Weights and linear measurements of the body and organs of the tiger salamander before and after metamorphosis compared with the adult.код для вставкиСкачать
Weights and Linear Measurements of the Body and Organs of the Tiger Salamander, Before and After Metamorphosis, Compared with the Adult HOMER B. LATIMER AND PAUL GIBBONS ROOFE Department of Anatomy, University of Kansas, Lawrence ABSTRACT Body weight and length, weights of 14 organs and 15 linear measurements are presented from 97 Amblystorna tigrinurn melanosticum before metamorphosis and 57 specimens after metamorphosis. These data are compared with similar measurements (previously published) on adult salamanders. Body weight and weights of the digestive tube and its subdivisions, liver, pancreas, spleen, eyeballs and brain are heavier in the larvae. The body weight decreases more than many of the organs and hence the percentage weights of the heart, lungs, liver, spleen, kidneys, gonads, eyeballs and brain are larger, relatively, in the postmetamorphosis salamanders. Since body length is not significantly changed, the percentage lengths are much the same. Length of the digestive tube and its parts, jaw width and the width of the body a t pectoral, belly and pelvic regions are all longer in the larvae. The limbs are the only percentage lengths greater in the post-metamorphosis salamanders. All of the weights and all of the linear measurements are significantly correlated with body weight or length, respectively. Four organs show increases in percentage weights at all three periods: gonads, lungs, liver and spleen. Two others have a n increase in post-metamorphosis: heart and kidneys. The digestive tube and its parts and the pancreas have a relative decrease at the end of metamorphosis. The eyeballs are relatively largest in the postmetamorphosis, and smallest in the adults. The metamorphosis of various species of urodeles has been observed and studied for many years, but this rather extensive literature will not be reviewed here. Grant ('30) has summarized much of the work previous to her study, which presents the sequence of the changes in the skin, the atrophy of the caudal fin and the gills in several species. She reports a good deal of difference in the time required for metamorphosis, varying from 24 hours to a week or ten days, in the several species. She finds that amblystoma punctatum requires four or five days for the completion of its metamorphosis. The relationship between metamorphosis and some of the endocrine glands has been studied rather fully. DuShane and Hutchinson ('44) have reported the embryonic growth of amblystoma, but no data have been found in the literature on the quantitative anatomy of any of these salamanders in the periods immediately before and after metamorphosis. This study presents body weight, external measurements of the body and weights and linear measurements of some of the viscera of 97 tiger salamanders before metamorphosis and 57, after metamorphosis. All were taken from the same pond in the Grand Teton National Forest. These data are compared with measurements of adult amblystoma previously published (Latimer, Roofe and Feng, '61). MATERIALS AND METHODS Over 500 salamanders (Amblystoma tigrinum malinosticum) were seined from one of the smaller ponds (Moran) in the Grand Teton National Forest in about half an hour. They were brought into the laboratory of the Jackson Hole Biological Station and placed in tubs. The water was changed daily, and they were fed aquatic insects. Ninety-seven of these larval a m blystoma were weighed and the external measurements made. Ten days later the remaining specimens had completely metamorphosed and 57 of these metamorphosed tiger salamanders were weighed and measured in a similar manner. 1 This investigation was supported in part by NIH, GM 08537-02. 139 140 HOMER B . LATIMER AND PAUL GIBBONS ROOFE The pre- and post-metamorphosis salamanders were all treated alike. Each specimen was anesthetized with MS 222 (Tricane methanesulfonate), weighed and the ten external measurements made with a sliding straight armed calipers reading to 0.1 mm. The body cavities were opened and they were immersed in 10% formalin and brought to Kansas. Here they were changed to larger containers with an ample supply of fresh 10% formalin solution and held for over four months. The specimens were weighed when freshly anesthetized on a laboratory balance sensitive to 0.01 gm and here in Kansas the entire amblystoma and each of the individual organs were weighed in glass stoppered weighing bottles on an analytical balance sensitive to 0.1 mg. The body weights were recorded to the nearest milligram. The methods of making the external measurements are described in the