Acta Parasitologica, Vol. 51, No. 4, 2006, 238-248 Stephen S. Curran(1)*, Vasyl V. Tkach(2,3) and Robin M. Overstreet(1) - A review of Polylekithum Arnold, 1934 and its familial affinities using morphological and molecular data, with description of Polylekithum catahoulensis sp. nov.
(1)Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Drive, Ocean Springs, Mississippi 39564, USA;
(2)Department of Biology, University of North Dakota, P.O. Box 9019, Grand Forks, North Dakota 58202-9019, USA;
(3)Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warszawa, Poland
*Corresponding author: Stephen.curran@usm.edu
ABSTRACT
The type material of Polylekithum ictaluri, P. halli, and Maculifer chandleri was examined from the United States National Parasite Museum, and we determined that the material was conspecific, making P. halli and M. chandleri junior subjective synonyms of P. ictaluri. Polylekithum catahoulensis sp. nov. was described from material collected from catfishes at the Catahoula Wildlife Refuge, LaSalle Parish, Louisiana, USA, and compared with P. ictaluri collected from catfishes in Reelfoot Lake, Obion County, Tennessee, USA, and the Pearl River, Hancock County, Mississippi, USA. Polylekithum catahoulensis had smaller eggs (77-88 um long by 51-63 um wide vs. 94-108 um by 52-76 um) and a longer forebody (35-41% of overall
body length vs. 29-34%). Comparison of more than 2,400 bp long fragments of nuclear ribosomal DNA (complete ITS and partial 28S regions) strongly supported the status of P. catahoulensis as a new species. Molecular phylogenetic analysis of 28S rDNA gene sequences from Polylekithum as well as representative species from Allocreadiidae, Atractotrematidae, Brachycoeliidae, Callodistomidae, Dicrocoeliidae, Encyclometridae, Gorgoderidae, Haploporidae, Opecoelidae, Plagiorchiidae, and Telorchiidae rooted by Monorchiidae and Lissorchiidae demonstrated that of the families tested, Polylekithum was most closely related to Encyclometridae as a gorgoderoid and not to Allocreadiidae as previously reported. Morphological features of three South American allocreadiids, Allocreadium patagonicum, P. percai, and A. pichi were inconsistent with generic diagnoses of Allocreadium and Polylekithum, so we suggested they belonged in a single unnamed genus similar to Creptotrema. Polylekithum catlai from India was assessed from the description and failed to conform to the generic diagnosis of Polylekithum. Morphology of Caudouterina suggested a close relationship with Polylekithum and not Allocreadiidae.
KEY WORDS: Digenea, Polylekithum catahoulensis sp. nov., P. ictaluri, P. halli, ITS and 28S rDNA, molecular phylogeny, Allocreadiidae,
Encyclometridae, Plagiorchioidea, Gorgoderoidea