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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.

In the summer and autumn of 1990, a cetacean morbillivirus caused a massive epizootic mortality of striped dolphins Stenella coeruleoalba in the western Mediterranean. Previous circumstantial evidence suggested that the disease could also have increased host susceptibility to infestations with epizoic crustaceans. In this study we provide strong evidence supporting this hypothesis. We examined striped dolphins stranded along the Mediterranean central coast of Spain from 1981Spain from to 2004, and recorded data on prevalence, intensity of infestation, size and reproductive status of 2 sessile crustacean species specific to cetaceans, the phoront cirriped Xenobalanus globicipitis and the mesoparasitic copepod Pennella balaenopterae. Compared with the pre-epizootic (n = 12) and post-epizootic (n = 62) dolphin samples, the following changes were noted in the dolphins stranded during the epizootic (n = 62): (1) the prevalence of both X. globicipitis and P. balaenopterae increased; (2) the intensity of X. globicipitis and P. balaenopterae infestations did not increase; indeed, it was even slightly lower than in the other periods, as was their degree of aggregation; (3) individuals of both species were smaller, and a higher proportion were non-gravid; (4) the 2 species tended to co-occur in the same dolphins, but their numbers did not co-vary. These patterns strongly suggest that, during the epizootic, there was a short-term increase in the probability of infestation of these 2 species because of the sudden rise in the population of susceptible hosts; the growth of the new recruits was limited by the early death of dolphins. The high susceptibility was likely related to the immunosuppressive effects of viral infection and the abnormally heavy loads of polychlorinated biphenyls found in sick dolphins; the level of inbreeding was also higher in dolphins from the 'epizootic' sample. Epizoic crustaceans could be suitable indicators of health in cetacean populations. KEY WORDS: Cetacean · Morbillivirus · Epidemics · Mass mortality · Epibiont · Parasite · Susceptibility Resale or republication not permitted without written consent of the publisherDis Aquat Org 67: [239][240][241][242][243][244][245][246][247] 2005 ease provokes immunological depression that leads to secondary opportunistic infections, or activation of latent infections, of a variety of bacteria, fungi and protozoons (Domingo et al. 1992, Duignan et al. 1996. One of the most prominent clinical signs of the striped dolphins affected by the CeMV was the occurrence of apparently abnormal burdens of some epizoites (Aznar et al. 1994). In particular, a phoront barnacle specific to cetaceans, Xenobalanus globicipitis, was more frequently found during the epizootic period than in previous years. Also, many individuals were young, suggesting recent infestation events. We speculated that these patterns might have resulted from an increase of host susceptibility due to the CeMV disease (Aznar et al. 1994). However, the evidence at that time was circu...

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Resistance towards deltamethrin (DMT) in the crustacean ectoparasite Lepeophtheirus salmonis (Caligidae) is a problem on fish farms lining the North Atlantic Ocean. Two Norwegian strains with different susceptibility towards DMT were crossed in the parental generation (P0), females from a sensitive strain were crossed with males from a resistant strain and vice versa. Individual susceptibility towards DMT was assessed in the second filial generation (F2). DMT resistance was only found in F2 descendants when the P0 females were from the resistant strain, pointing to maternal inheritance. Since maternal inheritance might be linked to the mitochondrial (mt) genome, the nucleotide sequences and the gene expressions of mt-genes were analysed. Twenty non-synonymous single nucleotide polymorphisms (SNPs) were identified in mt-transcripts from resistant F2 parasites, including SNPs in two cytochrome C oxidase subunits (COX1 and COX3) and two subunits of the NADH dehydrogenase complex (ND1 and ND5) previously linked to DMT resistance in the salmon louse. Differential expression analysis between the sensitive and resistant strain revealed strain effect in seven out of twelve mt-genes. The current study also show that DNA fragmentation (indicating apoptosis) was affected by DMT exposure in skeletal muscle tissue and that resistant parasites undergo less apoptosis than sensitive parasites.