Interannual differences in growth and hatch‐date distributions of early juvenile European anchovy in the Bay of Biscay: implications for recruitment

In order to understand better the recruitment variability in European anchovy in the Bay of Biscay, it is important to investigate the processes that affect survival during the early life stages. Anchovy juvenile growth trajectories and hatch‐date distributions were inferred over a 3‐year period based on otolith microstructure analysis. Otolith growth trajectories showed a characteristic shape depending on their hatch‐date timing. Earlier‐born juveniles had notably broader maximum increments than later born conspecifics, resulting in higher growth rates. This observation suggests that early hatching would be beneficial for larval and juvenile growth, and, therefore, survival. The estimated juvenile hatch‐date distributions were relatively narrow compared with the extended anchovy spawning season (March–August) in the Bay of Biscay and indicated that only individuals originated mainly from the summer months (June–August) survived until autumn. Hatch‐date distributions were markedly different among years and seemed to influence the interannual recruitment strength of anchovy. We conclude that years characterized by juvenile survivors originating from the peak spawning period (May and June) would lead to considerable recruitment success. Downwelling events during the peak spawning period seem to affect larval survival. Furthermore, size‐dependent overwinter mortality would be an additional process that regulates recruitment strength in the anchovy population in the Bay of Biscay.     

Acute toxicity of zinc and arsenic to the warmwater aquatic oligochaete <Emphasis Type="Italic">Branchiura sowerbyi</Emphasis> as compared to its coldwater counterpart <Emphasis Type="Italic">Tubifex tubifex</Emphasis> (Annelida,Clitellata)

Purpose

This study aimed at evaluating the acute effects of arsenic and zinc to the warmwater aquatic oligochaete Branchiura sowerbyi. Relative sensitivity with the coldwater species Tubifex tubifex was compared. Implications for the use of B. sowerbyi in the risk assessment of sediments in the tropics are discussed.

Materials and methods

Water-only (96 h) and sediment (14 days) toxicity tests were conducted with both species evaluating a concentration series of arsenic and zinc. The tests were conducted considering the environmental conditions in the natural habitat of T. tubifex (predominantly temperate) and B. sowerbyi (predominantly tropical). Both lethal and sublethal endpoints (autotomy of the posterior body parts, abnormal behavior and appearance) were determined in the tests. The lethal (LC₁₀ and LC₅₀) and effect (EC₁₀ and EC₅₀) concentrations were also determined to assess metal sensitivity for both species.

Results and discussion

Both test species were more sensitive to Zn than As in water-only tests, which is in agreement with previous studies evaluating the toxicity of these metals to aquatic oligochaetes. Sublethal effects were generally noted at concentrations lower than those leading to mortality. The warmwater oligochaete B. sowerbyi was more sensitive to both metals tested than the coldwater species T. tubifex.

Conclusions

Study findings support the need for using indigenous tropical species in risk assessments in the tropics. In addition, sublethal effect parameters should be included in toxicity testing with aquatic oligochaetes.

     

Exploitation of Exotic, Cultivated Solanum Germplasm for Breeding and Commercial Purposes

Native potato species (NPS) are cultivated potatoes which do not belong to S. tuberosum ssp. tuberosum. They are maintained by the farmers of the Andes for subsistence under harsh environmental conditions where other potatoes cannot compete. Within the huge phenotypic variability between and within these species certain accessions possess resistances to different pests and diseases, remarkable culinary and processing quality and favourable nutritional properties. We present first evaluation results of a set of NPS for these characters and discuss prospects for exploiting this valuable germplasm for breeding and for developing novel products for niche markets.     

Diagnosis of an Abdominal Splenosis in a Case of Ambulatory Paraparesis of the Hind Limbs in a Ferret (Mustela putorius furo)

A 2-year-old spayed female ferret (Mustela putorius furo) was presented with a 2-day history of ambulatory paraparesis of the hind limbs. On physical examination a mass was palpated in the cranial abdominal region, caudal to the stomach. A complete blood cell count revealed a normocytic normochromic anemia and reactive lymphocytes. A hypoechoic abdominal mass was observed during an ultrasound examination of the abdomen. An exploratory laparotomy was recommended and performed during which a pyramidal mass resembling a lobe of fatty liver tissue, plus omental torsion, was removed. The histopathologic diagnosis of the surgically removed mass was splenosis. The abdominal pain and ambulatory paraparesis resolved after surgery, which suggests that the paraparesis was due to pain. The findings in this report indicate that splenosis should be included as a differential diagnosis when a ferret presents with an abdominal mass and acute abdominal pain.     

Oryzalin Treatment of Potato Diploids Yields Tetraploid and Chimeric Plants from which Euploids could be Derived by Callus Induction

Shoot apices from six diploid potato genotypes for polyploidisation were treated with oryzalin and colchicine solutions at different concentrations and incubation times. In addition to chimeric plants, diploids, one octoploid and completely ploidy doubled plants (4x) were regenerated in these experiments. Tetraploid plants were obtained for three of the six genotypes treated with oryzalin, and no tetraploid plants were obtained after colchicine treatments of any of the genotypes. The best result of 43% tetraploid plants was achieved using 28.8 μM oryzalin and 24 h of incubation with the L37 genotype. Moreover, we determined that doubled plants should not be selected on the basis of a single measurement and require additional ploidy checks in successive clonal generations. Some L37 plants that were initially identified as tetraploids by flow cytometry produced diploid or mixoploid plants in the next clonal generation. Morphological characters of doubled L37 plants were compared with the original genotype. The PVY resistance present in a parental clone was maintained in all regenerants and significant differences among ploidy variants were found for some quantitative characters. Molecular AFLP analyses did not show any differences among genotypes. Since polyploidizing substances may produce a large proportion of chimeric plants, we applied a method to increase the number of tetraploid plants. Callus culture of chimeric leaf explants was performed on regeneration medium and tetraploid shoots were obtained in four of the six genotypes tested. The best result of 40% tetraploid plants was achieved with explants from the L37 genotype. This method was successful in producing additional tetraploid genotypes from mixoploid plants obtained after oryzalin treatments.     

