Two new Helobdella species (Annelida Hirudinida Glossiphoniidae) from the Intermountain region of the United States, formerly considered as Helobdella stagnalis Linnaeus, 1758

摘要

Two Helobdella stagnalis-like leech specimens (Annelida Hirudinida Glossiphoniidae) werehistologically examined from Nevada in the Great Basin, and from Utah in the Colorado RiverBasin (USA) to determine whether or not their crops were similar to those in H. californicaKutschera 1988. The Nevada form was brown and with pigmentation patterns, whereas theUtah form was plain and white. The dorsoventral histological sectioning of these 3 specimensshowed the Utah and Nevada forms had compact salivary glands, hitherto noted only in theSouth American Helobdella and Haementaria species. The pharynx of Nevada individuals wasS-shaped, and in the Utah form the ejaculatory ducts formed a Gordian knot in the distal-mostposterior region, further distinguishing these 2 intermountain Helobdella-isolates. Comparingthese two taxa to other published Helobdella internal morphologies, two new species are proposed: Helobdella humboldtensis n. sp. from Nevada (size and pigmentation similar to H. californica) and Helobdella gordiana n. sp. from Utah, which resembles H. stagnalis from Europe.These findings suggest the Intermountain area may be a prime region to study the evolution ofmembers of the Helobdella species complex.