Abstract.— Developmental series 

 of two sympatric flounders of the 

 genus Pamlichthys, found in the Bay 

 of Coquimbo, are illustrated and de- 

 scribed. The series consist of yolksac 

 to metamorphosed larvae of artifici- 

 ally-reared Paralichthys adsperstis 

 (1.7-13.0 mm SL) and P. microps 

 (1.5-ll.Omm SL). Field-collected 

 larvae correspond to the size ranges 

 found in reared larvae. Degree of 

 cephalic spination (in particular, 

 sphenotic spines), pigmentation pat- 

 tern, and number of elongated dor- 

 sal-fin rays are useful for identifica- 

 tion of yolksac-to-postflexion larvae 

 of both species. 



During early metamorphosis the 

 most valuable characteristics for 

 identification are the number of 

 elongated dorsal-fin rays, although 

 after their reabsorption several mor- 

 phometric relationships have to be 

 used. Paralichthys adspcrsus pre- 

 flexion larvae have two sphenotic 

 spines and almost no pigmentation 

 in the dorsal finfold, while P. microps 

 larvae have only one sphenotic spine 

 and a well-pigmented dorsal finfold. 

 Beginning at notochordal flexion, the 

 number of elongated dorsal-fin rays, 

 six for P. microps and three for P. 

 adspersus, can be used to identify the 

 larvae. During late metamorphosis, 

 morphometric relationships of SnL/ 

 HL, HL/SL, and BD/SL must be 

 used to identify the larvae. Flexion 

 is complete at 7.2mmSL and meta- 

 morphosis at ~11.0mmSL in P. 

 microps, and at 8.6mmSL and 13.0 

 mm SL in P. adspeisus, respectively. 



Larval development of two sympatric 

 flounders, Paralichthys adspersus 

 (Stelndachner, 1867) and 

 Paralichthys microps (Gunther, 1881) 

 from the Bay of Coquimbo, Chile 



Humberto N. Zuhiga 



Enzo S. Acuha 



Departemento Biologfa Manna, Universidad Cat6lica del Norte 

 Sede Coquimbo, Casilla 1 1 7, Coquimbo, Chile 



Manuscript accepted 20 May 1992. 

 Fishery Bulletin, U.S. 90:607-620 (1992). 



Paralichthys is one of the most im- 

 portant genera of flatfish on both 

 coasts of North and South America 

 (Ginsburg 1952), considering number 

 of species, geographic distribution, 

 and economic importance. Seven spe- 

 cies of the genus have been reported 

 in Chilean waters (Bahamonde and 

 Pequeno 1975), Paralichthys adsper- 

 sus (Steindachner 1867) and P. mm'ops 

 (Gunther 1881) being the most abun- 

 dant and most widely distributed. 

 The former is found from the coast 

 of Paita (Peru) to Lota (Chile) and 

 Juan Fernandez Island; the latter 

 from Huacho (Peru) to the austral tip 

 of South America (Chirichigno 1974). 

 Because these two morphologically- 

 similar species co-occur over most of 

 their distributional ranges, adult and 

 larval identifications have been dif- 

 ficult. Muiioz et al. (1988) described 

 larvae of P. microps, but recognized 

 the possibility that specimens of both 

 species were included in their sample. 

 They indeed have one P. adspersus 

 larva (3.2 mm, Fig. 2b). Silva (1988) 

 published photographs of the eggs 

 and some larvae of P. microps. 



In this paper, taxonomic characters 

 which separate these two species dur- 

 ing early-life-history stages, from yolk- 

 sac larva to juvenile, are described. 



Material and methods 



Most of the material examined in the 



present study was obtained from 

 several experiments, resulting from 

 artificial fertilization of eggs and 

 sperm from ripe specimens captured 

 in the Bay of Coquimbo (29°59'S). 



Larvae were cultured in 200 L 

 conical tanks, with a daily 25% water 

 renewal. From hatching through 

 flexion, larvae were fed the rotifer 

 Brachionus plicatilis in concen- 

 trations of 5/mL, and from flexion 

 through metamorphosis were fed 

 Arternia salina nauplii in concentra- 

 tions of 10/mL. Temperature range 

 during the experiment was 13-17°C 

 (Silva 1988). Larvae, sampled with a 

 Bongo net (Im, bOOju mesh) and an 

 epibenthic trawl (500 /.< mesh) at sta- 

 tions in Coquimbo Bay and adjacent 

 coastal areas, were compared with 

 cultured larvae. 



A total of 49 larvae of P. adsper- 

 sus and 46 of P. microps were used; 

 of these, 39 larvae of both species 

 were cleared and stained using Pott- 

 hoff s (1984) method to determine the 

 sequence of development of the axial 

 skeleton. Pterygiophores and rays 

 were counted when present, regard- 

 less of their state of development. 

 Larvae were anesthesized with MS- 

 222 before fixing in 5% formalin, and 

 were later preserved in 3% buffered 

 formalin. 



Specimens were divided into devel- 

 opmental stages following the defi- 

 nitions of Ahlstrom et al. (1976). 



607 



