CASTLE: NOTACANTHIFORMES, ANGUILLIFORMES 



65 



Table 9. Extended. 



or both (the genera of Nettastomatidae). There may be a re- 

 duction of the lateral line (Muraenidae. Xenocongridae) or, con- 

 versely, its great elaboration (the congrid Scalanago). In some 

 eels there is an enlargement of the mouth and teeth-bearing 

 surfaces, either by a forward prolongation of the premaxillary- 

 ethmovomer and dentary (Nemichthyidae, Cyematidae and 

 others), or by the turning backwards of the suspensorium with 

 a coincident reduction or loss of the palatopterygoid arch 

 (Ophichthidae, Muraenidae). 



In all eels the branchial region is elongate, the pectoral girdle 

 is separated from the skull and the posttemporal is lost. This 

 lengthening is accompanied by a reduction of the opercular 

 series, narrowing of the gill opening and increased importance 



of branchial pump respiration. The branchial series is displaced 

 backwards with enlargement of the 4th arch as pharyngeal jaws, 

 especially in the Muraenidae. The long branchial wall is sup- 

 ported by an increased number of branchiostegal rays which 

 curve up around the branchial region and expand distally. In 

 the ophichthids the throat is further supported by numerous 

 accessory branchiostegal rays (Parr's "jugostegalia") which are 

 not attached to the hyoid arch and overlap in the ventral mid- 

 line. 



Overall, there is clearly a strong functional correlation be- 

 tween the lengthening, narrowing and smoothing out of the body 

 outline, the increase in body flexibility and modifications in 

 nostrils, jaws, gill openings and lateral line with the mode of 

 life which is a feature of the eels as a group. 



Eggs.—T\\e best known stages in the early life history of the 

 Anguilliformes (less so in the Notacanthiformes) are undoubt- 

 edly their highly distinctive leptocephali. Eggs and earliest larvae 

 are very poorly known. Those of the saccopharyngoids and no- 

 tacanths have not been identified. Grassi (1913), Schmidt (1913), 

 D'Ancona(1931b)and Sparta (1937 e^^e^M.) described eggs and 

 developmental stages of several Mediterranean eel species, mostly 

 from reared material. The basis for identification of eel eggs was 

 thus reliably established. Some errors have been made: Eigen- 

 mann's (1902) eggs of Conger oceanicus were apparently those 

 of Ophichlhus cruenlifer {Nap\m and Obenchain, 1980); Fish's 

 (1928) Angiulla rostrala eggs were those of the muraenid An- 

 archias yoshiae (Eldred, 1968). Little further information has 

 been added recently, although Naplin and Obenchain's (1980) 

 detailed account of Ophichlhiis cruent ifer demonsUalcs the use- 

 fulness of matching planktonic, newly hatched larvae with late 

 stage embryos. Yamamoto et al. (1975a, b) described live eggs 

 and early larvae of Angnilla japonica spawned from a ripe fe- 

 male that had been artificially matured, but there have been few 

 //; v/vo studies. There is no comprehensive information available 

 for the identification and comparison of eel eggs, principally 



Tabi E 10. Extended. 



