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Flooding induced several physiological and morphological changes in Fraxinus pennsylvanica seedlngs, with stomatal closure among the earliest responses. Subsequent changes included: reduction in dry weight increment of roots, stems, and leaves; formation of hypertrophied lenticels and production of adventitious roots on submerged portions of the stem above the soil line; leaf necrosis; and leaf abscission. After 15 days of stomatal closure as a result of flooding, stomata began to reopen progressively until stomatal aperture was similar in flooded and unflooded plants. Adventitious roots began to form at about the time stomatal reopening began. As more adventitious roots formed, elongated, and branched, the stomata opened further. The formation of adventitious roots was an important adaptation for flooding tolerance as shown by the high efficiency of adventitious roots in absorption of water and in high correlation between the production of adventitious roots and stomatal reopening.Several investigators have emphasized that Fraxinus pennsylvanica Marsh. is highly tolerant of flooding. This species occurs on alluvial soils along rivers and brooks. It is commonly found on land that is subject to periodic flooding and grows vigorously even when flooded for much of the growing season (2, 7, 17).The high flooding tolerance of certain species of forest trees has been attributed to one or more adaptive mechanisms, including compensation for poor aeration of the normal root system by production of AR. Often species that survive flooding best are those that form AR3 at, or below, the water line (5, 6, 14, 20, 21). Although some investigators considered such roots to be merely symptoms of flooding stress (7), others concluded that the capacity of some species to survive flooding depended wholly or partly on the activity of AR (1, 1 1). Clemens et al. (4) showed that flooding tolerance of three species was in the following order: Eucalyptus grandis > Eucalyptus robusta > Eucalyptus saligna and that this order was correlated with capacity for production of AR.Our previous experiments (18) indicated that stomatal closure of several species of woody plants was one of the earliest responses to flooding. There is some evidence (13) Initial dry weights were obtained separately for leaves, stems, and roots after drying at 70 C for 48 h. The plants of groups b and c were transferred to a growth chamber in which PAR was 226 pE m2 s ' 20 cm above the pots; daylength was 16 h beginning at 0700 h; day and night temperatures were 25 and 20 C, respectively; and RH was approximately 80%Yo.After 11 days in the growth chamber, plants of group c (10 of each age class) were flooded by immersing the pots in tubs of water for 30 days. The water level was maintained at 2 cm above the soil line. Unflooded control plants were watered daily. Three days after termination of flooding, both flooded and unflooded plants were harvested. Roots, stems, and leaves of each plant were separated and their dry weights were determined.Leaf Diffusion ...

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RESUMO -Os peixes de uma estação de cultivo de tambaquis pararam de se alimentar e começaram a morrer. Um total de 72 peixes foi examinado. Todos os peixes estavam com uma alta infestação intestinal por acantocéfalos. A espécie parasita foi identificada como Neoechinorhynchus buttnerae Golvan, 1956. A prevalência foi de 100%, a intensidade por hospedeiro variou de 30 a 406 e a intensidade média e densidade relativa (abundância) foram de 125, 26. Ocorreu oclusão total do trato intestinal nas altas infestações.Palavras-chave: Acanthocephala; parasitas de peixes; tambaqui; mortalidade de peixes; aquacultura. ABSTRACT -The fishes Colossoma macropomum (Cuvier, 1818) from a farm fish stopped to eat and begun to die. Seventy-two fishes caught were examined. All fishes had a high intesti nal infestation for Acanthocephala. The species was Neoechinorhynchus buttnerae Golvan, 1956. The prevalence was 100%, intensity range 30-406 and mean intensity and relative density (abun dance) were 125,26. In the high infestations occurred the total occlusion of the gut lumen. Massive Infestation by

The study describes the morphological changes associated with parasitism by the intestinal acanthocephalan Neoechinorhynchus buttnerae in tambaqui juveniles Colossoma macropomum farmed in an excavated nursery, in Manaus (Amazon) in September 2013. After fish biometrics, analysis of macroscopic changes in morphology and counting of parasites, bowel fragments were fixed and submitted to histological and histochemical processing. All fish analyzed had acanthocephalans in the intestine; intestinal loops were milky white in color, with the presence of nodules with heavy parasitism. The changes in tissues that form the intestine varied according to the arrangement of the parasites: either free in the intestinal lumen or fixed by the proboscis on the organ wall. In the first case, the changes found were flaking, abrasion, compression, hypertrophy of goblet cells and disappearance of the villi on the mucosa, leukocytic cell infiltration in the submucosa, and muscle layer thickening. In the second case, in addition to these, other changes were observed as metaplasia in muscle tissue with its replacement by a loose connective tissue with severe leukocytic infiltration, edema in blood vessels, and necrotic foci. The histochemical analysis revealed that positive Alcian Blue mucosal cells (pH 2.5) were more expressive in parasitized intestines than in intestines not parasitized by N. buttnerae.

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