Comparative Study Highlights the Potential of Spectral Deconvolution for Fucoxanthin Screening in Live Phaeodactylum tricornutum Cultures

Microalgal biotechnology shows considerable promise as a sustainable contributor to a broad range of industrial avenues. The field is however limited by processing methods that have commonly hindered the progress of high throughput screening, and consequently development of improved microalgal strains. We tested various microplate reader and flow cytometer methods for monitoring the commercially relevant pigment fucoxanthin in the marine diatom Phaeodactylum tricornutum. Based on accuracy and flexibility, we chose one described previously to adapt to live culture samples using a microplate reader and achieved a high correlation to HPLC (R² = 0.849), effectively removing the need for solvent extraction. This was achieved by using new absorbance spectra inputs, reducing the detectable pigment library and changing pathlength values for the spectral deconvolution method in microplate reader format. Adaptation to 384-well microplates and removal of the need to equalize cultures by density further increased the screening rate. This work is of primary interest to projects requiring detection of biological pigments, and could theoretically be extended to other organisms and pigments of interest, improving the viability of microalgae biotechnology as a contributor to sustainable industry.     

Soil properties, grassland management, and landscape diversity drive the assembly of earthworm communities in temperate grasslands

Earthworms are widespread soil organisms that contribute to a wide range of ecosystem services. As such, it is important to improve our knowledge, still scanty, of the factors that drive the assembly of earthworm communities. The aim of the present study was to conjointly evaluate the effects on the assembly of earthworm communities of i) soil properties (texture, organic matter content, and pH), ii) grassland management (grassland age, livestock unit, and type of fertilization), iii) landscape diversity (richness, diversity of surrounding habitats, and grassland plant diversity), and iv) presence of hedgerows. The study was conducted in temperate grasslands of Brittany, France. Earthworms were sampled in 24 grasslands and, in three of these grasslands, they were sampled near a hedgerow or near a ditch (control without a hedgerow). Soil properties explained the larger portion of the variation in the earthworm community parameters compared to grassland management or landscape diversity. The increase in soil organic matter content and pH were the most favorable factors for earthworm abundance and biomass, in particular for endogeic species. Regarding grassland management, the increase in the livestock unit was the most damaging factor for earthworm communities, in particular for the anecic earthworm biomass and endogeic species richness. Surprisingly, landscape diversity negatively affected the total earthworm abundance and epigeic earthworm biomass, but it was related to an increase in the epi-anecic species. At a finer scale, we also demonstrated that the presence of hedgerows surrounding grasslands enhanced earthworm species richness, especially within the epigeic and anecic ecological categories. This study highlights that the earthworm ecological categories respond specifically to environmental filters; further studies need to be conducted to elucidate the factors that drive the assembly of earthworm communities at this ecological category level. We recommend that policymakers should act on landscape management to favor earthworm diversity in order to improve the ecosystem services they drive.     

Interspecific competition between restocked 0+ salmon parr (Salmo salar) and native fish species in a large European river

Atlantic salmon populations have experienced strong declines in most large European rivers. In the Loire Basin, France, a major restocking effort has been carried out on the Allier River to reduce the wild population decline. This study aimed at investigating the trophic insertion of hatchery‐reared salmon parr and whether they compete for resources with native fish species. For this purpose, two riffles located in the upstream and downstream parts of the restocked area have been surveyed monthly following the initial 0+ salmon fry release. 0+ parr densities remained high upstream, with autumnal values greater than those recommended to maximise smolt production. In contrast, downstream densities declined to weak values despite a faster increase in size, probably mainly due to summer temperatures rising above the discomfort threshold. By analysing the vulnerability to predation of ingested invertebrate prey, we highlighted the role of habitat constraints in driving most of the different fish species to a likely opportunistic utilisation of available food resources. As a result, species such as stone loaches and barbel juveniles exhibited narrow trophic niches and high overlaps with 0+ parr. Nonetheless, both abundant prey resources and spatial or temporal habitat segregation have limited interspecific competition, enabling competitive coexistence of sympatric species, except for barbel juveniles in certain circumstances. Therefore, our findings suggest that future restocking programmes should carefully consider the thermal and hydraulic conditions regarding further smolt production as well as their general trophic context, according to the potential inconvenience of restocked salmon fry arrival relative to native species.     

