378 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Fig. 200. Larvae oi Stylephorus chordalus 21.4 mm SL, ZMUC uncataloged. 



primary basis for the present identification of larval L. guttatus 

 (Figs. 196 and 197). Aletavelifer multiradialits {Fig. 198) and 5. 

 chordalus (Figs. 1 99 and 200). Total vertebral/myomere counts 

 range from 62-200 (Table 98) in trachipterid, radiicephalid, 

 lophotid and regalecid fishes, but care should be taken since 

 these elongate forms are often damaged in capture and the pos- 

 teriormost myomeres are difficult to discern in larvae. 



Rays of median fins are either stout, unsegmented, spine-like 

 elements or typical soft rays. Previous researchers have been 

 inconsistent in their treatment of these elements as spines or 

 rays and ontogenetic variability likely exists. For these reasons, 

 total element counts are reported without reference to spine or 

 ray designation (Table 98). Furthermore, because of the lack of 

 developmental series in collections, few data exist on the se- 

 quence of development of these and other fin elements. As a 

 result, dorsal element counts delimit the genera of veliferid fishes 

 for example (Table 98), but are not developed in a 5.7 mm NL 

 Hawaiian specimen (Fig. 198). Identification of this specimen 

 (Fig, 198) as M. midtiradiatus is based on distributional records 

 (Walters, 1960; Heemstra, in press). In larval L. guttatus (Fig. 

 196; identification based on distributional records of Parin and 

 Kukuyev, 1983), total dorsal elements are developed by 8.6 mm 

 SL but counts indicate some overlap with veliferid species (Ta- 

 ble 98). In the elongate forms, dorsal element counts are less 

 valid identification criteria since complete differentiation of ele- 

 ments occurs late in development (approximately 44 mm SL in 

 Lophotus lacepedei, HML 6851; 83 mm SL in Eumecichthys 

 fiski. MCZ 42264). 



The absence of the anal fin characterizes adult trachipterid 

 and regalecid fishes (Table 98), but its absence in early larvae 

 cannot be considered diagnostic. In genera possessing an anal 

 fin, differentiation of elements is evident in our material at 18 

 mm SL in R. elongatus (Fig. 198); 7.5 mm NL in S. chordatus 

 (Fig. 199); 33.5 mm SL in E.fiski; 5.7 mm NL in M. multiradia- 

 tus (Fig. 198); and 8.6 mm SL in L. guttatus (Fig. 196). Size at 

 first differentiation of anal elements of Lophotus spp. is un- 

 known but total element counts can serve to delimit young 

 Radiicephalus and Lophotus (Table 98; compare Figs. 198,201). 



Larvae of these two forms can be easily confused due to the 

 common possession of the distinctive ink gland (Figs. 1 98, 20 1 ). 

 Total number of pectoral rays overlap considerably among 

 lampriform fishes and are of limited diagnostic value (Table 

 98). Total pelvic elements are of potential use in identification 

 but ontogenetic variability is great and care should be taken 

 until descriptions of full transformation series are available. 

 Total caudal elements are diagnostic among some lampriform 

 genera (Table 98), and, as previously discussed, details of caudal 

 morphology are important larval identification criteria. 



Relationships 



Our present knowledge of the egg and larval taxonomy of 

 lampriform fishes is inadequate to the task of fully understand- 

 ing phylogenetic relationships. Although larval stages have been 

 described for 8 of 1 2 genera (those of Agrostichthys. Desmo- 

 dema, Velifer and Eumecichthys remain unknown), full de- 

 velopmental series and detailed studies of developmental os- 

 teology and morphology are lacking. Among those taxa for which 

 some ontogenetic data are available, selected characters may 

 elucidate relationships within the Lampriformes and between 

 this group and other teleostean fishes. These are: (1) Egg mor- 

 phology. The distinctive eggs of lampriforms (Table 99, Figs. 

 193, 194) are likely specializations for epipelagic incubation 

 (Breder, 1962) and, if considered a derived condition, tend to 

 support the conclusion of a common ancestry for the group. 

 Complicating this interpretation is the lack of data on egg mor- 

 phology in all lampriform genera (Table 99) as well as the com- 

 mon possession of somewhat similar (although probably inde- 

 pendently evolved) egg morphology in other fishes (Orton, 

 1955a); (2) Precocious embryonic development. At hatching, all 

 known lampriform larvae possess fully developed, protrusible 

 jaws; functional, differentiated guts; and pigmented eyes. This 

 complement of precociously developed features shared by lam- 

 priform taxa may be a specialization for early, successful feeding 

 in the low prey densities of the epipelagic habitat. To my knowl- 

 edge, only exocoetoid fishes exhibit similar development; (3) 

 Elongate anterior dorsal elements. All known lampriform larvae 



