Acanthurus triostegus sandvicensis — RANDALL 
juveniles and adults, the third dorsal and third 
anal spines are much longer than the second 
dorsal and second anal spines, respectively. The 
latter, however, remain thicker. All of the acron- 
urus spines are T-shaped in cross-section; all are 
solid. The nature of the venom apparatus is un- 
known. The T-shape of the spines persists into 
the juvenile stage. 
One of the most striking changes during 
transformation is the alteration of the configura- 
tion of the head. This consists primarily of an 
increase in the length of the snout, resulting in 
the mouth being in a more ventral position. 
The rostral prolongation may be seen in Fig- 
ures 14 and 17. The diameter of the eye (which 
does not change during transformation) of the 
transparent specimen of Figure 14 is slightly 
longer than the length of the snout; in the just 
transformed manini the eye diameter is con- 
tained about 1.5 times in the length of the 
snout. The osteological changes which accom- 
pany the changes in the proportions of the head 
were not investigated. 
A slight increase in standard length occurs 
during the metamorphosis to juvenile form. 
After 5 days in an aquarium, three transforming 
specimens, 24.1-25.0 mm. in standard length, 
increased 1.2-1. 5 mm. in standard length. Most 
of the increase is attributable to the prolonga- 
tion of the snout. 
A remarkable lengthening of the digestive 
tract takes place during transformation (Fig. 
3 ) . In a period of 4 to 5 days the total length 
of the alimentary tract of the manini increases 
about three-fold. This lengthening occurs at the 
time of a change in food habits from feeding 
on zooplankton to feeding on algae (see pp. 
222-223). 
The teeth of the manini acronurus just be- 
fore transformation are very different from the 
simple conical teeth of the postlarval manini 
(as seen in 6.6 to 7.0 mm. specimens). They 
are close-set and flattened with denticulations 
on the edges similar to adult teeth. There are 
about 14 of these teeth, each with 6 or 7 den- 
ticulations, in the upper jaw with a broad gap 
between teeth at the symphysis of the jaw. There 
are 14 such teeth in the lower jaw with 5 den- 
ticulations each. During transformation 8 large 
adult-type teeth (with about 12 denticulations), 
251 
which are preformed within the premaxillary 
bone above the upper series of larval teeth, grow 
down over the larval teeth which are shed. The 
more medial of these large teeth are the largest 
and the first to emerge. In the lower jaw the 
same process occurs. Six large adult-type teeth 
with 7 denticulations grow over the larval teeth. 
Larval teeth lateral to these large ones may per- 
sist beyond the period of transformation. 
The sequence of tooth replacement is not 
without variation from specimen to specimen. 
At the stage when the scales are just completely 
formed on the body some specimens have fewer 
than 8 upper and 6 lower teeth in position. 
Some specimens taken at night lights in deep 
water appear to be getting their adult teeth 
prematurely. One specimen of Accmthurus tri- 
ostegus triostegus obtained at a night-light trap 
at anchorage at Christmas Island already had 6 
large upper and 2 large lower teeth. 
GROWTH 
No information could be found in the litera- 
ture on growth of any species of surgeonfish. 
The closest family, phylogenetically, to the 
Acanthuridae in which growth data are avail- 
able for comparative purposes is the Teuthididae 
( Siganidae of most authors ) . Like the acanthu- 
rids, the teuthidids are herbivorous (Suyehiro, 
1942; Al-Hussaini, 1947). Whitehouse (1923: 
68-70, 83-85) reported that juveniles of Teu- 
this java grew from a length of 25 mm. in April 
to 75 mm. in September in Silavatturai Lagoon, 
Tuticorin, India. Ommanney (1949: 48-49) 
stated that Siganus corallinus ( = Teuthis cor- 
allinus) reached a length of 180-220 mm. after 
2 years’ growth, and about 280 mm. at the end 
of the third year, in Mauritius. 
Information on growth of the manini was 
obtained by the rearing of fish in a tank of the 
Hawaii Marine Laboratory, at Coconut Island, 
Oahu, analysis of the progression of modes 
among the juveniles of Figure 6, recovery of 
young fish marked by fin clipping, and the re- 
covery of tagged adults. The data are discussed 
separately under these headings below. 
The standard-length measurement for all of 
the work on growth of the manini is the length 
from the tip of the snout to the middle of the 
