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Animal Physiology and Development: Insects' Reproductive System

This lecture explores the male gonads and sperm development, as well as the different types of oogenesis in insects. It also covers the early processes following fertilization and the evidence for maternal information in the specification of the blastoderm.

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Animal Physiology and Development: Insects' Reproductive System

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  1. Animal Physiology and Development • Insects – 2 JCS • Lecture Outcomes: • By the end of this lecture students should have: • Appreciated the structure of the male gonads and how sperm develop • Understood the two types of oogensis in insects, the structure of a dipteran ovary and the interaction of the primary oocyte, the nurse and follicle cells to produce the egg. • Become aware of the early processes following fertilisation and, • Understood the evidence for maternal information in the specification of the blastoderm. • JCS 31/10/02

  2. Reproductive system of the male mealworm beetle

  3. Drosophila testis T = testis, V = vas deferens, D = testicular duct, G = accessory gland, AD = ant. ejacaculatory duct, B = ejaculatory bulb, PD = post. ejac. duct

  4. Detail of first half-turn of Drosophila testis a-d are cross-sections of the testis to show shape and size of spermatocyte cysts.

  5. Age and position of 25 Drosophila cysts – all descendants of a single stem cell

  6. Sperm development – initial stages of sperm elongation From a) spermatids in contact with testicular wall of cyst to d) spermatids separated from the wall.

  7. Sperm elongation Relative sizes N = nucleus NK = nebenkern BB = basal body C = cilium AX = axoneme AS = axonemal sheath M = mitochondrion ER = endoplasmic reticulum

  8. Three types of insect oogenesis distal Panoistic Telotrophic Polytrophic

  9. Female Drosophila reproductive system

  10. germarium Mitotic divisions to produce an egg chamber

  11. A single ovariole with maturing egg chambers

  12. Stage 7 Stage 8 Stage 9

  13. Stage 10A Stage 10b Stage 11

  14. Stage 12 Stage 13 Micropyle Stage 14 Chorion ‘Horns’ Horns are aeropyles (air entry) Micropyle is medial and for sperm entry

  15. Sperm transfer in some insects occurs as a Spermatophore e.g. mealworm beetle The process from transfer to female to release of sperm takes 5 minutes

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