An integrated phylogenetic analysis on ascaridoid nematodes (Anisakidae, Raphidascarididae), including further description and intraspecific variations of Raphidascaris ( Sprentascaris ) lanfrediae in freshwater fishes from Brazil
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Abstract
Genetic and morphological variations in two component populations of Raphidascaris
(Sprentascaris) lanfrediae collected in the intestine of Geophagus argyrosticus and
G. proximus (Cichlidae) from States of Pará and Amapá, Brazil, respectively, were
explored for the first time. A phylogenetic study including two genes (18S and 28S
of the rDNA) plus morphological and life history traits of "anisakid-related" nematodes
(Anisakidae, Raphidascarididae) was also performed in order to clarify taxonomic and
systematic issues related to these taxa. Gene alignments were subjected to maximum
likelihood (ML) and Bayesian Inference (BI), and combined data of the genetic and
morphological datasets was subjected to maximum parsimony (MP) analysis. Despite of
the subtle differences in the morphology (mainly in male caudal papillae) and morphometry
between specimens of R. (S.) lanfrediae from the two different hosts and from the
type material of the species, no genetic variation was found among representatives
of the newly collected material. This find may represent an example of gene-environment
interactions, similar to that recently observed for Raphidascaroides brasiliensis.
Phylogenetic reconstructions indicated the paraphyly of Anisakidae represented by
two subfamilies, i.e., Anisakinae and Contracaecinae and the monophyly of Raphidascarididae.
Analysis of the combined datasets revealed that some morphological traits may represent
apomorphic characters of Raphidascarididae and Anisakidae, whereas others are highly
homoplastic and some may be interpreted with careful to avoid errors. The results
support the premise that taxonomists should consider Anisakidae and Raphidascarididae
as separate families, and only two subfamilies of Anisakidae, i.e., Anisakinae and
Contracaecinae.