154 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Fig. 81. (A) Yolk-sac larvae of Spirinchus starksi. Osmeridae, 7.4 mm, from Morris (1951); (B) Yolk-sac larvae of Plecoglossus altivelis. 

 Plecoglossidae, ca. 6.0 mm, from Okada (1960); (C) Post yolk-sac larva of Salangichlhys inicrodon (Salangidae), ca. 7.0 mm, drawn from two 

 specimens in CAS 504 1 5. 



Ahlstrom (pers. comm.) deteimined that, in general, osmerid 

 larvae were unique from other elongate larvae in the California 

 Current system by having a single mid-ventral row of mela- 

 nophores below the gut. Based on all the available larval de- 

 scriptions for osmerids, including the Atlantic forms, this single 

 row of melanophores appears to be a hallmark of the family. 

 Listed in Table 37 are sources of larval and juvenile descriptions 

 for the ten species of smelts. 



These descriptions use various characteristics for each species 

 and are not comparative in design. Melanophore counts are 

 referred to by Yapchionges (1949), Follett (1952), Simonsen 

 (1978), Morris (1951), Dryfoos (1965) and Moulton (1970). 

 Myomere counts were used by Delacy and Batts ( 1 963). Cooper 

 (1978) and Morris (1951) used both myomere and melanophore 

 counts. 



Larval osmerids have the following external features in com- 

 mon: elongate body shape; gut about 75% body length; mouth 

 sub-terminal; head dorso-ventrally flattened; lower jaw not well- 

 developed in early larvae; conspicuous choroid fissure in ventral 

 third of eye with ventral rim of clear choroid tissue; stalked 

 pectorals, stalk becoming more pronounced in late larvae; yolk 

 sac positioned 6-12 myomeres posterior to the pectoral base; 

 finfold extending from midbrain area to tail, from mid-yolk sac 

 to anus, and from anus to tail; no dorsal melanophores; scattered 

 melanophores (20-50) on ventral half of yolk sac; 0-2 mela- 

 nophores on posterior ventral half of yolk sac; single row of 

 melanophores along ventral midline of gut, sometimes extend- 

 ing into finfold; 1-3 melanophores on dorsal surface of gut at 

 the anal bend; single row of melanophores on ventral midline 

 of tail; conspicuous opaque liver ventral to foregut (Ehrenbaum, 

 1894; Yapchionges, 1949; Morris, 1 95 l;DeLacy and Batts 1963; 



Dryfoos, 1965; Eldridge, 1970; Blackburn, 1973; Cooper, 1978; 

 Heame, 1983). 



A comparative study of four of the species oflTOregon (Heame, 

 1983) used ventral melanophore counts and myomere counts 

 in an attempt to characterize the larvae of these species. Ten- 

 dencies in these counts showed Hypomesus pretiosus and Spi- 

 rinchus starksi to have high ventral melanophore counts while 

 Spirinchus thaleichthys and Thaleichthys pacificus have lower 

 melanophore counts. Myomere counts showed tendencies that 

 further separated each similarly pigmented pair. 



Table 37, Sources of Larval and Juvenile Descriptions of Smelts, (x 

 no description found.) 



Taxon Larvae Juveniles 



Hypomesus 



pretiosus 

 Hypomesus 



transpacificus 

 Spirmchus 



lanceolatus 

 Spirinchus 



starksi 

 Spirinchus 



thaleichthys 

 Thaleichthys 



pacificus 

 Alios merus 



elongatus 

 Mallotus villosus 

 Osmerus mordax 

 Osmerus eperlanus 



Yapchionges, 1949 



X 



Hikita, 1958 

 Morris, 1951 



Dryfoos, 1965; 



Moulton, 1970 

 DeLacy and Batts, 



1963 



X 



Schmidt, 1906c 

 Cooper, 1978 

 Ehrenbaum, 1894 



Follett, 1952 



Simonsen, 1978 



Hikita, 1958 



Heame, 1983 



Simonsen, 1978 



Baraclough, 1964 



Heame, 1983 



Templeman, 1948 

 Cooper, 1978 

 Ehrenbaum, 1894 