earlier report (Latimer, Roofe and Feng, ’61) and will not be repeated here. The organs were dissected as free of the mesenteries as possible, and placed briefly in a moist chamber until weighed. The lengths and the weights of the entire digestive tube are the sums of the measurements of its four parts. The contents of the digestive tube were not removed and the variable amount of the contents is partially responsible for the high variability of the digestive tube and its subdivisions. The lengths of the three shorter divisions of the digestive tube were measured with a sliding straight armed calipers reading to 0.1 mm and the lengths of the intestines were measured with a metric ruler. These intestines of the tiger salamanders were sufficiently pliable so that they could be straightened out fully for making these measurements. The stomachs of 19 of the larval amblystoma had been opened for a study of their contents and hence the weights of the stomach and the entire digestive tube are reported for only 78 larval amblystoma. The gall bladders contained a variable amount of secretion. The weights of the gall bladders and their contents are included in the weights of the livers. The specimens were collected, weighed and the external measurements were all made by one person (P. G . R.) and the dissections and measurements of the or- gans were all made by the other author (H. B. L.) and he is responsible for the preparation and presentation of all of the data. Weights and percentage weights The body weight and the weights of the organs are shown in panel A of table 1. The “L” or “ M preceding the “t” values in the last column indicate that the measurement of the larval ( L ) or the metamorphosed (M) amblystoma is heavier or forms a larger percentage of body weight (panel B). The fresh body weight shown in the first line was made immediately after the amblystoma were anesthetized and before any preservation. The second line has the weight of the entire animal after preservation in 10% formalin for four months. Both the fresh and the preserved weights are significantly heavier in the larvae than in the metamorphosed amblystoma, as shown in the last column. The preserved larval amblystoma average 5.66% heavier than the fresh larvae while the preserved metamorphosed amblystoma average 8.52% lighter than the fresh metamorphosed amblystoma. Thus the preservation increases the body weight in the larvae but decreases it in the metamorphosed animals. Both groups were treated in the same manner and weighed on the same balances. Hence there must be some differences in the constitution of the two groups which makes them react differently to the formalin. Further study of the quantitative effects of preservation upon the organs and tissues is needed to clarify this. There was an apparent reduction in the loose areolar subdermal tissue in the metamorphosed specimens, with the skin more closely adherent to the underlying musculature; also there was less loose areolar tissue throughout the metamorphosed amblystoma. All of these weights are more variable in the larvae than in the metamorphosed salamanders except the weights of the pancreas and the gonads. The pancreas is not encapsulated and it was very difficult to remove it accurately and hence these weights are not too significant. The sex of the gonads was not determined in either group, but the gonads are significantly heavier in the metamorphosed specimens. MEASUREMENTS, TIGER SALAMANDER 141 TABLE 1 Weights in grams and as percentages of body weight. The “t” values of 2.00 and above are significant at 5 % , and values at 2.66 and above are significant at 1% 97 Larval amblystoma Average and stand. dev. Coef. of variation 57 Metamorphosed amblystoma Coef..of Average and stand. dev. Body wt. (fresh) Body wt. (formal.) Heart Lungs Digestive tube Esophagus Stomach Intestines Cloaca Liver Pancreas Spleen Kidneys Gonads Eyeballs Brain Panel A Weights in grams 5.65 21.20 21.18 4.46 k0.64 5.97 21.12 18.76 4.08 20.54 28.06 0.0260f 0.0056 0.0261 20.0073 39.01 0.0389f 0.0105 0.0362f0.0141 0.4487k0.2115 I 47.13 0.1974f0.0401 0.0163k0.0059 36.47 0.0049k 0.0015 0.157720.1239 78.55 0.066720.0179 0.208020.0726 34.92 0.0727f0.0160 0.0925f 0.0508 54.87 0.0531f 0.0186 0.169320.0487 28.77 0.149220.0332 0.011720.0045 38.81 0.0069k0.0028 0.006520.0024 36.57 0.0046f0.0008 0.031420.0101 32.11 0.0307f 0.0058 0.012520.0062 49.79 0.015220.0083 0.0177~0.0030 16.84 0.01612 0.0024 12.47 0.0318& 0.0033 0.032120.0040 14.29 13.14 21.59 26.92 20.33 29.92 26.90 22.06 35.10 22.27 40.83 18.42 18.82 54.71 15.17 10.46 Heart Lungs Digestive tube Esophagus Stomach Intestines Cloaca Liver Pancreas Spleen Kidneys Gonads Eyeballs Brain Panel B Percentages of body weight 0.436 20.113 26.05 0.640 k0.131 0.604 20.184 30.49 0.954 20.222 7.474 22.197 29.40 4.864 20.915 0.267 20.081 30.53 0.121 fO.036 2.554 21.391 54.45 1.636 20.392 3.216 20.745 23.18 1.794 20.380 1.437 20.650 45.24 1.312 f0.470 2.794 20.586 20.97 3.636 20.510 0.199 fO.077 38.51 0.168 20.062 0.106 20.038 35.22 0.114 fO.017 0.523 20.120 23.06 0.754 20.114 0.207 k0.096 46.29 0.366 20.185 0.302 f0.052 17.13 0.397 20.061 0.552 20.095 17.26 0.787 f0.088 20.46 23.22 18.81 29.89 23.94 21.21 35.80 14.03 37.00 14.99 15.19 50.42 15.40 11.14 1 Weights “t” variation L 6.91 L 11.90 L 0.09 M 1.27 L 8.79 L 14.13 L 5.63 L 13.78 L 5.63 L 2.74 L 7.19 L 5.88 L 0.48 M 2.29 L 3.41 L 0.48 M 10.10 M 10.60 L 8.39 L 12.55 L 4.81 L 13.10 L 1.33 M 8.96 L 2.58 M 1.53 M 11.61 M 6.99 M 10.23 M 15.24 of 78 specimens only. Their weight in these specimens has the highest coefficient of variation in this group and the highest in the entire table 1 with the exception of the stomach and cloaca in the larvae. This is evidently due to the beginning of their growth in some of the animals while in others the gonads remained small, as in the larvae. The right and left gonads were not weighed separately but it was observed that the left gonad was appreciably larger in some of the amblystoma after metamorphosis and the smaller right gonad was frequently divided into two or three segments, or fusiform masses, but always apparently connected. This larger left gonad in these salamanders is interesting when one recalls that only the left ovary is developed in birds. In a study of the growth of 100 Leghorn chickens (Latimer, ’24) only one bird was found with a small rudimentary mass on the right side where the ovary should have been located. A further study of the size of the right and left ovaries in adult amblystoma would be interesting. None of the gonads was examined microscopically. The weights of the gonads in the metamorphosed specimens were plotted to see if they would form a bimodal curve, but the distribution was only very scattered with no appreciable double trends. Evidently a few of these glands had just begun to develop. This irregular growth in the gonads is also indicated in their larger coefficients of variation in the post-metamorphosed animals. The greatest variability is evident in the digestive tube and its subdivisions, espe- 142 HOMER B. LATIMER AND PAUL GIBBONS ROOFE cially in the larvae. This may be accounted for, very largely, by the variable amount of material contained within the tube. In rabbits, with a closely regulated supply of food, the contents of the digestive tube is highly variable (Latimer and Sawin, '55). As is to be expected, the brain is the most constant in weight in both groups of these salamanders. The average of all of the coefficients of variation in the larvae is 35.62% and in the post-larval, 24.43%. Panel B, table 1 has the weights of the various organs expressed as percentages of the body weight (preserved body weight). These percentages, as expected, are less variable than the weights in grams in panel A. The average of the coefficients of variation for the larvae is 31.27%, which is a reduction of 12.21% from the average of the weights in panel A. The average for the metamorphosed specimens is 23.68%, or 3.07% less than the average for the weights in grams. These percentages, like the weights in panel A, are much less variable in the metamorphosed salamanders. The coefficients of variation for the percentage weights of the eyeballs and brain in both groups are larger than for their weights in grams. This confirms earlier findings that the central nervous system develops to its normal size more or less irrespective of body weight (Latimer and Sawin, '58). These coefficients of their percentage weights are the lowest in the larval salamanders and the percentage weight of the brain in the post-metamorphosed specimens has the lowest coefficient in panel B. The liver, spleen and kidneys have slightly lower coefficients than the eyeballs in these older salamanders. The two most variable organs in both groups are the cloaca and the gonads. The cloaca's variability is due probably to its variable contents and that of the gonads would be less if these animals had been divided as to sex, for the ovaries are larger in older salamanders, as well as in mammals (Latimer, Roofe and Feng, '61, and Latimer, '56). The percentage weight of the stomach in the larvae has the highest coefficient in this panel, due without doubt to its variable contents. Six of these percentage weights are larger in the larvae and these are the digestive tube and its subdivisions and the pancreas. The other eight organs are relatively heavier in the metamorphosed salamanders. These percentage weights indicate that there are some differences between the preand post-metamorphosis amblystoma. The larvae seem to have relatively larger digestive tubes, while the heart, lungs, liver, kidneys, eyeballs and brain comprise a larger proportion of the entire body weight in the metamorphosed specimens. One would expect to find relatively heavier gonads in the older animals. Hoskins and Hoskins ('19) have made an exhaustive study of the effect of the thyroid gland at time of metamorphosis in the frog. They record their observations upon the change in size of the organs in the control, or nonoperated, frog (Rana sylvatica). They report a decrease in body weight and a decrease in actual size of the heart, liver, spleen and kidneys, but all of these organs are relatively heavier after metamorphosis, due to the greater decrease in the body weight. They find that the left gonads in the frog are usually larger than the right. Thus their observations suggest that the changes in the frog and the tiger salamander during metamorphosis are alike in many respects. Linear measurements in millimeters and as percentages of body length The body, or nose-anus length is shown in the first line of panel A, table 2. This measurement was used to determine all of the percentage lengths in panel B. The total length from tip of nose to tip of tail is given in the second line. The difference between these two dimensions is the length of the tail. This averages 42.10 mm in the larvae and 39.38 mm in the post larval specimens, or a reduction of 6.5% . The last column of panel A shows that there are no significant differences in either of these body lengths in the two groups of salamanders. There are only two measurements in panel A significantly greater in the metamorphosed amblystoma, namely: the lengths of the two pairs of extremities. There are four external measurements significantly greater in the larvae, and all of these are transverse dimensions. The larval specimens have been shown to be heavier (table 1) and now we see that they 143 MEASUREMENTS, TIGER SALAMANDER are broader but not significantly different in body length from the metamorphosed animals. Most of the external measurements are less variable than the linear measurements of the digestive tube and its subdivisions. The average of the coefficients of variation of the external measurements in the larvae is 9.94% and for the digestive tube, 15.14%. The comparable averages in the metamorphosed amblystoma are respectively, 6.42% and 14.32%. Thus all of these measurements are less variable in the amblystoma after metamorphosis. This decrease in the variability of the external measurements may be accounted for, to a degree, by the reduction of the subdermal areolar tissue which would make the external measurements more easily and accurately determined in the metamorphosed amblystoma. The average of all of the coefficients in the larvae is 11.67% and for the older specimens, 9.05%. Thus all of the dimensions are less variable in the older group. The most variable dimension in both groups is the length of the esophagus. It is very short and not sharply demarked from the pharynx or the stomach. The other parts of the digestive tube were easily separated from one another. The most variable of the external measurements are the widths of the body at the belly and the pelvic width. Panel B, table 2 has the linear measurements from panel A changed to percentages of the body, or nose-anus, length. The variability of these percentages of body length is slightly less than that for the lengths in millimeters. The average of all TABLE 2 Linear measurements in millimeters and as percentages of body (nose-anus) length. The “t” values have the same significance as in table 1 97 Larval amblystoma Average and stand. dev. Panel A Coef. of variation 57 Metamorphosed amblystoma Average and stand. dev. “t” Coef. .of vanation Measurements in millimeters Body length (nose - anus) Body length (snout - tip of tail) Jaw length Jaw width Biocular diam. Fore limb Hind limb Pectoral width Belly width Pelvic width Dig. tube length Esophagus Stomach Intestines Cloaca 56.532 3.80 6.72 57.482 2.49 4.34 97.63% 6.01 13.74f 1.53 14.602 1.44 10.632 0.88 16.602 1.47 17.622 1.49 9.802 1.04 10.542 1.32 3.172 0.53 151.50221.55 3.812 0.66 19.142 2.66 115.41f19.21 13.112 1.79 6.15 11.12 9.86 8.27 8.84 8.46 10.66 12.50 16.78 14.22 17.22 13.91 16.64 13.69 96.862 4.31 13.63+-0.94 12.792 0.61 10.422 0.58 17.282 1.10 18.872 1.11 9.482 0.71 9.732 1.00 2.852 0.23 107.11% 14.28 2.192 0.44 15.672 1.48 76.64212.91 12.61-r-1.47 4.45 6.94 4.74 5.60 6.40 5.90 7.46 10.26 8.11 13.33 20.13 9.45 16.99 11.68 L L L L M M L L L L L L L L 0.84 0.50 8.97 1.61 3.01 5.20 2.04 3.99 4.28 13.83 16.47 8.99 13.46 1.78 Jaw length Jaw width Biocular diam. Fore limb Hind limb Pectoral width Belly width Pelvic width Dig. tube length Esophagus Stomach Intestines Cloaca Panel B Percentages of body (nose-anus) Iength 23.752 1.30 24.35f 2.68 11.00 22.26f 0.89 10.52 25.892 2.72 18.122 0.73 7.68 18.882 1.45 30.072 1.69 9.49 29.452 2.79 32.832 1.61 31.252 2.76 8.82 16.502 1.14 10.16 17.362 1.76 16.922 1.55 18.712 2.44 13.07 4.952 0.34 5.622 0.95 16.89 186.15222.00 7.42 266.67f 19.78 3.812 0.75 6.702 1.04 15.58 27.242 2.15 33.792 4.94 14.60 133.13f20.54 203.602 10.89 5.35 21.962 2.57 23.002 3.10 13.48 5.47 4.01 4.04 5.61 4.90 6.92 9.15 6.97 11.82 19.65 7.90 15.43 11.69 L L L M M L L L L L L L L 1.55 9.70 3.70 1.51 3.92 3.28 4.94 5.10 23.31 16.48 9.44 27.61 2.13 M 1.68 144 HOMER B. LATIMER AND PAUL GIBBONS ROOFE of the coefficients of variation for the larvae is 11.08% and for the amblystoma after metamorphosis, 8.74%. This is a reduction of 5% and 3% respectively. As in the preceding panel, the external measurements are less variable than the linear measurements of the digestive tube. The average of the coefficients of variation for the percentages of the digestive tube is 11.29% in the larvae and 13.30% for the metamorphosed specimens. The average of the coefficients for the external measurements is 10.95% for the larvae and 5.88% for the amblystoma after metamorphosis. Changing the measurements of length to percentages of body length usually reduces their variability, and all of these except the external measurements in the larvae are less variable as percentages of body length. An explanation for the increase in these percentages of the external dimensions in the larvae is possibly the greater variability of the body length in the larvae. The length of the jaws is not significantly different in the two groups, but the width of the jaws in the amblystoma after metamorphosis is reduced both in length in millimeters and in relative length. The lengths of the limbs are the only percentage values which are larger in the metamorphosed specimens, although the fore limbs are only slightly longer. Thus the relative length of the hind limb is the only dimension significantly greater in the older amblystoma. The digestive tube and its subdivisions are all longer in the larvae, both in milli- meters and as percentages of body length, but how much of this is due to the greater amount of food in the larval digestive tube is unknown. The percentage length of the entire tube is relatively 30% shorter in the older specimens. The greatest difference is in the length of the intestines for these are 35% shorter in the metamorphosed amblystoma. Does this indicate a change in the type of food in these amblystoma similar to that known to occur in some frogs? Briefly, the hind limbs are relatively longer in the salamanders after metaniorphosis, the body length is not significantly changed and the transverse diameters are relatively shorter, including the width of the jaws. Thus the metamorphosed salamander is a more slender animal than the larval, with longer legs and narrower jaws. Percentages of digestive tube For a better understanding of the relative proportions of the subdivisions of the digestive tube, the weights and lengths of its four subdivisions were changed to percentages of the weight or length of the entire tube and these percentages are shown in table 3. The relative weights are in panel A and the lengths, in panel B. The lowest coefficients of variability are for the weights and lengths of the intestines, but when one considers that the intestines comprise about 40% of the weight and 75% of the length of the digestive tube, this is not surprising. The percentage weights and lengths of the esophagus are the most variable. Its size and difficulty of accurate separation from adjacent parts TABLE 3 Weights and linear measurements as percentages of the weight or length of the digestive tube. The “t” values are the same as in table 1 78 Larval amblystoma Average and stand. dev. Coef. of variation 57 Metamorphosed amblystoma Average and stand. dev. “t” Coef. of variation Esophagus Stomach Intestines Cloaca Panel A Percentage weights 3.722 1.23 33.07 2.532 0.74 19.43 33.802 5.26 33.39 6.49 43.86’5.79 13.20 37.01t4.19 34.47 26.65t6.24 19.02f.6.56 29.19 15.55 11.33 23.41 L M L M Esophagus Stomach Intestines Cloaca Panel B Percentage lengths 2.6020.53 20.58 2.082 0.50 12.5921.65 13.11 14.77* 1.59 75.99 22.71 3.57 71.23+-3.00 8.8221.36 15.42 11.922 1.72 23.86 10.77 4.21 14.40 L 5.67 M 7.57 ’ 6.39 0.39 7.47 6.71 L 9.47 M 11.51 145 MEASUREMENTS, TIGER SALAMANDER has been mentioned above. These may at least contribute to its high coefficient of variability. As in the two preceding tables, the intestines are significantly heavier and longer in the larval amblystoma. In both panels of this table, the esophagus and the intestines are significantly heavier and longer in the larvae, while the stomach and cloaca are larger relatively in the salamanders which have undergone metamorphosis. This contributes additional evidence that there is a change in the proportions of the digestive tube during metamorphosis. were more easily and accurately measured because of the decrease in the subdermal loose tissue. On the whole these weights and linear measurements will predict body weight or body length, respectively, with a fair degree of accuracy. Correlations with body weight and body length The coefficients of correlation between the measurements and body weight and body (nose-anus) length are shown in table 4. AU of the correlations in this table are significant at the 5% level or above. All of the ponderal correlations in panel A, except the weight of the pancreas in the larval salamanders are significant at the 1%level. Seven of the ten correlations are higher in the larval salamanders than in the post metamorphosis specimens. All of the weights of the organs are rather well correlated with body weight in both series of these amblystoma. The correlations of the linear measurements of the larvae in panel B, table 4 are all significant at the 5% level and all except three transverse dSmensions (jaw width, biocular diameter and belly width) are significant at 1 % . All of the linear measurements of the metamorphosed salamanders are significantly correlated with body length, and all except one (pelvic width) are significant at 1 % . In general, these weights and linear measurements are well correlated with body weight or body length respectively. Those measurements with lower correlations are organs with very high variability such as the pancreas, which was very hard to remove accurately. Some of the transverse dimensions have low coefficients of correlation, but these are naturally variable (belly width), or difficult to measure accurately (pelvic width), The linear correlations of the external measurements are generally higher in the metamorphosed animals. It has been suggested that these Heart TABLE 4 Coeficients of Correlation with body weight and body length (nose-anus) 97 Larval amblystoma Panel A Lungs Dig. tube Liver Pancreas Spleen Kidneys Gonads Eyeballs Brain Panel B Jaw length Jaw width Biocular Fore limb Hind limb Pectoral width Belly width Pelvic width Dig. tube leng. Weights 0.615 0.711 0.695 0.816 0.257 0.570 0.724 0.568 0.589 0.354 57 Metamorphosed amblystoma 0.454 0.640 0.442 0.812 0.384 0.648 0.598 0.462 0.405 0.599 Linear measurements 0.858 0.622 0.247 0.665 0.237 0.649 0.642 0.661 0.366 0.521 0.390 0.446 0.225 0.423 0.336 0.263 0.599 0.495 “t” Values for the larval of 2.00 and above are significant at 5% and values of 2.60 and above are significant at 1%. “t” Values for the .metamorphosed amblystoma of 2.61 and above are significant at 5% and 3.40 and above are significant at 1%. Comparison of pre- and postmetamorphosis and adult stages The only known study of the growth of the salamander is that by DuShane and Hutchinson (’44) and they studied only the larval growth in salamanders. Data similar to the present data, but from mature tiger salamanders, have been published (Latimer, Roofe and Feng, ’61). These adult salamanders were collected from three separate ponds and the specimens from one pond differed significantly from the other two ponds. These three ponds and the pond from which the present specimens were collected are all in the Teton National Forest and not too far from the Jackson Hole Biological Station. The 146 HOMER B. LATIMER AND PAUL GIBBONS ROOFE averages of the weights and percentage weights of the specimens in the earlier report are used in making these comparisons. The average body weight of the mature salamander is 8.9 times that of the post metamorphosis animal and there are four organs which increase at nearly the same rate. These organs together with their multiples of increase are: eyeballs (6.2 times), heart (7.4 times), kidneys (7.8 times) and the lungs (9.8 times). The increase in the eyeballs suggests that in the amblystoma as in most mammals the central nervous system is precocious in its development. The liver increases 13.7 times during this period and the entire digestive tube, 17.1 times. Following in order are, the pancreas with an increase of 22.5 times and the spleen with a n increase of 30.4 times. The greatest increase is found in the gonads which increase 57.9 times. However, this is expected for these animals have become sexually mature in this period. Changing the weights of the organs to percentages of body weight, possibly will make these comparisons