Rajchard J., Šerý M., Pachta Z., Hartvich P.
Abstract
The aim of this contribution was to demonstrate swordtail
(Xiphophorus helleri Heckel, 1848) as an interesting animal laboratory model,
its basic morphometric, growth and reproduction characteristics. This species
is originated from Mexico. Selected biological features were investigated in
two lines: original form („WILD“) and one of aquarium lines („BERLIN“).
Some difference by head length between females of both lines was found only:
head length of females of original form was 26.2 % of standard length, while
in individuals of aquarium line was 32.0 % of standard length. The same marker
measured in males of both lines about 25 % was found. In fish of the original
form, growth intensity decreased during the four months of the observation.
Similar decrease was not found for fish of the aquarium line. We have found
a statistically significant positive correlation either between the interval
between births and female body size, between the interval between births and
the number of offspring and between female standard length and number of offspring
for the original for, but not any for aquarium line. The sex ratio at the achievement
of sexual maturity was generally 1:1.
Key words:
Swordtail (Xiphophorus helleri Heckel, 1848); original form; aquarium line;
morphometric characteristics; body size; growth; reproduction; birth; offspring.