Nano Gobies

Trimma cana, the Candystripe
Goby, is eminently suitable for
keeping in pairs.
numerous genera (for example, the coral gobies, genus
Gobiodon) to group together those species that are more
or less similar. But the family Gobiidae is a taxonomic
catch-all for the largest family of fishes, born of the necessity
to create some sort of unified designation for a
group of fishes that have about as much in common as
cats and dogs.
That comparison is in no way inappropriate: the
family Gobiidae is—in contravention of the taxonomic
ideal—not monophyletic. In other words, the genera do
not all trace their ancestry back to a single original form.
The family can be compared to a tree with several trunks,
or even to a number of trees that have separate roots.
Most gobies live in marine environments, but there are
also brackish water and freshwater species—and some
that migrate between fresh and salt water.
And there is more: some of the species we term “pygmy
gobies,” for example those of the genus Tryssogobius,
actually belong not to the family of the “true” gobies
(Gobiidae), but to the dartfish family (Ptereleotridae).
It’s no wonder, then, that the systematics of the gobies is
a subject of continuing zoological debate.
However, necessity is often the mother of invention,
and thus it has proved expedient in aquarium circles to
consider size alone as a differentiating character rather
than obvious systematically relevant factors (body form,
fin rays, etc.) and genuine phylogenetic relationships.
Because there are numerous goby species that are notable
for their particularly small size, the term “pygmy
gobies” seems very appropriate. But what size does a goby
have to be to count as one of these dwarfs?
WHICH GOBIES ARE NANO SIZE?
There is no generally accepted definition of the term
pygmy goby, so the CORAL editorial team has decided
to set the upper size limit at 2 inches (5 cm) SL. One
advantage of this arbitrary division is that it means we
are talking about gobies with very similar requirements
for aquarium husbandry. Coincidentally, the majority of
the marine members of the family Gobiidae that measure
less than 2 inches (5 cm) in body size are strongly
bound to the reef and sedentary in their habits, primarily
feeding on plankton and substrate-spawning in their reproduction.
On this basis, these externally variable fishes
can be grouped together. Note, however, that the species
discussed here have very little in common with the freshwater
“pygmy gobies” of the subfamily Gobionellinae.
Another rather arbitrary limitation: in selecting the
pygmy gobies to be discussed in this article, we have
concentrated on those species that are both suitable for
maintenance in the nano reef aquarium and also imported
for the aquarium hobby, albeit sometimes rarely.
ANATOMY
Naturally, it is impossible to generalize regarding the
anatomy of such a heterogenous group, but there are
D. KNOP
58 CORAL