A piscirickettsiosis-like syndrome in cultured Nile tilapia in Latin America with Francisella spp. as the pathogenic agent

In 2004, cultured Nile tilapia Oreochromis niloticus in several Latin America farms began to succumb to a disease similar to the piscirickettsiosis-like syndrome previously reported in tilapia in Taiwan and the United States. Mortality increased during 2005; reductions in tilapia biomass ranged from 5% to 80% in individual ponds and averaged 50% overall. All ages of fish have been involved. Clinical signs include lethargy, loss of appetite, petechia, exophthalmia, and abnormal swimming behavior. Gross lesions have included splenomegaly, renomegaly, and numerous white nodules observed in the spleen, kidney, testes, heart, ovaries, and occasionally the liver. A previously unreported black granulomatous lesion was reported in up to 30% of the fillets. Histologically, granulomatous infiltrates were observed in the kidney, spleen, liver, testes, ovary, and choroid gland, and rarely in the brain and heart. A small pleomorphic bacterium was observed in Giemsa-stained blood smears and spleen imprints. The bacterium did not grow on standard microbiological media and has not been isolated in cell culture. We obtained a near-complete 16S ribosomal DNA sequence with high similarity to Francisella spp. sequences previously identified in tilapias Oreochromis spp. (Taiwan), Atlantic cod Gadus morhua (Norway), and three-line grunts Parapristipoma trilineatum (Japan).     

Assessment of ecosystem services as an opportunity for the conservation and management of native forests in Chile

This paper quantifies two important native forest ecosystem services in southern Chile: water supply and recreational fishing opportunities. We analyzed streamflow in relation to forest cover in six watersheds located in the Valdivian Coastal Range (39°50′–40°05′S), the effect of forest management on streamflow in two watersheds in the Valdivian Andes (600–650 m of elevation; 39°37′S), and fish abundance as a function of forest cover in 17 watersheds located in the Coastal Range and the Central Depression (39°50′–42°30′S). We found that the annual direct runoff coefficient (quickflow/precipitation) and total streamflow/precipitation in the dry summer season were positively correlated with native forest cover in the watershed (R² = 0.67 and 0.76; ^*P = 0.045 and 0.027, respectively) during four years of observations. Conversely, a negative correlation was found between summer runoff coefficients (total streamflow/precipitation) and cover of Eucalyptus spp. and Pinusradiata plantations (R² = 0.84; ^*P = 0.010). We estimated a mean increase of 14.1% in total summer streamflow for every 10% increase in native forest cover in the watershed. The analysis of streamflow changes between two paired watersheds dominated by native secondary Nothofagus stands, one thinned with 35% of basal area removal and a control, showed that the former had a 40% increase during summer (four years of observations). The best correlation between fish abundance and forest cover was found between trout abundance (%) and secondary native forest area in 1000 m × 60 m stream buffers (R² = 0.65, ^***P < 0.0001). We estimated a 14.6% increase in trout abundance for every 10% increase of native forest cover in these buffers. Similar approaches to quantify forest ecosystem services could be used elsewhere and provide useful information for policy and decision-making regarding forest conservation and management.     

Multilocus sequence typing (MLST) analysis of California Flavobacterium psychrophilum reveals novel genotypes and predominance of CC‐ST10 in California salmonid hatcheries

The Gram‐negative bacterium, Flavobacterium psychrophilum, is endemic to California, USA, where it is an important pathogen in salmonid aquaculture, especially in rainbow trout (Oncorhynchus mykiss). Disease outbreaks caused by F. psychrophilum in rainbow trout fingerlings can approach 90% mortality, resulting in millions of dollars of economic losses annually. The focus of this study was to investigate the genetic diversity of 49 F. psychrophilum isolates collected from disease outbreaks in 17 salmonid hatcheries in California, USA, from 2015 to 2018 using multilocus sequence typing. Results suggest California F. psychrophilum isolates are diverse, representing 11 distinct sequence types (STs), three of which were previously undescribed. Still, the majority of genotyped isolates (n = 41) belonged to a single clonal complex (CC), CC‐ST10, which is the largest CC worldwide and has been linked to disease outbreaks on several continents. Results of this study provide evidence of marked intraspecific genetic diversity of F. psychrophilum from California. The biological significance of this genetic variability is unclear but could have implications for future vaccine development and treatments. Further studies investigating the virulence, antigenic, and antimicrobial susceptibility profiles of F. psychrophilum are warranted to better understand the epizootiology of this pathogen in the Western United States.     

Assessment of soil degradation in the Canary Islands (Spain)

In the Canary Islands a number of factors, both natural and induced by human activity, act on the fragile ecosystems and agricultural land to cause increasing problems with desertification and progressive degradation of soil productivity. the results of an assessment of soil degradation in the Canary Islands, The processes, causes and impacts, are presented in this paper. Although several processes and factors contribute to soil degradation in the Canary Islands, two have been found to exert a greater qualitative influence: (a) accelerated erosion (water and aeolian); (b) salinization-sodification (natural and induced by agricultural use). Approximately 40 per cent of the Canary Islands' land is undergoing rapid erosion. the factors involved May, be grouped into: natural erosion—torrential rainfall, sparse vegetation, high soil erodibility, rugged relief; and erosion due to human activities—unsuitable management of arable soils on the steep slopes, overgrazing and deforestation. About 60 per cent of the surface of the archipelago, including areas given over to intensive agriculture, is affected by salinization.The main factors responsible are: natural—an arid climate and a regime of oceanic winds; and human activities—overexploitation of the aquifers, irrigation with water having a high salt and/or sodium content, intensive monoculture, and excessive and indiscriminate use of chemical fertilizers and other agrochemicals.     

