Origin and peripheral distribution of the thoracic and abdominal median nerves in the fifth instar larva of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Abstract

Abstract:The origin and peripheral distribution of the median nerves of the prothoracic and sixth abdominal ganglia have been traced using methylene blue staining technique. Each median nerve (MN), after originating from the posterior part of the ganglion, bifurcates into two transverse nerves (TN) that extend laterally into the right and left halves of the hemi-segment. The TN of thoracic median nerve bears two motor branches that innervate spiracular muscles and dorsolateral muscles, while the TN of sixth abdominal ganglion bears five motor branches and two sensory branches. Its motor branches innervate three groups of muscles, namely, musculi laterales interni, musculi dorsales interni laterales and musculi dorsales interni mediales, while its sensory branches extend over the body wall in the ventrolateral and dorsolateral areas of the hemi-segment. The median nerves are connected to ganglionic nerves by median nerve connectives that facilitate intersegmental coordination. The functional role of median nerves in respiration, blood circulation and intersegmental coordination is discussed keeping in view their projections and innervations.

Photoperiod-modulated instar-specific clock-shifting in the circadian protein and amino acid rhythms in the larval segmental muscle of Bombyx mori

“…1 and 2). As reported in our previous reports for the silk gland and the fat body a, 2010, the peaks and troughs in the phase response curves (PRCs) of the skeletal muscle protein rhythm probably indicates two vital stages of gene expression; translation (protein synthesis) and transcription, and the combined mean interval between a peak and trough reflects the duration Table 5. Comparative analysis of the phase response curves of the protein rhythm in the muscle of the fourth and fifth instar larvae of Bombyx mori, in terms of mean number of peaks and troughs and the mean interval between them, under 12h light / dark cycle (LD), continuous light (LL) and continuous dark (DD) conditions.…”

“…Since, Bombyx mori is viewed as a potential model for the study of circadian biology, several investigations were carried out on the identification of circadian clocks, silk genes and their products (Ishikawa and Suzuki, 1985;Kimura et al, 1985;Obara and Suzuki, 1988;Michaille et al, 1989;Fukuta, et al, 1993;Gizelak, 1995;Sehadova et al, 2004;Iwai et al, 2006), which opened new vistas for probing the molecular and genetic basis of circadian clock mechanism in silkworm. However, no significant contributions have since been made on tissue-specific biochemical profiles vis-à-vis the impact of photoperiod on circadian rhythms, except for our preliminary investigations on the silk gland and fat body of the silkworm a, 2010. In order to provide further impetus to studies in this direction, we made an attempt to analyze circadian changes in the segmental muscle protein and amino acid profiles in the silkworm during the fourth and fifth instar larval stages under the influence of altered photoperiodic conditions.…”

“…The dorsal group includes the musculi dorsales interni mediales (DIM) and musculi dorsales interni laterales (DIL), musculi dorsales externi mediales (DEM) and musculi dorsales externi laterales (DEL), the ventral group includes musculi ventrales interni mediales (VIM) and musculi ventrales interni laterales (VIL), musculi ventrales externi mediales (VEM) and musculi ventrales externi laterales (VEL) and the lateral group includes the spiracular, tergosternal, tergopleural, tergocoxal, pleurosternal, sternocoxal and pleurocoxal muscles. The insect muscle performs a multitude of functions such as respiration, thermiogenesis, circulation of body fluids, body movements, maintenance of posture, oviposition, copulation, locomotion, jumping movements and in stabilizing joints (Kawasaki and Kita, 2004;Triplehorn and Johnson, 2005;Sivaprasad, 2010). It is imperative to study the physiological and biochemical basis of insect muscle due to diverse habits and wide spread distribution of insects in almost every conceivable environment on the earth.…”