﻿REVIEW OF GENUS DOROSOMA — ^MILLER 



407 



Table 11. — Proportional measurements o/Dorosoma smithi at various sizes, shomng 



changes with age 



[Expressed in thousandths of the standard length. Compiled from table 8] 



Measurement 



Rfo del Fuerte, U.S.N.M. 

 No. 129952 



Young (6) 



Range Aver. 



Adults (8) 



Range Aver. 



Rio Mocorito, U.S.N.M. 

 No. 129951 



Young (4) 



Range Aver^ 



Adults (6) 



Range 



Aver- 

 age 



Standard length, mm 



Dorsal origin to tip of snout... 

 Pelvic insertion to tip of snout 



Anal origin to caudal base 



Head: 



Length 



Depth 



Width. 



Eye, length 



Snout-feye 



Dorsal filament, length 



Anal fin, basal length 



Pectoral fin, length 



Pelvic fin, length 



Mandible, length 



Upper jaw, length — 



62- 79 

 493-531 

 484-526 

 321-304 



318-335 

 246-257 

 131-146 



76- 86 

 132-143 



84-158 

 239-254 

 204-218 

 126-138 

 103-117 



88- 92 



65 

 514 

 506 

 340 



323 

 251 

 141 



80 

 138 

 126 

 245 

 212 

 134 

 111 



90 



85-122 

 475-506 

 461-479 

 363-382 



286-305 

 215-234 

 124-138 

 63- 69 

 116-125 

 131-174 

 247-275 

 191-209 

 110-123 

 90-101 

 76-83 



104 

 484 

 468 

 374 



295 



224 



128 



66 



120 



161 



263 



199 



117 



95 



80 



74-80 

 615-627 

 503-507 

 352-302 



323-333 

 254-256 

 123-139 



78- 79 

 137-141 

 163-177 

 248-268 

 214-223 

 136-138 

 106-110 



87- 90 



77 

 521 

 505 

 357 



329 

 255 

 134 

 78 

 139 

 169 

 258 

 217 

 137 

 109 



82- 91 

 506-525 

 482-494 

 362-378 



305-321 

 237-248 

 127-134 



74- 77 

 128-136 

 168-197 

 255-273 

 207-215 

 131-137 



99-104 



83- 89 



86 

 612 

 489 

 367 



312 



243 

 130 



75 

 132 

 179 

 264 

 211 

 13 a 

 102 



85 



The reliability of the above discussion of the changes with growth 

 in the dorsal filament is subject to considerable refinement, because 

 there is obvious individual variation, probable racial variation, and 

 possible sexual variation in the length of this structure. The general 

 picture, however, seems clear. 



Other changes with age appear to take place in some of but not all 

 the species of Dorosoma Thus the relative position of the dorsal 

 fin advances with age in all but anale; the head becomes narrower 

 with growth in chavesi and smithi, broader in cepedianum, but shows 

 no significant change in anale; the relative length of the anal fin (as 

 expressed by the length of its base) increases in all but anale; the 

 pectoral fins appear to become shorter with increasing size in chavesi 

 and smithi and longer in cepedianum, but show no significant change 

 in anale; the pelvic fins also seem to decrease in size in smithi but not 

 in the other species (tables 7, 10, and 11 and Hubbs and Miller, 1941, 

 p. 235). The changes in the proportionate sizes of the pectoral and 

 pelvic fins may well be correlated with sex ^° rather than with age, or 

 they may represent a direct environmental response, such as that 

 demonstrated by Hubbs and Whitlock (1929) for certain characters 

 of the young of Dorosoma cepedianum. 



w Because much of the material measured represented types or rare specimens, no sex determinations 

 were made. There appear to be no clear-cut external differences between the sexes. 



