Abstract:
In the past ten years, many researchers have focussed their
attention on parasites regarding the role they may play in causing
variations in male secondary sexual traits and subsequent effects on
female choice. Male age has also been suggested to be an important
factor in female choice if old age reflects superior genes. This study
investigated the effects that gregarine gut parasites, age, and diet have
on the calling and mating behaviour of the male Texas field cricket,
Gryllus integer.
Male calling songs were recorded in the laboratory using a
Digital Signal Processing Network. The song parameters measured were:
pulse rate, pulse width, burst duration, pulses per burst, interburst
interval, and percent missing pulses. The effects of parasite load and
age on the various calling song parameters was investigated in crickets
that were fed two different diets varying in nutritional quality. None of
the calling song parameters were affected by either parasite load or age
in either diet grou p.
Courtship behaviour was ob served and recorded using an
Eventlog recorder on an IBM computer in the laboratory. Females
mated equally with paras(tized and unparasitized males and with old
and young males The total duration and proportion of time spent
performing each of 9 courtship displays were recorded for males on
each diet. Only one display was affected by parasite load. Highly
parasitized males fed the nutritionally inferior diet juddered for a
proportionately shorter time than males with low parasite loads. Also,
older males performed juddering and shaking antennae proportionally
longer and juddering and raising wings for longer durations than
younger males.
Males that successfully mated were observed for performance of
8 post-copulatory guarding behaviour displays. None of the guarding
behaviours were affected by parasite load. However, one display was
affected by age, with older males performing guard turning for shorter
durations than younger males. Results are discuss,ed in terms of the
influence of parasites and age on female choice.
