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The role of the frontal ganglion in locust feeding and moulting related behaviours

Yael Zilberstein and Amir Ayali^*

Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel

View larger version (60K): [in a new window]   Fig. 1. Simultaneous extracellular recording from two of the frontal ganglion (FG) efferent nerves, frontal connective (FC) and median pharyngeal nerve (MPN), in a fully intact preparation. The boxed areas on the right panels are played (left) at a higher sweep speed to reveal phase relations between different members of the frontal ganglion (FG) central pattern generator.

View larger version (42K): [in a new window]   Fig. 2. (A) Differences in burst frequency of the frontal ganglion (FG) rhythmic pattern in vitro and in vivo reflecting the effect of the amount of food present in the gut. Values are means ± S.D. ***P<0.001. (B) Extracellular recording from an FG nerve before (i) and after (ii) injecting petroleum jelly into the locust's previously empty crop, demonstrating the effect of the state of the gut on the rhythm.

View larger version (51K): [in a new window]   Fig. 3. Recording from an abdomen wall muscle (Ab) and simultaneous output of a force transducer (FT) connected to the foregut wall in a fully intact preparation. The foregut may participate in the ventilation rhythm in almost full synchrony (A). At other times it may show no rhythmic movements (B) (same preparation as in A); or a totally independent motor pattern (C).

View larger version (47K): [in a new window]   Fig. 4. (A) Simultaneous extracellular recordings from an abdomen wall muscle (Ab) and a frontal connective (FC) in a fully intact preparation, exhibiting full synchrony between the ventilation and the frontal ganglion (FG) patterns. (B) Uncoupling of the ventilation and FG patterns after the thoracic ventral nerve cord has been cut between the pro- and mesothoracic ganglia. The trace shown in Bi, precedes the one shown in Bii, demonstrating an independent FG rhythm after only a few minutes.

View larger version (82K): [in a new window]   Fig. 5. (A) Simultaneous extracellular recordings from an abdominal wall muscle (Ab) and frontal ganglion (FG) efferent nerve (MPN) of pre-moult fifth instar larvae, showing full synchrony between the ventilation and the FG patterns. (B) New bursting pattern after cutting the recurrent nerve. (C) An independent FG pattern, similar to the in vitro preparation, emerges after disconnecting both frontal connectives.

View larger version (38K): [in a new window]   Fig. 6. Alternation between bouts of ventilation rhythm and frontal ganglion (FG) rhythm can be seen during air swallowing in recordings from an abdominal muscle (Ab) and a foregut dilator muscle (37).

View larger version (50K): [in a new window]   Fig. 7. Simultaneous extracellular recordings from an abdominal wall muscle (Ab) and frontal ganglion (FG) efferent nerves at three different stages of the moult. (A) The old cuticle is split. (B) The head, thorax and pro- and mesothoracic legs emerge. (C) Expansion of the wings. (D) Variation in cycle periods and squeeze duration (first long, high frequency burst in each cycle) in the different moult-related behaviours. The ventilation and the FG patterns are fully synchronized throughout these different stages of the moult. Values are means ± S.D. MPN, median pharyngeal nerve; PPN, posterior pharyngeal nerve; FC, frontal connectives; RN, recurrent nerve.

View larger version (62K): [in a new window]   Fig. 8. (A) Simultaneous extracellular recordings from an abdominal wall muscle (Ab) and two frontal ganglion (FG) nerves (FC and MPN), showing full synchrony between the ventilation and the FG patterns at the time of wing expansion. (B) Uncoupling of FG and ventilation patterns generated by puncturing a hole in the inflated gut. The FG rhythm resembles feeding/air-swallowing pattern. The boxed areas on the right panels are played (left) at a higher sweep speed.

View larger version (41K): [in a new window]   Fig. 9. Simultaneous extracellular recording from an abdominal wall muscle (Ab) and frontal ganglion nerve (MPN), showing the evolution of the air-swallowing pattern on the MPN after puncturing a hole in the inflated gut. The number of bursts within each bout gradually increases.

View larger version (29K): [in a new window]   Fig. 10. Schematic illustration of the two activity patterns of the frontal ganglion (FG). The synchronized pattern shows full synchronization of activity recorded on the FG nerves together with the ventilation pattern. The uncoupled patterns show an FG rhythm that is independent of ventilation. See text for details.