MATARESE ET AL.: ICOSTEOIDEI 



577 



Fig. 306. Larvae of Icosteus aenigrnaticus from top to bottom: 9.5 mm SL; 10.2 mm; and 28.5 mm SL, drawn by H. Orr. 



to those for the adults except adults lack a pelvic fin (Abe, 1954; 

 Miller and Lea, 1972; Hart, 1973). The caudal fin contains the 

 perciform number of principal rays, 1 7, with 6-9 procurrent 

 rays on each side. Pectoral fin blades are present at hatching 

 and rays form during flexion. Pelvic fin rays begin development 

 during flexion and are complete in postflexion larvae. At what 

 size the pelvic fins disappear is not known. The last fin rays to 

 form are the dorsal and anal, with their anlagen appearing in 

 the middle of the posterior half of the finfolds at about mid- 

 flexion. Formation of these fins proceeds forward and toward 

 the body margin (Fig. 306). The largest larva available, 28.5 

 mm, has the complete fin ray complement. 



Relationships 



The foregoing brief description of the eggs and larvae of /. 

 aenigrnaticus provides some additional information toward the 

 understanding of the life history of this unique but poorly under- 

 stood fish. Characters discussed here (e.g., sequence of fin for- 



mation and meristics) help support its position among perciform 

 relatives. Sequence of fin formation and reduced number of 

 pelvic fin rays are blennioid-like characters, and 1 7 principal 

 caudal fin rays are the typical percoid number. Eggs, larvae, and 

 early juveniles superficially resemble stromateoid fishes but ad- 

 ditional data are needed before a precise relationship can be 

 determined. To understand this family more fully, we need 

 information regarding the critical juvenile phase as well as a 

 complete osteological examination from preflexion larvae to 

 adults. 



(A. CM.) National Marine Fisheries Service, Northwe.st 

 AND Alaska Fisheries Center, 2725 Montlake Boule- 

 vard East, Seattle, Washington 98112; (E.G.S.) Na- 

 tional Marine Fisheries Service, Southwest Fisheries 

 Center, PO Box 27 1 , La Jolla, California 92038; (W.W.) 

 Marine Ecological Consultants, 53 1 Encinitas Boule- 

 vard, Suite 1 10, Encinitas, California 92024. 



