Host specificity ofOschmarinella rochebruniandBrachycladium atlanticum(Digenea: Brachycladiidae) in five cetacean species from western Mediterranean waters

Abstract

We investigated patterns of specificity of liver flukes (fam. Brachycladiidae) in a community of cetaceans from the western Mediterranean. The liver and pancreas of 103 striped dolphins, Stenella coeruleoalba, 18 Risso's dolphins, Grampus griseus, 14 bottlenose dolphins, Tursiops truncatus, 8 common dolphins, Delphinus delphis, and 5 long-finned pilot whales, Globicephala melas, were analysed for brachycladiid species. Two species were found: Oschmarinella rochebruni in striped dolphins (prevalence (P): 61.2%; mean intensity (MI) (95% CI): 34.2 (25.7-45.6)), and Brachycladium atlanticum in striped dolphins (P: 39.8%; MI: 7.1 (4.8-13.1)) and a single individual of common dolphin (P: 12.5%; intensity: 19), which represents a new host record. A molecular analysis using the internal transcribed spacer 2 (ITS2) region of the rDNA gene confirmed that specimens of B. atlanticum were conspecific regardless of host species. Available dietary data suggest that Risso's dolphins, bottlenose dolphins and long-finned pilot whales would contact rarely, if at all, the infective stages of O. rochebruni and B. atlanticum. Neither the prevalence nor the mean abundance of B. atlanticum differed significantly between striped and common dolphins, but a principal component analysis using seven morphometric variables indicated that specimens collected from the common dolphin were stunted. These worms also had fewer eggs compared with specimens typically found in striped dolphins, although the size of the eggs was similar in both host species. Dwarfism and low fecundity have typically been found in helminths infecting unusual host species, and might reflect the lower compatibility of B. atlanticum for common dolphins. In summary, both O. rochebruni and B. atlanticum appear to exhibit a narrow specificity for striped dolphins in the western Mediterranean.

A new brachycladiid species (Digenea) from Gervais’ beaked whale Mesoplodon europaeus in north-western Atlantic waters

“…The specimens from Gervais' beaked whale were morphologically similar to some of the specimens of Brachycladium atlanticum (Abril, Balbuena and Raga, 1991) Gibson, 2005 reported by Mateu et al (2011) in the western Mediterranean. These authors described two forms of B. atlanticum: "normalsize" individuals from striped dolphins Stenella coerueoalba Meyen and "dwarf" individuals from common dolphins Delphinus delphis.…”

“…B. curilense and B. petrowi, from single records (Yamaguti, 1942;Delyamure, 1955;Skrjabin, 1970;Dailey and Perrin, 1973;Gibson and Harris, 1979 (Margolis and Pike, 1955;Zam, 1971;Raga and Balbuena, 1987;Gibson et al 1998), and now B. parvulum. Brachycladium atlanticum has also been reported in the Mediterranean Sea (Mateu et al, 2011;Quiñones et al, 2013). In the waters off the coast of Florida, only B. delphini, from Tursiops truncatus Montagu, and B. palliatum, from Grampus griseus Gray, Stenella frontalis Cuvier, Steno bredanensis Lesson and T. truncatus, have previously been reported (Woodard et al 1969;Zam, 1971;Forrester and Robertson, 1975).…”

“…These authors indicated that this feature could vary among the various species within 50% of the mean. However, body size has not always proved to be a reliable diagnostic character in brachycladiids, because dwarfism has been reported when 6,300-7,900 × 6,300-6,800 500-2,600 × 650-2,500 2,700-4,700 × 3,300-4,800 2,000-5,000 × 2,500-4,100 1,658 (1,440-,979 since, in the original description, the length of the oral sucker does not resemble that in the illustration of the specimen (see Delyamure, 1955) a species infects an unusual host (Adams et al 1998;Mateu et al 2011). Although we consider that body size must be used with caution as a diagnostic character in isolation for differentiating Brachycladium spp., the huge range of body (and organ) sizes within the genus suggests that there must be limits to hostinduced differences.…”

“…However, dwarfism has been recorded in brachycladiids, including B. atlanticum, occurring in unusual host species (Adams et al 1998;Mateu et al 2011). Body areas, obtained from the available material of Mateu et al (2011), were 26.42 ± 8.73 mm 2 for specimens, which these authors described as "normal" B. atlanticum (ex Stenella coerueoalba) and 15.49 ± 6.82 mm 2 for specimens, which they described as "dwarf" B. atlanticum (ex Delphinus delphis). The discriminant analysis between "dwarf" specimens of B. atlanticum and specimens of B. parvulum indicated that there are significant morphometrical differences between these two species (Wilks´ Lambda 0.201; F = 35.349, df = 4, p<0.005) ( Table II).…”

A review on the molecular characterization of digenean parasites using molecular markers with special reference to ITS region

“…Mateu et al (2011) identifi ed and genetically distinguished brachycladiid species (Oschmarinella rochebruni and Brachycladium atlanticum) parasitizing cetaceans from Western Mediterranean using ITS-2 rDNA sequences. The molecular data affi rmed that samples of B. atlanticum were conspecifi c in spite of host species.…”