Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
The thermal environment of arboreal pools and its effects on the metabolism of the arboreal, oophagous tadpoles of a Taiwanese tree frog, Chirixalus eiffingeri (Anura: Rhacophoridae)
Introduction
Aquatic ectotherms have evolved various behavioral, biochemical and physiological strategies to minimize the effect of ambient temperature fluctuations on the rate at which their life functions proceed. For example, animals reared at cool temperatures may have higher metabolic rates at a given temperature than animals with a warmer thermal history (Bullock, 1955, Fry, 1958, Rome et al., 1992, Ultsch et al., 1999). Metabolic compensation is one of the physiological strategies commonly used by fishes and invertebrates to minimize the effects of ambient temperature fluctuations on physiological homeostasis. Based on these observations, we might expect the aquatic larvae of amphibians to be capable of metabolic compensation. However, available data show conflicting results: a temperate ranid, Rana berlandieri and Xenopus laevis are capable of metabolic acclimation (Feder, 1985), but another temperate ranid, Rana pipiens, is not (Parker, 1967). In addition, tadpoles of an Australian frog, Limnodynastes peroni, also showed no evidence of undergoing thermal metabolic acclimation (Marshall and Grigg, 1980). The ability of a species to modify its standard metabolic rate through thermal acclimation is correlated with the amount of variation in environmental temperature it experiences on a time scale of weeks–months (Feder, 1982a). Thus, metabolic acclimation seems to provide the greatest benefits to species that experience the greatest thermal fluctuation (Feder, 1985). Therefore, more data are needed on the prevalence and possible advantages of metabolic acclimation to tadpoles, and more studies should be conducted on a variety of species that live under different thermal regimes.
In this study, we determined the prevalence of metabolic thermal acclimation in rhacophorid tree frog tadpoles (Chirixalus eiffingeri) that live in arboreal pools, by studying their thermal physiology. We determined the temperature of the arboreal water pools in bamboo stumps by measuring the diurnal, seasonal air and water temperatures. We also measured the oxygen consumption () of tadpoles collected early (February) and late (August) in the breeding season and acclimated to 12 and 22°C.
Chirixalus eiffingeri, a small frog with a snout-vent length of 30–40 mm, is endemic to Taiwan and two adjacent small islands, Iriomote and Ishigaki (Kuramoto, 1973, Ueda, 1986, Lue, 1990). Chirixalus eiffingeri has a prolonged breeding season from February to August (Kam et al., 1996) and female frogs lay 2–3 clutches of eggs each breeding season. During the breeding season, females deposit fertilized eggs on the inner walls of bamboo stumps or tree holes, just above the waterline (Kam et al., 1998a). Upon hatching, tadpoles drop into the pool of water where they grow and develop until metamorphosis. The water pools in bamboo stumps, like other arboreal pools (Laessle, 1961, Wassersug et al., 1981, Caldwell and Olivéra, 1999) typically contain small volumes (approx. 250 ml) of stagnant water (Kam et al., 1996). In addition, their physiochemical characteristics should be quite different from those of ponds, streams and rivers (Noland and Ultsch, 1981, Nie et al., 1999). The tadpole stage lasts from 40–60 days (Kam et al., 1998b). Tadpoles are obligatorily oophagous, with trophic eggs provided by female frogs.
Section snippets
Study site
We conducted field studies and collected tadpoles in bamboo forests of the Experimental Forest of National Taiwan University at Chitou (elevation 1016 m, approx. 23° 39′20″ N, 120° 48′10″ E) in Nantou County, Taiwan. Two species of bamboo, Phyllostachys edulis and Sinocalamus latiflorus, were the most abundant plants in the study sites. The bamboo is cut periodically for commercial purposes and the stumps remain for several years before disintegrating. Bamboo trunks are hollow, when cut, the
Seasonal fluctuations of water temperatures in bamboo stumps
From February 21 to August 5, 1994, a total of 205 egg clutches was deposited by female frogs. We found 30, 36, 28, 53, 18, 38 and 5 egg clutches in February, March, April, May, June, July and August, respectively.
Water temperature was lowest in February, increased rapidly during March and April and was highest from May to August (Fig. 1). The mean air and water temperatures were 20.2±3.78°C (range 13–28.5°C) and 18.6±3.16°C (range 10.5–28.5°C), respectively. These variables were highly
Discussion
Arboreal pools are characterized by a small volume of water. Bamboo stumps contain approximately 250 ml of water (Kam et al., 1996) and bromeliad leaf axils contain no more than 150 ml of water (Laessle, 1961). Sometimes, a very small volume of water (approx. 15 ml) is found in the tree holes of woody vines (Caldwell and Olivéra, 1999). We found that the temperature of pools of water in bamboo stumps was not constant and fluctuated simultaneously with the air temperature (Fig. 2). Heat exchange
Acknowledgements
This study was supported by a National Science Council Grant (NSC 90-2311-B-018-002) to YCK. We would like to thank the staff of the Experimental Forest of the National Taiwan University at Chitou for providing accommodation and permitting us to work in the experimental forest. Comments and suggestions on an earlier draft of this manuscript by A. F. Warneke are appreciated.
References (32)
Environmental variability and thermal acclimation of metabolism in tropical anurans
J. Thermal Biol.
(1982)Compensation for temperature in the metabolism and activity of poikilotherms
Biol. Rev.
(1955)Maternal brood care by Dendrobates pumilio: a frog that feeds its young
J. Herpetol.
(1993)- et al.
Determinations of biparental care in the spotted poison frog, Dendrobates vanzolinii (Anura: Dendrobatidae)
Copeia
(1999) - Chou, W.H., Lin, J.Y., 1997. Tadpoles of Taiwan. Spec. Publ. No. 7, Natl. Mus. Nat. Sci.,...
Principles of comparative respiratory physiology
(1981)- et al.
Ontogeny of temperature selection in larval amphibians
Copeia
(1985) Effects of developmental stage and body size on oxygen consumption of anuran larvae: a reappraisal
J. Exp. Zool.
(1982)Thermal acclimation of oxygen consumption and cardiorespiratory frequency in frog larvae
Physiol. Zool.
(1985)Temperature compensation
Ann. Rev. Physiol.
(1958)
Thermal biology of Anolis lizards in a complex fauna: the cristatellus group of Puerto Rico
Ecology
Thermal selection of bullfrog tadpoles (Rana catesbeiana) at different stages of development and acclimation temperatures
J. Thermal Biol.
Reproduction and parental care of the coronated treefrog, Anotheca spinosa (Steindachner, 1864) (Anura: Hylidae)
Herpetologica
Reproduction, oviposition-site selection and larval oophagy of an aboreal nester, Chirixalus eiffingeri (Rhacophoridae), from Taiwan
J. Herpetol.
Water balance, growth, development, and survival of arboreal frog eggs (Chirxalus eiffingeri, Rhacophoridae): importance of egg distribution in bamboo stumps
Physiol. Zool.
Density effects of oophagous tadpoles of Chirxalus eiffingeri (Anura: Rhacophoridae): importance of maternal brood care
Herpetologica
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2007, Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology