EARLY DEVELOPMENT OF THE TEN-POUNDER 



643 



Table 12. — Standard length measurements for individual 

 specimens, determined periodically during laboratory 

 growth experiments 



Table 13. — Variations in rates of change in standard 

 length during and following metamorphosis for speci- 

 mens in laboratory growth experiments 



include data on shrinking in three early meta- 

 morphic larvae. Kates of change in standard 

 length through the early metamorphic period, to 

 a size of about 25 mm., ranged from —0.750 to 

 — 1.428 mm. per day, and averaged — 1.061. Fur- 

 ther shrinking to a size of about 20-21 mm. pro- 

 ceeded at a slower rate, — 0.231 to — 0.500 mm. per 

 day, and averaged —0.342. Initial length in- 

 crease following shrinking, from a size of about 

 20 mm. to 25 mm., was considerably slower, + 0.118 

 and +0.154 mm. per day for the two specimens, 

 and averaged +0.140. The slow rate during the 

 period of initial increase following shrinking is 

 not explained. 



Alikunhi and Rao (1951, p. 103) stated concern- 

 ing their experiments with E. saurus in Madras, 

 India, "Events leading to the transformation of 

 the transparent, ribbon-shaped post-larva, 35.0 

 mm. long, into the young adult, measuring only 

 23.5 to 25.0 mm. in length, have been progressing 

 at a quick pace and were completed in the course 

 of only 9 days." It is impossible to determine the 

 rate of change accurately from this statement; 

 but if the change was from 35 mm. down to 20 mm., 

 and up to about 24 mm. in 9 days, the overall 

 change would be 19 mm., and the rate, 2.11 mm. 



Specimen 

 number 



Early meta- 

 morphic: 



1 



8 



9 



Mid-meta- 

 morphic: 

 1 



Late meta- 

 morphic: 



1.. 



2 



3 



4. 



5 



Juvenile: 



1. 



3 



5 



6 



7 



Period covered 



Apr. 22-May 4.. 

 Apr. 22-May 6.. 

 Apr. 13- Apr. 20. 



May 4-May 19. _ 

 May6-May 19.. 

 Apr. 20-Apr. 30 

 May 19-June 14. 

 May 19-June S.- 



June 14-Aug. 28. 

 May 20-July 4.. 

 June6-July 17.. 

 May 20-June 27. 

 June 6-July 4 



Aug. 28-Sept. 25. 

 July 17-July31... 

 July 4-Aug. 15. .. 



June 4-Oct. 1 



June 4-Aug. 15. .. 



Average 

 rate of 



increase 

 (or de- 

 crease) 



per day 

 (mm.) 



-0.750 

 -1.143 

 -1.428 



-.333 

 -.231 

 -.500 

 +.154 

 +. 118 



+.467 

 +.622 

 +.756 

 +.658 

 +.821 



+ 1.286 

 +.643 

 +.667 

 +.630 

 +.597 



per day. The average rate for a similar change 

 for my specimens was 0.474 mm. per day, or about 

 one-fifth that for their experiment. If in the pe- 

 riod of 9 days, their larva decreased from 35 mm. 

 down to 24 mm., the rate would be —1.222 mm. 

 per day, or comparable to my average rate for this 

 period (early metamorphic), —1.061 mm. per day. 

 The Indian Council of Agricultural Research 

 (1951) reported the transformation completed in 

 about 20 days for E. saurus, but gave no sizes. 



Growth during the late metamorphic and ju- 

 venile periods. — The rates of change in standard 

 length during the late metamorphic and juvenile 

 periods range from +0.467 to +0.821 mm. per 

 day, and averaged +0.626, for the late meta- 

 morphic period (from 25 mm. to 60 mm.) ; and 

 + 0.597 to +1.286 mm. per day, and averaged 

 + 0.694, for the juvenile period (above 60 mm.). 

 Excluding the + 1.286-mm.-per-day value for 

 specimen No. 1, the juvenile period average was 

 + 0.628 per day, which is comparable to the + 0.626 

 average for the late metamorphic period. 



Undoubtedly the growth rates from these ex- 

 periments varied from those of fish in their nat- 

 ural habitat, and probably were affected by water 

 temperature, type and quantity of food, limited 

 space in aquaria, and periodic handling during 



