The activity of hydrolytic enzymes in the digestive system of Acanthobdellida, Branchiobdellida and Hirudinida (Annelida, Clitellata) – considerations on similarity and phylogeny

Activities of nineteen hydrolases were measured in the digestive systems of predatory and blood-feeding true leeches (Hirudinida) and their closest relatives, Branchiobdellida and Acanthobdellida. Hydrolase activities were analyzed in different parts of the digestive systems: the species-specific anterior part, i.e. jaws, pharynx or proboscis, crop and intestine. The results obtained suggest that food digestion and possible absorption predominate in the intestine of most of the studied Hirudinida and A. peledina, whereas in B. astaci these processes take place in the anterior part of the digestive system and crop. In Erpobdellidae and Piscicola respirans, the activity of acid and alkaline phosphatases, N-acetyl-β-glucosaminidase, leucine and valine arylamidases, and α-fucosidase was also detected in the anterior part of the digestive system. We also detected differences in enzyme occurrence between the studied species, which are probably connected with their different food preferences. Moreover, the presence of the whole spectrum of enzymes in predatory leeches and the absence of trypsin and α-chymotrypsin activity in the crop of all the leeches support the hypothesis that the leech ancestor was a blood-feeder. Our study showed that “Rhynchobdellida” constitute a paraphyletic group which confirms the previous results based on molecular phylogenetics, while Arhynchobdellida appears to be a non-monophyletic group which is not consistent with previous molecular results.

本研究测定了捕食性与吸血性真蛭（Hirudinida）及其近缘类群鳃蛭目（Branchiobdellida）和棘蛭目（Acanthobdellida）消化系统内19种水解酶（hydrolases）的活性。研究分析了消化系统不同部位的水解酶活性：具有物种特异性的前部结构，即颚、咽或吻（proboscis）、嗉囊（crop）以及肠（intestine）。所得结果表明，在多数受试真蛭纲物种及A. peledina的肠道中，食物消化与潜在吸收过程占主导地位；而在B. astaci体内，此类过程则发生于消化系统前部与嗉囊。在石蛭科（Erpobdellidae）和呼吸鱼蛭（Piscicola respirans）的消化系统前部，同样检测到了酸性磷酸酶、碱性磷酸酶、N-乙酰-β-氨基葡萄糖苷酶（N-acetyl-β-glucosaminidase）、亮氨酸芳基酰胺酶、缬氨酸芳基酰胺酶以及α-岩藻糖苷酶（α-fucosidase）的活性。本研究还发现，受试物种间的酶谱分布存在差异，这大概率与其不同的食物偏好相关。此外，捕食性蛭类体内存在完整的酶谱，且所有蛭类的嗉囊中均未检测到胰蛋白酶（trypsin）与α-胰凝乳蛋白酶（α-chymotrypsin）的活性，上述发现支持"蛭类祖先为吸血生物"这一假说。本研究表明，"吻蛭目（Rhynchobdellida）"为并系群，这一结果验证了此前基于分子系统发育学得出的结论；而无吻蛭目（Arhynchobdellida）似乎为非单系群，这与此前的分子研究结果并不一致。