Development II: Endocrinology

Endocrine System in Insects

Regulation of Development in a Paurometabolous Insect

Regulation of Development in a Paurometabolous Insect

Regulation of Development in a Holometabolous Insect

Regulation of Development in a Holometabolous Insect

aRAIN CELLS

CARDIACUM

GLAND

,.(-.;;:) .... . -: ·< .):)·_\ (' CHROMOSOMES .'. '

\ ·.;).' +

t:-...·,/

'·" "\ RNA (Al ..<t ""< ...._,.. .· .·\ . _.. ......... . .•,...A. ·

PROTEIN SYNTHESI S

+ ADULT STRUCTURES

LARVA PUPA ADULT

FIGURE 21.12. Schematic reprsentatlon of endocrine control of development. [After L. l. Gilbert, 1964, Physiology of growth and development: Endocrine aspects, in: The Physiology of Insecto, 1st ed., Vol. I (M. Rockstein, ed.). By permission of Academic Press and the author.]

penultimate larval instar

Figure 5.8. Typical juvenile hormone titer profiles during the end of larval life of hemimetabolous and holometabolous insects. Hypothetical JH-sensitive peri- ods

are indicated by gray bars. In the Hemimetabola there is a JH-sensitive period near the end of each larval instar, during which the commitment to larval versus adult development is controlled. In the Holometabola there is a JH-sensi-

tive period for larval versus pupal determination near the end of each larval instar, except in the final larval instar. The two JH-sensitive periods in the final larval instar are based on the findings in Manduca sexta (fig. 5.7). There is an additional JH-sensitive period for pupal versus adult determination early in the

pupal stage, at the outset of adult development.

Hemimetabola LIA

penultimate larval instar final larval instar

epidermis

LIP

lmaglnaldisks epidermis

LIP P/A

epidermis P/A

final larval instar pupa adult

LIA

adult

Holometabola

Comparison of Development in Paurometabolous & Holometabolous Insects