Survival and growth of geoduck clam larvae (Panopea generosa) in flow‐through culture tanks under laboratory conditions

The geoduck clam, Panopea generosa, is a species from the west coast of Baja California, Mexico, and the optimization of seed production systems is still a limiting factor for its aquaculture. In this study, a flow‐through culture system was designed and tested in P. generosa larvae. Survival and growth was compared in triplicate 45‐L fiberglass tanks using three larval densities (5, 10 and 15 larvae/ml). A head tank kept constant the water inflow, with a daily renewal rate of 1.8× tank volume. The food (Isochrysis spp.) was dosed according to the ingestion rate of larvae and the dilution rate. Survival decreased linearly during the first 10 days and reached asymptotic values of ca. 20% (15 larvae/ml) and 50% (densities of 5 and 10 larvae/ml) afterwards. Mean shell length at the end of the experiment (243 ± 1.8 to 270 ± 0.7 μm) was not statistically different among treatments, even though a trend towards higher gross growth rate was observed in the treatment with the lowest density (9.5 μm/day) relative to the rest of the treatments (8.5 μm/day). It is concluded that P. generosa larvae can be successfully grown in flow‐through systems at maximum densities of 10 larvae/ml without significantly affecting their survival and growth rates. The system design was reliable, kept a constant water flow with reduced maintenance, and may represent an important option in the laboratory for increasing the stocking density of Panopea species during the larval phase.     

Genomic prediction of the general combining ability of maize lines (Zea mays L.) and the performance of their single crosses

The objective of this study was to assess the effectiveness of genomic selection (GS) on predicting the general combining ability (GCA) of maize lines and the performance of their single crosses. Eight maize lines developed from the different self‐pollination generations of Chalqueño race, along with their 24 single crosses, were evaluated in the field during the years of 2011, 2012 and 2013. Genomic prediction results using genotyping‐by‐sequencing‐based single nucleotide polymorphisms showed that the GCA classification of the parental lines estimated from the SNP information was consistent with the phenotypic classification of the lines evaluated from the field trial data. The prediction accuracy values estimated from the cross‐validation method ranged from 0.49 to 0.61 in the different prediction models. Yield performance of the unevaluated single crosses was predicted based on their SNP information. The total genetic variance of the yield of the single crosses was most explained by the GCA effects. Compared with phenotyping method, GS is a more effective and efficient approach to predict the GCA of maize lines and their hybrid performance.     

Characterisation of canine parvovirus strains isolated from cats with feline panleukopenia

Unlike the original canine parvovirus type 2 (CPV-2), CPV-2 variants have gained the ability to replicate in vivo in cats but there is limited information on the disease patterns induced by these variants in the feline host. During 2008, two distinct cases of parvoviral infection were diagnosed in our laboratories. A CPV-2a variant was identified in a 3-month-old Persian kitten displaying clinical sign of feline panleukopenia (FPL) (acute gastroenteritis and marked leukopenia) and oral ulcerations, that died eight days after the onset of the disease. Two pups living in the same pet shop as the cat were found to shed a CPV-2a strain genetically identical to the feline virus and were likely the source of infection. Also, non-fatal infection by a CPV-2c strain occurred in a 2.5-month-old European shorthair kitten displaying non-haemorrhagic diarrhoea and normal white blood cell counts. By sequence analysis of the major capsid protein (VP2) gene, the feline CPV-2c strain showed 100% identity to a recent canine type-2c isolate. Both kittens had been administered multivalent vaccines against common feline pathogens including FPL virus. Whether and to which extent the FPL vaccines can protect cats adequately from the antigenic variants of CPV-2 should be assessed.     

Survey of mealybug (Hemiptera: Pseudococcidae) vectors of <Emphasis Type="Italic">Ampelovirus</Emphasis> and <Emphasis Type="Italic">Vitivirus</Emphasis> in vineyards of northwestern Italy

Mealybugs (Hemiptera: Pseudococcidae) are sap-sucking insects which infest a broad range of crops worldwide. They represent an important threat to viticulture as they are vectors of viruses associated with leafroll and rugose wood complex diseases. In this study, we surveyed the presence of mealybugs and their associated viruses in vineyards of the Piemonte and Liguria regions, northwestern Italy. In order to determine the collected specimens correctly, we added a species-specific marker for Heliococcus bohemicus to an existing molecular identification key. The only species collected in Piemonte was H. bohemicus, whereas in Liguria, H. bohemicus, Planococcus ficus and Pseudococcus longispinus were found; Ps. longispinus has never before been reported in Italian vineyards. Several specimens of all three species were infected by the ampeloviruses GLRaV-1 and GLRaV-3 and the vitivirus GVA. Both nymphs and adult females tested positive for the viruses and mixed infections were commonly found within the same insect. Population levels and virus incidence were higher in Liguria than in Piemonte, suggesting a greater risk of disease spread. We conclude that the mild, Mediterranean climate of Liguria favors the development of a diverse mealybug fauna while only H. bohemicus, known to be tolerant to the severe continental winter temperatures, colonize grapevines in colder viticultural areas.     

