P. Trontelj et al., Molecular phylogeny of leeches: Congruence of nuclear and mitochondrial rDNA data sets and the origin of bloodsucking, J ZOOL SYST, 37(3), 1999, pp. 141-147
Citations number
39
Categorie Soggetti
Animal Sciences
Journal title
JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH
Complete 18S rDNA sequences and sequences of domain III of mitochondrial 12
S rDNA were obtained to assess phylogenetic relationships among major supra
generic taxa of leeches and the possibly closely related clitellate taxa Br
anchiobdellida and Acanthobdellida. The monophyly of the families Erpobdell
idae, Piscicolidae, and Glossiphoniidae, the suborders Erpobdelliformes and
Hirudiniformes, and the order Arhynchobdellida have been confirmed by pars
imony and maximum likelihood phylogenetic analysis of separate and combined
data sets. Both the nuclear 18S rDNA sequences and the mitochondrial 12S r
DNA sequences were consistent in not supporting a monophyletic order Rhynch
obdellida, represented by the families Piscicolidae and Glossiphoniidae. A
topology with the Piscicolidae as the first branch in the leech tree follow
ed by the Glossiphoniidae received the highest support in terms of taxonomi
c, character: and outgroup congruence. According to this topology, the puta
tive apomorphies of the Rhynchobdellidae (e.g. the proboscis) can be parsim
oniously explained as plesiomorphies already present in the ancestral leech
. This common ancestor was probably a bloodsucking leech with a proboscis r
ather than an unspecialized ectocommensal. as suggested by previous hypothe
ses. During the course of leech evolution, a reduction of the proboscis cou
ld have taken place in predatory arhynchobdellid ancestors to enable swallo
wing of larger prey. A second gain of sanguivory by the jawed Hirudiniforme
s could have been facilitated by pre-adaptations to ectoparasitic blood fee
ding. The 18S rDNA analysis further indicates a close relationship between
the clitellate groups Branchiobdellida and Acanthobdellida, although this r
elationship is not strongly supported.