The bambooleaf wrasse, Pseudolabrus japonicus, is a species of fish found off the coast of Japan. During the breeding season male wrasse release gametes (a process known as spawning) on a daily cycle in the presence of a single female.
The graph below shows some of the events occurring inside the testes of bambooleaf wrasse during a 24 hour period.
Note that lobules are regions within fish testes.
Which of the following statements relating to spermatogenesis and fertilisation in wrasse are correct?
I.
Wrasse spawning occurs between 06:00 and 10:00.
II.
Both mitosis and meiosis are occurring between 00:00 and 15:00.
III.
The percentage increase in the number of sperm per lobule between 00:00 and 06:00 is 66. %.
IV.
Wrasse use external fertilisation.