66 



ONTOGENY AND SYSTEMATICS OF FISHES- AHLSTROM SYMPOSIUM 



Table 1 1. Some Osteological Characters of the Anguilliformes. + = All or most species; ( + ) = some species; * = presumed primitive 



condition. 



because only a few species have been studied from just six 

 families. Major characters of eggs of these families are collated 

 in Table 12, which also includes selected references. Eggs and 

 earliest larvae of Ophichthus cruentifer are illustrated as an ex- 

 ample in Fig. 30. 



Eel eggs are large; the chorion is thin and clear, but may have 

 minute chromatophores; the perivitelline space is wide; the yolk 

 makes up about one half of the egg diameter and is segmented, 

 with or without chromatophores. Oil globules are usually pres- 

 ent (absent in Muraenidae and Nettastomatidae) but the number 

 and size may vary during development. Development takes 

 around 4 days at about 20 C in Gnathophis mystax (Thomo- 



poulos, 1956) and in O. tTM£'n//7er(NaplinandObenchain, 1980) 

 but may be several days longer. The yolk reduces in size and 

 the embryo reaches a hatching length of about 4.5-5.5 mm, 

 coiling once or more around the yolk. While the late embryo 

 may possess conspicuous melanophores and segmentation, the 

 definitive number of myomeres and the characteristic pigmen- 

 tation of the lai~vae, if any, are not usually fully established until 

 after hatching. 



Leptocephali.—The yolk-sac larva ("preleptocephalus" or en- 

 gyodontic stage) which is liberated from the egg is characteris- 

 tically elongate, with a tear-drop shaped to elongate yolk. It 



Table 12. Characters of Anguilliform Eggs. 



