Mesobdella, Blanchard, 1893

SIDDALL, MARK E. & BORDA, ELIZABETH, 2004, Leech Collections from Chile Including Two New Species of Helobdella (Annelida: Hirudinida), American Museum Novitates 3457 (1), pp. 1-20 : 15-16

Mesobdella

The terrestrial sanguivore Mesobdella gemmata was traditionally classified a haemadipsid ( Blanchard, 1893, 1900; Ringuelet, 1942b, 1943b, 1944 a, 1985a; Sawyer, 1986) based on gross morphological characters (i.e., ocular arch; wide dorsal median field; position of first nephropores; Richardson, 1971) and life­history strategies (i.e., terrestrial and sanguivorous). These apparent affinities suggested that M. gemmata shared a common ancestry with the terrestrial Indo­ Pacific leeches ( Blanchard, 1893, 1917; Caballero, 1940; Ringuelet, 1943b, 1944c; Sawyer, 1986), but its geographic distribution, in Chile, and apparent shared reproductive homologies with South American hirudinids (e.g., Oxyptychus species ) suggested otherwise ( Richardson, 1969; Ringuelet, 1972).

Moore (1946) proposed a subfamily Xerobdellinae to include M. gemmata with members of other terrestrial genera, such as Xerobdella Frauenfeld, 1868 from Europe, and the Mexican Diestecostoma Vaillant, 1890 . He believed these shared a resemblance in the position of nephropores and the absence of auricles ( Moore, 1946). Xerobdellinae was synonymized with Dietecosto­ matidae ( Ringuelet, 1954), but later Ringuelet (1972) established the family Mesobdellidae to the exclusion of the genera Xerobdella and Diestecostoma . Ringuelet (1972) created the family Mesobdellidae in light of Richardson’s (1969, 1971) comparative work showing affinities with Neotropical aquatic sanguivores (i.e., Oxyptychus spp. ) and included only the South American taxa, Mesobdella spp. and Nesophilaemon skottsbergi , the latter from the Juan Fernandez archipelago. Richardson (1971: 218) suggested the external ‘‘haemadipsine­like features’’ to be a secondary adaptation to terrestrialism, whereas the ‘‘systems which have not come under the influence of this habit, the female median region and the simple form and paramedial position of the anterior region of the male paired duct, [are] unlike the auriculate land­leeches.’’

Recent phylogenetic work ( Trontelj et al., 1999; Borda and Siddall, 2004) supports the divergence of a second terrestrial sanguivorous lineage separate from the IndoPacific haemadipsids. Further studies including additional representative taxa from the genera Mesobdella and Xerobdella (i.e., Mesobdella lineata , Mesobdella notohilica , Xerobdella anulata , and Xerobdella prealpina ), as well as other New World terrestrial genera, Diestecostoma and Nesophilaemon , could resolve their phylogenetic relationships and therefore lead to the redefinition of previously proposed families ( Ringuelet, 1953, 1972, 1982; Harant and Grasse´, 1959; Soós, 1966).