An appraisal of the problems related to species identity and species diversity within chelonian polystomes (Polystomatidae: Monogenea)
Abstract
The subfamily Polystomoidinae Yamaguti, 1963, belongs to the class Monogenea that are
parasites of terrapins and of the caecilian polystome Nanopolystoma Du Preez et al., 2008.
Chelonian polystomes include three genera: Neopolystoma Price, 1939, whose members have
no hamuli, or large hooks, Polystomoidella Price, 1939, whose members possess one pair of
hamuli, and finally Polystomoides Ward, 1917, whose members possess two pairs of hamuli.
Chelonian polystomes comprise of a total of 59 species collectively, with Neopolystoma
having 21, Polystomoidella three, and Polystomoides 35 species respectively. Together with
these species names, it is unfortunately true that a great many synonyms also exist. This is as a
result of the polystomes of chelonians that have been poorly studied, and/or a large number of
the species that have been described in obscure journals. To further complicate matters,
terrapin classification is not stable and various changes have occurred over the past few
decades. This taxonomic complexity is further exacerbated by the fact that no definite protocol
exists for one to follow in the event of describing new species, and very important
measurements and characteristics are often omitted.
The aims of this study are, firstly, to provide a systematic summary of the existing
chelonian polystome species in order to simplify the clutter of information that currently exists
and also to facilitate the identification of new species by presenting the data in the form of a
simple reference system. Secondly, the paucity of morphometric polystome marginal hooklet
measurements is addressed, and a protocol is developed and proposed for a simplified
measurement strategy to facilitate distinguishing between chelonian polystomes. Finally, two
new eye polystome species from two Florida terrapin hosts collected in 2004 are reported and
described.