Function of the Brain-Suboesophageal Ganglion Complex in the Silkworm, Bombyx mori

1. The action of the diapause hormone has been studied by injecting extracts of the heads of male moths or of the brain-suboesophageal ganglion complexes of pupae into pupae expected to produce non-diapause eggs. 2. The effect of the injection of hormone upon young oocytes is to make them develop into diapause eggs. Older oocytes, which have already acquired non-diapause characters, are not affected. 3. The hormone is almost completely inactivated when injected on the day of pupation. The hormone is most effective when injected into pupae 2-3 days old, at which stage the ovarioles have started to grow vigorously. It is ineffective 1-2 days before adult emergence, by which time all the oocytes have acquired non-diapause characters. 4. The hormone is inactivated in all pupae irrespective of whether they are destined to produce diapause eggs or non-diapause eggs. Inactivation of diapause hormone (in contrast to that of juvenile hormone) is partially relieved by exposure to low temperature or by simultaneous injection of indian ink. 5. The extracts prepared as in (1) above do not serve as a stimulant for the brain causing the suboesophageal ganglion to produce diapause hormone. The action of the extract faithfully reflects the function of the diapause hormone which originates in the suboesophageal ganglion.

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Neuromuscular systems in the fifth instar larva of silkworm Bombyx mori (Lepidoptera: Bombycidae): I-Cephalothoracic musculature and its innervation

Journal of Applied and Natural Science ◽

10.31018/jans.v1i2.80 ◽

2009 ◽

Vol 1 (2) ◽

pp. 201-209

Author(s):

S. Sivaprasad ◽

P. Muralimohan

Keyword(s):

Bombyx Mori ◽

Instar Larva ◽

Compound Eyes ◽

Suboesophageal Ganglion ◽

Ventral Region ◽

Thoracic Ganglia ◽

Neuromuscular Systems ◽

Frontal Ganglion ◽

The Brain ◽

Silkworm Bombyx Mori

The cephalo-thoracic musculature of the fifth instar larva of Bombyx mori comprises distinct groups of segmental muscle bands arranged in a stereotyped pattern. It includes dorsal, ventral, tergopleural, tergocoxal, lateral intersegmental, pleurosternal, sternocoxal, pleurocoxal and spiracular muscles. The cephalothoracic segments are innervated by the nerves of brain, suboesophageal ganglion (SG) and three thoracic ganglia (TG1, TG2, TG3).The brain gives nerves for compound eyes, antennae, labrum, frontal ganglion and the integument in the head. The SG, TG1,TG2,and TG3 give out a pair of lateral segmental nerves each, called the dorsal (DN) and ventral (VN) nerves. The DN of SG innervates muscles in the cephalic region, while its VN innervates muscles in the prothorax. The DN of thoracic ganglia innervates muscles in the dorsal, lateral and ventral regions of the hemi-segment while the VN innervates muscles in the ventral region. The innervation pattern indicates the presence of mixed nerves and multiple innervations that facilitate coordinated body movements and locomotion.

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