Bedingungen für die Metamorphose des Axolotls

Marx, Lisa

doi:10.1007/978-3-642-91057-9_4

Cited by 7 publications

(5 citation statements)

References 114 publications

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“…The earliest sign of metamorphosis that they described was regression of the anterodorsal tail fin (dorsal ridge regression). This feature has been observed in three different populations of A. tigrinurn in this lab (Norman, unpublished observations) and has been described in A. mexicanurn by Marx (1935). Although dorsal ridge regression may be a consistent feature of early metamorphosis in Ambystoma, it is difficult to determine exactly when it appears and how long it has been present.…”

Section: Discussionmentioning

confidence: 83%

“…Time of appearance of adult-like markings is variable among populations and does not lend itself to staging techniques (e.g., Marx, 1935;Larras-Regard et al, 1981). In addition, larvae in this study that were highly marked at the start of the experiment showed no tendency to initiate metamorphosis earlier than other, unmarked subjects.…”

Section: Discussionmentioning

confidence: 91%

“…These results are supported by previous osmoregulatory studies of larval A. tigrinum in which handling caused a 14% reduction in initial body weight over a 6-hour period (Norman, 1982). In addition, the results illustrate the limitations of earlier studies of urodele metamorphosis, which stressed the importance of changes in gill, tail, and body weight measurements as indicative of the onset of metamorphosis (e.g., Marx, 1935).…”

Section: Discussionmentioning

confidence: 92%

“…Gill regression has been used previously as a rough indicator of the extent of a larva's progression through metamorphosis (Marx, 1935;Norris et al, 1973). Complete gill regression does indeed accompany metamorphosis, but a repeatable staging technique based on this phenomenon would require prior knowledge of an animal's 100% gill values.…”

Section: Discussionmentioning

confidence: 99%

“…The primary aim of the present study was to devise a method for staging urodele metamorphosis that 1) would provide a reliable and quantifiable indicator of the early phases of metamorphosis, and 2) would not be dependent on knowledge of initial (100%) values of such parameters as gill length or tail height. Gill regression has been used previously as a rough indicator of the extent of a larva's progression through metamorphosis (Marx, 1935;Norris et al, 1973). Complete gill regression does indeed accompany metamorphosis, but a repeatable staging technique based on this phenomenon would require prior knowledge of an animal's 100% gill values.…”

Section: Discussionmentioning

confidence: 99%

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A practical method for staging metamorphosis in the tiger salamander Ambystoma tigrinum

Norman

1985

Anat. Rec.

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The aim of this study was to develop a set of practical metamorphic stages for the tiger salamander Ambystoma tigrinum that would 1) provide an early and quantifiable marker of the onset of metamorphosis and 2) not be dependent on knowledge of maximal values of gill length or tail height. Twenty morphological parameters were obtained from Ambystoma tigrinum larvae as they progressed through laboratory-induced metamorphosis (21 degrees C, continuous light). These parameters included measures of body weight, gill length, and tail height. Initiation or duration of metamorphosis could not be predicted when parameters were expressed relative to the number of days larvae were held in laboratory conditions. Early phases of metamorphosis were characterized by regression of the lower tail fin. Selected morphological parameters were expressed relative to the day on which each subject exhibited complete regression of the lower fin. This technique made it possible to order these parameters into a progressive series of metamorphic phases. Seven stages of metamorphosis were derived from this series, ranging from larvae (stage I) to complete regression of the gills (stage VII). Application of these stages does not require prior knowledge of maximal (initial) values of gill length or tail height.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A practical method for staging metamorphosis in the tiger salamander Ambystoma tigrinum

Norman

1985

Anat. Rec.

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The development of thyrotropic function in pituitary grafts in the tadpole

Etkin

1938

J. Exp. Zool.

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A study of induced metamorphosis in the Axolotl

Prahlad

DeLanney

1965

J. Exp. Zool.

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Metamorphic changes occurred in dark and white Mexican axolotls injected with 3,3',5-triiodo-L-thyronine (Ta) or DL-thyroxine (T4), when exposed at the following ages (in days) after spawning: 3-8, 45, 62, 117, 521-541, 541-571, at 20°C. The dosage of the hormone administered as a single injection varied from 10 pg to 100 pg. Optimum conditions in group 1 proved to be 10 pg T s injected into the perivitelline space of six-day-old embryos which were subsequently released from the jelly to fresh water nine days later at 15 days of' age. After two days in fresh water tissue changes were observed in this order: gills -ventral, middle, dorsal; tailtip; skin; upper eyelid. Ts-treated animals had a shorter latent period than T4 groups. There was heavy mortality in younger animals. Surviving axolotls completed metamorphosis within 25 to 35 days. Embryonic tissues,, therefore, are capable of taking up the hormone and responding after the treatment is terminated, raising doubts as to the obligatory persistence of the hormone. The implications of these observations with regard to the effect of hormone at the molecular level are discussed.In this report evidence will be presented to show that very early in their ontogeny the embryonic tissues of the Mexican axolotl (Siredon m e x i c a n u m ) are capable of taking up exogenous thyroid hormones, especially triiodothyronine, and of responding after the treatment is terminated. In addition, results on differential tissue sensitivity, quantitative aspects of the regression of the susceptible tissues, comparison of responses to thyroxine (T4) and triiodothyronine (TI 1, and the nature of response in different age groups and dark and white strains will be presented.Many investigators have studied various aspects of metamorphosis in the life history of both urodeles and anurans: the majority of such studies have been included in the reviews by Marx ('35), Lynn and Wachowski ('51) and Etkin ('64). It is well established that Mexican axolotl tissues are sensitive to exogenous thyroid hormones and that their own pituitary does not produce TSH to release endogenous thyroid hormones even though the thyroid is filled with colloid (Lynn and Wachowski, '51). Very little evidence exists in the literature as to how early the tissues of the axolotl or any other urodeles become sensitive to exogenous hormones. Uhlenhuth ('21) immersed Ambystoma maculatum embryos (first 4 visceral arches formed) in iodine-free water containing 1 mg% Bayer's iodothyrine for 20 days. Then he increased the concentration to 10 mg% J. EXP. ZOOL., 160: 137-146.for seven days more. At the end of a total period of 27 days the gills as well as fin of the tail were greatly atrophied. EXPERIMENTALIn the experiments reported below as many standardized conditions as possible were maintained and the animals were neither thyroidectomized nor hypophysectomized as they were already genetically hypophysectomized with respect to thyroid function (Blount and Blount, '47; Blount.' 5 0 ) . Treatment 3,5,3'-triiodo-~-thyro...

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Bedingungen für die Metamorphose des Axolotls

Cited by 7 publications

References 114 publications

A practical method for staging metamorphosis in the tiger salamander Ambystoma tigrinum

A practical method for staging metamorphosis in the tiger salamander Ambystoma tigrinum

The development of thyrotropic function in pituitary grafts in the tadpole

A study of induced metamorphosis in the Axolotl

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