Characterisation of Curtobacterium flaccumfaciens Pathovars by AFLP, rep-PCR and Pulsed-Field Gel Electrophoresis

The bacterial species Curtobacterium flaccumfaciens encompasses a group of closely related phytopathogens subdivided into pathovars that exhibit differences in host range. To date, reliable differentiation of pathovars and identification of unknown isolates to the pathovar-level can only be achieved on the basis of host testing. In this study, representative strains from C. flaccumfaciens pathovars and related species were examined using a range of genomic fingerprinting techniques to ascertain their application as additional or potential alternatives to host testing. Amplified fragment length polymorphism (AFLP) and repetitive sequence polymerase chain reaction (rep-PCR) analyses enabled the categorisation of some, but not all strains, in their respective pathovars. In contrast, all strains were correctly assigned to pathovars using HindIII and XbaI macro-restriction digests in conjunction with pulsed-field gel electrophoresis (PFGE). Fingerprints generated by PFGE not only supported the current pathovar rankings within C. flaccumfaciens, they also identified subgroups within pathovars flaccumfaciens, oortii and poinsettiae.     

Determining the toxicity and hazard to fish of a rice insecticide

The experiments described were carried out to establish whether the effects of the insecticide, Ripcord (active ingredient cypermethrin), on fish, would limit its use in rice. Laboratory and field experiments were carried out, and the effects of cypermethrin were compared with those of a ‘standard insecticide’, carbofuran, widely used for pest control in rice, and a ‘positive control’, chlorfenvinphos, expected to be toxic to fish in rice paddies at insecticidally effective rates. Acute toxicity tests in the laboratory with the technical materials on the fish Tilapia nilotica showed cypermethrin, with a 96 h LC₅₀ value of 2 μg/l, to be some 20 times more toxic than chlorfenvinphos, with a 96 h LC₅₀ value of 39 μg/l, and some 250 times more toxic than carbofuran with a 96 h LC₅₀ of 480 μg/l. The LC₅₀ values obtained from laboratory tests with formulated products (cypermethrin EC, chlorfenvinphos granules and carbofuran granules) on T. nilotica and Cyprinus carpio were broadly in agreement with those obtained from the tests with the technical materials and confirmed C. carpio to have a similar susceptibility to that of T. nilotica. However, a field experiment carried out in paddy rice in Korea with commercial formulations and at commercial application rates showed that mortality of caged C. carpio was much less with cypermethrin (< 15%) than with chlorfenvinphos (97%) or carbofuran (67%). A second field experiment in Spain where cypermethrin was applied by air resulted in no mortality of caged C. carpio held in the paddy. It is concluded that the limited toxic effects of cypermethrin on fish in the field, when compared with those of chlorfenvinphos and carbofuran, make it acceptable for use in rice. The effects of cypermethrin were limited in comparison with those of chlorfenvinphos and carbofuran because only very low application rates of cypermethrin are needed to give pest control. The penetration of the liquid cypermethrin formulations into the water was also lower than that of the granular insecticides and, finally, cypermethrin was more rapidly lost from water. Together, these factors are sufficient to explain the minimal toxic effects of cypermethrin in the field when compared with chlorfenvinphos and carbofuran, despite its considerably higher acute toxicity determined in laboratory tests.     

Biochemie

Ohne Zusammenfassung     

Patterns of nodal metastases,biological behaviour and prognosis of canine mast cell tumours of the pinna: A multi-institutional retrospective study

Canine cutaneous mast cell tumours (cMCTs) of the pinna have been associated with an aggressive biological behaviour, although data remain scarce. The knowledge acquired over the past years on histologic gradings, and the value of lymph node (LN) staging, may help in better characterizing this anatomical presentation. The first aim was to describe the frequency, location, and histologic appearance of LN metastases in cMCT of the pinna. A second aim was to evaluate prognosis. Medical records of dogs with cMCT of the pinna, that underwent tumour and sentinel (SLN) or regional LN (RLN) excision, were reviewed. The influence of potential prognostic variables on time to progression (TTP) and tumour-specific survival (TSS) was investigated. Thirty-nine dogs were included: 19 (48.7%) had Kiupel high-grade (K-HG) and 20 (51.3%) had low-grade (K-LG) MCTs. Eighteen (46.1%) dogs underwent SLN mapping: the superficial cervical LN was at least one of SLN in 17 (94.4%) cases. Twenty-two (56.4%) dogs had LN metastases; the superficial cervical LN was always involved. On multivariable analysis, only K-HG was associated with increased risk of progression (p = .043) and tumour-related death (p = .021). Median TTP and TSS were 270 and 370 days in K-HG, respectively; these were not reached in dogs with K-LG tumours (p < .01). cMCTs of the pinna are often K-HG and are also associated with a higher frequency of LN metastasis; however, we confirmed the independent prognostic value of histologic grading. A multimodal treatment may lead to favourable long-term outcome. Moreover, the superficial cervical LN is most often the SLN.     

Extreme ocean acidification reduces the susceptibility of eastern oyster shells to a polydorid parasite

Ocean acidification poses a threat to marine organisms. While the physiological and behavioural effects of ocean acidification have received much attention, the effects of acidification on the susceptibility of farmed shellfish to parasitic infections are poorly understood. Here we describe the effects of moderate (pH 7.5) and extreme (pH 7.0) ocean acidification on the susceptibility of Crassostrea virginica shells to infection by a parasitic polydorid, Polydora websteri. Under laboratory conditions, shells were exposed to three pH treatments (7.0, 7.5 and 8.0) for 3‐ and 5‐week periods. Treated shells were subsequently transferred to an oyster aquaculture site (which had recently reported an outbreak of P. websteri) for 50 days to test for effects of pH and exposure time on P. websteri recruitment to oyster shells. Results indicated that pH and exposure time did not affect the length, width or weight of the shells. Interestingly, P. websteri counts were significantly lower under extreme (pH 7.0; ~50% reduction), but not moderate (pH 7.5; ~20% reduction) acidification levels; exposure time had no effect. This study suggests that extreme levels – but not current and projected near‐future levels – of acidification (?pH ~1 unit) can reduce the susceptibility of eastern oyster shells to P. websteri infections.     

An experimental assessment on the effects of photoperiod treatments on the somatic and gonadal growth of the juvenile European purple sea urchin Paracentrotus lividus

Determining the optimum light conditions for sea urchins reared in land‐based systems is vital for the future use and assessment of possible commercial systems of sea urchin farming. The effects of two different light regimes, complete darkness and a long day photoperiod of 16 h light:8 h darkness, on the somatic and gonadal growth of the European sea urchin Paracentrotus lividus (19.5–23.0 mm) was investigated using the commercial UrchinPlatter^? System over a 6‐month period (5 March to 5 September). Hatchery‐produced P. lividus were transported to the Aquaculture Fisheries Development Centre (AFDC, University College, Cork UCC). Before arrival at the AFDC, sea urchins were reared on a diet of Laminaria digitata. Females were the predominant species of the animal group, displaying a reproductive Stage III (growing stage) where gametogenesis was commencing. Results show that darkness supports higher somatic growth than the photoperiod treatment. Feeding rates were higher for sea urchins reared under darkness with gonadal growth increasing for both experimental treatments. Individuals reared under darkness had a higher per cent change in gonad index from the initial sample taken at the beginning of the experiment.