Control of growth and ultrastructural maturation of a cricket flight muscle

Abstract

The metathoracic dorsal longitudinal muscle (DLM) in the cricket Teleogryllus oceanicus increased in mass and rapidly acquired interfibrillar tracheoles and an increased proportion of mitochondria around the time of the adult molt. Both neural input and juvenile hormone levels were investigated as possible factors controlling this rapid maturation. Motor axons to the muscle were cut early in the last nymphal instar, and muscle growth slowed but ultrastructural maturation continued; the percentage of muscle volume occupied by mitochondria tripled and tracheoblasts invaded the fibers in both the denervated and contralateral innervated muscles. Newly molted last instar nymphs were treated with methoprene, a juvenile hormone analog, and examined four days following the next molt. Muscle growth was slowed but not stopped. Both mitochondrial proliferation and tracheoblast formation were completely blocked by hormone treatment. This study shows that both neural input and low levels of juvenile hormone are required for muscle growth. However, ultrastructural maturation seems to depend exclusively on low levels of juvenile hormone.

Morphological and functional maturation of a skeletal muscle regulated by juvenile hormone

“…Studies on crickets underline the importance of metamorphosis for subsequent flight muscle maturation. Injection of the JH analog methoprene into last-instar nymphs of the cricket Teleogryllus oceanicus slowed subsequent flight muscle growth and blocked ultrastructural maturation (Novicki, 1989). It seems reasonable to suppose therefore that parts of the structural maturation of insect muscles are influenced by their hormonal history during metamorphosis, although it must be pointed out that flight behaviour occurs shortly after moulting, while oviposition is delayed until at least 2 weeks later.…”

“…The importance of metamorphosis for flight muscle differentiation and development has been shown by manipulating the levels of JH. Treatment of larval stages with the JH analog methoprene, or implantation of corpora allata, which shortened the length of the larval stadium, caused slowing of muscle growth and inhibited the development of mitochondria and tracheolation in locust (Poels and Beenakkers, 1969;Cotton and Anstee, 1990) and cricket (Novicki, 1989). Chemical allatectomy, however, enhanced flight muscle development and resulted in normal flight muscles of the adultiform (Wang et al, 1993).…”

The Hot-Blooded Insects

“…Fixing the wings after the final molt to eliminate practice wing beating does not prevent the establishment of the normal, alternating motor pattern between the antagonistic flight muscles (Altman, 1975). Meanwhile, in crickets neural input is required for muscle growth (Novicki, 1989b) and muscle development continues even after the adult molt (Novicki, 1989a). The connections are apparently complete and then switched on, perhaps hormonally, at or before the final molt (Bentley and Hoy, 1970).…”

Variations in the ultrastructure of the flight muscles of the polymorphic cricket, Gryllus firmus (Orthoptera: Gryllidae)

“…The ultrastructure of the flight muscles, especially those associated with insect growth and development is well described (Herold, 1965;Reedy, 1968;Davies, 1974;Mizisin & Ready, 1986;Novicki, 1989;Reedy & Beall, 1993;Mentel et al, 2003;Biserova & Pfluger, 2004). The juvenile hormone (JH) is critical for both the growth and degeneration of flight muscles (Novicki, 1989;Rose, 2004).…”

“…The juvenile hormone (JH) is critical for both the growth and degeneration of flight muscles (Novicki, 1989;Rose, 2004). In the cricket Acheta domestica, the dorsal longitudinal muscle increases in size during the first 2 days of adulthood and begins to degenerate on day 4 when the level of JH increases (Chudakova & Bocharova-Messner, 1968;Srihari et al, 1975).…”