Parasitology



Morphological and molecular characterization of tetraphyllidean merocercoids (Platyhelminthes: Cestoda) of striped dolphins (Stenella coeruleoalba) from the Western Mediterranean


C. AGUSTÍ a1c1, F. J. AZNAR a1, P. D. OLSON a2, D. T. J. LITTLEWOOD a2, A. KOSTADINOVA a1a3 and J. A. RAGA a1
a1 Marine Zoology Unit, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, P.O. Box 22085, 46071 Valencia, Spain
a2 Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
a3 Department of Biodiversity, Central Laboratory of General Ecology, Bulgarian Academy of Sciences, 2 Gagarin Street, 1113 Sofia, Bulgaria

Article author query
agusti c   [PubMed][Google Scholar] 
aznar fj   [PubMed][Google Scholar] 
olson pd   [PubMed][Google Scholar] 
littlewood dt   [PubMed][Google Scholar] 
kostadinova a   [PubMed][Google Scholar] 
raga ja   [PubMed][Google Scholar] 

Abstract

Two types of tetraphyllidean merocercoids, Phyllobothrium delphini and Monorygma grimaldii, are well known from most cetaceans world-wide. The role of cetaceans in the life-cycle of these merocercoids is unclear because their specific identity is as yet unknown. The problem is compounded by poor descriptions of both merocercoids. We used light and scanning electron microscopy, and histological techniques to provide a thorough description of merocercoids collected from 11 striped dolphins, Stenella coeruleoalba, from the Spanish Mediterranean. We also described, for the first time, specimens of P. delphini with immature proglottides. Our merocercoids were morphologically similar to those described previously, except in the structure of the apical organ. Intra- and inter-sample variability in the morphology of the apical organ suggested that it degenerates during larval development. A subsample of 16 specimens of P. delphini and M. grimaldii was characterized for the D2 variable region of the large subunit ribosomal RNA gene (LSU) and compared with published tetraphyllidean cestode LSU sequences. P. delphini showed 2 unique signatures that differed from one another by a single base, whereas all sequences of M. grimaldii were identical. This suggests that each type may represent a single species, contrary to previous speculations based on morphological data. All merocercoid specimens formed a clade together with Clistobothrium montaukensis. Based on the low degree of divergence, all specimens of this clade are predicted to be congeneric.

(Received July 27 2004)
(Revised September 10 2004)
(Accepted September 10 2004)


Key Words: Tetraphyllidea; merocercoid; Phyllobothrium delphini; Monorygma grimaldii; Clistobothrium montaukensis; striped dolphin; molecular diagnostics.

Correspondence:
c1 Marine Zoology Unit, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, P.O. Box 22085, 46071 Valencia, Spain. Tel: +34 96 354 36 85. Fax: +34 96 354 37 33. E-mail: celia.agusti@uv.es


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