Stop me if you can: quantification of the effect of interfaces between plots on the dispersal of Cosmopolites sordidus

BACKGROUND

Cosmopolites sordidus is one of the most damaging pests of banana worldwide. To date, most studies have addressed the control of this pest at the plot level, without considering the landscape scale, whereas between plots dispersion could be important. The aim of this study was to investigate the ability of C. sordidus to cross contrasted field interfaces. The 10 following interfaces were investigated: forests, hedgerows, field tracks, grassy areas, finely and coarsely tilled soil zones, ditches with and without water, vegetable gardening zones, and pheromone trap lines. Individually marked weevils were released on one side of the interface and recovered daily on the other side, allowing the estimation of the velocity and the crossing success of C. sordidus for each interface.

RESULTS

Highest permeabilities (with a crossing success above 70%) were obtained for vegetable gardening zones, finely tilled soil zones, forests, and coarsely tilled soil zones. Intermediate permeabilities were measured for hedgerows, field tracks, grassy areas, and ditches without water. Only the line of pheromone traps and submerged ditches had a strong barrier effect on C. sordidus, with a crossing success below 12%. Wind strength, percentage of sky, and vegetation height were negatively correlated to the C. sordidus crossing success.

CONCLUSION

Overall, our results showed that only ditches with water and lines of pheromone traps were efficient in stopping the dispersal of C. sordidus. The next step will be to conduct research to incorporate the use of these two interfaces at farm and landscape scale into integrated pest management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Modeling effects of weather and source-sink relationships on mango fruit growth

We modeled the effects of weather and source-sink factors on mango fruit growth. The peach fruit-growth model "Cashoo" was adapted for mango fruit. The model accounts for the main processes of fruit growth, i.e., leaf photosynthesis, fruit demand, fruit respiration, and storage and mobilization of leaf and stem reserves. Simulations for three successive years and for various leaf-to-fruit ratio treatments showed good agreement with observed fruit growth data. Simulations of fruit growth under different climatic conditions, especially with contrasting temperature and radiation, and for different values of initial fruit dry mass and leaf-to-fruit ratio, showed that variations in fruit growth among years can be partly explained by climatic variations through their effects on leaf photosynthesis, fruit demand and fruit growth rate. However, climatic changes contribute substantially less to observed variability in fruit growth than to initial fruit dry mass and leaf-to-fruit ratio.     

New insight into the genetic structure of the Allolobophora chlorotica aggregate in Europe using microsatellite and mitochondrial data

The taxonomic status of Allolobophora chlorotica is still the subject of considerable discussion. After the recent experimental demonstration that the two regularly observed colour morphs (pink and green) were not fully interfertile and likely represent two distinct species, molecular analyses revealed a more complex picture with the occurrence of five mitochondrial lineages (named L1 to L5) in A. chlorotica, two within the green morph and three within the pink morph. Although nuclear markers (AFLPs) confirmed that the pink morph might consist of three different taxa, AFLPs data suggested that the green morph may be a single taxon. In order to further characterize the population genetic structure within A. chlorotica in addition to test for reproductive isolation between lineages, eight polymorphic microsatellite loci were developed using a microsatellite-enriched genomic library from an individual belonging to lineage L2. The number of alleles per locus varied from 9 to 29 in a set of individuals belonging to L2. Considerable sub-structure was observed within L2 populations suggesting a low dispersal capability in this species and a distribution of the individuals in patches that could function as panmictic units. These markers were transferable to the other lineages but only five loci could be amplified consistently in four of the lineages (L1, L2, L3 and L4). Microsatellite data confirmed that the green morph represents a single taxon. Although the integrity of the three previously documented lineages within the pink morph was also generally supported by the data, microsatellites provided evidence for hybridization between lineages and between morphs in the field. Moreover, mitochondrial data revealed the existence of two additional mitochondrial lineages within the pink morph. The taxonomic status of the pink morph remains thus unclear, requiring a thorough and comprehensive study.     