Life cycle and in vitro sporulation dynamics of Corinectria constricta,the causal agent of Pinus radiata stem canker,in Chile

In 2008, a canker disease caused by the fungus Corinectria constricta was detected in southern Chile. The causal agent was previously identified as Neonectria fuckeliana (now Corinectria fuckeliana), which has been associated with stem cankers in Pinus radiata plantations in New Zealand since the 1990s. Many basic aspects of the life cycle of C. constricta remain unknown. The current study aimed to (a) document the periods during which C. constricta fruiting bodies are present in P. radiata plantations and associated factors; (b) determine the C. constricta life cycle in P. radiata plantations in southern Chile; and (c) evaluate, under in vitro conditions, the sporulation dynamics of ascospores. The first and second aims were carried out by evaluating affected plantations every 15 days, identifying asexual and sexual fungal structures, and recording the time periods when the structures were present. The third aim was achieved with in vitro tests in Petri dishes simulating humidity chambers. The life cycle was characterized by the presence of sporodochia from the Cylindrocarpon‐like (asexual form of C. constricta) morph during the autumn of 2012 (March–May). Subsequently, perithecia began to form on the sporodochia during April of 2012, taking approximately 3 months to mature (May–July), persisting for the rest of the year and providing inoculum to infect new trees. The development of perithecia in winter demonstrates that this is the most important period for dispersal and infection. In terms of sporulation dynamics, perithecia can release ascospores up to eight days following a wetting event; without this event, the spores are not released.     

Low‐density culture of red abalone juveniles,Haliotis rufescens Swainson 1822, recirculating aquaculture system and flow‐through system

Commercial abalone culture is carried out using flow‐through systems with a high water volume exchange in Baja California, Mexico. The objective of this work was to compare the growth rate and survival of red abalone cultured in two systems. Flow through (daily water exchange rate of 800%) and recirculating systems consisted of a 250 L fibreglass tank and constant aeration, but biofiltration in the recirculating system was provided with a 28 L (1 ft³) bubble‐washed bead filter. Water variables were measured either daily (dissolved oxygen, temperature, pH and salinity) or three times a week (total ammonia nitrogen, nitrate‐nitrogen, nitrite‐nitrogen and alkalinity). Shell length was measured every 2 weeks for 18 weeks. Only the alkalinity and pH were significantly different due to the addition of sodium bicarbonate to the recirculating system. Abalone growth rate was 26.1 ± 15.96 μm day^?1 in the recirculating systems and 22.21 ± 18.69 μm day^–1 in the flow‐through systems. The final survival was 78.74% in the recirculating systems and 71.82% in the flow‐through systems. Significant differences in the final size and survival of the abalones were found between systems (P<0.05). Therefore, recirculating aquaculture systems is a feasible alternative for juvenile red abalone culture.     

Physiological and anatomical traits associated with tolerance to long‐term partial submergence stress in the Lotus genus: responses of forage species,a model and an interspecific hybrid

Cattle production based on natural pastures is often subject to flooding periods, which affect plant performance and as a result, forage production. Although most forage legumes are not tolerant to flooding, Lotus spp. are outstanding alternatives, since species, such as L. tenuis (Lt) and L. corniculatus (LcT), have high forage quality and are adaptable to different environments. We recently obtained a L. tenuis × L. corniculatus hybrid (LtxLc) with potential new cultivar traits, although its tolerance to flooding stress has not yet been evaluated. In the present study, the performance of LtxLc, its parental diploid accessions, the model legume L. japonicus and tetraploid LcT were evaluated under 55 days of partial submergence stress and a 35‐day recovery period. Physiological, morphological and anatomical traits were analysed, showing that tolerance to partial submergence was positively associated with aerenchyma and adventitious root formation and relative growth rates. Overall, Lt and LtxLc showed the best responses under stress and during the recovery period. Nevertheless, the higher forage value of LtxLc makes it recommendable for use in environments affected by flooding. Our results could be used as breeding criteria for the generation of new cultivars tolerant to partial submergence stress.     

Presymptomatic detection of prions in blood

Prions are thought to be the proteinaceous infectious agents responsible for transmissible spongiform encephalopathies (TSEs). PrP(Sc), the main component of the infectious agent, is also the only validated surrogate marker for the disease, and its sensitive detection is critical for minimizing the spread of the disease. We detected PrP(Sc) biochemically in the blood of hamsters infected with scrapie during most of the presymptomatic phase of the disease. At early stages of the incubation period, PrP(Sc) detected in blood was likely to be from the peripheral replication of prions, whereas at the symptomatic phase, PrP(Sc) in blood was more likely to have leaked from the brain. The ability to detect prions biochemically in the blood of infected but not clinically sick animals offers a great promise for the noninvasive early diagnosis of TSEs.