130 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 





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Fig. 64. Representative characiform larvae. Serrasalmidae: Serrasalmus nattereri (UMMZ 211677) 8.2 mm TL (upper). Characidae: Hy- 

 phessobrycon cf. callistus (UMMZ 21 1676) 6.6 mm TL (lower). 



1960), but this is in doubt (N. Komada, pers. comm.) and has 

 not since been confirmed. 



Characiform eggs are poorly known; most information is from 

 the aquarium hobby literature. Known characid (sensu Gery, 

 1977) eggs are small (0.8 to 1.2 mm). However other families 

 have eggs between 2 and 4 mm (e.g., Alestidae, Anostomidae, 

 Curimatidae, Hepsetidae, Serrasalmidae). Apparently most 

 species have eggs that adhere to plants. Franke (1981) described 

 adhesive threads (gallertigen Klebfdden) on the surface of the 

 egg of Ctenolucius hujeta (Ctenoluciidae) and noted that this 

 was the mechanism by which they attached to plants. My ex- 

 amination of eggs supplied by Dr. Franke found the adhesive 

 structure to be a membranous pedestal rather than adhesive 

 threads (Fig. 6 1 ). This is the only known chorionic modification 

 of ostariophysans. 



Most siluroids have demersal, medium sized eggs ( 1 to 4 mm). 

 Some are tended by one or both parents [e.g., Clarias batrachus 

 (Mookerjee, 1946; Mookerjee and Mazumdar, 1950), Ictalurus 

 punctatus (Tin, 1982c)]; others are not given parental care [e.g., 

 Clarias gariepinus (HoW, 1968; Bruton, 1979), Pangasius sutchi 

 (Varikul and Boonsom, 1969)]. The eggs are typically spherical; 

 however, Clarias eggs are often slightly elliptical (Mookerjee, 

 1946; Greenwood, 1955; Bruton, 1979). Some callichthyids de- 

 posit small eggs (ca. 1.0 mm) in a foam nest on the surface of 

 still waters (Kryzhanovskii, 1949). Parents in several families 

 carry their eggs. Some loricariids (e.g., Loricaria spp.) carry a 

 mass of eggs by means of fleshy appendages of the lower lip. 

 Aspredo laevis eggs apparently are attached by vascularized stalks 

 to the venter of the female (Wyman, 1859). Finally, ariids are 

 oral incubators with perhaps the largest eggs of all oviparous 



teleosts (10 to 25 mm) (Chidambaram, 1942; Gudger, 1912, 

 1916, 1918; and other authors). Although yolk is usually yellow 

 to slightly orange or brown, several species have unmistakably 

 green yolk [e.g., Bagarius bagarius (David, 1961), Clarias ba- 

 trachus (Mookerjee, 1946; Mookerjee and Mazumdar, 1950), 

 Heteropneustes fossilis (Pal and Khan, 1969), Loricariichthys 

 sp. (Taylor, 1983), Phractura ansorgei (Foersch, 1966)]. At least 

 one siluroid, the silurid Ompok bimaculatus, has reddish brown 

 yolk (Chaudhuri, 1962). A few species have a jelly-like coat 

 surrounding the chorion [e.g., Bagarius bagarius (David, 1961), 

 Parasilurus asotus (Kryzhanovskii et al., 1951), Phractura an- 

 sorgei (Foersch, 1966), Trachycorystes insignis (Burgess, 1982)]. 



Larvae 



Most ostariophysans hatch in an altricial state at about the 

 time when pectoral buds form, but before the head becomes 

 free from the yolk sac and retinal pigment develops, although 

 there is variability in the exact stage. The yolk sac is usually 

 large and cumbersome, enforcing a stationary existence during 

 the first days, either on the substrate (most commonly) or at- 

 tached to plants by means of a cephalic adhesive mechanism 

 (found in most characiforms and a few cyprinids, but structur- 

 ally diflTerent in these groups). Caudal fin rays diflierentiate first, 

 followed by nearly simultaneous formation of dorsal and anal 

 fin rays. Pectoral and pelvic fin rays develop near the end of the 

 larval period. The gonorynchiform Chanos hatches at about the 

 same stage of development as ostariophysans, but Atosa and 

 Osmerus hatch somewhat later (i.e., pectoral buds and retinal 

 pigment are clearly developed). These outgroups generally have 

 pelagic larvae at hatching. Fin rays in Chanos develop in the 



