52 
Fishery Bulletin 108(1) 
middle of the pectoral-fin bud. Most of these pigments 
are lost in specimens preserved in formalin. Nine or 
more similar melanophores are also present on the 
swim bladder. 
The pigmentation of postflexion larvae (Fig. 2A) is 
similar to that of flexion-stage larvae (Fig. 1C). The 
major difference in pigmentation between flexion and 
postflexion larvae is the increase in the extent of the 
dorsal and ventral bands of star-shaped melanophores 
which extend towards the midline of the body, as well 
as to the dorsal- and anal-fin rays. One solid dark line 
extends down the midline of the body over the noto- 
chord from the first vertebra towards the end of the 
third dorsal band. One star-shaped melanophore ap- 
pears above the first vertebra (Fig. 2A). 
The pigmentation pattern of the juvenile specimens 
is similar to those of late postflexion specimens (Fig. 2, 
A and B). In the juvenile stage, formation of the three 
bands on the dorsal margin and two bands on the ven- 
tral margin of the body reach their greatest extension 
in length and width. These pigment bands extend over 
the dorsal and anal fins, covering half to two-thirds of 
the fin rays (Fig. 2B). 
One discontinuous dashed line of melanophores is 
present on the body midline over the notochord extend- 
ing from the posterior region of the brain to the poste- 
rior third of the postabdominal region. A second solid 
dark line is observed down the midline of the body over 
the notochord from the posterior of the brain towards 
the end of the third dorsal band (Fig. 2B). 
Clusters of small star-shaped melanophores are pres- 
ent near the anteriormost section of this series and an- 
other group between the first and second dorsal bands. 
Additionally, small star-shaped melanophores form an 
inverse ‘Y’ between the second and third dorsal bands; 
this group of pigments extends from the base of dorsal- 
fin rays 46 and 47 toward the first ventral band, where 
it forks near the midline of the body but never reaches 
the base of the anal fin. 
The pigmentation in the cephalic region increases 
dramatically during the transformation to the juve- 
nile stage especially on the dorsal margin of the head, 
around the eyes, and ventrally in the branchial and 
pelvic region (Fig. 2B). On the stomach, four groups of 
star-shaped melanophores are present on the anterodor- 
sal section, the posterodorsal section, the posteroventral 
section and the near pelvic-fin base (Fig. 2B). 
Unpaired fin development In early preflexion larvae, 
the dorsal, anal, and caudal fin folds are wide and dis- 
tinct. The dorsal fin fold begins behind the brain area 
(Fig. 1A). In larger, preflexion larvae, the first three 
dorsal fin rays are inserted at the level of the posterior 
margin of the brain (Fig. IB). In flexion larvae, the 
second, third, and fourth dorsal fin rays are elongate 
and almost all specimens have all the rays in dorsal 
and anal fins formed. The caudal fin is incomplete, with 
only three or four rays (Fig. 1C). In postflexion larvae 
by 18 mm BL, all unpaired fins are completely formed 
(Fig. 2A). 
Paired fin development From the preflexion to post- 
flexion stages, the pectoral fins are fanlike, and have 
a massive fin lobe and surrounding membrane. During 
the flexion stage, the pelvic fins become apparent, but 
are not well developed and contain only the rudiments 
of four rays. In postflexion larvae, the pelvic fin rays are 
completely formed (Fig. 2A). During the juvenile stage, 
the pectoral fins are absorbed (Fig. 2B). 
Discussion 
Tonguefishes of the central-eastern Pacific are placed 
in a single genus ( Symphurus ) comprising 18 species. 
Previous studies have indicated the problems for identi- 
fication of Symphurus species with overlapping meristic 
and morphometric characteristics and there have been 
few taxonomic studies of this genus. Insertion patterns of 
dorsal pterygiophores between dorsal neural spines (ID 
pattern) have proved to be useful in identifying members 
of this complex group if the ID pattern is combined with 
traditional meristic and morphometric characteristics 
(Munroe, 1992; Munroe et al., 1995). 
The pigmentation pattern in early preflexion larvae of 
S. oligomerus is similar to that found in preflexion lar- 
vae (6.5 mm BL) of S. atricaudus (Charter and Moser, 
1996) and S. williamsi (2.2 mm BL) by Aceves et al. 
(1999). However, S. atricaudus has up to four blotches 
on the dorsal and anal finfolds and S. williamsi has 
three melanophores along the dorsal margin of the body, 
two or three melanophores on the dorsal finfold, three 
melanophores along the ventral margin of the body, and 
one or two similar melanophores on the anal finfold. At 
this stage, it is not possible to distinguish the pigmenta- 
tion patterns of early preflexion larvae of S. callopterus 
(Evseenko, 1990), S. elongatus (Charter and Moser, 
1996), S. chabanaudi and S. prolatinaris (Evseenko and 
Shtaut, 2000), and S. atramentatus (Saldierna-Martinez 
et al., 2005) because the required diagnostic informa- 
tion is unavailable in the literature. 
The pigmentation pattern in flexion larvae of S. oligo- 
merus typically is composed of three oblique bands be- 
ginning in the dorsal margin of the body and running 
toward to the midline of the body. Only the third band 
reaches the mid line of the body. There is an oblique 
band on the ventral margin converging at the later- 
al midline with the third band of the dorsal margin 
and these two together have the appearance of a belt 
(Fig. 1C). This type of pigmentation is very similar 
to that described for flexion larvae of S. callopterus 
(7.5 mm SL), but S. callopterus has one more oblique 
band than S. oligomerus, which also has a larger ab- 
dominal projection (Evseenko, 1990). 
All larvae Symphurus species from the eastern Pacific 
that have been described can be placed into three main 
groups based on pigmentation patterns (Saldierna-Mar- 
tfnez et al., 2005): 1) those with blotches on the dorsal 
and ventral margins of the body, such as S. elongatus 
(Charter and Moser, 1996), S. williamsi (Aceves et al., 
1999), S. chabanaudi, and S. prolatinaris (Evseenko 
