Saldierna-Martinez et al.: Larval development of Symphurus oligomerus 
47 
Table 2 
Abbreviations and definitions of terms used to describe the morphometric and meristic characters of Symphurus oligomerus 
larvae and juveniles. 
Body length (BL) 
In preflexion and flexion stages, horizontal distance from snout tip to tip 
of notochord, referred to as notochord length (NL); in postflexion-stage 
larvae, from snout tip to posterior margin of hypural bones as standard 
length (SL) 
Caudal region length (CRL) 
Horizontal distance from posterior end of anus to tip of notochord in 
young larvae or to posterior margin of hypural bones in more developed 
larvae 
Snout-anus length (SAL) 
Horizontal distance t hrough midline of body from snout tip to posterior 
margin of anus 
Head length (HL) 
Horizontal distance through midline of the head from snout tip to 
margin of cleithrum preceding pectoral fin base in small specimens, or 
to posterior margin of opercle in larger specimens 
Eye diameter (ED) 
Horizontal distance between anterior and posterior margins of left eye 
Body depth at pelvic fin base (BD) 
Vertical distance from dorsal to ventral margin of body, measured at 
pelvic fin base 
Body depth at anus (BDA) 
Vertical distance across body at anus prior to formation of dorsal fin 
pterygiophores (Moser, 1996) 
Loop intestinal length (LIL) 
Horizontal distance from cleithrum to tip of the conical appendix on the 
abdominal projection 
Abdominal projection length (APL) 
Horizontal distance from cleithrum to base of conical appendix on 
abdominal projection 
Conical appendix length (CAL) 
Horizontal distance from base to tip of conical appendix 
Pterygiophore interdigitation pattern (ID pattern) 
Number of proximal dorsal-fin pterygiophores in each of the five anterior 
interneural spaces (Munroe, 1992). 
Internal cartilaginous struts (ICS) 
Support internal of the intestinal sac, make-up for cartilaginous struts 
specimens and the remaining 14 larvae and two juve- 
niles, we counted 48-49 vertebrae (more frequently 48), 
87-94 dorsal-fin rays (more frequently 89-91), 73-77 
anal-fin rays (more frequently 74-75), and 12 caudal-fin 
rays (Table 3). Of 18 species of Symphurus recognized in 
the eastern Pacific, only S. gorgonae, S. oligomerus , S. 
microlepis, and S. diabolicus have the 1-3-2-2-2 ID pat- 
tern. Symphurus gorgonae differs from the other species 
in having only four hypural bones, and S. oligomerus, 
S. microlepis, and S. diabolicus have five hypural bones 
(Munroe, 1992). Symphurus diabolicus and S. microlepis 
have more dorsal- (106-110 and 106, respectively) and 
anal- (89-96 and 92) fin rays and a higher number of 
vertebrae (57-59 and 57) than S. oligomerus (87-97 
dorsal-fin rays, 72-83 anal-fin rays, and 48-52 total ver- 
tebrae). Symphurus gorgonae has fewer dorsal- (80-89) 
and anal- (63-74) fin rays than S. oligomerus (Munroe, 
1992; Munroe and McCosker, 2001). Furthermore, S. 
diabolicus, is apparently endemic to the Galapagos 
Archipelago (Munroe and McCosker, 2001), whereas S. 
microlepis is collected off the coast of Panama in 530 m 
(Munroe et al., 1995; Munroe and McCosker, 2001). The 
combination of meristic features indicates that these 
larvae and juvenile specimens are S. oligomerus. 
Description of larval and juvenile stage 
of Symphurus oligomerus 
Morphological features The early preflexion larvae (1.6 
and 2.6 mm BL) have an elongate, slightly compressed 
body. The abdominal cavity with an intestinal loop 
extends beyond the lower contour of the body, forming 
a short and freely hanging abdominal projection. This 
projection is an elongate and relatively slender sac with 
transparent walls; the loop intestinal length ranges 
between 21% and 31% of the BL (Table 4). The end por- 
tion of the abdominal projection is a conical appendix 
whose length is 2.5-10% of the BL. During flexion until 
the juvenile stage (7.8-18.2 mm BL) the loop of the 
intestine is supported by three internal cartilaginous 
struts (ICS); two are located on either side of the intes- 
tinal sac (Figs. 1C and 2A) and the third is located near 
the pectoral fin base, supporting the lateral cartilages. 
The anus opens on the left side of the body. The head is 
small, 25% of BL (Table 4) and has a small and oblique 
snout. The posterior corner of the mouth never extends 
beyond the middle part of the left eye (Fig. 1A). In larvae 
between 3.4 mm BL and 3.8 mm BL, the swim bladder 
is located above the dorsal region of the intestinal sac 
