Gastric function in Caiman crocodilus (Crocodylia: Reptilia)—II. Effects of temperature on pH and proteolysis

Abstract

In Caiman crocodilus, the pH of the gastric secretions during digestion may reach 1.2 in specimens kept between 20 and 30°C. C. crocodilus feeds and digests at 15°C, but the pH of gastric secretions did not drop below 1-8. 2. The gastric secretion increased in rate and hydrochloric acid concentration after injections of histamine (400 t~g/kg body weight, given in four hourly doses). The rate increased from 0.05 ml/kg, hr (resting rate, at 20°C) up to an average of 0.66 ml/kg, hr, at 30°C. 3. There is a latent period of 4-8 hr before the effects of histamine can be detected in tests carded out at 20, 25 and 30°C. 4. Peptic proteolysis of gastric secretions has pH optima in the range 2.0-2.6, when carded out at 25°C, using the hemoglobin method of Anson & Mirsky. 5. There were instances of more than one pH optimum for proteolysis, suggesting the occurence of isozymes. 6. Inside the range in which C. crocodilus feeds and digests, peptic proteolysis has an average Qlo of 1.62 (between 15 and 25°C) and of 1.50 (between 25 and 35°C). 7. In animals maintained at 25°C peptic proteolysis was highest at 24-48 hr after feeding.

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function

“…In contrast, falconiform pellets contain little to no bone and have a pH less than two [37]. Reports of gastric pH in crocodilians vary from 1.2 to 3 [38,39]. Although gastric pH overlaps with that of raptorial birds, some of which as mentioned also completely digest bone [36,37], the longer GRT in crocodilians [32] is probably due to their more limited gastric motility compared to birds, in which digestion is facilitated by more efficiently mixing foodstuffs with gastric juices [29,37].…”

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function

“…In contrast, falconiform pellets contain little to no bone and have a pH less than two [37]. Reports of gastric pH in crocodilians vary from 1.2 to 3 [38,39]. Although gastric pH overlaps with that of raptorial birds, some of which as mentioned also completely digest bone [36,37], the longer GRT in crocodilians [32] is probably due to their more limited gastric motility compared to birds, in which digestion is facilitated by more efficiently mixing foodstuffs with gastric juices [29,37].…”

Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?

“…Prey size is limited primarily by gape size, and consequently, crocodilians are capable of ingesting relatively large items (Cleuren & De Vree, ). Given the mechanics of ingestion, most fruits are probably intact upon entering the stomach, and then rapidly digested in the highly acidic (pH = 1.2 to 2.0) gastric environment (Diefenbach, 1975 b ; Coulson, Herbert & Coulson, ) leaving only the seeds. While fate of seeds in the digestive system has not been specifically investigated, inferences can be made based on other hard objects ingested by crocodilians.…”

“…Gastric residence time for ingested items is highly variable and depends on temperature, meal size, food consumption rate and composition of the food (Diefenbach, 1975 b ; McWilliams, Afik & Secor, ; Janes & Gutzke, ). Most items remain in the stomach for 24 to 45 h and pass through the entire digestive tract in 4–5 days (Davenport et al ., ), a gut passage rate comparable to many birds and larger mammals (Willson, ).…”

Gastric function in Caiman crocodilus (Crocodylia: Reptilia)—I. Rate of gastric digestion and gastric motility as a function of temperature

“…The pH of the gastric samples was measured within 2 min after collection and immediately afterwards the samples were cooled to -I°C and centrifuged at 4000 rev/min for determination of solid residues. The results of the measurements of pH are reported in another publication (Diefenbach, 1975a).…”

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function

“…In contrast, falconiform pellets contain little to no bone and have a pH less than two [37]. Reports of gastric pH in crocodilians vary from 1.2 to 3 [38,39]. Although gastric pH overlaps with that of raptorial birds, some of which as mentioned also completely digest bone [36,37], the longer GRT in crocodilians [32] is probably due to their more limited gastric motility compared to birds, in which digestion is facilitated by more efficiently mixing foodstuffs with gastric juices [29,37].…”

Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?

“…Prey size is limited primarily by gape size, and consequently, crocodilians are capable of ingesting relatively large items (Cleuren & De Vree, ). Given the mechanics of ingestion, most fruits are probably intact upon entering the stomach, and then rapidly digested in the highly acidic (pH = 1.2 to 2.0) gastric environment (Diefenbach, 1975 b ; Coulson, Herbert & Coulson, ) leaving only the seeds. While fate of seeds in the digestive system has not been specifically investigated, inferences can be made based on other hard objects ingested by crocodilians.…”

“…Gastric residence time for ingested items is highly variable and depends on temperature, meal size, food consumption rate and composition of the food (Diefenbach, 1975 b ; McWilliams, Afik & Secor, ; Janes & Gutzke, ). Most items remain in the stomach for 24 to 45 h and pass through the entire digestive tract in 4–5 days (Davenport et al ., ), a gut passage rate comparable to many birds and larger mammals (Willson, ).…”

Gastric function in Caiman crocodilus (Crocodylia: Reptilia)—I. Rate of gastric digestion and gastric motility as a function of temperature

“…The pH of the gastric samples was measured within 2 min after collection and immediately afterwards the samples were cooled to -I°C and centrifuged at 4000 rev/min for determination of solid residues. The results of the measurements of pH are reported in another publication (Diefenbach, 1975a).…”

Microraptor with Ingested Lizard Suggests Non-specialized Digestive Function

“…In contrast, falconiform pellets contain little to no bone and have a pH less than two [37]. Reports of gastric pH in crocodilians vary from 1.2 to 3 [38,39]. Although gastric pH overlaps with that of raptorial birds, some of which as mentioned also completely digest bone [36,37], the longer GRT in crocodilians [32] is probably due to their more limited gastric motility compared to birds, in which digestion is facilitated by more efficiently mixing foodstuffs with gastric juices [29,37].…”

Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?

“…Prey size is limited primarily by gape size, and consequently, crocodilians are capable of ingesting relatively large items (Cleuren & De Vree, ). Given the mechanics of ingestion, most fruits are probably intact upon entering the stomach, and then rapidly digested in the highly acidic (pH = 1.2 to 2.0) gastric environment (Diefenbach, 1975 b ; Coulson, Herbert & Coulson, ) leaving only the seeds. While fate of seeds in the digestive system has not been specifically investigated, inferences can be made based on other hard objects ingested by crocodilians.…”

“…Gastric residence time for ingested items is highly variable and depends on temperature, meal size, food consumption rate and composition of the food (Diefenbach, 1975 b ; McWilliams, Afik & Secor, ; Janes & Gutzke, ). Most items remain in the stomach for 24 to 45 h and pass through the entire digestive tract in 4–5 days (Davenport et al ., ), a gut passage rate comparable to many birds and larger mammals (Willson, ).…”

Gastric function in Caiman crocodilus (Crocodylia: Reptilia)—I. Rate of gastric digestion and gastric motility as a function of temperature

“…The pH of the gastric samples was measured within 2 min after collection and immediately afterwards the samples were cooled to -I°C and centrifuged at 4000 rev/min for determination of solid residues. The results of the measurements of pH are reported in another publication (Diefenbach, 1975a).…”