aspects involved in vessel navigation, such as the combined actions of human control and drift by sea current and wind (if present). The drift component is not observed, but is estimated within the method, using the VMS data. This method has been developed in order to model the behaviour of vessels that operate using different gear types. The CRm method was compared to the cHs method, using three reference datasets (each containing VMS signals at intervals of 20 min) corresponding to three different metiers largely used in Mediterranean fisheries: bottom otter trawl for demersal species (OTB), trammel nets for demersal species (GTR), and purse seine for small pelagic fish (PS), which differ each other for the dynamic aspects connected to the use of fishing gears, and represent an archetype of the three groups actually used to classify fishing gears (namely towed, active and passive). The comparison was carried out both analyzing the error affecting interpolation of single tracks and converting the interpolated tracks into gridded data to be used for computation of ecological indicators of fishing pressure. All the results coherently evidences that the CRm algorithm performs better in interpolating trawl tracks (OTB) and that, moreover, it is able to capture the complex behaviour characterizing the trajectories of vessels performing the other two inspected m tiers (GTR and PS). Finally, CRm allows a better estimation of fishing effort, as measured by ecological indicators. These findings support the idea that the conceptual formulation of CRm method is appropriate to model whatever fishing tracks presently generated by fishery vessels and could be efficiently applied in order to obtain better estimation of fishing pressure and, if sensitivity data are available, of fishing impacts. (C) 2010 Elsevier B.V. All rights reserved
Correspondence between shape and feeding habit changes throughout ontogeny of gilthead sea bream Sparus aurata L., 1758
No full textThe shape development through ontogeny of the gilthead sea bream Sparus aurata was studied by means of geometric morphometry and elliptic Fourier analysis. In parallel, observations are reported on the feeding habits of the same specimens until the end of the larval stage. Data for later stages were obtained from the literature. Sparus aurata underwent ontogenetic shifts in diet from zooplankton, selected by larvae, to mysids, errant polychaete, amphipods and isopods for juveniles, and finally to hard prey (decapods, gastropods and bivalves) in adults. The aims were: (1) to provide a complete description of shape development, from hatching to the adult stage, (2) to identify distinguishable morphological stages during ontogenesis, (3) to search for correspondence between morphological devel- opment and diet shifts, and (4) to examine the functional effect connecting shape changes to diet shifts and habitat selection. The growth trajectory obtained reflected a saturating curve made up by different sections. Each section corresponded to a developmental shape stage characterized by different allometric trends of different body regions. Indeed, these shape stages matched those based on widespread features of development. Furthermore, the size- defined limits of the shape stages closely match the feeding shifts in the development of dietary behaviour of gilthead sea bream. The different constraints underpinning this pattern of covariation are discussed by showing that the growth profile of early stages is mainly determined by organogenesis of important apparati, whereas that of later stages seems optimized to improve feeding on hard prey in complex microhabitat and swimming abilities, and to reduce predation risk
Spatial indicators of fishing pressure: preliminary analyses and possible developments
No full textEcological indicators of fishing pressure in space are an important part of the Data Collection Framework (DCF) established by the European Commission in its attempt to apply an ecosystem approach to fisheries. These indicators are devised to use the information provided by the Vessel Monitoring System, a mandatory tool for EU fishing vessels which allows to record fishing activity in space and time. This study reports and analyzes trends of DCF fishing pressure indicators in the years 2007--2010 for the Italian trawlers in seven Mediterranean geographic sub-areas and the related trends of landing per unit effort. In addition, new versions of these indicators are developed and their performances compared to the DCF ones by a simulation approach. The rationale for these new version of indicators is based on: (i) the development of a formal definition of ``fishing ground'', allowing for innovative statistical analyses of fishing patterns in space and time; (ii) the revision of issues affecting DCF indicators. Results provide: (i) the first extensive documentation of space use by fisheries through time; (ii) evidences of subtle yet significant changes in fishing pattern which, in agreement to other studies, indirectly support a decline of fisheries resources in the Mediterranean; (iii) improved versions of DCF fishing pressure indicators, obtained via the identification and analysis of fishing grounds and the assessment of aggregation by Gini's G index. The latter point could mark an important progress in order to overcome some critical weakness evidenced by DCF indicators. Moreover, the statistical identification and analysis of fishing grounds could represent a valuable insight in quantitative investigations of fisheries impacts and effects, even beyond indicators computation
Neural stem and progenitor cells: choosing the right Shc
No full textNeural stem cell (NSCs) are self-renewing, multipotent cells able to generate neurons, astrocytes and oligodendrocytes. Since their identification, these properties have made NSCs an attractive subject for therapeutic applications to the damaged brain. In this context, understanding the mechanisms and the molecules regulating their biological properties is important and it is focused to gain control over their proliferative and differentiative potential. Here we will discuss values and unsolved aspects of the system and the employment of potentially key molecular targets for proper control of NSCs fate
Relationship between body shape and trophic niche segregation in two closely related sympatric fishes
No full textDiet, shape and their covariation were analysed in juvenile flounder Platichthys flesus and plaice Pleuronectes platessa specimens from a tidal inshore habitat (Dublin Bay) in the Irish Sea. Stomach content analysis revealed differences in the diet, suggesting a substantial degree of resource partitioning between the species. Geometric morphometrics detected significant and discriminating differences in body shape, particularly in the head region. Most interestingly, a high degree of correlation was detected between diet and shape. The ontogenetic and ecological implications of the diet and shape covariation pattern were discussed, suggesting that morphological differences, in particular in the head region, may represent the functional platform which allows for the existence of ecologically significant differences in prey search and capture between P. platessa and P. flesus
Feeding preferences of the dusky grouper (Epinephelus marginatus, Lowe 1834) larvae reared in semi-intensive conditions: A contribution addressing the domestication of this species
No full textDespite research efforts addressing artificial propagation, dusky grouper aquaculture still relies on experimental trials owing to the low survival rates of larvae and juveniles, thus rendering mass rearing difficult to attain. Although some authors suggested that the preys offered to the early larval stages represent the major problem facing the rearing of all grouper species, very little information is available in literature on larval development and the behaviour of dusky grouper. The objective of this study was to investigate the trophic preferences of larval stages of the dusky grouper by rearing using a semi-intensive technology. Larvae were reared in pilot scale mesocosms (60 m3) from 3 to 35 days post hatching. The rearing system was supplied with wild zooplankton collected in a natural coastal lagoon in order to augment the chances of satisfying the larvae's feeding requirements; the feeding preferences were analyzed during ontogenesis. The relationship between mouth gape and dimensions of preys, considered as 3-D objects, was investigated to identify possible critical factor.
The results of this study suggested a sequence of suitable food items from the beginning of exogenous feeding until day 35 post hatching. In particular, dusky grouper larvae actively select copepod nauplii in the size range between 2 and 12 mm in TL, and Artemia salina nauplii for TL larger than 9 mm. The rearing approach applied seemed to be promising. Indeed, while previous rearing trials of dusky grouper failed within ten days or finished at 30 days post hatching with a lower percent of survivors, this paper reports the best survival rate reported for this species (10%±7.0 survivors at 35 days post hatching). Finally, mouth width was observed to be the limiting factor in the selection of prey, while the smallest prey size plays a critical role in determining ingestion. Our results contribute to clarifying some aspects of the larval ecology of this species, furnishing some suggestions for its cultivation
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