Henry C. Schultz III
This month, I cover an article on sex change
in Centropyge ferrugata...
Yoichi Sakai, Kenji Karino, Tetsuo Kuwamura,
Yasuhiro Nakashima and Yukiko Maruo. 2003. Sexually Dichromatic
Protogynous Angelfish Centropyge ferrugata (Pomacanthidae)
Males Can Change Back to Females. Zoological Science 20: 627-633.
Protogynous hermaphroditism, female-to-male
sex change, is well known among reef fishes where large males
monopolize harems of females. When the dominant male disappears
from a harem, the largest female may change sex within a few
weeks. Recently, from experiments with some protogynous haremic
fishes in which two males' cohabitated, it was confirmed that
sexual behavior and gonads were completely reversible according
to individual social status. However, the ability to reverse
secondary-developed sexual body coloration has never been
examined in any protogynous fish. We conducted two male cohabitation
experiments with the protogynous haremic angelfish, Centropyge
ferrugata, which has conspicuous sexual dichromatism on
the dorsal fin. Smaller males of C. ferrugata soon
performed female-specific mating behaviors when they became
subordinated after losing a contest. They then completed gonadal
sex change to females 47 or 89 d (n=2) after beginning cohabitation.
In the course of the reversed gonadal sex change, male-specific
coloration on the dorsal fin changed to that of a female.
Thus, the sex of C. ferrugata, including secondary
developed sexually dichromatic characteristics, can be completely
reversible in accord with their social status.
In 1978 Moyer and Nakazono showed Centropyge
interruptus to be a protogynous hermaphrodite. In its
day this was an important discovery toward advancing our knowledge
of marine angelfishes. Subsequently, Centropyge shepardi
was shown also to be a protogynous hermaphrodite (Randall
and Yasuda, 1979). All marine angelfish males are now believed
to result from a female having undergone a female-to-male
The discovery of bi-directional sex change
(Sakie et. al. 2003) is as important today as the Moyer
and Nakazono discovery was in 1978. Considering the history
of our knowledge of this genus, would it be fair to assume
that all species of Centropyge are capable of bi-directional
sex change? Only further research can definitively answer
that question; however, some relevant observations may be
gleaned from "experiments" conducted by astute aquarists.
Our access to and willingness to keep multiple aquariums;
our sometimes seemingly endless flow of "grants"
that help fund our endeavors; and the passion with which we
dedicate ourselves, and that makes hours of observation nothing
short of a complete joy; all contribute to make serious hobbyists
Be forewarned: the journey is not without
risks. Eight male Centropyge ferrugata began the experiment,
but only three survived and two reverted to females. The first
pair's male was able to revert to female and produce eggs,
which were fertilized by the male of the pair, 47 days after
the start of the experiment. Additionally, the intense 400
- 500nm wavelength color pattern characteristic of the male
C. ferrugata dorsal fin, which was present only two
months before, was now absent. It is important to note that
the male coloration was still present 32 days into the experiment,
the day that nuzzling was first observed between the two subjects.
Nuzzling is the third stage of Centropyge courtship.
The second pair's male reverted from releasing sperm to having
"considerably developed ovarian parts though it lacked
vitellogenic oocytes or preovulated eggs in the gonad"
after 89 days of cohabitation. Their conclusion was that the
fish was "in the process of the gonadal sex change to
become a functional female." It is important to note
they ended the experiment themselves at roughly the same time
the spawning season ended at Sesoko Island, the location where
the males were first observed for six months, and where they
were later captured for use in the experiment.
Such a series of observations can be attempted
at home with any two Centropyge of the same species.
Centropyge species exhibit sexual dichromatism and/or
dimorphism along the rear edges of their soft dorsal fins,
in the form of color changes, fin structure or both (Moyer,
1990). Documenting the sex-change process photographically
from start to finish, especially concentrating on images of
the dorsal fins, would be paramount to noting changes over
the course of 30 to 90 days or more.
Following the research protocol used by
Sakie et. al. (2003) would be the best course to follow.
The article detailing the research should be read before starting,
to ensure both similarity of research methods and comparability
of results. Among other things, they used a 4' long aquarium
divided in half by a 10mm mesh barrier. The barrier was fixed
in place for 10 days to keep the territorial disputes non-destructive.
The net was removed for 15 minutes on day 11, 20 minutes on
day 12, and completely removed on day 13. The larger of the
two fish attacked aggressively on day 11, but by day 12 the
smaller of the two was displaying laterally in a show of conceding
the battle. After this concession and the permanent removal
of the mesh net the pair reportedly calmed and the male ceased
its aggressive attacks. I expect that the smaller fish will
become the female. If your chosen species of Centropyge
is similar to C. ferrugata, you may begin to witness
spawning courtship within the month and fertilized eggs within
Moyer, J.T. and A. Nakazono, 1978. Population
structure, reproductive behavior, and protogynous hermaphroditism
in the angelfish Centropyge interruptus at Miyake-jimi,
Japan. Japan J. Ich
Moyer, J.T. 1981. Interspecific spawning of the pygmy angelfishes
Centropyge shepardi and C. bispinosus at Guam.
Micronesica 12(1-2): 119-124.
Moyer, J.T. 1990. Social and reproductive behavior of Chaetodontoplus
mesoleucus (Pomacanthidae) at Bantayan Island, Phillipines,
with notes on pomacanthid relationships. Jpn. J. Ichty. 25:
Randall, J.E. & F. Yasuda. 1979. Centropyge shepardi,
a new angelfish from the Mariana and Ogasawara Islands. Japan.
J. Ichthyol. 26: 55-61.