Do goldfish have a stomach?2012/08/31 at 08:00 | Posted in Veterinary Fish Medicine | 11 Comments
Why raise such a question?
I was watching an episode of “Tanked” (Animal Planet Discovery Show) and there was a pop-quiz that I hate to admit it, but I got wrong…. well… according to them anyway.
The question was… which of these fish do not have a stomach?…. The answer they gave was Goldfish. And so it was proposed that goldfish need very much more regular feeding than twice a day.
Whether a goldfish has a stomach has been a subject for debate on may fish forums on the net – just Google “tanked tv show goldfish stomach” and you’ll see.
In animals, the stomach is located between the oesophagus and the duodenum (the most anterior part of the small intestine).
Many texts and scientists (and the producers of “Tanked”) believe that goldfish do not have a stomach. In a reply by Dr Brian Jones, he pulled out this excerpt:
About 15% of teleosts, including cyprinids, have no stomach and no region of low pH or pre-digestion. Anterior portion of intestine has some storage function, intestine in these species is usually very long compared to, say, a trout (Rombout, et al. 2011. Teleost intestinal immunology. Fish and shellfish immunology 31:616-626.).
I looked up Balliere’s Comprehensive Veterinary Dictionary for the definition of stomach and this is what I found – the curved, muscular, saclike structure that is an enlargement of the alimentary canal between the oesophagus and the small intestine.
Then I carefully dissected the carcass of a formalin-fixed goldfish I had spare on my shelf (as you do) to see whether the goldfish has a stomach. I found that there was certainly a saclike distension to the anterior part of the alimentary tract, immediately caudal to the oesophagus.
So what would you call the dilated portion of the gut immediately posterior to the oesophagus in the goldfish?
In birds, you have a crop, a proventriculus (the secretory stomach) and a gizzard (the muscular stomach) between the oesophagus and duodenum.
Ruminants are known to have 4 stomachs, they have the rumen, reticulum, omasum and abomasum between the oesophagus and duodenum.
In an alpaca, you have compartments 1, 2 and 3 between the oesophagus and duodenum.
So, if you do not call the structure (arrow) in the diagram a stomach, what would you call it?
“Intestinal bulb” was proposed.
I may have to accept defeat on a technicality….
I open it up to you now for debate…