216 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



Synodontidae (Fig. 1 1 IF-G). — Synodus includes about 30 species 

 and has a circumglobal distribution with distinctly high diversity 

 in the Indo-Pacific. Another monotypic genus of this family 

 (Trachinocephalus) shows world-wide distribution. A recent re- 

 vision of the Indo-Pacific Synodus (Cressey, 1981), including 

 many new species, critically changed its systematic status. Thus, 

 most of the known eggs and larvae are subject to nomenclatural 

 revision. Early stages of this family can be separated from those 

 of the previous family by the presence of the preanal finfold 

 (Ozawa, 1983). 



Trachinocephalus myops larvae are distinct in possessing six 

 pairs of large peritoneal pigment sections of uniform size, a 

 rounded head with short snout, and additional unique pigmen- 

 tation (Rudometkina, 1980; Ozawa, 1983). This species and 

 most species of Synodus have an extremely elongated body. An 

 exception is the eastern Pacific species, S. lucioceps. which has 

 a slightly deeper body. A complete developmental series is known 

 only for this species in Synodus; eggs are spherical, 1.33-1.44 

 mm in diameter, without an oil globule, with moderately broad 

 perivitelline space and hexagonally sculptured chorion: larvae 

 are characterized by 7 evenly spaced pairs of pigment sections 

 formed gradually, a ventral melanophore lying at the midpoint 

 of tail, and one near the notochord tip. 



As in the Harpadontidae, meristic characters and pigmenta- 

 tion patterns are of particular aid in identifying the early stages 

 of this family. If established pigmentation patterns are retained 

 in the metamorphosed juveniles or adults, numbers of the per- 

 itoneal pigment sections of all Indo-Pacific species of Synodus 

 (Cressey, 1981) vary between and 17 with a maximum range 

 of infraspecific variation of 0-3 in 5. binotalus and 14-17 in S. 

 usitatus; some species appear to lack this pigment (i.e., S. kaian- 

 us and S. binotalus), however this needs to be documented by 

 complete developmental series. Another point of interest is the 

 asymmetry and size disparity of the pigment pairs known in 

 "S. variegatus" of Okiyama (1974b). 



Size at metamorphosis and sequence of fin formation of this 

 family appear to be identical to those in Harpadontidae. Ozawa 

 (1983) revealed the following pattern of fin formation: C-A-D- 



P,P2. 



Alepisauridae (Fig. //2,4-BA— This widely distributed bathy- 

 pelagic family includes only two species, .Hepisaurus fero.x and 

 A. brevirostris. with slightly different ranges: the latter is appar- 

 ently absent from the North Pacific (Francis, 1981). Eggs are 

 unknown. A series of early developmental stages of Alepisaurus 

 sp. (6.9-17.2 mm) has been described and illustrated (Rofen, 

 1966b). In addition, three larvae (9.6-16.5 mm) from the col- 

 lection of the Southwest Fisheries Center, La Jolla have different 

 features. They share with previous specimens a large head and 

 mouth, prominent canine teeth on the dentary, small fins in- 

 cluding pigmented pectorals of moderate size, gently curved 

 head profile and short gut with heavy pigmentation. The peri- 

 toneal pigment section is indistinct. This new material is unique 

 in having 4 small preopercular spines, pigment patches at the 

 anal fin origin, and distinct bony ridges dorsally on the head. 

 Judging from the locality of these specimens, near Hawaii in 

 the North Pacific, Alepisaurus sp. larvae of Rofen (1966b) can 

 be identified with A. brevirostris. and these with A.ferox. 



Metamorphosis may be gradual with possible sequence of fin 

 formation P, C-D-A-Pj. 



Anotopteridae (Fig. 112C).— One world-wide species, Anotop- 

 terus pharao, constitutes this open ocean family, uniquely lack- 



ing the dorsal fin. Eggs are not known. A larva (ca. 1 5 mm) has 

 been briefly described without illustration (Nybelin, 1948): this 

 specimen is unavailable now (Thulin, pers. comm.). Another 

 larva of similar size (14.2 mm) is available from the collection 

 of the Southwest Fisheries Center, La Jolla. It is characterized 

 by a slender thin body, absence of peritoneal pigment sections, 

 large head with pointed snout, a fleshy prolongation at the tips 

 of both jaws, two large canine teeth on each palatine, and a 

 fairly long gut extending beyond midbody. Pigmentation is scat- 

 tered on various parts of body including the snout, jaw tips, 

 dorsal midline of body, near the tail tip, and peritoneum (par- 

 ticularly along the dorsum of gut). Except for the pectoral fin, 

 fin aniages are lacking. A juvenile of about 50 mm illustrated 

 in Rofen ( 1 966c) is similar to the described larva, except all fins 

 are differentiated including the adipose fin: body pigmentation 

 is remarkable in this juvenile. Perhaps, this species has the most 

 direct pattern of early development in this order. 



Evermannellidae (see R. K. Johnson, this volume). 



Omosudidae (Fig. ] 12D-F).—A single mesopelagic species, 

 Omosudis lowei. constitutes this cosmopolitan family. Pelagic 

 eggs are not known. Excellent developmental series have been 

 described and illustrated, chiefly based on Atlantic material 

 ranging from 5.7 to 75.2 mm (Ege, 1958: Rofen, 1966b). Re- 

 cently, a larva (11.5 mm) with different features was briefly 

 described and illustrated (Belyanina, 1982b). Its locality in the 

 tropical western Pacific is peculiar and additional specimens are 

 available in ORI collections (pers. obs.). 



These have in common a very large head and mouth, stubby 

 body, long pointed snout, straight head profile, small fins, par- 

 ticularly the pectoral, large canine teeth on denlary and palatine, 

 and several closely spaced peritoneal pigment sections. How- 

 ever, trenchant morphological differences between the Atlantic 

 and Pacific specimens are known: head smooth vs armed (along 

 edge of preopercle and dorsum of head): pigmentation light vs 

 dense at a similar size: pigmented band above posterior part of 

 anal fin absent vs present. For this first character, there is a 

 possibility that the minute preopercular spines have been over- 

 looked in the Atlantic larvae. 



Sequence of fin formation known in the Atlantic specimens 

 is C-DA-Pj-P,. Metamorphosis is gradual with possible dif- 

 ferences in the size of completion between the two types as 

 suggested above. The presence of two larval types is in sharp 

 contrast with the current concept of a monotypic family. In this 

 connection, Ege's comments ( 1 958) on the significant differences 

 in dorsal ray numbers between the populations from the South 

 China Sea and north Atlantic are of particular interest. 



Paralepididae (Fig. 1 13. 4-G}.— This oceanic pelagic family in- 

 cludes about 1 1 genera and 50 species and constitutes the second 

 largest group in the order after Myctophidae. Some genera are 

 still in need of critical revision, while the two established 

 subfamilies seem valid. Paralepidiinae includes two tribes, the 

 Paralepidiini (3 genera) and Lestidiini (7 genera), and Sudinae 

 has I genus (Sudis). Ege (1930) and Rofen (1966a) mcluded 

 early larval stages in their extensive studies of this family. Eggs 

 are not known but developmental stages are known for 9 out 

 of 1 1 genera. Larval development of Sudis has been closely 

 studied for 5. hyalina and S. a/ro.v (Sanzo, 1917: Shores, 1969: 

 Belyanina, 1981). These unusual larvae are readily discrimi- 

 nated from those of the other subfamily by the relatively short 

 body with large head, long pectoral fins, long gut and early 



