518 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 1 26. Distinguishing Characters Useful in Identification (to Genus) of Flexion and Postflexion larvae of Carangidae. Presence 



of character indicated by " + ," absence by "-" and no data by "'0." Species and sources on which this table is based are listed in preceding table. 



except for original observations on Gnathanodon speciosus, Naucrates diictor. Parastromaleus niger. and Scomheroides lysan. Character definitions 



follow Laroche et al. (MS). Information in this table should be considered preliminary, awaiting more thorough descriptions. 



posterior margin of the preopercle, usually first appearing in 

 larvae 2.0 to 4.0 mm NL, which coincides with yolk sac ab- 

 sorption. 



Carangids develop two series of preopercular spines, one se- 

 ries along the posterior margin of the preopercle and another 

 along the anterior margin, called the "preopercular crest" by 

 Ahlstrom and Ball (1954). Both series have an upper and lower 

 segment (Fig. 270). The number of preopercular spines does not 

 seem to reach a constant number as in larvae of many other 

 fish families. Instead, the number of spines in both series in- 

 creases through preflexion, flexion, and postflexion stages to a 

 maximum of usually about 9 in the anterior and 1 1 in the 

 posterior series, then decreases in number during transformation 

 and early juvenile stages. Usually just prior to or during the 

 early juvenile stage, preopercular spines become completely 

 overgrown by tissue and bone. Development of preopercular 

 spines in both the anterior and posterior series proceeds along 

 the margins away from the angle of the preopercle. Conversely, 

 reduction in preopercular spination proceeds toward the angle. 

 When spines are present on either the anterior or posterior 

 margin, a spine is always present at the angle of the margin, and 

 it is always the largest. The size and shape of this spine are 

 particularly useful in distinguishing carangid taxa (Table 126). 



For example, Seriola zonata and OUgoplites saurus (Fig. 273C, 

 273B) have a preopercular spine with a spinule(s), and Elagatis 

 hipinmilata has serrated preopercular spines (Fig. 273A). 



A median supraoccipital crest develops on the head during 

 the preflexion stage in many species (Table 1 26) and persists 

 until late in the transformation stage when it becomes overgrown 

 by tissue and bone. The supraoccipital crest is very useful in 

 distinguishing carangids since there are relatively few marine 

 fish families which have larvae with a crest. The shape of the 

 supraoccipital crest has been used to distinguish carangid larvae 

 of various taxa (Aboussouan, 1975), however, the difliculty in 

 defining shape characters makes them somewhat subjective and 

 of questionable reliability. However, some taxa, i.e., Elagatis 

 hipinmilata (Fig. 273A) and Chloroscombrus chrysurus (Fig. 

 270D), have crests which do appear quite distinct from those of 

 other known carangid larvae. 



Among other head spines, supraocular spines and serrations 

 develop in many taxa (Table 126). The larger multiple supra- 

 ocular spines present in Naucrates diictor (Fig. 272B) and ser- 

 rated pterotic ridge in Trachinotus spp. (Fig. 272A) are notable. 

 All species develop posttemporal and/or supracleithral spines 

 which vary in number, usually 1-5, and relative size among 

 taxa (Fig. 270-274). 



