JUHNSUN and LOESCH: MOKPHULUGY A.NU UE\ ELUfMKM UK AMERICAN SHAD 



10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 

 10 



9 

 9 

 9 

 9 



9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 

 9 



TABLE 5. — Summary of fin development sequence in larvae of Alosa sapidissima (Wilson) 



Standard length 1 - 2 



'Rays were present but not necessarily ossified. 



! Rays were stained blue or red for counting. (Blue = cartilaginous; Red = ossified bone.) 



-'Includes the radial and basipterygium bones. 



'Incipient rays are evident in yolk-sac larvae, but do not stain with Alcian Blue or Alizarin Red S. 



SL, and is completed by 18 mm SL. A specimen 12.1 

 mm SL exhibited the following characteristics of ear- 

 ly notochord flexure: The posterior end of the 

 notochord was beginning to tip up dorsally; one 

 parhypural and the first four hypurals were formed; 

 the anterior portion of the first, second, and third 

 hypurals and parhypural absorbed Alizarin Red S 

 stain, indicating that the structures were ossifying; 

 the fourth hypural and the posterior portion of the 

 first three hypurals and parhypural absorbed Alcian 

 Blue stain; a cartilaginous haemal spine was also evi- 

 dent in this specimen. Another specimen, 13.2 mm 

 SL, exhibited the following characteristics for a lar- 

 vae in midflexion (Fig. 8C): The posterior end of the 



notochord was curved dorsally and then flattened in- 

 to an S shape; five hypurals were distinct, with 

 hypurals 1,2, and 3 absorbing Alizarin Red S in the 

 anterior portion of the structure; both haemal and 

 neural spines were present, absorbing both Alcian 

 Blue and Alizarin Red S stains; the first evidence of 

 the first uroneural appeared in this specimen. 



Late flexion larval A. sapidissima are characterized 

 by complete flexure of the notochord and evidence of 

 segregation into the uroneurals and ural vertebra 

 (Fig. 8D). A cartilaginous sixth hypural plate is also 

 evident. Two slightly fused epural bones are evident, 

 along with the first formation of the neural arch. Both 

 the neural arch and epurals appear as cartilage. 



331 



