Biology of the Lousefish — S trasburg 
minute when attached but unfed (Strasburg, 
1957). Stuffing the digestive tract with food 
possibly inhibits the respiratory rate on some 
mechanical basis. Once when the lousefish fed 
until it bulged, and then attached to the bottom, 
it had a rate of 84 respirations per minute. Six 
minutes later, when it regurgitated four cubes 
of shark flesh, the rate increased to 114 respira- 
tions per minute. 
FOOD AND FEEDING 
The results of stomach analyses of four louse- 
fish were presented in an earlier paper (Stras- 
burg, 1959:246). It has since been possible to 
examine 16 more stomachs and obtain better 
definition of the scope of the diet, and also to 
observe the feeding behavior of a living speci- 
men. 
Of the 20 lousefish stomachs examined 2 
were empty. The balance contained mostly 
planktonic crustaceans, especially small and 
larval forms. The crustaceans and the number 
of stomachs in which they occurred were as 
follows: hyperiid amphipods (1), unidentified 
amphipods (6), crab larvae (2), unidentified 
decapod larvae (1), stomatopod larvae (2), 
Euphausiacea ( 1 ) , Mysidacea ( 1 ) , Ostracoda 
(3), unidentified crustacean fragments (3), and 
the following copepods: Candacia pachydactyla 
(5), C. aethiopica (2), Candacia sp. (1), 
Scolecithrix danae (1), Euchaeta sp. (3), un- 
identified calanoids (3), Sapphirina sp. (1), 
Oncaea sp. (1), and unidentified cyclopoids 
(1). Also, 2 stomachs contained fish flesh and 
bones, and 2 had small flakes of rusty iron. 
None of the food species is parasitic, and it 
is thus unlikely that the lousefish is a cleaner, in 
contrast to most other echeneids (Szidat and 
Nani, 1951:413; Maul, 1956:14; Strasburg, 
1959:246). Instead, it appears to feed rather 
selectively on planktonic animals, especially on 
such conspicuous creatures as the black-and- 
white copepods Candacia pachydactyla and C. 
aethiopica , the iridescent blue copepod Sap- 
phtrina, and large stomatopod larvae. Rust 
flakes from the fishing vessel probably were 
ingested because they were relatively conspic- 
uous. Mysids had been eaten only by the 
! 59.6-mm lousefish attached to a living Diodon 
hystrix caught in Kahana Bay, Oahu. Mysids 
263 
abound in this shallow bay, and the fish had 
gorged on 41 of them. 
The captive lousefish was fed small cubes of 
bread, shrimp, or shark flesh once or twice a 
day. Presentation of food was preceded by a 
cue (described below) and continued until 
the offerings were ignored. The fish reacted to 
food particles from a distance of about 3 ft ; the 
water was very clear. It refused particles lying 
on the bottom, and preferred to feed on sinking 
food pieces near the surface. Pieces less than 
about 3 mm in greatest dimension were ignored 
in favor of larger ones (up to about 1 cm in 
greatest dimension). The 3-millimeter pieces 
were "inhaled” without noticeable jaw move- 
ments, whereas those in the 7- to 10-mm range 
were gulped with conspicuous jaw action. As 
noted earlier, the fish was a greedy feeder and 
ate until its belly and cheeks bulged. A full 
meal required 3 or 4 minutes to consume. 
When fed once a day for 3 successive days, the 
volume of shark flesh eaten per meal was 5.1, 
5.0, and 2.6 cc. On the last day the fish also 
ate bread crumbs whose volume had not been 
measured. 
The lousefish was accidentally placed in the 
wrong pool at first, and for a time I planned to 
recapture it by dip net for transfer elsewhere. 
It was necessary to condition the fish to the 
dip net, for its earlier capture had made it 
wary. A dip net was placed in the pool before 
each feeding, and food was offered over the 
net so that the fish had to swim above the 
meshes to feed. On the third day of this pro- 
cedure (the fifth feeding) the fish swam slowly 
but directly to the net when it was placed in the 
pool. At the next feeding it dashed immediately 
to the net, and continued to do so whenever 
the net was shown. Because it proved unneces- 
sary to transfer the fish, this conditioning went 
for nought. The fish was subsequently trained 
to come to the feeding area when the water’s 
surface was slapped with the hand. 
COLOR AND COLOR CHANGE 
A description of the life colors of the louse- 
fish could not be found in the literature and is 
therefore presented here. In sunlight the dorsal 
surfaces of the head and body are navy blue and 
the ventral surfaces are white. In shade the 
