Page 23 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

EVOLUTION AND CLASSIFICATION 21

With the exception of lampreys and hagfish, which are distant
relatives of the early jawless fish, living fish fall into one of two
groups. Sharks, rays, and their relatives are Chondrichthyes CLASSIFICATION AND SCIENTIFIC NAMES
(cartilaginous fish), in which the skeleton is made of cartilage. Fish are members of the kingdom Animalia. Within this, they
The remainder, making up about 95 percent of all fish, are fall into the Chordata phylum, which contains all vertebrates.
Osteichthyes (bony fish), which have a bony skeleton. Bony fish The farther down the hierarchy you go, the more the species in
form the most diverse group of vertebrates on the planet, with each group have in common. As far as hobbyists are concerned, it
is the groupings from family downward that are most significant.
about 23,500 different species.
Family: This grouping typically Family
How fish are classified encompasses a number of genera,
although occasionally a family may
The classification of living things is called taxonomy. The basic consist of just a single genus.
unit of classification is the species—a collection of similar Family names are never italicized.
This Dwarf Gourami belongs to the
organisms that are capable of breeding together in the wild and Osphronemidae family, one of 72
producing fertile offspring. Related species are organized into families in the order Perciformes. Trichogaster lalius
groups called genera, which in turn are arranged into families.
The grouping process continues, working upward through ever
larger and more general groups known as orders, classes, phyla, Genus: This contains one or more Genus
species. The genus name always
and, lastly, kingdoms—the highest level in the hierarchy. starts with a capital letter and is
An integral part of classification is assigning unique scientific always italicized. The Red Fighter
names to individual species. Although scientific names may seem shown here is part of the genus
Betta, which along with 14 other
unwieldy because they are usually in Latin, they are understood genera goes to make up the Betta coccina
by scientists around the world and so are far more useful than family Osphronemidae.
common names, which often differ from country to country.
When a new fish is discovered, certain procedures have to
be followed before it can be identified as a species in its own Species: The two-part title Species Species
comprises the genus name and the
right. First, a specimen is lodged with a scientific institute, such species epithet. The Siamese Fighting
as a museum. This is called the type specimen. Then a detailed Fish is Betta splendens, and the
description is published in a recognized scientific publication. Slender Gourami Betta
bellica (or B. splendens
Finally, the fish is ascribed a scientific name and placed in the and B. bellica). There are
genus containing those species to which it is most closely 47 species in the genus Betta. Betta splendens Betta bellica
related. At present, classification relies primarily on comparing
the anatomical features of the type specimen to those of other
species, but DNA analysis is increasingly being used, since it gives Varieties and subspecies: Variety Variety
Cultivated color or fin varieties
a more accurate picture of the relationships between organisms. end with “var.” A third Latin
word in the name (e.g.,
Betta bellica bellica)
The loricariid catfish family is a rapidly denotes a subspecies—a
expanding group. To cope with the complexities population within a species
of classifying these fish, the L-numbering that shows distinct variation.
system was devised. For example, this Betta splendens var. Betta splendens var.
loricariid is known as L109.
The difficulties inherent in recognizing and differentiating
both species and subspecies has led the aquarium trade
to develop its own classification system, known as
L-numbering, for loricariid catfish (see pp.128–131)—
a little-studied family that shows remarkable diversity
in appearance. This system uses numbers prefixed by
the letter “L” to identify individual pattern and
color forms that are not currently recognized by
scientists. It sometimes happens that by the time a
species is formally classified, it already has several
L-numbers associated with it throughout its range.

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