福寿螺和田螺消化酶活性比较

为比较福寿螺(Pomacea canaliculata(Lamarck,1828))和当地中国圆田螺(Cipangopaludina chinensis(Gray,1832))消化能力的差异,探索福寿螺成功入侵的机制,以田螺为对照,测定了1—4龄的福寿螺和田螺的胃和肝脏的消化酶——纤维素酶(羧甲基纤维素法)、淀粉酶(3,5-二硝基水杨酸法)和脂肪酶(滴定法)的活性。结果表明:1)相同年龄的福寿螺胃和肝脏中的消化酶活性明显高于田螺。其中,纤维素酶活性分别高出1.00—2.11倍、1.66—2.84倍;淀粉酶活性分别高出1.53—3.47倍、1.47—1.80倍;脂肪酶活性分别高出2.07—4.73倍、6.13—9.93倍。2)在生长发育过程中,福寿螺胃和肝脏中的消化酶活性变化幅度(51.2%—131.2%)明显高于田螺(23.3%—47.1%)。3)福寿螺的各种消化酶之间存在协同作用。如福寿螺的淀粉酶活性与脂肪酶活性呈极显著正相关(胃中r=0.736**、肝脏中r=0.867**)。此外,胃中的淀粉酶活性还与纤维素酶活性呈显著正相关关系(r=0.696*)。相应地,田螺胃中的淀粉酶和脂肪酶之间也存在显著的正相关关系(r=0.706*),而肝脏中的纤维素酶与脂肪酶活性呈显著负相关(r=-0.593*)。4)福寿螺对纤维素类和淀粉类物质都有较强的消化能力,且能较好地消化脂肪类物质,而田螺能消化纤维素类和淀粉类物质,对脂肪的消化能力却很弱。福寿螺的纤维素酶和淀粉酶活性分别是田螺的2.42和1.88倍,脂肪酶活性达到了5.66倍。可见,福寿螺具有较高的消化酶活性,且各消化酶之间存在正协同性。这可能是导致福寿螺食量大、食性杂,使其能快速生长和成功入侵的重要原因之一。

Comparative study on the digestive enzyme activities between golden apple snails (Pomacea canaliculata) and local field snails (Cipangopaludina chinensis)

To investigate the differences of digestive ability between the alien golden apple snails (Pomacea canaliculata (Lamarck was, 1828)) and local field snails (Cipangopaludina chinensis (Gray, 1832)), and hence to explore the successful invasion mechanism of golden apple snails, we assayed the following digestive enzyme activities: cellulose enzyme activity (carboxymethyl cellulose method), amylase activity (3, 5-2 nitro salicylic acid method) and lipase activity (titration), with the samples taken from liver and stomach of the apple snails and local snails at different ages (from 1 to 4) using local snails as control. The results demonstrated that: 1) The digestive enzyme activities in stomach and liver of golden apple snails of the same age group were significantly higher than those of the local field snails. Among them, the cellulase activity of golden apple snails was 1.00 to 2.11 times and 1.66 to 2.84 times higher than those of local field snails, respectiviely; Amylase activity of golden apple snails was 1.53 to 3.47 times and 1.47 to 1.80 times higher, respectively; Lipase activity was 2.07 to 4.73 times and 6.13 to 9.93 times higher, respectively. 2) The variation amplitudes of different digestive enzyme activities in the stomach and liver of golden apple snails (51.2%-131.2%) were significantly higher than those of local field snails (23.3%-47.1%) during growth and development. 3) There were synergistic effects between digestive enzymes of golden apple snails. For example, the amylase activity of golden apple snails were significant positively correlated with the activity of lipase (r=0.736^{* *} in the stomach, r=0.867^{* *} in the liver). In addition, the amylase activity in the stomach was significant positively correlated with cellulose enzyme activity (r=0.696^*). Accordingly, there was also a significant positive correlation between amylase and lipase activities in the stomach of local field snails (r=0.706^*), while the cellulase and lipase activities in the liver were significant negatively correlatied (r=-0.593^*). 4) Golden apple snails have strong abilities to digest cellulose and starch, and could digest fatty substances as well. Local field snails could digest cellulose and starch, but the digestion ability for fat was very weak. The cellulase and amylase activities of golden apple snails were 2.42 and 1.88 times higher than those of local field snails, respectively, and the lipase activity even reached 5.66 times. In conclusion, golden apple snails have much higher digestive enzyme activities, and there are positive synergies between various digestive enzymes, which lead to its big appetite and omnivorous predation. This could be one of the important factors that result in the golden apple snails growing very fast and invading successfully.