Transintestinal Expulsion of Surgically Implanted Dummy Transmitters by Channel Catfish

Paraffin-coated polystyrene capsules, the same as used for commercial ultrasonic transmitters, were surgically implanted into the abdominal cavity of adult channel catfish Ictalurus punctatus. Capsules had a weight in water equal to either 1% or 2% of the fishˈs body weight. After an average 112 days from surgery, surgical implantation of transmitters had not increased mortality or decreased growth compared to fish without implants. However, 25 of 35 fish with implants had lost their capsules; the loss rate was greater for the capsules that were 2% of body weight (16 of 18 lost) than for the capsules that were 1% of the body weight (9 of 17). Of the 10 capsules retained, five were in the abdominal cavity, four were in the intestinal lumen, and one was enveloped in a mesentery. Loss of surgical implants of dummy transmitter capsules involved encapsulation, adhesive peritonitis, and, in some cases at least, the formation of an accessory or adventitious loop of intestine that grew about the encapsulated transmitter capsules at the point of adhesion. Once the capsule was in the lumen, peristalsis could pass the caspule down the remaining portion of the intestine and out the anus.