Acanthurus triostegus sandvicensis—KANDKLL 
Fig. 13. Postlarval Acanthurus triostegus sandvi- 
censis taken in a 1 m. plankton net at a depth of 50 
m. at 22° 38' N., 157° 11' W. 
in length probably elude a meter plankton net. 
The presence of the 18 mm. Zebras oma veli- 
ferum in the collections from the 6-ft. trawl 
suggests that this would be a better means of 
catching larger larval acanthurids. The failure 
to take more acanthurids in the trawl is prob- 
ably due to the great distance from land of 
most of the trawl tows. 
The only records of the early stages of Acan- 
thurus found in the literature are two postlarval 
A. coeruleus identified by Liitken (1880: pi. 5) 
and an unidentified 7 mm. postlarval Acanthurus 
in Weber (1913: fig. 70). Sparta (1928) re- 
ported on a long, ribbon-like, transparent, pela- 
gic egg mass of an unknown teleost fish from 
the Mediterranean. The early developmental 
stages which he succeeded in rearing from this 
egg mass are remarkably similar to those of the 
manini. Sparta concluded that the eggs were 
from a species as yet unrecorded from the Med- 
iterranean. 
TRANSFORMATION 
The late postlarval form of the genus Acan- 
thurus is characteristic in morphology, yet iden- 
tifiable to family Acanthuridae by the presence 
245 
of the caudal spine and a diagnostic number of 
fin rays. Originally this stage was placed in a 
genus by itself, Acronurus. The name acronurus 
has persisted as a common name for this stage, 
reminiscent of the leptocephalus of eels. 
Acronuri are commonly taken at night-light 
stations. Sixty-two manini acronuri and many of 
other species collected at night lights and by 
night-light traps offshore in the vicinity of the 
Hawaiian, Line, and Phoenix islands were exam- 
ined. No specimens in night-light collections 
were found which were smaller than the acron- 
urus stage. It is inferred, therefore, that a posi- 
tive phototaxis develops in the acronurus. The 
lack of food material in the gut of night-light 
specimens (see p. 223) indicates that the pres- 
ence of numerous small planktonic animals 
around a light at night is not the attractant. 
Once transformation to the juvenile stage has 
begun, the positive phototaxis disappears. 
Figure 14 is a photograph of a live specimen 
of the manini acronurus taken shortly after its 
arrival in a tide pool. The characteristic trans- 
parent scaleless body with silvery abdomen and 
head (except snout and nape), disk-like form, 
and vertical striae on the body are apparent. 
The vertical bars are just beginning to form. 
The acronurus comes into inshore regions 
Fig. 14. The acronurus of Acanthurus triostegus 
sandvicensis. Captured at dawn in a tide pool at Dia- 
mond Head, Oahu, and photographed alive. 
