50 



ONTOGENY AND SYSTEMATICS OF FISHES -AHLSTROM SYMPOSIUM 



shape, modification, autogenous or fused to the centra) of neural 

 and haemal spines on preural centra associated with the caudal 

 fin (Washington and Richardson, MS; Dunn and Matarese, this 

 volume), and number of vertebral centra supporting the caudal 

 fin (Washington and Richardson, MS; Fahay and Markle, this 

 volume). 



Attention has recently been directed toward the presence of 

 radial cartilages (their position and shape during development) 

 in the caudal fin of certain teleosts (Kendall'; PotthofT et al., 

 1984). These structures may contain information of value in 

 assessing phylogenetic relationships. 



Squamation.—The development of scales in teleosts has been 

 described for a variety of taxa (e.g.. Berry, 1960; Burdak, 1969; 

 Fujita, 1971; White, 1977; Potthofl'and Kelley, 1982). The se- 

 quence of development of scales and their origin on the fish 

 differs among taxa, and scales undergo changes with ontogeny 

 (e.g.. White, 1977; Potthoffand Kelley, 1982). The acquisition 



' Kendall, A. W., Jr. 1981. Ventral caudal radials— oft overlooked 

 structures. (Paper presented at annual meeting Amer. Soc. Ichthyol. 

 Herpetol., Corvallis, OR, June 1981; Abstract in Copeia 1981:935). 



of scales on fish usually occurs during their transformation to 

 the juvenile stage; however, a number of groups (e.g., Zaniolepis. 

 serranids, holocentrids, and xiphiids) acquire scales during the 

 larval period. Such developmental changes have apparently not 

 been analyzed among diverse groups of fishes. 



Perspective 



Developmental osteology of teleosts appears to be an under- 

 exploited approach of potential value in increasing our under- 

 standing of the relationships of fishes. Studies of developmental 

 osteology of teleosts may contribute much to our understanding 

 of homology, the central concept of all biological comparisons 

 (Inglis, 1966; Bock, 1969; Wake, 1979) in our search for prim- 

 itive and derived character states. A number of investigators 

 present at this symposium are actively engaged in evaluating 

 ontogenetic changes in ossified structures in their studies of 

 various taxa of larval fishes. An appraisal of this method may 

 well be in the future, but evidence provided during the course 

 of this meeting will contribute to such an evaluation. 



Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, 2725 Montlake Boulevard East, 

 Seattle, Washington 981 12. 



Otolith Studies 

 E. B. Brothers 



ALTHOUGH the value of otolith studies in systematic ich- 

 thyology is well established, essentially all studies to date 

 deal with the otoliths of adults, or only incidentally juveniles, 

 and are usually limited to the external morphology of the typ- 

 ically largest otolith, the sagitta (see reviews of Weiler, 1968; 

 Casteel, 1974; Hecht, 1978; Huygebaert and Nolf, 1979). Oto- 

 liths of larvae, which are of recent interest in terms of age, 

 growth, mortality, and life history studies (Brothers et al., 1976; 

 Struhsaker and Uchiyama, 1976; Methot and Kramer, 1979; 

 Townsend and Graham, 1981; Kendall and Gordon, 1981; La- 

 roche et al., 1982; Lough et al., 1982; Bailey, 1982; Brothers et 

 al., 1983) have been ignored from a taxonomic point of view. 

 This is perhaps not surprising due to their very small size and 

 generally simpler form, with an apparent lack of obvious dis- 

 tinguishing external features. Although the internal structure of 

 larval otoliths appears to be more variable than the external 

 form, no comparative taxonomic studies have been attempted 

 to date. In addition, relatively little has been done on compar- 

 isons of these features of adult otoliths, noting that in a real 

 sense, the internal anatomy of the adult otolith is just the cu- 

 mulative historical record of ontogenetic changes in external 

 structure and growth patterns. Comparative studies on features 

 other than external appearance have tended to be at the crys- 

 tallographic, mineraiogical and chemical level. Carlstrom's ( 1 963) 

 research on the crystallographic structure of fish otoliths and 

 otoconia was a pioneering attempt to apply structural and com- 



positional information to understanding the broad outlines of 

 vertebrate evolution. A few studies have followed this line of 

 investigation (Lowenstam, 1980, 1981; Lowenstam and Fitch, 

 1978, 1981), however the discrimination ability of crystallo- 

 graphic techniques is certain to be limited by the relatively few 

 crystalline varieties known to exist in ear stones. Analysis of 

 the amino acid composition of the major organic fraction of 

 otoliths (Degens et al., 1969) offers another possibility for taxo- 

 nomic information, however it is unlikely to be useful for spe- 

 cific identification of individuals. Finally, trace element analysis 

 of otoliths (Gauldie et al., 1980; Papadopoulou et al., 1978, 

 1980) may allow for stock and perhaps species discrimination, 

 but again the small sample sizes offered by larval otoliths impose 

 severe or impossible methodological problems unless x-ray mi- 

 croprobes or ion microscopes are employed. New analytic tools 

 for chemical studies could offer unique insights into fish sys- 

 tematics. 



Recently renewed interest in fish otoliths, due primarily to 

 the recognition of daily growth increments (Pannella, 1971, 

 1980). has resulted in an expanding effort toward collecting, 

 examining and cataloging the otoliths of larval fishes. As we 

 begin to study the external and internal structure of this material 

 for systematically useful characters, we should begin to develop 

 a new set of morphological criteria for species identification, 

 taxonomic relationships, and perhaps phylogenetic reconstruc- 

 tion. 



