16 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Table 3. Examples of Use of Characters of Early Life History Stages in Taxonomic and Systematic Studies. X indicates range of stages 



and taxonomic levels at which characters vary. (X) indicates infrequent state. 



Developmental stage 



Character 



Meristic characters 

 Fin spines/soft rays 

 Principal caudal rays 

 Pelvic fin 

 Dorsal/anal fin 

 Pectoral fin 

 Vertebrae 



Branchiostegals 

 Gill rakers 



Larval characters 



Body shape 



Snout shape 

 Pigment patterns 



Head spines 



Fin ray elongation 

 Fin ray ornamentation 

 Fin ray serration 

 Pinfold size/shape 

 Preanal finfold 

 Pectoral size shape 

 Larval gut 



Shape 



Length 

 Larval eye 



Shape 



Stalked 



Choroid tissue 



Migration 



Other characters 

 Egg characters 

 Osteological development 

 Scale formation 

 Photophore formation 

 Size at developmental stage 

 Fin development sequence 



• Emphasis on oil globule placement in yolk-sac larvae. 



interested in tracing the sequence of development. The em- 

 bryologist's approach will probably provide more useful infor- 

 mation for systematic investigations. 



Although excellent, early descriptive work was done on teleost 

 embryology (e.g. Wilson, 1891), comparative research on de- 

 velopment needs to be done to allow an evaluation of its value 

 to syslematics, a subject that has proven so fruitful among in- 

 vertebrates. It appears, from the characters that have been stud- 

 ied in greatest detail, that convergence may overshadow phy- 

 letically significant information. For instance, the egg envelope 

 sculpturing on Pleuronichthys, a pleuronectiform, was found 



even on scanning electron microscope examination to be quite 

 similar to that on Synodus, a myctophiform (Sumida et al., 

 1979). Phylogenetically diverse fishes often have round pelagic 

 eggs, about 1 mm in diameter, with a single oil globule. Demersal 

 eggs from equally diverse fishes are generally larger than I mm 

 and develop a vitelline circulatory system. Yolk segmentation 

 seems to be a character of more primitive fishes, but some 

 carangids and other perciforms have yolks that are secondarily 

 segmented in an evolutionary sense. Detailed studies are needed 

 to sort out these and other features of the teleost egg and its 

 embryonic development in a systematic context. 



