ABSTRACT
In order to decide which is the best growth model for the tambaqui Colossoma macropomum Cuvier, 1818, we utilized 249 and 256 length-at-age ring readings in otholiths and scales respectively, for the same sample of individuals. The Schnute model was utilized and it is concluded that the Von Bertalanffy model is the most adequate for these data, because it proved highly stable for the data set, and only slightly sensitive to the initial values of the estimated parameters. The phi values estimated from five different data sources presented a CV = 4.78%. The numerical discrepancies between these values are of not much concern due to the high negative correlation between k and Linfinity viz, so that when one of them increases, the other decreases and the final result in phi remains nearly unchanged.
Subject(s)
Fishes/growth & development , Models, Biological , Age Factors , Animals , Biometry , Fishes/anatomy & histologyABSTRACT
Para determinar qual o modelo de crescimento que melhor se ajusta ao tambaqui Colossoma macropomum Cuvier, 1818, foram utilizados 249 e 256 observações de comprimento-idade obtidos por meio de leituras de anéis em otólitos e em escamas, respectivamente, para os mesmos indivíduos. Para tanto, foi utilizado o modelo de Schnute, modelo genérico em que vários modelos tradicionais de crescimento estão incluídos. Com esse procedimento constatou-se que o modelo de von Bertalanffy realmente é o mais adequado, pois se mostrou altamente estável para o conjunto de dados, sendo pouco sensível aos valores iniciais adotados para as estimativas dos parâmetros. Os valores de F' estimados a partir de cinco conjuntos diferentes de dados apresentaram CV = 4.78%, o que não é preocupante, pois as discrepâncias numéricas entre esses valores são conseqüência da alta correlação negativa entre k e L¥ , visto que quando um aumenta o outro diminui e o resultado final expresso por F' permanece praticamente inalterado
Subject(s)
Animals , Fishes/growth & development , Models, Biological , Age Factors , Biometry , Fishes/anatomy & histologyABSTRACT
Acetaldehyde (AcH) administered intravenously or into the right ventricle induces reflex bradycardia, hypotension, and apnea in the rat. The efferent pathway for this reflex is vagal and probably secondary to pulmonary J receptors stimulation. Located between the alveoli and the pulmonary capillary, J receptors are accessible through the pulmonary circulation and the airways. For this reason, a method for indirect nebulization (IN) of AcH into the airways, that provides a continuous record of respiration without changes in intrapulmonary pressure, was developed. IN of AcH (n = 14) induced bradycardia (64 +/- 3.1%), hypotension (34 +/- 4.2%), and apnea (79%), which were blocked by vagotomy (n = 9). The latencies (s) for bradycardia (0.34 +/- 0.06), hypotension (0.68 +/- 0.11), and apnea (0.25 +/- 0.11) were significantly shorter than those obtained by the intravenous route. Three rats that did not develop apnea had an equivalent response, where both tidal volume and minute ventilation decreased about 40% and these effects were also blocked by vagotomy. Indirect nebulization of AcH allowed us to demonstrate that pulmonary J receptors are responsible for this reflex response.
