Neural pathways involved in mutual interactions between optic lobe circadian pacemakers in the cricket Gryllus bimaculatus

The cricket, Modicogryllus siamensis, shows clear photoperiodic responses at 25°C in nymphal development. Under long-day conditions (LD16:8), nymphs became adults about 50 days after hatching, while under short-day conditions (LD8:16) the duration of nymphal stage extended to more than 130 days. Under constant dark conditions, two developmental patterns were observed: about 60% of crickets became adults slightly slower than under the long-day conditions, and the rest at later than 100 days after hatching, like those under the short-day conditions. When the compound eye was unilaterally removed on the 2nd day of hatching, an increase of molting and an extension of the nymphal period were observed under the long-day conditions, while under the short-day conditions, some crickets developed faster and others slower than intact crickets. These results suggest that this cricket receives photoperiodic information through the compound eye, that a pair of the compound eyes is required for a complete photoperiodic response, and that interaction between bilateral circadian clocks may be also involved in the response.

Section: Discussionmentioning

confidence: 99%

Effects of Unilateral Compound-Eye Removal on the Photoperiodic Responses of Nymphal Development in the Cricket Modicogryllus siamensis

Sakamoto

Tomioka

2007

“…They show circadian rhythms both in spontaneous and light induced responses (Yukizane et al, 2002). Partial destruction of the optic stalk including the MBNs abolishes the circadian locomotor rhythm driven by the optic lobe clock (Yukizane and Tomioka, 1995). Thus the lateral protocerebral areas are the likely output area of the clock signal for driving the locomotor activity.…”

Section: Output Pathway Of the Circadian Clockmentioning

confidence: 99%

Circadian Organization in Hemimetabolous Insects

Tomioka

Abdelsalam

2004

ABSTRACT-The circadian system of hemimetabolous insects is reviewed in respect to the locus of the circadian clock and multioscillatory organization. Because of relatively easy access to the nervous system, the neuronal organization of the clock system in hemimetabolous insects has been studied, yielding identification of the compound eye as the major photoreceptor for entrainment and the optic lobe for the circadian clock locus. The clock site within the optic lobe is inconsistent among reported species; in cockroaches the lobula was previously thought to be a most likely clock locus but accessory medulla is recently stressed to be a clock center, while more distal part of the optic lobe including the lamina and the outer medulla area for the cricket. Identification of the clock cells needs further critical studies. Although each optic lobe clock seems functionally identical, in respect to photic entrainment and generation of the rhythm, the bilaterally paired clocks form a functional unit. They interact to produce a stable time structure within individual insects by exchanging photic and temporal information through neural pathways, in which serotonin and pigment-dispersing factor (PDF) are involved as chemical messengers. The mutual interaction also plays an important role in seasonal adaptation of the rhythm.

“…The circadian clock of this insect is located one in each of the paired optic lobes Chiba, 1984, 1992). The two clocks are mutually coupled to move in synchrony by exchanging coupling signals through a neural pathway Tomioka, 1993;Yukizane and Tomioka, 1995). Immunocytochemistry with anti-Uca -b -PDH antibody revealed that there were widely distributed PDH immunoreactive neurons in the optic lobe.…”

Section: Introductionmentioning

confidence: 99%

Phase Shifts of the Circadian Locomotor Rhythm Induced by Pigment-Dispersing Factor in the Cricket Gryllus bimaculatus

Singaravel¹,

Fujisawa²,

Hisada³

et al. 2003

-Pigment-dispersing factors (PDFs) are octadeca-peptides widely distributed in insect optic lobes and brain. In this study, we have purified PDF and determined its amino acid sequence in the cricket Gryllus bimaculatus . Its primary structure was NSEIINSLLGLPKVLNDA-NH 2 , homologous to other PDH family members so far reported. When injected into the optic lobe of experimentally blinded adult male crickets, Gryllus -PDF induced phase shifts in their activity rhythms in a phase dependent and dose dependent manner. The resulted phase response curve (PRC) showed delays during the late subjective night to early subjective day and advances during the mid subjective day to mid subjective night. The PRC was different in shape from those for light, serotonin and temperature. These results suggest that PDF plays a role in phase regulation of the circadian clock through a separate pathway from those of other known phase regulating agents.