694 



Fishery Bulletin 101(3) 



and A. 24 [23-25]; Table 1), and by the presence of the 

 unique digitiform opercular processes (Parin, 1990; Oki- 

 yama, 2000). Identification was verified by using fin meris- 

 tics from cleared and stained specimens (Potthoff, 1984). 



26.70 



26 90 



27.10 



5 



zr.x> 



27 50 



Dactylopsaron dimorphicum 



A total of 55 postflexion larvae of D. dimorphicum 

 (8.2-15.3 mm standard length) were examined to describe 

 morphometries, meristics, and pigmentation. Three larvae 

 (9.1, 13.1 and 13.4 mm SL) were cleared and stained fol- 

 lowing the method of Potthoff ( 1984). Terminology 

 and morphometric measurements follow Neira et 

 al. (1998). Measurements were made to the near- 

 est 0.01 mm by using a dissecting microscope 

 fitted with an eyepiece micrometer Body length 

 (BL, Neira et al., 1998) in postflexion larvae cor- 

 responds to standard length (SL), i.e. tip of snout 

 to posterior margin of hypurals. Measurements of 

 body depth (BD), head length (HL), and preanal 

 length (PAL) were converted to a percentage (%) of 

 SL (Table 2). Eye diameter (ED) and snout length 

 (SnL) were converted to a percentage (%} of HL. 

 Pigment described refers solely to melanin. Illus- 

 trations were made with the aid of a camera lucida. 



Larvae per 1000 m 



o 



1 -5 

 5-10 

 10-50 



50-100 



>100 



109 80 



109 60 



109 40 

 Longitude (W) 



109 20 



109 00 



Figure 1 



Spatial distribution of postflexion larvae of Dactylopsaron dimorphi- 

 cum (numbers/1000 m^) around Easter Island in November 1999. 



ID 



■a 



3 



26.66 



106.56 



105.45 



105.35 



Longitude (W) 



105.25 



Figure 2 



Spatial distribution of postflexion larvae of Dactylopsaron dimorphi- 

 cum (numbers/1000 m^) around Salas y G6mez Island in November 

 1999. 



Results 



Description of larvae 



Postflexion larvae of Dactylopsaron dimorphicum 

 are elongate (BD 13.1-18.3%; Table 2), and have 

 a moderate to large head (HL 28.6-36.7%) and 

 an elongate snout (Fig. 3). Eyes are round and 

 pigmented by 8.2 mm SL. The mouth is large, pro- 

 trusible, and has a long ascending premaxillary 

 process giving a characteristic "duckbill" appear- 

 ance. Small villiform teeth are present along the 

 premaxilla and dentary. There are no head spines. 

 The digitiform processes on the upper opercular 

 margin are present in larvae >13.2 mm SL; the 

 lower, rearward-directed process that reaches the 

 end of the pectoral-fin base in adults was still 

 forming in the largest larva examined (15.3 mm 

 SL). The branchiostegal membranes are free from 

 the ithsmus. The short first dorsal fin is located at 

 the nape and lies in line with the mid-operculum; 

 pterygiophores of the five first-dorsal fin spines in 

 two of the cleared and stained larvae ( 13.1 and 13.4 

 mm SL) were located between the neural spines of 

 the second and third trunk vertebrae. The 9. 1-mm- 

 SL cleared and stained larva possessed only 15 

 of the 17-20 pectoral-fin rays, and first dorsal-fin 

 spines were developing. The elongate pelvic fins 

 are thoracic, i.e. inserted in front of the pectoral- 

 fin bases. Lateral line scales begin to form at >13 

 mm SL. Larvae are unpigmented, although a few 

 had a small melanophore at the base of the 17 or 

 18* dorsal-fin ray There are 31-35 myomeres. The 

 number of vertebrae in the cleared and stained 

 larvae is 34-35 (11-12 -h 22-24). 



Larval distribution 



Postflexion D. dimorphicum larvae were collected 

 within 6 nmi off both Easter and Salas and Gomez 



