Model‐based assessment of local‐scale fish larval connectivity in a network of marine protected areas

We assessed by numerical modeling the coastal fish larval dispersion along the southern coast of Mallorca (Balearic Islands, NW Mediterranean) with the objective of determining the factors that contribute to successful recruitment. We assumed that fish larvae dispersal is mainly regulated by physical transport. Currents are mainly wind driven in this area; therefore, changes in wind forcing have a first‐order impact on larval transport. The synoptic wind patterns were systematically analyzed based on self‐organizing map analysis. The wind fields were clustered using a neural network pattern recognition approach into two modes, producing opposite along‐shelf flow. The seasonal changes between spring and summer in the dominance of either mode modulate the along‐shelf circulation, producing flow shifts under some circumstances. This variability in the wind regime was consistent throughout the 10 years analyzed (2000–2009). Using the Princeton Ocean Model (POM) and a particle‐tracking algorithm, we analyzed the effect of wind‐forced currents in the connectivity among near‐shore habitats. We show that, at the spatial scale considered, the coastal morphology and stochastic wind forcing favor local recruitment (mean of 30% self‐recruitment). Maximum transport distances of 20–30 km were typically associated with particles left to drift for 21 days. The implications for the performance of the four marine protected areas near SW Mallorca Island are discussed. Our results suggest that, although wind episodes determine the fate of short‐time spawning events, on a seasonal basis, regular larval supply to coastal zones is ensured by wind stochasticity.     

Demography of Digitaria sanguinalis: Effect of the emergence time on survival,reproduction, and biomass

Knowledge of weed population dynamics is crucial for designing effective weed management practises. A field experiment was carried out at Torre Marimon (near Barcelona, north‐eastern Spain) in 2006 and 2007 in order to study the effects of the seedling emergence time on Digitaria sanguinalis fitness. Three and four cohorts were monitored in 2006 and 2007, respectively. In 2007, the seedling density was fourfold greater than in 2006. At the end of the growing season, no statistically significant differences in survival were detected among the cohorts in 2006 (the mean survival rate was 88%); in contrast, in 2007, individual survival varied depending on the cohort, ranging from 25–88%. The reproductive traits and seed production were significantly influenced by the emergence time. In the cohorts that emerged very close in time, the individuals of the first cohort on average had more than threefold the amount of seed production than those of the last cohort. However, not all the surviving individuals were able to reproduce because they were infected by the smut, Ustilago syntherismae.     

Experimental Study of Bone Lengthening in Dogs by Means of Backscattered Scanning Electron Microscopy

Objective— To describe the morphology of calcified tissues involved in distraction osteogenesis (DO) by means of backscattered scanning electron microscopy (BS-SEM).
Study Design— Experimental study.
Animals— Adult female Beagle dogs (n=12).
Methods— Nonsimultaneous and bilateral transverse mid-diaphyseal osteotomies performed in tibiae were stabilized and distracted by a Type Ia external skeletal fixation device. After a latency period of 5 days, distraction was applied at a rate of 0.5 mm every 12 hours for 10 days. Then, the external fixator was maintained in a static mode during the consolidation period until bone healing or euthanasia at 1, 2, 3, 4, 6, 8, 10, 12, 14, and 18 weeks after operations, whichever came first. Distracted regions were isolated and their structure was examined by BS-SEM.
Results— Calcified chondroid tissue was prominent during distraction and calcified cartilaginous tissue during consolidation; both tissues were successively replaced by woven, lamellar, and osteonal bone.
Conclusions— In osteotomized tibia, chondroid tissue is the main component of the mineralization front during distraction, calcified cartilaginous tissue during consolidation, and then both tissues are replaced by woven, lamellar, and osteonal bone. The ossification mechanism of distraction callus is transchondroidal.
Clinical Relevance— BS-SEM is an effective technique for studying progression of bone healing during DO. The presence of chondroid tissue during DO explains why callus mineralization occurs more rapidly during distraction than during static stabilization.