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
Relative sizes

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

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