FUIMAN: OSTARIOPHYSI 



131 



same order as described above, but the sequence differs for Alosa 

 and again for Osmerus. 



Within Ostariophysi, cypriniform larvae (Figs. 62, 63) are 

 largest at hatching (Table 26), the largest sizes represented most- 

 ly by catostomids. The pyriform yolk sac extends from below 

 the head posteriorly to the anus (Fig. 62a). Barbels, when pres- 

 ent, develop very late in Cyprinidae but early in Cobitoidea 

 (sensit Sawada, 1982). Cyprinids display considerable variation 

 in the elaboration of the larval circulatory system. Temporary 

 networks of blood vessels invade portions of the finfolds and 

 the surface of the yolk sac in a variety of patterns to form the 

 larval respiratory system (Kryzhanovskii, 1947). Cobitoideans 

 usually have greatly expanded finfolds, especially those of the 

 pectoral buds. Pronounced external gill filaments are known in 

 the cobitine genera Coto/5 (Kryzhanovskii, 1949;Okada, 1960; 

 Sterba, 1962), Lepidocephaliis (Bhimachar and David. 1945), 

 and A/;5^r«wi (Kryzhanovskii, 1949; Okada, 1960), but not in 

 the non-cobitine cobitoidean genera Botta. Lefua, or Nemach- 

 eilus, nor in other ostariophysans. Cyprinids with cephalic ad- 

 hesive glands include: Ahramis brama (Penaz and Gajdusek, 

 1979); Brachydanio rerio (Frank. 1978); Cypri niis carpio (Hoda 

 and Tsukahara, 1971); Danio malabancus (Jones, 1938); and 

 Notemigonuscrysoleucas (Snyder tXa\., \911\ Loosetal., 1979). 



In characiforms, the yolk sac is short and rounded, not ex- 

 tending to the anus posteriorly (Fig. 64). Most known characids 

 (sensii stricto) and a hepsetid (Bertmar, 1959; Budgett, 1902. 

 1 903), erythrinid (de Azevedo and Gomes, 1 942), and curimatid 

 (de Azevedo et al., 1938) have a temporary larval cephalic ad- 

 hesive organ (more distinct than the apparent glandular mech- 

 anism in cyprinids). Those without such an organ mclude: Ser- 

 rasalmus nattereri (pers. obs.), Metynnis maciilatiis (Azuma, 

 1982), and Brycinus longipinnis (Frank, 1972). The adipose fin 

 appears to develop de novo toward the end of the larval period, 

 not as a remnant of the median finfold. However, the small size 

 of the adipose fin and lack of specimens, photographs, illustra- 

 tions, and descnptions of late larval characiforms prevents ver- 

 ification of this inference. 



Although few species are known as larvae, Siluroidei may 

 contain the greatest diversity of larval characters among Ostar- 

 iophysi (Fig. 65). Most siluroids hatch as altricial larvae with a 

 physiognomy similar to that of characiforms. Ictalurids are more 

 precocial and lack a postlarval (sensu Hubbs, 1 943) phase. Ariids 

 (Gudger, 1918; Ward, 1957) and some loricariids (Lopez and 

 Machado, 1975; Machado and Lopez, 1975) hatch in a highly 

 precocial state, resembling the adult in many aspects of external 

 morphology but retaining a large yolk sac (Fig. 65C). In most 

 families, barbels are usually present at hatching or soon there- 

 after (Fig. 65a). Cephalic adhesive organs are usually absent, 

 but at least one loricariid (Ancistrus sp.) possesses these (Franke. 

 1979). Clarias gariepinus (=C. mossambicus) and Ompok bi- 

 maculatus have an adhesive organ on the venter of the yolk sac 

 (Greenwood, 1955, 1956; Chaudhuri, 1962; Holl, 1968;Bruton, 

 1979). The adipose fin is clearly a remnant of the median fin- 

 fold, as in "'salmoniforms." Larvae of a single gymnotoid, Ei- 

 genmannia virescens. are known (Fig. 65D, E; Table 26; Kirsch- 

 baum and Balon, in prep.). 



