Before we elaborate upon this point let’s have
a look at the origins of this species. Found in scattered localities
the tropical Eastern Pacific and is caught in shallow water particularly
in the Philippines. It is known to feed upon zooplankton and benthic
invertebrates. This only tells part of the story however as this species
has a deep-water form that inhabits depths of over 200 meters. This
gives us a clue to how this species might be unique. Anomalops belongs
Family Anamolopidae , collectively known as the flashlight fish. This
common name is given to them as they possess specialised organs that
contain symbiotic bacteria capable of bioluminescence. Nourish these
bacteria and protect them and a fish can utilise their amazing properties
to their own ends.
The splitfin flashlight fish covers the bioluminescent organ with
a moveable flap of skin enabling it to “turn off” the light
at will. After all, most species of fish would not want to attract
the attention of potential predators and carrying a light around with
you all of the time is not necessarily a good idea. But what are the
advantages of producing light? Well, it is fairly common knowledge
that light has an effect upon many animals of the world particularly
those that synchronise certain behaviour with the lunar cycle. Think
of moths being “attracted” to lights at night. This is
because many species of moth use the moon to navigate by. Rather than
flying towards the source of the light as it seems they are flying
with it to one side, the left or right. If the moon is the only light
source available to them they will never get any closer to it but if
they are attempting to navigate by the light of a street lamp they
will end up flying in a spiral pattern with an ever decreasing diameter
and eventually the collide with it and spend their time continually
butting it as its fills their vision. Many marine animals, including
fish, will experience a positive effect when stimulated with a light
source at night. Larval fish will swim towards light when they hatch
in order to join the plankton layers and many other animals do likewise,
even if it is just a vertical migration of plankton at night.
Flashlight fish exploit this ruthlessly by harbouring bacteria that
produce light and attract zooplanktonic animals, enticing them in close
enough to be consumed. Apart from the use of the bioluminescence as
a lure it also serves to partially illuminate the potential victims
of this fish. The splitfin flashlight fish possess relatively huge
eyes to catch the tiniest amount of reflected light bouncing back from
other animals. It has also been suggested that this species uses its
ability to control the light flashes produced in communication in which
the eyes may also have a role.
So the flashlight fish is a pretty animal that may not be to everyone’s
taste if we judge it by looks alone. However, its fascinating behaviour
and almost unique bioluminescence with the marine aquarium hobby (one
other species of marine fish is sporadically available in the trade-
Monocentrus japonicus is known by the common name Pinecone fish and
is a fascinating species with close affinities to the family Anomolopidae)
soon endear it to aquarists and those that can afford the price, around £40-75
each depending upon their size, will be treated to a regular nocturnal
Captive care of the splitfin flashlight fish is not completely straightforward
and you should bear in mind the following before you commit to a purchase.
First of all this is a shoaling species and will do better when maintained
as such in an aquarium situation. The absolute minimum number that
should be acquired is two and this certainly will put this out of the
budgets of many aquarists. Bear in mind that the more individual fish
a shoal contains, the greater the light show at night!
Froese, R. and D. Pauly. Editors. 2005. FishBase.
World Wide Web electronic publication.
www.fishbase.org, version (02/2005).
Arch Microbiol. 1990;154(5):496-503.
Relationship of the luminous bacterial symbiont of the Caribbean flashlight
fish, Kryptophanaron alfredi (family Anomalopidae) to other luminous
bacteria based on bacterial luciferase (luxA) genes.
Marine Biology (Historical Archive)
Publisher: Springer-Verlag GmbH
ISSN: 0025-3162 (Paper) 1432-1793 (Online)
Issue: Volume 37, Number 4
Date: September 1976
Pages: 325 - 328
Some observations on spawning and fecundity in the luminescent fish
V. B. Meyer-Rochow1