4 research outputs found
Auto-spermatophore extrusion in male crickets
The reproductive cycle of the male cricket consists of
the mating stage and the sexually refractory stage. The
latter is further divided into the first refractory stage
(RS1) from spermatophore extrusion in copulation to
spermatophore preparation after copulation, and the
second refractory stage (RS2) from spermatophore
preparation to recommencement of a calling song. RS2 is
time-fixed and unaffected by the female or by stress, hence
RS2 is assumed to be controlled by the reproductive timer.
Previously, we suggested that the timer is located in the
terminal abdominal ganglion (TAG), because functional
inactivation of the TAG by local cooling lengthened RS2 in
proportion to cooling time. To obtain further evidence
of timer localization and to examine the operation of
the timer in dissected animals, we investigated the
characteristics of auto-spermatophore extrusion, a
phenomenon in which males eject the mature
spermatophore themselves without any prior courtship.
The occurrence of auto-spermatophore extrusion was
100% in dissected males with the TAG separated,
compared to 1.7% in intact males. The time interval
(SPaSE) between spermatophore preparation and autospermatophore
extrusion was comparable to RS2
measured by the calling song. Spike recording from a
genital motor neurone in the separated TAG indicated
that burst discharge associated with auto-spermatophore
extrusion occurred with a SPaSE comparable to RS2.
Other efferent neurones, some of which were identified as
dorsal unpaired median (DUM) neurones, showed a timedependent
spike frequency increase during SPaSE. These
results strengthen our previous conclusion that the
reproductive timer is located within the TAG, and
demonstrate that the timer functions normally even when
the TAG is separated from the central nervous system.</p
Reproductive behaviour in the male cricket Gryllus bimaculatus DeGEER: I. Structure and function of the genitalia
We have investigated the morphology and physiology of the genitalia of the male cricket to establish a basis for neuroethological study of its reproductive behaviour. First, the structure of the phallic complex, including the
dorsal pouch, guiding rod, epiphallus, ventral lobes and median pouch, are described, as are the muscles, cuticle, membranes and biomechanics of copulation. The innervation and sensory receptors have also been examined. Second, the functional role of the muscle in each genital organ has been determined by direct observation
of muscle contraction during spontaneous or evoked movements and by analysis of the changes in movements after the ablation of the muscle. Third, for the flexible membranous organs, the ventral lobes and median pouch, the passages for haemolymph and their dynamic properties have been examined using petroleum jelly. Fourth, the
sequence of coordinated motor actions performed by the internal and external genital organs, which were induced in both restrained and dissected males using newly developed techniques, has been analyzed during tethered
copulation and spermatophore formation. As a result, the mechanisms of copulation and spermatophore formation are now more fully understood
Reproductive behaviour in the male cricket Gryllus bimaculatus DeGEER: II. Neural control of the genitalia
To understand the neural mechanisms of reproductive behaviour in the male cricket, we identified motor neurones innervating the muscles in each genital organ by backfilling
with cobalt/nickel and recording their extracellular spike activity from nerve bundles of the terminal abdominal ganglion during tethered copulation and spermatophore formation. During tethered copulation, at least two
motor neurones innervating two ipsilateral muscles were activated during projection of the guiding rod of the phallic dorsal pouch. Only one motor neurone, innervating four ipsilateral muscles of the dorsal pouch, was responsible for
spermatophore extrusion by deforming the dorsal pouch. For spermatophore transfer, three motor neurones, singly innervating three epiphallus muscles, played a major role in opening passages for haemolymph to enter the ventral lobes and median pouch by bending the epiphallus. Two
ventral lobe and 3ā5 median pouch motor neurones seemed to play a role in expanding or folding the two membranous structures by relaxing or contracting their muscle fibres. After spermatophore transfer, most of the genital motor
neurones exhibited a rhythmic burst of action potentials causing movement of the phallic complex coupled with strong abdominal contractions. For spermatophore formation, the genital motor neurones began to accelerate
their rhythmic bursts approximately 30 s prior to
subgenital plate opening and then changed their activity to tonic bursting or silence. The results have allowed us to describe the timing of the onset and termination of genital muscle contraction more precisely than before, to examine the neural mechanisms of copulatory motor control and to speculate on the neural organization of the reproductive centre for spermatophore extrusion and protrusion