Page 170 - Encyclopedia of Aquarium and Pond Fish, 3rd Edition

168 FRESHWATER FISH DIRECTORY

Poecilia butleri
Pacific Mexican Molly The coloration of Pacific Mexican Mollies in derives from melanistic examples of the wild form.
the wild is variable, ranging from shades of Like the Pacific Mexican, the Black Molly has
ORIGINS Central America, ranging from northern Mexico blue to yellowish and silvery tones. Darker a low dorsal fin, a relatively elongated body, and a
into Guatemala and Honduras. coloration is seen in some individuals, notably compact, rounded caudal fin. The black coloration
1
SIZE 3 ⁄2 in (8.5 cm). in the race known as Limantour’s Molly (P. m. has also been combined with marbled and balloon
DIET Prepared foods, vegetables, and small live foods. limantouri). The wild Pacific Mexican Molly is the characteristics. Black varieties look good in an
WATER Temperature 75–81°F (24–27°C); hard ancestor of the Black Molly, the most popular of aquarium alongside bright orange swordtails (see
(100–150 mg/l) and alkaline (pH 7.5). the domesticated varieties available today. The p.160). These fish often fare better when kept in
TEMPERAMENT Placid and social. Black Molly was created in the 1930s by a breeder slightly brackish water. This seems to make them
in New Orleans, although the exact route of less vulnerable to the parasitic illness known as
its development is now unclear. “ich,” or white spot (see p.58), which shows up
Its distinctive matt-black clearly against the color of their bodies. Females
coloration almost certainly typically produce 40–300 offspring per brood.
Black marbled patterning Marbled Lyretail Molly In this form, the upper and lower
extends onto the fins rays of the caudal fin are elongated. However, changes to
the structure of the caudal fin are not common in mollies.
Upturned mouth indicates
that these fish are
naturally surface feeders
Marbled Molly A relative
of the Black Molly and
another descendant of
the Pacific Mexican Molly,
this fish has a varied
pattern of large, irregular
black blotches, making it
easy to distinguish from
spotted or dotted forms.

CLONED FISH

The Amazon Molly (P. formosa) is believed to
be a wild hybrid of the Yucatán and Pacific
Mexican species. Its common name refers not
to its distribution (which extends from parts of
the southern U.S. into Central America) but to
the fabled all-female tribe
of South America. Only
one in every 10,000 of
these fish is a biological
male, and the arrangement
of the males’ chromosomes
suggests that they are sterile.
The offspring produced by female
mollies are therefore clones of their
mothers, making the Amazon Molly the
first unisexual vertebrate to be discovered.
Female Amazons still need to mate in
order to give birth, so they attract males of
other molly species, by interrupting their
courtship rituals, and also simply by living
alongside them so that the males eventually
come to identify with them. While sperm
produced by these males triggers the
development of an Amazon Molly’s eggs,
it does not fertilize them. The eggs contain
the complete genetic blueprint of the young,
rather than just the half normally contributed
by female vertebrates that reproduce sexually.

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