Hot‐water drench treatments were evaluated for disinfesting roots of potted anthurium Anthurium andraeanum of the burrowing nematode Radopholus similis. A continuous drench of roots and media in pots with 50°C water for 5 to 20 min eliminated or reduced nematode populations to < 1 g?1 of dry root. A second hot water drench, 2 months after the first drenching, tended to increase the efficacy of the heat treatment. A few survivors persisted in the roots and/or stems of a few plants 2 to 4 months after heat treatment. Non‐treatment of the shoots and possible migration from stem to root tissues are probable causes of nematode survival. Drenching potting media and roots in pot were as effective against R. similis in the roots as hot water dipping bare‐rooted plants. Plant response to hot‐water drenching varied among cultivars, but most exhibited tolerance to the heat treatments. Visual inspection of the plants showed little difference between treated and untreated plants in the heat tolerant cultivars. However, all heat‐treated ‘Marian Seefurth’ plants, especially hot water‐dipped bare‐rooted plants, appeared to suffer some degree of growth reduction as measured by lower root and stem dry weights when compared to untreated plants 3 months after treatment. Conditioning anthurium plants with hot water or hot air prior to hot water drenching did not benefit plant quality when compared to unconditioned, heat‐treated plants. 相似文献
Numerous unicellular glands are present in the forebody of the metacercariae and adults of Microphallus similis. The gland cell bodies lie beneath the tegumental perinuclear cytoplasm and ducts pass upwards penetrating the tegumental distal cytoplasm. Electron dense granules are secreted onto the forebody surface and into the oesophagus via small pits in the tegument. Histochemical tests revealed that the glands contain diastase-resistant neutral mucosubstances, RNA, protein, esterase and small amounts of acid phosphatase; inhibitor studies indicated that the esterase was acetylcholinesterase (EC 3.1.1.7). Ultracytochemistry showed that the mucosubstances were located in the general cytoplasm of the gland cells and that cholinesterase was present in the granules. The forebody of M. similis is covered by large toothed spines whereas the hindbody only bears short peg-like spines. It is suggested that the forebody spines may have an irritating, abrasive effect on the host's intestinal mucosa and that the secretion of acetylcholinesterase in the region of these spines may produce a ‘local anaesthetic’ effect on the host's gut by reducing movement in the immediate vicinity of the fluke, so decreasing the likelihood of expulsion. 相似文献
This study examined predation by the blue crab, Callinectes sapidus Rathbun, within intertidal Spartina alterniflora (Loisel) marshes of Dauphin Island, Alabama. Species and size preferences displayed by the predator when foraging within the marsh were investigated using nektonic, epifaunal, and infaunal prey populations including Fundulus similis Baird and Girard, Littorina irrorata Say, and Geukensia demissa Dillwyn.
Short-term field experiments involving the use of predator inclusion cages, in which the relative abundances of all prey species and the density of macrophyte vegetation were manipulated, indicated that mean mortality differed significantly among species. Blue crabs exhibited a distinct species preference for Littorina, and to a lesser extent, for Fundulus. However, the predator rarely choses infaunal individuals. Within predator inclusion cages, size selection by the crabs among three size classes of each prey was evident for Littorina and Fundulus but not for Geukensia. Blue crabs tended to select intermediate-sized snails and large fish while not exhibiting a size preference for infaunal bivalves.
In the marsh, mean percentage of the Littorina population within the 14–18 mm size class exhibited an increased mortality as compared to two other size classes, which was negatively correlated with increasing tidal height. Such a relationship may have been due to a decreasing gradient of crab predation associated with increasing tidal height. Geukensia size class distributions showed little evidence of differences along the tidal height gradient. No data are available for Fundulus, a mobile species which would not experience such differential predation along a marsh gradient.
In comparing crab predation patterns among prey species, it is apparent that Callinectes utilizes prey species differentially. Such differential utilization may be based on optimization of energy yield and minimization of energy expenditure. Thus, the preference of blue crabs for nektonic and epifaunal prey is hypothesized to be the result of a smaller energy expediture as a result of the crab's visual evaluation of these prey. Infaunal prey species (e.g., Geukensia) require a greater energy investment because of the necessity of excavating the prey item. Such prey also allow little selection by size because of being cryptic. 相似文献
Radopholus spp. were reared in carrot tissue culture via established procedures, with slight modification. Several plant tissue maceration enzymes and flotation media (salts and sucrose) were evaluated with regard to nematode toxicity and extraction efficiency. Best extraction of viable nematodes and eggs was attained when carrot tissue infested with Radopholus citrophilus or R. similis was macerated with a mixture of 0.50% driselase and 0.50% cellulysin, w/v each, with 2.5 ml of enzyme solution based for each gram of carrot tissue. Maceration slurries containing carrot tissue and nematodes were maintained in open flasks on a rotary shaker (175 rpm) at 26 C for 24 hours. Nematodes and eggs were extracted from resultant culture slurries by flotation with MgSO₄-7H₂0 (sp gr 1.1). A protocol is presented to extract large quantities of viable burrowing nematodes and their eggs from carrot disk cultures. 相似文献
Wolbachia is an endosymbiotic bacterium widely present in arthropods and animal-parasitic nematodes. Despite previous efforts, it has never been identified in plant-parasitic nematodes. Random sequencing of genes expressed by the burrowing nematode Radopholus similis resulted in several sequences with similarity to Wolbachia genes. The presence of a Wolbachia-like endosymbiont in this plant-parasitic nematode was investigated using both morphological and molecular approaches. Transmission electron microscopy, fluorescent immunolocalisation and staining with DAPI confirmed the presence of the endosymbiont within the reproductive tract of female adults.16S rDNA, ftsZ and groEL gene sequences showed that the endosymbiont of R. similis is distantly related to the known Wolbachia supergroups. Finally, based on our initial success in finding sequences of this endosymbiont by screening an expressed sequence tag (EST) dataset, all nematode ESTs were mined for Wolbachia-like sequences. Although the retained sequences belonged to six different nematode species, R. similis was the only plant-parasitic nematode with traces of Wolbachia. Based on our phylogenetic study and the current literature we designate the endosymbiont of R. similis to a new supergroup (supergroup I) rather than considering it as a new species. Although its role remains unknown, the endosymbiont was found in all individuals tested, pointing towards an essential function of the bacteria. 相似文献