Estimating bergamot juice adulteration of lemon juice by high-performance liquid chromatography (HPLC) analysis of flavanone glycosides

The chemical composition of 30 samples of juices obtained from bergamot (Citrus bergamia Risso and Poit.) fruits is reported and compared to the genuineness parameters adopted by Association of the Industry of Juice and Nectars (AIJN) for lemon juice. It was found that the compositional differences between the two juices are distinguishable, although with difficulty. However, these differences are not strong enough to detect the fraudulent addition of bergamot juice to lemon juice. Instead, we found the high-performance liquid chromatography (HPLC) analysis of the flavanones naringin, neohesperidin, and neoeriocitrin, which are present in bergamot juice and practically absent in the lemon juice, is a convenient way to detect and quantify the fraudulent addition of bergamot juice. The method has been validated by calculating the detection and quantification limits according to Eurachem procedures. Employing neoeriocitrin (detection limit = 0.7 mg/L) and naringin (detection limit = 1 mg/L) as markers, it is possible to detect the addition of bergamot juice to lemon juice at the 1% level. When using neohesperidin as a marker (detection limit = 1 mg/L), the minimal percentage of detectable addition of bergamot juice was about 2%. Finally, it is reported that the pattern of flavonoid content of the bergamot juice is similar to those of chinotto (Citrus myrtifolia Raf) and bitter orange (Citrus aurantium L.) juices and that it is possible to distinguish the three kinds of juices by HPLC analysis.     

Assessment of genetic variation in a working collection of Vigna vexillata (L.) A. Rich. by isozyme and RAPD analyses

Genetic variation based on isozyme and RAPD analyses was investigated in 47 and 34 accessions respectively of Vigna vexillata from different geographical origins and belonging to three botanical varieties. A total of 9 enzyme systems were studied, accounting for 14 putative loci, 8 of which were polymorphic. The analysis of genetic diversity revealed a low level of within accession variation (H_S=0.013), while between accession diversity (D_ST) was 0.120. Coefficient of gene differentiation (G_ST) was 0.905, indicating that most variation was among accessions. Nei's genetic distances were calculated on the basis of allelic frequencies and a UPGMA dendrogram was constructed. Twenty arbitrary 10-mer oligonucleotides were used in RAPD analysis. Amplification profiles disclosed a higher level of polymorphism than isozymes. Based on amplification patterns, the similarity index of Jaccard was calculated and a dendrogram constructed on the basis of the similarity matrix. The final clustering based on RAPD data was similar to the one obtained using isozyme allelic frequencies. The classification in botanical varieties did not reflect the allelic constitution of the different samples. On the other hand, referring to geographical origin, most accessions from Africa and from Latin America were distributed respectively in two distinct clusters in the dendrogram. This grouping might also reflect the differences observed in the germination behaviour of V. vexillata from the two continents.     

Interactions between temperature and size on the growth,size heterogeneity,mortality and cannibalism in cultured larvae and juveniles of the Asian catfish,Pangasianodon hypophthalmus (Sauvage)

Temperature effects vary throughout the ontogeny, but are proportionally more variable during the early life stages than in older fish. The larvae of a few species have been studied but contrasting trajectories were observed, thereby making it difficult to predict how temperature impacts on the growth, survival and size heterogeneity in a particular species. This study examined these interactions in young [0.9 mg–1 g wet mass (WM)] Pangasianodon hypophthalmus, one of the most extensively cultured tropical fish. Fish were raised at five temperatures from 23 to 33 °C in a recirculated water system, fed in excess with a high‐energy feed (Artemia then a formulated feed, >50% protein), and examined at 1‐day (first feeding days) or 4‐day intervals (older fish). The temperature that produced the fastest growth (T°_opt) was 31 °C at the start of exogenous feeding (0.9 mg); it increased to 32.7 °C at 8 mg then decreased by 0.7 °C for each 10‐fold increase of WM. Size heterogeneity was lower and survival was higher (70–85% from 0.9 mg to 1 g) when the temperature was close to T°_opt. Comparisons with other species suggest that the slope of the relationship between T°_opt and fish size has a strong latitudinal component, and may also reflect the fish sensitivity to oxygen.     

Cattle grub infestation by Hypoderma sp. in Albania and risks for European countries

In order to estimate the presence and the seroprevalence of hypodermosis in Albania, 625 head of cattle were bled during two sampling seasons (i.e. from February to March 2003 and from November to December 2003). The cattle came from three collection sites in Northern (site A), Central (site B) and Southern (site C) Albania. Milk samples were collected monthly from four animals from October 2002 to May 2003 during the lactating period. The animals were also clinically examined for the presence of warbles by manual palpation from April to July 2003 and 2004 and third instar larvae were collected and morphologically identified. Serum and milk samples were processed by ELISA. One hundred and thirty-three (38.6%) out of 344 and 116 (41.3%) out of 281 animals were found to be seropositive for Hypoderma during the first and the second sampling season. In particular, the animals from site C presented the highest percentage of seropositive results (i.e. 72.8% and 97.8% in the first and in second year, respectively) followed by the animals from sites A (i.e. 35.8% and 23.8% in the first and in second year, respectively) and B (i.e. 17.8% and 3.4% in the first and in second year, respectively). The kinetics of anti-Hypoderma antibodies in milk samples showed the highest antibody titres from October to February 2003. All the seropositive animals in both the sampling periods showed the presence of one or more warbles under the skin during April and May 2003 and 2004 and the third-stage larvae collected were morphologically identified as Hypoderma bovis. The results of this survey indicate that hypodermosis is widespread in Albania and that early prophylactic treatments must be carried out accordingly. The hope is not only to reduce the parasitic intensity with obvious benefits for livestock production, but also to avoid the risk of spreading this parasitic disease to neighboring countries.