Relationships 



The Ostariophysi are thought to be the sister group of the 

 Gonorynchiformes (Greenwood et al., 1966; Rosen and Green- 

 wood, 1970; Gosline, 1971; Fink and Fink, 1981). The next 



closest relatives are Clupeiformes (Gosline, 1971) or "Salmon- 

 iformes" (Greenwood et al., 1966; Fink and Weitzman, 1982). 

 All concepts of Ostariophysi (those with a Weberian appa- 

 ratus) recognize four major groupings, "cyprinoids," "chara- 

 coids," "gymnotoids," and "siluroids." The traditional view of 

 relationships holds that "characoids" are the ancestral stock, 

 giving rise to the remaining lineages, with "gymnotoids" being 

 modified "characoids," and "cyprinoids" being the closest rel- 

 atives of the "characoids" plus "gymnotoids." Fink and Fink 

 (1981) gave a detailed history of the classification schemes for 

 the Ostariophysi and their relatives as an introduction to their 

 work on the subject, which is the only attempt to reconstruct 

 the phylogeny on the basis of a large set of data ( 1 27 characters). 

 Their proposed cladistic phylogeny differs significantly from the 

 traditional one by aligning "gymnotoids" with "siluroids" as 

 the Siluriformes (Fig. 66). 



Developmental characters in systematics 



Few attempts have been made to apply developmental char- 

 acters to the systematics of ostariophysans. Kryzhanovskii (1947) 

 grouped cyprinids into four subfamilies according to details of 

 the larval respiratory system. He also included characters re- 

 lating to reproductive guild (later elaborated in Kryzhanovskii, 

 1948), original (ontogenetically) position of the mouth, and rel- 

 ative size of the pectoral buds. He supported these subfamilial 

 designations with experimental results on the morphology and 

 viability of larvae produced by artificial hybridizations within 

 and among the proposed subfamilies. 



Nakamura (1969) dealt with the cyprinids of Japan. In his 

 English summary, he stated that currently proposed closely re- 

 lated forms (meaning genera, species, and subspecies) have sim- 

 ilar life history characteristics. He noted a few exceptions, such 

 as similar (as adults) species oi Moroco whose early larvae differ 

 morphologically and ecologically. In contrast, he noted that the 

 eggs and early larvae of Ctenopharyngodon idella and Hypoph- 

 thalmichthys molitri.x were very similar although the species 

 were placed in different subfamilies. He used differences in egg 

 and larval morphology to support the previously uncertain sep- 

 aration of the genera Squalidus and Gnathopogon. 



In a similar survey. Loos and Fuiman (1978) attempted to 

 characterize the subgenera of the New World cyprinid genus 

 Notropis in terms of their egg and larval morphology. However, 

 they found substantial variability within the established sub- 

 genera and were unable to characterize them precisely. 



Each of these attempts to apply developmental characters to 

 systematics was concerned only with establishing group mem- 

 bership and not with determining relationships among the groups. 

 Further, none of the work was based on a large data set nor was 

 it approached in a rigorous manner. The difficulties encountered 

 by Nakamura ( 1 969), and especially by Loos and Fuiman (1978), 

 probably were due to the apparently convergent ecomorpho- 

 types expressed by unrelated taxa. The low taxonomic level 

 investigated, combined with the morphological similarity im- 

 plied by von Baer's law, probably accounted for much of the 

 remaining difficulty in detecting consistent differences among 

 taxa. 



Fink and Fink's (1981) classification is based largely on os- 

 teological characters. The great size and diversity of Ostario- 

 physi make a detailed study of developmental osteology and 

 concomitant investigations of bone homologies impractical at 

 this time. Yet, available information permits a preliminary eval- 



