Desserobdella phalera adult and juveniles from Virginia
Mark E. Siddall *
| |___ Helobdella group
|___.___ Placobdella group
|___.___ Marsupiobdella africana
|___.__ Hemiclepsis marginata
|___ Glossiphonia group
Based on: CO-I, ND-1, and morphology in Light and Siddall, 1998
Introduction to the group
The leech family Glossiphoniidae is a diverse group with representatives found in freshwater habitats on all continents except Antarctica. Glossiphoniid leeches are members of the order Rhynchobdellida which is characterized by the presence of a proboscis for feeding from the blood of vertebrates or the haemolymph of invertebrates. In freshwater systems, however, those species that feed from vertebrates are out-numbered both in number of species and absolute abundance by leeches that prey on invertebrates (Klemm, 1972, 1977, 1982, 1991; Sawyer, 1986). Also, glossiphoniid species are characterized as the only annelids that brood their eggs and carry their young under their dorso-ventrally flattened bodies. This unique family of leeches exhibiting such marked parental care has several important implications. Glossiphoniid leeches are both ecologically and economically important. For example, they can serve as environmental stress indicators due to their relative abundance in certain freshwater habitats (Klemm, 1991; Grantham and Hann, 1994). Also, glossiphoniids that feed from the blood of vertebrates serve as definitive hosts and vectors of apicomplexan blood parasites of vertebrates (Barta and Desser, 1986, 1989; Barta, 1991; Siddall and Desser, 1990, 1991, 1992, 1993; Siddall and Burreson, 1998). This habit suggests that there may have been co-evolution of blood parasites with their respective leech hosts (Siddall and Burreson, 1998). Glossiphoniids that feed from the haemolymph of invertebrates, on the other hand, can serve as hosts for helminths (McCarthy, 1990; Spelling and Young, 1986; Vojtek, et al., 1967). In spite of this broad ecological and parasitological importance, identification and classification has been problematic.
Identifying glossiphoniid leeches has been difficult due to ambiguous, incomplete, and inaccurate descriptions, lack of appropriate observations, and use of obsolete nomenclature. Soós (1969) noted that specific and generic characteristics need to be established for the whole family Glossiphoniidae prior to proper identification. Once there is an established system, determining relationships between glossiphoniid species is expected to be less difficult.
The family Glossiphoniidae presently is divided into three subfamilies: Theromyzinae, Glossiphoniinae, and Haementeriinae (Sawyer, 1986). The subfamily Theromyzinae (genus Theromyzon) is characterized by four pairs of eyes and mating by male to female gonopore copulation. Members of the subfamily Glossiphoniinae (genera included in this study: Desserobdella, Glossiphonia, Hemiclepsis, Placobdella, and Torix) mate by hypodermic implantation of spermatophores, have cocoons attached directly onto a substrate (however, once the embryos hatch, they attach to the venter of the leech), and have multiple pairs of eyes (two to three pairs). The leeches in the subfamily Haementeriinae (genera included in this study: Desmobdella, Haementeria, Helobdella, Marsupiobdella, Oligobdella, and Alboglossiphonia) also mate by hypodermic implantation of spermatophores, but cocoons appear to be attached directly to the venter. Representatives of this subfamily have one to three pairs of eyes.
The characterizations that Sawyer (1986) used for delimiting glossiphoniid subfamilies are not universal nor have all of the characteristics been observed for all species. There also is overlap of characters between subfamilies. Continual recognition of these subfamilies in light of phylogeny would require the acceptance of the paraphyletic groups Glossiphoniinae and Haementeriinae. The Theromyzon species sampled are monophyletic, but they fall out within a larger clade consisting of representatives from both Glossiphoniinae and Haementeriinae subfamilies. It is apparent that the subfamilies currently used for systematics of the glossiphoniids must be revised. Several genera and species may also require revision.
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Mark E. Siddall
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