Patagoniobdella, Ringuelet, 1972

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 : 16

Patagoniobdella

The family Semiscolecidae Scriban & Autrun, 1934 was emended by Ringuelet (1972) to include the genera Semiscolex Kingberg, 1867 and Patagoniobdella Ringuelet, 1972 . Currently ( Ringuelet, 1985b), the genus Semiscolex includes five species ( S. intermedius Ringuelet, 1942 , S. juveniles Kingberg, 1867, S. notatus Cordero, 1937 , S. similis Weyenbergh, 1879 , and S. zonatus Oka, 1930 ) and the genus Patagoniobdella includes three species ( P. adomonia Ringuelet, 1976 , P. fraterna , and P. variabilis ). Ringuelet (1972) established the genus Patagoniobdella for Semiscolex variabilis , which has two pairs of testisacs per interganglionic space and thick ejaculatory ducts. Otherwise, external morphological characters, digestive track, and reproductive organs are much like in Semiscolex species.

Members of Semiscolecidae variously have been classified among the erpobdelliforms or the hirudiniforms ( Weyenberg, 1879; Blanchard, 1896; Ringuelet, 1954), but have mostly been associated with the family Haemopidae ( Moore, 1911; Ringuelet, 1944 a, 1944b, 1954; Richardson, 1969; Sawyer, 1986). Blanchard (1896) anticipated that these South American predators were not closely related to other hirudinids and had them in their own subfamily ( Semiscolecinae ). Ringuelet (1954: 5; see also Blanchard, 1896; Moore, 1911; Richardson, 1969) pointed to the apparent ‘‘mixture’’ of characteristics such as ‘‘las conspicuas papilas cutaneas y otros detalles mas son como en los Erpobdéllidos’’, but with hirudinid eyes, basically hirudinid anatomy, and a haemopid alimentary tract. Richardson (1969) suggest­ ed there were differences in reproductive morphology (i.e., acaecate vagina) in the semiscolecids compared to haemopid leeches, but he still tentatively retained them in the Haemopidae . In the most recent classification, Sawyer (1986) placed the semiscolecids under Haemopidae , but under the subfamily Semiscolecinae , to distinguish the South American genera Cyclobdella , Orchibdella , Patagoniobdella , and Semiscolex , from the North American haemopids. On the other hand, Ringuelet (1985 a, 1985b), in his final contributions, adhered to his earlier classification ( Ringuelet, 1972). The inclusion of representative semiscolecids, Semiscolex similis from Bolivia and the two Patagoniobdella species described here, in Borda and Siddall’s (2004) phylogenetic analysis has shed some light on their phylogenetic and systematic position within Arhynchobdellida . They appear to share common ancestry with the South American Oxyptychus species and North American Macrobdella species and not with the haemopids at all. The latter were found in a separate lineage together with the medicinal leeches, typified by the genus Hirudo and allies. Therefore, we formally resurrect the family Semiscolecidae as defined by Ringuelet (1972).