1. Testes: the source of sperm
• Usually paired
• Usually abdominal
• Exception: scrotal testes (some
mammals)
• Connected via paired sperm
ducts to the outside
• specialised regions: epididymis,
vas deferens
Evolution of the
scrotum in mammals
(Kleisner et al. 2010):
1)
-
Probably evolved twice
blue & black lineages
2) Probably multiple
pressures:
-
selection
cooling hypothesis
galloping hypothesis
signalling hypothesis
(testis by kidneys)
(prepenial scrotum)
One of two representations of the mammalian tree showing
different states of testicular location (Kleisner et al. 2010, p 31)
Testicular structure in mammals
= interstitial cells
(Norris 1997 p 373. Also in Norris 2007, p 337)