Oxygen consumption of tadpoles during metamorphosis

Abstract

It is well known that thyroid hormone is necessary for metamorphosis in tadpoles. Since this substance causes an increase in the metabolic rate in mammals, it has often been suggested that the immediate cause of metamorphosis in amphibia is an increase in tissue metabolism. Huxley (1922), for instance, has suggested that the thyroid causes an increase in the rate of metabolism of all the tissues and that in these conditions certain organs develop whereas others are caused to atrophy.Several workers have tried to determine whether the rate of metabolism changes during metamorphosis, but their results have been contradictory. Abelin & Scheinfinkel (1923) found that C02 output usually fell during metamorphosis of Rana esculenta. Helif (1926)

Growth in Amphibians

“…The QOj (microlitres of Oi per hour per mg dry weight) increased steadily from 2.0 to 9.0 during the first 5 days after hatching. The val ue decreased between the 10th and the 20th day to about 3.0; thereafter it remained con stant till the tadpole reached the stage of metamorphosis [123], However, the expo nent b between metabolic rate and tadpole weight varies with environmental conditions like temperature, photoperiod, nutrition and time of feeding with the average value being about 0.83 [124], For tropical anuran tad poles, it is 0.56 (R. tigrina) and 0.59 (B. melanostictus) [58], but the b value for winter dor mant tadpoles of Rana muscosa in a tem perate region is 0.92 [125], All these b values indicate that the adult as well as the larval amphibians exhibit a variety of metabolic compensations for the growth in body mass. In some tadpoles, the growth rate influences their behavioural response to oxygen concen trations and water pH.…”

“…How ever, in a variety of anurans, it can range from 0.52 to 0.94 due to temperature varia tions [120][121][122]. Moreover, the oxygen con sumption of Xenopus laevis tadpoles during their growth phase differed when their wet weight and dry-weight are compared [123], The wet-weight of tadpoles increased from the 1st day of hatching until the onset of metamorphosis. On the other hand, the dry weight remained rather constant until the 5th day after hatching and then began to increase.…”

Dynamics of body mass and oxygen consumption in the ontogeny of the Spanish ribbed newt (Pleurodeles waltl): 2. Larval stage

“…The oxygen consumption intensity decreases dur ing newt larval development, as in the case of most studied amphibian species (Etkin, 1934;Fletcher, Myant, 1959;Funkhouser, Mills, 1969;Feder, 1982;Vladimirova et al, 2003). During the metamorphosis period, only an insignificant decrease in the oxygen consumption intensity can be pointed out.…”

“…As a result, the newts that have undergone metamorphosis have a greater body mass than the larvae entering it. This trait sets the Spanish ribbed newt apart from the studied represen tatives of anurans, in which the metamorphosis pro cess is accompanied by body mass decrease caused by cessation of feeding due to the reorganization of mouth parts and the gastrointestinal tract (Wills, 1936;Fletcher, Myant, 1959;Funkhouser, Mills, 1969;Schwartz et al, 1973;Beck, Congdon, 2003;Orlofske, Hopkins, 2009). The morphological and functional changes in organs, including the digestive system, that take place during metamorphosis, in the case of the Spanish ribbed newt, a representative of tailed amphibians, are less profound than in anurans, which, obviously, explains why their larva body mass does not decrease during metamorphosis (Fig.…”

“…During the early stages of development, when larvae receive only endotrophic nutrition, the intensity of oxygen consumption grows, and later, after larvae switch to external nutrition, it decreases (Fletcher, Myant, 1959;Ozernyuk, Lelyanova, 1985;Seymour, Loveridge, 1994;Vladimirova et al, 2000Vladimirova et al, , 2010Ozernyuk, 2000). During metamorphosis, oxy gen consumption in some species decreases or stays the same (Etkin, 1934;Fletcher, Myant, 1959;Funk houser, Mills, 1969;Feder, 1982;Hastings, Burggren, 1995;Beck, Congdon, 2003) and increases in others (Wills, 1936;Hopkins, Handford, 1943;Sivula et al, 1972;Schwartz et al, 1973;Koval'chuk, 1976;Orlof ske, Hopkins, 2009).…”