18 - Avian Male Reproduction

Question 1

Why do waterfowl have longer phalluses than terrestrial birds

Answer 1

Water has debris (could affect sperm viability)
Phallus goes further into the vagina to increase fertility

Question 2

Wolffian duct develops into…

Answer 2

vas deferens and epididymus

Question 3

Mullerian duct regresses when? Regression hormone?

Answer 3

By ~mid incubation

Hormone unknown

Question 4

Chromosomes in birds

Answer 4

ZW sex determination

Females are heterogametic (ZW) males are homogametic (ZZ)

Question 5

Theories on mechanism related to avian sexual development

Answer 5

A) presence of female-specific W chromosome that triggers female (determining factor produced by W?)
B) Presence of two Z chromosomes (double dose) confers maleness?

Question 6

Testis development and incubation age

Answer 6

8 days = 1.6 cm
19 days = 2.2 cm
21 days = 4.7 cm

Question 7

Slide 12, 15

Answer 7

Avian male endocrinology (same)

Question 8

Main factors influencing avian male sexual maturation

Answer 8

• age
• body weight
• photoperiod (increasing day length)

Question 9

Testes position and temperature

Answer 9

Located in the body cavity attached to dorsal body wall
Spermatogenesis occurs at body temperature ~41C

Question 10

Theories on how spermatogenesis can occur at that temp

Answer 10

• testes located close to air sac = cooling?
• spermatogenesis at night? (wrong: no diff found in T of testis during 24 hour period)

Question 11

Majority of testicular mass is…

Answer 11

Seminiferous tubules in parenchyma (same as mammals)

Question 12

Blood testes barrier creates…

Answer 12

immunologically privileged site that prevents immune system from affecting the developing sperm

Slide 18**

Question 13

Slide 19

Answer 13

Testes structure

Question 14

Steps of spermatogenesis in avian

Answer 14

1. proliferation: mitotic division of spermatogonia to form 1 spermatocyte (constant spermatogonia)
2. meiosis: 1 spermatocytes meiosis 1 to produce 2 spermatocytes which undergo meiosis 2 to become round spermatids
3. differentiation: spermatids to fully formed spermatozoa

Question 15

Length of primary to secondary spermatocyte

Secondary to spermatid

Spermatid to spermatozoa

Length of spermatogenesis?

Answer 15

5-6 days

2.5 days

8 days

Spermatogenesis = 14-16 days (short)

Question 16

Differences in sperm morphology in birds

Answer 16

Heads are filiform (antenna) rather than paddle shaped
- highly condensed nucleus
- high surface: volume ration
- sensitive to changes in osmolarity (cannot dilute well for AI, susceptible to damage to organelles)

Question 17

Differences in epididymus in avians

Answer 17

Straight piping (not coiled), not subdivided
No tail for storage

24-72 hours from testis to vas deferens

Motility and fertilizing ability gained in epidid (same as mammal)
Changes to sperm plasma membrane = recognition from female repro tract

Question 18

What is the vas deferens

Answer 18

Equivalent to ductus deferens

Sperm stored in ends
24-48 hours to travel through
Primary storage site

Question 19

What is missing from avian repro system? Why

Answer 19

Pampiniform plexus (spermatogenesis can occur at high T so no temp regulation required)

Accessory sex glands (ejaculate concentration very high but in low volume, ASG provide volume/fluid to sperm)

Question 20

Diff between rooster and tom average ejaculate and sperm concentration

Answer 20

Rooster
- ave ejaculate = 0.5 mL
- 3-7 billion sperm/mL

Tom
- ave ejaculate = 0.3 mL
- 11-12 billion sperm/mL

Bull
- ave ejaculate = 4-6 mL
- 1-1.2 billion sperm/mL

Question 21

Advantage of having highly concentrated semen

Answer 21

• frequent matings of short duration to large group of hens
• higher probability of fertilization
• 1% of sperm ejaculated enter hen’s sperm storage tubule