FUIMAN: OSTARIOPHYSI 



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r//J Cyprinidae 

 I I Cobitoidea 

 ^B Siluroidei 



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Barbel Formation 

 (onset as percentage of larval period) 



Fig. 70. Frequency dislnbution of relative timing of" barbel forma- 

 tion in ostanophysan species. Cyprinids are represented by 1 barbelled 

 species, not all of which are discussed in the text. 



taxon (Cypriniformes. Characiformes, Siluroidei) are placed near 

 one another, but larval characters are insufficient to demonstrate 

 the monophyly of characiforms or siluroids. The largest number 

 of primitive characters is found in Hoplias (Characiformes), but 

 the cypriniform lineage differs from Hoplias by only three char- 

 acter state changes (node 3). As suggested by Fink and Fink 

 (1981), the gymnotoids are most closely related to siluroids 

 (node 26). 



The cyprinifoim lineage (node 4) is united by two unreversed 

 synapomorphies: an elongate yolk sac (Figs. 62A and 68) and 

 the absence of jaw teeth. Cypriniforms and characiforms uniquely 

 share large eyes at the larger standard size (PCI = 0.6; Fig. 69). 

 This character reverses to a plesiomorphous condition for the 

 siluriform lineage. Synapomorphies of siluriforms include a long 

 peduncle at the larger size (Fig. 69) (a unique state for the group, 

 except for a single reversal in Bagarius), short head at the larger 

 size (highly homoplasious), and small eyes at the smaller size 

 (PCI = 0.0; Fig. 69) (unique except for a reversal in Ictalurus). 

 The gymnotoid, Eigenmannia (node 28), expresses six auta- 

 pomorphies, two unique and two occurring in only one other 

 place on the tree. The uniquely derived conditions are a short 

 trunk at the larger size (Fig. 69) and numerous postanal myo- 

 meres (Table 29). 



Several morphometric characters make valuable contribu- 

 tions to the phylogenetic reconstruction. The axial measure- 

 ments (head, trunk, and peduncle lengths) exhibit a clear trend 

 for increasing head and peduncle lengths at the expense of trunk 

 length through the cypriniform - characiform ^ siluroid - 

 gymnotoid phyletic sequence. A portion of the variation in pe- 

 duncle size is attributable to migration of the anus anteriad in 



this phyletic sequence, as evidenced by decreasing preanal and 

 increasing postanal myomere counts (Table 29). However, the 

 remaining peduncle variation and that of the head length are 

 the result of allometry. 



In Fink and Fink's (1981) study, a single character involving 

 the evolution of a new structure, a pair of barbels, conflicted 

 with their adult-based cladogram. Ontogenetic evidence sup- 

 ports their contention that the presence or absence of barbels is 

 a poor indicator of relationship in ostariophysans. An ontoge- 

 netic character for timing of barbel development (constructed 

 in the same manner as described earlier for other ontogenetic 

 characters) displays two distinct modes (Fig. 70). Cyprinids de- 

 velop barbels during the latter third of the larval period, often 

 after finfold absorption (i.e., as juveniles). Siluroids and co- 

 bitoideans' do so during the first third of the larval period, 

 sometimes prior to hatching. Although the sample size of cob- 

 itoideans is small, it appears that they develop barbels somewhat 

 later than the siluroids. Thus, although barbels are present in 

 adults of all three groups, there is an important difference in 

 these structures between the groups: heterochrony. That het- 

 erochrony is a major cause of evolutionary change was amply 

 attested by Gould (1977). 



Heterochrony in barbels may be an important consideration 

 for classification within siluroids. The number of pairs of barbels 

 (usually counted in the adult stage) is an important character 

 for recognizing siluroid families. At least one pangasiid, Silonia 

 silondia. has been described in which the larvae have three pairs 

 of barbels (nasal, maxillary, and mandibular) that gradually be- 

 come smaller until only one pair of minute maxillary barbels 

 are present on the surface of adults (Karamchandani and Mot- 

 wani, 1956). 



The phylogenetic analysis presented here is based on devel- 

 opmental characters. It shows general congruence with the most 

 thoroughly researched adult-based cladogram (Fink and Fink, 

 1981); however, larval characters alone are not as informative 

 as adult characters. Larval characters support the new idea that 

 gymnotoids are more closely related to siluroids than to char- 

 aciforms. Characiforms appear to be primitive ostariophysans 

 by virtue of the basal location of the relatively primitive char- 

 aciform Hoplias. The apparent paraphyly of characiforms and 

 siluroids is due to the lack of shared characters for each of these 

 groups and would be altered by the reasonable addition of the 

 numerous adult autapomorphies discussed by Fink and Fink 

 (1981). Once monophyly is demonstrated by adding adult char- 

 acters, Hoplias would probably occupy a basal position (with 

 respect to the other three characiforms examined here) on a 

 characiform lineage. However, the position of this lineage with 

 respect to that of the cypriniforms may or may not agree with 

 Fink and Fink's (1981) adult-based cladogram. 



School of Natural Resources, S. T. Dana Building, 

 University of Michigan, Ann Arbor, Michigan 48109. 



' Cobitoideans included here and in Fig. 70 were: Cobitidae— Bo/;a 

 .vafir/i; (Changjiang, 1976); Cobilis taenia (Chyung. 1961; Koblitskaia, 

 1981; Kokhanova, 1957; Kryzhanovskii, 1949; Kryzhanovskii et al., 

 1951; Menasse, 1970); Mtsgurnus anguillicaudalus {Chyung,. 1961; Ko- 

 bayasi and Moriyana, 1957; Okada, 1960; Okada and Seiishi, 1938; 

 Suzuki, 1955, 1968); Homalopteridae— A'emac/jei/jis dorsalis (Kry- 

 zhanovskii, 1949). 



