CIRRHILABRUS | THE FAIRY WRASSES
Part 1 of 2: Life History
by Leonard Ho
A male Hawaiian Cirrhilabrus jordani
of the ideal captive reef-safe fish, one genus comes immediately to
Cirrhilabrus, commonly referred to as Fairy Wrasses, are arguably the most vibrant and gaudy of all reef-dwelling fish. Over three dozen recognized species comprise this genus, with several more species yet to be formally described. All known species are perfectly adaptable to captivity, granted certain care conditions are met. What makes Cirrhilabrus the perfect reef fish are their mild disposition, durability, and a diet absent of decorative invertebrates.
Morphology, Behavior, &
This is a
relatively small genus: Cirrhilabrus’ maximum length ranges from 3 inches
(C.rubrisquamis, C rubriventralis) to 6 inches (C.cyanopleura),
with an average mature size in the neighborhood of 5 inches.
All Cirrhilabrus possess body forms known as sagittiform.
Sagittiform fish are “arrow-like,” with an elongated tubular body
is accomplished primarily by paddling their pectoral fins.
The caudal and anal fins serve as balancing agents, while the soft
dorsal performs rudder functions. Cirrhilabrus
can achieve high velocities in short bursts, but aren’t able sustain these
speeds for extended periods of time.
Fairy Wrasses occur in almost every reef biotope throughout an extremely broad distribution range in the Pacific and Indian Oceans. They can be found in shallow, sheltered back-reefs to wave-washed rubble zones to turbulent deep fore-reef slopes. Cirrhilabrus spend most of their day leisurely cruising the waters a few meters above the substrate. At night, they wedge their bodies in small crevices and produce a mucus net that envelops their body. The mucus cocoon is a protective mechanism against nocturnal predation. Fish that hunt at night are predominantly olfactory predators (IE they locate prey via smell); Cirrhilabrus’ mucus net effectively thwarts nocturnal predators’ olfactory senses, preventing detection while they sleep. Other Labrids – most infamous are Parrotfish – possess this same defensive mechanism.
Cirrhilabrus are carnivorous fish with a diet consisting predominately of pelagic zooplankton. However, contrary to popular belief, Fairy Wrasses are not all exclusively mid-water planktivores. Although the majority of species capture zooplankton in the water column as their primary sustenance, several species are known to predate small benthic crustaceans to supplement their diet. Species known to actively pursue amphipods and mysis shrimp include the popular Flame Wrasse (C.jordani) and Exquisite Wrasse (C.exquistus). Larger crustaceans, such as cleaner shrimps (Lysmata sp.), are usually safe from predation, although it is inadvisable to introduce smaller specimens into a tank with an established Cirrhilabrus (depending on species). Cirrhilabrus do not consume cnidarians (e.g. corals & anemones), bivalves (e.g. Tridacna sp. clams), or polycheates (e.g. bristle worms & tube worms). All in all, there are few fishes that are more “reef-safe” then Cirrhilabrus.
Although Fairy Wrasses do not move in schools, their social structure is extremely intimate nonetheless. Cirrhilabrus are haremic fish, and live in substantial (but usually loose) aggregations. One dominant male will oversee several to dozens of females within a large defended territory (upwards of a 1,500 square feet). Like most species of haremic fish, Cirrhilabrus are sequential protogynous hermaphrodites (i.e. “female first”). If a male should die, the dominant female of the territory will undergo gonadal transformation, resulting in a complete sex change from female to male. The new male will then resume the reproductive and territorial responsibilities of the previous male. This social structure ensures a constant reproductive partner for the species.
Sex & Reproduction
Cirrhilabrus are all born
asexual. As they grow into adults, all Cirrhilabrus develop ovaries
and become sexually mature females. Under conducive circumstances (e.g. the
absence of a male), select female specimens may undergo a full sex change,
developing a complete set of male gonads to replace its female gonads.
Sex changes are outwardly expressed in a specimen’s physical
appearance as well. The sexes
of Fairy wrasses are dichromatic (differing in color) and dimorphic
(differing in shape) – so much so, in fact, that different sexes of the
same species have historically been misidentified as completely distinct
species. Most sex changes are
permanent in the wild, with a male defending its territory until it dies.
In captivity, sex reversals have been observed when males are not
housed with conspecific females.
During mating, dominant
males become exceedingly colorful, and thus are commonly referred to as
“super males” or “displaying males.”
Males possess the incredible ability of dramatically altering their
colors by expanding or contracting special pigment cells called
chromatophores, resulting in
brilliant flashes of varying colors. When
courtship commences, males will aggressively swim through their harems,
displaying its colors to females in an attempt to lure them into mating.
Having found a receptive female, the male will begin fast, vertical
loops in the water column, with the female following suite.
At the apex of each loop, each releases their respective gametes.
In most species, eggs are fertilized in the water column, where they will develop adrift in the ocean. Newly hatched Cirrhilabrus are extremely small and completely transparent. During this developmental stage (often referred to as their larval stage), some juveniles are known to consume bacteria off other fishes for sustenance until they’re old enough to consume for zooplankton.
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