Cactus has a hole

Hi, all you gardeners!
My cactus has developed a hole. I don't think anything is attacking it. It lives in a lab at a university. It is the only plant. There aren't many (any?) insects around.
I don't know whether I am underwatering the plant, and that has caused the hole? Overwatering? Perhaps the cactus is being attacked by a fungus (although I don't see any signs of a fungus)? Maybe it's just normal for cacti to develop a hole occasionally, and it will close up after a while.
You will ask what kind of cactus it is. My answer will tell you how much I know about plants: It is the cactus I bought my son for Christmas, and he rejected. It is kind of barrel-shaped. It has long ridges that run from its base to its crown. There are thorns (light, wispy) emanating from the top of the ridges. There are also valleys (of course) between the ridges, and it is in one of these that the cactus has become "unzipped."
On some days, the cactus is the only bright spot in the day. We got a cactus so it wouldn't die, and depress us, but . . .
Is there a cactus expert out there?
Regards,
Rick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@yahoo.com wrote in

It is a Holey Cactus.
Sell on fleabay for $$$.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.