Dynamic DNS: do I need a CNAME Record?

[webmastor]

Hi,
I've read here and there that one needs a CNAME record in order to use a
dynamic DNS. But I've just set up my free DDNS by zoneedit.com, without
adding a CNAME Record, and it seems to work.

Zoneedit's documentation on the subject seems contradictory:
on this link:
http://www.zoneedit.com/doc/dynamic.html#faq2
they only speak of adding a A record
but on the page "Do I need to use an Alias (CNAME) Record",
they state:
"The main instance that a CNAME is useful is for those domain name owners
who use a dynamic IP address service. These services will keep track of the
IP address of your server, etc..."

So do I need a CNAME?

Here are some details of my setup, in case it makes a difference:
- My DSL provider gives me a new IP address every 24-48 hours.
- I plan to have two (name-based) virtual hosts on my Apache server.
- I do not intend at this point to run a mail server.
- I've bought two domains, mycat.org and mydog.org, I don't want to have a
domain name like mycat.dyndns.org.

Thank you!