Echeneid Fishes— STRASBURG 
55 
Fig. 2. Echeneis naucrates attached to Ostracion lentiginosus. Standard lengths 
estimated to be 57 and 49 mm respectively. (Photograph by Charles E. Cutress, 
U. S. National Museum.) 
to immotile objects, Remora is found externally 
on sharks, and Remoropsis pallidus takes refuge 
beneath the opercula of marlins. Although it is 
known that the early stages are planktonic, there 
has hitherto been no information on the size at 
which attachment first occurs, or whether there 
are trial hosts. 
The material at hand indicates that the transi- 
tion from the free-swimming to the attached 
state occurs at about 40-80 mm standard length. 
Phtheirichthys then attaches to immotile ob- 
jects, as occasionally do some of the others. 
Rhomb ochirus selects a variety of marlin-like 
fishes for its attachment, while Remora attaches 
to sharks. One of the Echeneis studied was at- 
tached to a 49-mm trunkfish, Ostracion lentigi- 
nosus (Fig. 2), collected on the reef at Waikiki, 
Oahu, Hawaii. Except for a few brief excursions 
to the host’s belly, it remained inverted as 
shown. Unfortunately, neither the echeneid nor 
the trunkfish was preserved, and their lengths 
are only estimates derived from the relative 
proportions shown in the photograph. The sec- 
ond Echeneis could not be captured but was 
also about 50 mm in length. It joined me while 
swimming in 10-ft deep water at Beaufort, 
North Carolina. Its black and white pattern 
made it conspicuous, and it was sighted at a 
distance of 15 ft, swimming directly toward 
me. The fish made numerous attempts to attach 
to my black swim fins, touching them but not 
actually attaching because of my continuous 
movements. It eluded all attempts to capture it. 
It would seem that attachment becomes ob- 
ligatory somewhere in the 40 to 80-mm length 
range. Alternate hosts, such as Acanthocybium, 
Te trap turns, and Carcharhinus melanopterus, 
may then be selected in the absence of the 
definitive host species. These small hosts may be 
regarded as trial vehicles because they bear only 
small echeneids. The size of the echeneids car- 
ried by them would be restricted by the rela- 
tively fewer ectoparasites available as food or, 
as in the case of the O stracion-Echeneis associa- 
tion, by problems of list and drag resulting from 
a bulky adherent. 
