Saldierna-Martinez et al.: Larval development of Symphurus ol/gomerus 
53 
0 
S. nigrescens 
1140- 
> 
350- 
300- 
1 250- 
.C 
S' 200 
150 
100 
50 
S. gmsburgi 
• r 
S. callopterus (EL) 
S. ohgomerus (EL) 
S prolatmaris 
S. trewavasae 
S. kyraropteygium 
S. plagiusa • 
S. tessellatus 
I *S atramentatus 
J S civitatum • ^ • S atricaudus 
S. elongatus 
• S. chabanaudi 
S. Williams/ 
10 15 20 
Size at metamorphosis (mm BL) 
25 
30 
Figure 3 
Size at metamorphosis recorded for species of Symphurus plotted against maximum 
depth distribution for adults of the same species. Arrows indicate that metamorphosis 
should occur at larger size because data in the graphic for these two species correspond 
to the largest postflexion larva described (source: Kyle, 191.3; Evseenko, 1990; Schneider, 
1990; Kurtz and Matsuura, 1994; Munroe et al., 1995; Munroe, 1998; Aceves et al., 
1999; Evseenko and Shtaut, 2000; Saldierna-Martinez et al., 2005; Farooqi et al,. 2006; 
Fahay, 2007). EL = exterilium larvae. 
and Shtaut, 2000); 2) those with a discontinuous series 
of dash-like melanophores on the dorsal and ventral 
margins of the body, such as S. atricaudus (Charter 
and Moser, 1996) and S. atramentatus (Saldierna-Mar- 
tinez et al., 2005); and 3) those with heavily pigmented 
oblique bands extending from the dorsal to the ventral 
margins of the body, such as occurs in S. callopterus 
(Evseenko, 1990) and S. oligomerus (this study). 
In addition to the three groups categorized by pig- 
ment patterns, Saldierna-Martinez et al. (2005) catego- 
rized Symphurus spp. larvae by the number of elongate 
dorsal-fin rays and the ID pattern as 1) those with 0-3 
elongate dorsal-fin rays and the 1-5-3 ID pattern; 2) 
those with 5 elongate dorsal-fin rays and the 1-3-3 ID 
pattern; and 3) those with 7 elongate dorsal-fin rays 
and the 1-4-3 ID pattern. Saldierna-Martinez et al 
(2005) suggested that the number of elongate dorsal- 
fin rays is a derived character, as was also suggested 
by Hensley and Ahlstrom (1984). Our study showed 
that the three elongate dorsal-fin rays in S. oligomerus 
are associated with the 1-3-2 ID pattern, which does 
not correspond to previously established findings and 
indicates a high variability for this characteristic, thus 
reducing its value for phylogenetic interpretation among 
cynoglossids. 
Larvae of S. oligomerus have a slightly compressed 
and ribbonlike body. The intestine, similar to that of 
S. callopterus, is an elongate and relatively slender sac 
with transparent walls that form a short and freely 
hanging abdominal projection ending in a short coni- 
cal appendix. The length of the intestinal sac is almost 
one-quarter of the body length and is shorter than that 
in S. callopterus, which is almost one-half to two-thirds 
of the body length. In both species, the intestinal sac 
is supported by three cartilages. Larvae with this kind 
of intestine have been called exterilium larvae (Fraser 
and Smith, 1974; Moser, 1981); they are found in S. 
callopterus, at 7.5-21 mm SL, (Evseenko, 1990), and in 
some ophidiiform larvae (Gordon et al., 1984) that have 
a well-developed coracoid process (Fahay and Nielsen, 
2003; Okiyama and Yamaguchi, 2004). The length of 
the loop intestine and the exterilium support of the 
intestinal tract in S. oligomerus and S. callopterus are 
useful features for differentiateing them from other 
central-eastern Pacific species of Symphurus. 
An ontogenetic relationship within this genus is the 
apparent connection between size at metamorphosis 
and the depth range of adults. Saldierna-Martinez et 
al. (2005) found that species inhabiting deep waters 
usually are larger at metamorphosis than species in- 
habiting shallow waters. This relationship has been 
observed in several groups of fishes (Moser, 1981). It 
appears that species of Symphurus are not an excep- 
tion (Fig. 3). At metamorphosis, S. oligomerus is 18 
mm BL and adults inhabit waters down to 300 m (Ma- 
hadeva and Munroe, 1990; Munroe et al., 1995). In 
the Atlantic Ocean, S. nigrescens has been collected 
over an extensive vertical range (47-1140 m) on the 