more clear. The averages of the percentages from the preceding report will be used. The digestive tube and its subdivisions and the pancreas increase in their relative weights from the larvae to the mature salamanders, but they all manifest a decrease in relative weight in the post metamorphosis period. The decrease in the amount of the contents of the digestive tube may account for at least some of this decrease and may also account for a part of the decrease in the weight in grams of the entire body. There are four organs which suggest a continuous growth, for they show an increase at each of these stages. These are: gonads, lungs, liver and spleen. Two organs which increase from larval to adult, but have an increased percentage of body weight in the post metamorphosis stage, are the heart and the kidneys. The eyeballs are unique in that they decrease from the larval to the adult amblystoma, but have their maximum percentage weight in the post metamorphosis period. Again, these are merely the weights and percentage weights at three periods of the entire growth and they do not replace a real growth study of the tiger salamander which is needed. They are presented in lieu of anything more complete. The eight external linear measurements show interesting changes as well as the ponderal measurements. The average body length from the tip of the nose to the tip of the tail increases two times from metamorphosis to maturity. There are five measurements which increase less than the body length and these and their multiples of increase are: jaw length and length of fore limb, both of which increase 1.6 times; the biocular and the jaw width, both 1.7 times; and the hind limb, 1.8 times. Increasing more than the body length are the length of the entire digestive tube, 2.5 times; pectoral width, 2.4 times; belly width, 3.04 times, and pelvic width, 3.9 times. These measurements of total growth suggest that the head and the length of the two pairs of extremities are smaller in the adult while the length of the digestive tube and the width of the body are larger in the adult. Changing the eight l i n e z measurements to percentages of body length will make the differences in these salamanders more evident. These lengths are shown in panel B, table 2 as percentages of nose-anus length while in table 3 of the earlier report (Latimer, Roofe and Feng, '61), they are expressed as percentages of nose-tip of tail. To better compare these percentages the lengths of the linear measurements of the present series have been changed to percentages of nose-tip of tail dimension. The three new percentages (not shown in table 2, panel B) of the head region decrease from their maxima in the larvae to their minima in the adults, indicating the head is relatively largest in the larvae and smallest in the adults. The relative length of the digestive tube is the largest in the larvae decreasing to its minimum in the amblystoma after metamorphosis and then increasing somewhat in the adults. Thus although the digestive tube is relatively heaviest in the adults it is relatively longest in the larval amblystoma. The three transverse diameters of the body are the shortest relatively in the amblystoma after metamorphosis and longest in the adult. This wider body in the adults with reference to length would accommo- MEASUREMENTS, TIGER SALAMANDER 147 Latimer, H. B. 1924 Postnatal growth of the body, systems and organs of the single comb White Leghorn chicken. J. Agri. Res., 29: 363-397. 1956 The ponderal growth of the ovaries and uterus in the fetal dog. Anat. Rec., 225: 731-744. Latimer, H.B., P. G. Roofe and L. S. Feng 1961 Weights and linear measurements of the body and of some of the organs of the tiger salamanLITERATURE CITED der. Anat. Rec., 141: 35-44. DuShane, G. F., and C. Hutchinson 1944 Differences in size and developmental rate between Latimer, H. B., and P. B. Sawin 1955 Morphogenetic studies of the rabbit. XII. Organ size Eastern and Midwestern embryos of Amblyin relation to body weight in adults of small stoma maculatum. Ecology, 25: 414-423. sized race X. Anat. Rec., 223: 81-102. Grant, M.P. 1930 Diagnostic stages of urodele 1958 Morphogenetic studies of the rabmetamorphosis. Anat. Rec., 45: 1-25. bit. XX. A comparison of the weights of the Hoskins, E. R., and M. M. Hoskins 1919 Growth brain and of its parts in a large and in a small and development of amphibia as affected by race of rabbits. Anat. Rec., 132: 619-632. thyroidectomy. J. Exp. Zool., 29: 1-69. date the relatively heavier internal organs as described above. The two pairs of extremities are relatively longest immediately after metamorphosis. Thus the adult salamander has a relatively smaller head, shorter limbs and a more robust body.