Evidence of soil-located competition as the cause of the reduction of sunflower verticillium wilt by entomopathogenic fungi

The increasing limitation of agrochemicals for disease control is a major challenge for European agriculture and a spur to developing environmentally friendly approaches such as biological control. Entomopathogenic fungi, which have been used in the control of insect pests for a long time, also have other uses, such as being antagonists of fungi, including plant pathogens. We determined the in vitro effect of three strains of Metarhizium brunneum and two of Beauveria bassiana against Verticillium dahliae and Cadophora helianthi, causal agents of sunflower wilts. Both M. brunneum and B. bassiana were able to inhibit the mycelial growth of the sunflower pathogens and, according to the dual culture and microscopy results, two types of antagonism were observed as being dependent on the strain: competition and/or antibiosis. Greenhouse experiments showed that, after soil treatments with entomopathogens and plant inoculation by root immersion in conidial suspensions of V. dahliae, the entomopathogens were able to efficiently persist in the soil, and three of the four strains even significantly reduced the severity of symptoms in sunflowers. Interestingly, molecular analysis showed that all the strains were able to establish themselves as endophytes in sunflowers in the absence of V. dahliae. When the plants were inoculated with V. dahliae, we detected the pathogen, but not the entomopathogen, in the sunflowers by molecular methods. The results of this work suggest that the protection conferred by M. brunneum and B. bassiana against verticillium wilt might not be plant-located, but is probably the consequence of their competition with V. dahliae in the soil.     

Genetic relationships among local potato cultivars from Spain using SSR markers

Microsatellite markers (SSR) were used to fingerprint a total of 105 local potato cultivars from Spain. A set of 41 cultivars from Tenerife Island, 19 from the island of La Palma, and 45 local varieties from peninsular Spain were analysed. Some of these varieties represent relicts of the early introductions originating from South America and have been characterised previously morphologically and ecophysiologically. We observed within our materials a total of 76 SSR alleles. Only seven of them were present in all varieties. Several accession and group specific alleles were detected. Similarity coefficients were computed from the molecular data and cluster analyses were performed. The obtained dendrogram was generally in good agreement with previous classifications of the accessions as Solanum tuberosum L. subsp. andigena (Juz. et Bukasov) Hawkes S. tuberosum L. subsp. tuberosum and S. chaucha Juz. et Bukasov genotypes. Also cultivar groups with identical or related common names showed the same SSR patterns or clustered closely together. In addition we performed Principal Coordinate Analysis with the set of genotypes. Results of both analysis methods were generally in good agreement, but also some smaller differences were detected in the associations of groups and genotypes. According to the molecular patterns for some accessions misleading or confounded names were evident, and in some cases the molecular patterns showed also discrepancies with previous species assignments, suggesting the need for a more detailed comparative study of these accessions.     

Validation of molecular markers for pathogen resistance in potato

DNA markers have a large potential to improve efficiency and precision of conventional plant breeding programmes based on marker‐assisted selection (MAS). In our study, we have evaluated the predictive abilities of the SCAR marker RYSC3 and the CAPS marker GP122₅₆₄ with regard to the PVY resistance genes Ry_adg and Ry_sto, respectively, and of marker TG689 linked to H1 conferring resistance to Globodera rostochiensis and marker HC associated with high levels of G. pallida resistance. The evaluations were made in 28 cultivars and accessions and in 219 progeny genotypes descending from ten different crosses. We observed in all evaluated cultivars and accessions the expected marker patterns according to their phenotypic classification into resistant and susceptible genotypes. However, in part considerable discrepancies were observed when analysing progeny of controlled crosses involving these resistance sources, particularly with respect to H1. Based on these results, practical aspects for the efficient implementation of marker‐assisted selection are discussed, which consider the genetic origin of the material, costs aspects and methodology applied.     

Ectopic expression of germline genes drives malignant brain tumor growth in Drosophila

Model organisms such as the fruit fly Drosophila melanogaster can help to elucidate the molecular basis of complex diseases such as cancer. Mutations in the Drosophila gene lethal (3) malignant brain tumor cause malignant growth in the larval brain. Here we show that l(3)mbt tumors exhibited a soma-to-germline transformation through the ectopic expression of genes normally required for germline stemness, fitness, or longevity. Orthologs of some of these genes were also expressed in human somatic tumors. In addition, inactivation of any of the germline genes nanos, vasa, piwi, or aubergine suppressed l(3)mbt malignant growth. Our results demonstrate that germline traits are necessary for tumor growth in this Drosophila model and suggest that inactivation of germline genes might have tumor-suppressing effects in other species.