Investigation into the possible natural occurence of semicarbazide in Macrobrachium rosenbergii prawns

In the past year there has been an increased incidence in Belgium of cases of positive semicarbazide (SEM) tests in imported freshwater Macrobrachium rosenbergii prawns, seemingly indicating the possible abuse of nitrofurazone, a banned antimicrobial agent. This was in contrast to all other European countries where no significant increase in SEM-positive samples was detected. A possible explanation for this discrepancy between Belgium and the other European Union member states could be the fact that only in Belgium were whole prawns (meat + shell) analyzed for the presence of tissue-bound metabolites of nitrofurans, whereas in the other countries only the edible part (meat) of these prawns was analyzed. To investigate the possible natural occurrence of SEM in freshwater prawns, an animal trial was set up. In this experiment two groups of 10 juvenile M. rosenbergii, previously raised under standardized laboratory conditions, were stocked into two separate aquaria, a control group under reference conditions (no addition of nitrofurazone) and a group exposed to a daily dose of 50 mg of nitrofurazone L(-1) of culture water. Results of this animal trial proved that SEM naturally occurs in M. rosenbergii prawns but that at the current minimum required performance limit (MRPL) no tissue-bound SEM can be found in the meat of nontreated animals. In addition to this animal trial, commercial samples of other crustacean species, the shell and meat of which were analyzed separately, were also analyzed for the presence of SEM.     

One stage functional end-to-end stapled intestinal anastomosis and resection performed by nonexpert surgeons for the treatment of small intestinal obstruction in 30 dogs

Objectives: To describe stapled 1‐stage functional end‐to‐end intestinal anastomosis for treatment of small intestinal obstruction in dogs and evaluate outcome when the technique is performed by nonexpert surgeons after limited training in the technique. Study Design: Case series. Animals: Dogs (n=30) with intestinal lesions requiring an enterectomy. Methods: Stapled 1‐stage functional end‐to‐end anastomosis and resection using a GIA‐60 and a TA‐55 stapling devices were performed under supervision of senior residents and faculty surgeons by junior surgeons previously trained in the technique on pigs. Procedure duration and technical problems were recorded. Short‐term results were collected during hospitalization and at suture removal. Long‐term outcome was established by clinical and ultrasonographic examinations at least 2 months after surgery and from written questionnaires, completed by owners. Results: Mean±SD procedure duration was 15±12 minutes. Postoperative recovery was uneventful in 25 dogs. One dog had anastomotic leakage, 1 had a localized abscess at the transverse staple line, and 3 dogs developed an incisional abdominal wall abscess. No long‐term complications occurred (follow‐up, 2–32 months). Conclusion: Stapled 1‐stage functional end‐to‐end anastomosis and resection is a fast and safe procedure in the hand of nonexpert but trained surgeons.     

Craniomandibular osteopathy with a unique neurological manifestation in a young Akita

This report describes a 4 mo old intact male Akita that presented for evaluation of a life-long history of facial swelling and failure to thrive. Physical examination revealed an enlarged cranium with prominent bony swellings on the maxillary bone, excessive laxity and crepitus involving multiple joints, and proprioceptive deficits. Radiographs demonstrated multiple osseous abnormalities including endosteal thickening of the femurs and ilium. Necropsy revealed gross compression of the cerebellum and brainstem. Physical exam findings, radiographic abnormalities, and histopathology of multiple bony lesions were all consistent with craniomandibular osteopathy. In this unique case of craniomandibular osteopathy, the dog was affected with severe bony proliferations leading to generalized hyperostotic lesions and brainstem compression resulting in neurologic deficits.     

Soil microbial biomass as affected by groundcover management in a Fraser fir (Abies fraseri [Pursh] Poir) plantation after 1?year

We investigated soil microbial biomass response to incorporating a non-leguminous [perennial ryegrass (Lolium perenne)] and two leguminous [Dutch white clover (Trifolium repens) and alfalfa (Medicago sativa)] cover crops into a newly established Fraser fir (Abies fraseri) plantation. Groundcover treatments consisted of growing each cover crop in the interspaces of the plantation, mowing the aboveground biomass every 3?weeks, and leaving the plant residues on the ground to decompose. Conventionally managed plots were used as a control. Soil total C, total N, and microbial biomass carbon (SMB-C) and nitrogen (SMB-N) were assessed at the 0–15-, 15–30-, and 30–35-cm soil depths. Soil total C was unaffected by groundcovers at any depths, whereas soil total N was significantly (P?=?0.031) higher in the cover crop treatments than in the conventional system at the top soil layer. Groundcovers increased SMB-C and SMB-N by 20–50% and 35–80%, respectively, in the top soil layer relative to the control. These results suggest that groundcovers could potentially improve soil fertility and be a good strategy for sustainable fir tree production.