Aceves-Medina et al.: Larval development of Symphurus wilhamsi from the Gulf of California 



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Table 1 



Meristics for species of Symphurus of the Gulf of California with the same pterygiphore interdigitation pattern ( 1-5-3-2-2) taken from 

 Munroe(1992). 



S. williamsi S. atricaudus S. chabanaudi S. elongatus S. melasmatotheca S. melanurus S. prolatinaris 



Dorsal-fin rays 89-95 



Anal-fin rays 73-79 

 Caudal-fin rays 12 



Total vertebrae 47-51 



Materials and methods 



Plankton samples were taken during eight oceano- 

 graphic expeditions made in the Gulf of California 

 in April. July-August, and November-December 

 1984, June and August 1986, July 1991, September 

 1993, and June 1994. Samples were obtained by us- 

 ing oblique tows with 60-cm diameter bongo nets 

 equipped with nets of 333-|.im and 505-|.ini mesh, as 

 detailed in Kramer et al. (1972). All larvae and juve- 

 niles used in this study were deposited in the larval 

 fish collection of the Plankton and Marine Ecology 

 Department of Centro Interdisciplinario de Ciencias 

 Marinas of the Institute Politecnico Nacional 

 (CICIMAR-IPN). 



All Symphurus larvae collected with the 505-|im 

 net were separated from the other net contents. Flex- 

 ion, postflexion, and juvenile specimens were cleared, 

 stained (Potthoff, 1984), and identified on the basis 

 of meristic characteristics (Munroe, 1992). Subse- 

 quently, a developmental series of preflexion larvae 

 showing similar pigmentation patterns and meris- 

 tic features was assembled. Counts of the dorsal- and 

 anal-fin elements were sometimes extrapolated from 

 pterygiophore counts, which occasionally appeared 

 earlier in development than did corresponding rays. 

 The following measurements were done on the left 

 side of the body of the specimens: 



Body depth at 

 anus (BDA); 



Body length (BL): 



Head length (HL): 



Snout-anus 

 length (Sn-A): 



Body depth (BD): 



anterior end of snout to end of 

 notochord in young larvae, or 

 to posterior margin of hypural 

 plate in more developed larvae, 

 anterior end of snout to clei- 

 thral margin in small speci- 

 mens, or to posterior margin 

 of the opercle in larger ones. 



anterior end of snout to poste- 

 rior margin of anus. 



vertical distance between dor- 

 sal and ventral margins (dor- 

 sal- and anal-fin pterygio- 



phores excluded) at origin of 

 pelvic fin. 



vertical distance between dor- 

 sal and ventral margins (dor- 

 sal- and anal-fin pterygio- 

 phores excluded) at origin of 

 anal fin. 



Eye diameter (ED): horizontal distance between 

 anterior and posterior margins 

 oflefteye(Moser, 1996). 



The description of larval development was based 

 on 69 specimens (2.2-13.2 mm BL). None of these 

 larvae were in the yolksac stage, indicating that eclo- 

 sion must have taken place at a smaller size. To char- 

 acterize larval development intervals, divisions pro- 

 posed by Ahlstrom et al. ( 1976) were followed. 



Results 



Cleared and stained larval and prejuvenile specimens 

 {n = ll, between 7.7-13.2 mm BL) showed the follow- 

 ing pterygiophore patterns: 1-5-3-2-2 (41.2'7f ), 1-5-2- 

 3-2 (35.2'7f), 1-5-2-2-2 (11.8^f), 1-4-2-2-2 (5.9'7f). and 

 1-5-4-2-2 (5.9%). There are seven species in the 

 area with the same main pterygiophore pattern 

 (Table 1). Using these 17 specimens and the remain- 

 ing 52 larvae (Table 2), we counted 9 precaudal ver- 

 tebrae, 38-42 caudal vertebrae (mode=40), 89-97 

 dorsal rays (mode=92 and 94), 71-80 anal rays 

 (mode=75), and 12 caudal-fin rays. The combination 

 of these characteristics indicates that the species is 

 S. williamsi. 



Description of the larvae 



Diagnosis Symphurus williamsi larvae typically 

 have a pigmentation pattern of 5 spots along the 

 middorsal line at the bases of the dorsal-fin 

 pterygiophores and 2 to 3 similar spots located on 

 the bases of the dorsal-fin rays. There are also 3 to 4 



