Monsters of the sea serpent: parasites of an oarfish, Regalecus russellii

Molecular Identification of Plerocercoids of Clistobothrium montaukensis (Cestoda: Phyllobothriidea) Parasitizing the King of Herrings Regalecus glesne

PURPOSE

Endo-parasites of the bathypelagic king of herrings Regalecus glesne and oarfish Regalecus russelii are only known from few specimens opportunistically examined. As a consequence, there are few records of parasites from either Regalecus species. We report plerocercoid larvae of phyllobothriidean cestodes parasitizing an adult R. glesne stranded in Bahía de La Paz, Baja California Sur, Mexico.

METHODS

Sixty-three plerocercoids were obtained from the intestine of R. glesne and characterized using morphological and molecular methods (nuclear 28S rDNA and mitochondrial cytochrome c oxidase I gene sequences).

RESULTS

Following the morphological diagnostic criteria of scolex and muscle bands in the strobila, plerocercoids specimens were preliminary assigned to the genus Clistobothrium. Mitochondrial and nuclear DNA sequences indicate these plerocercoids correspond to Clistobothrium montaukensis Ruhnke, 1993.

CONCLUSION

Regalecus glesne is a new host known for C. montaukensis and this report is a new geographical record of C. montaukensis parasitizing species of the genus Regalecus previously known only from California and Florida, USA.

Clistobothrium sp. (Cestoda: Tetraphyllidea) in oarfish (Regalecus russelii) stranded on the coast of Akita Prefecture, Japan

Oarfish (Regalecus russelii Cuvier) are mesopelagic fish with little known about their life history. Oarfish live in deep water, making it difficult for researchers to collect specimens; thus, records of their parasitic helminths are limited. Two plerocercoids were found for the first time in an oarfish stranded on the coast of Akita Prefecture, Japan. These plerocercoids were identified as Clistobothrium sp. RR-1 using morphological and molecular analyses. It was revealed that oarfish represent one of the intermediate hosts of the genus Clistobothrium, and large sharks are the definitive hosts for these parasites.

Intrigue surrounding the life-cycles of species of Clistobothrium (Cestoda: Phyllobothriidea) parasitising large pelagic sharks

This study aimed to locate the adults, and thus also the definitive hosts, of three species of marine mammal-parasitising larval cestodes that have molecular affinities with Clistobothrium. New collections led to the discovery of adults of two new species of Clistobothrium, one from the longfin mako shark and one from the salmon shark. New material of Clistobothrium tumidum was collected from the great white shark and new material of a previously reported undescribed species of Clistobothrium was collected from the porbeagle shark. Larvae of Clistobothrium were opportunistically collected from sockeye salmon and four species of small squaliform sharks. Sequence data for the D1-D3 region of the 28S rDNA gene were generated for all but one of these taxa. The tree resulting from maximum likelihood analysis of those data, in combination with comparable data from GenBank, indicates that squaliform sharks can serve as intermediate hosts for the species from the porbeagle shark. The larvae from salmon exhibit a unique molecular signature and, based on diet data, may be conspecific with adults from the salmon shark. Informed by sequence data for new material of Monorygma and existing data for Phyllobothrium, the larvae provisionally identified as Monorygma grimaldii and Phyllobothrium delphini were formally transferred to Clistobothrium. Especially puzzling was that the molecular signatures of none of the eight species of Clistobothrium match those of the three marine mammal-parasitising larval forms. We are at a loss as to where else to look for the three corresponding adult forms. The great white shark remains the most likely candidate given it consumes marine mammals with some regularity, but seems unlikely to host five species of Clistobothrium. Alternatively, we are left wondering if the large marine mammal predator Carcharocles megalodon may not be extinct after all.

Molecular Characterization of Clistobothrium sp. Viable Plerocercoids in Fresh Longfin Inshore Squid (Doryteuthis pealeii) and Implications for Cephalopod Inspection

Cephalopods, an appreciated seafood product, are common hosts of marine cestodes. The aim of this work is to report visible alive plerocercoids in longfin inshore squid (Doryteuthis pealeii), a cephalopod species commercialized as fresh and whole in Italy. Seventy D. pealeii from the Northwest Atlantic (FAO area 21) were collected and visually inspected. In total, 18 plerocercoid larvae were found in the viscera of 10 host specimens (P: 14.3% 95% CI 7.1–24.7; MI: 1.8, MA: 0.26; range 1–4) and molecularly analyzed targeting the variable D2 region of the large subunit (LSU) rRNA gene and the cytochrome c oxidase subunit I (COI) gene. The molecular characterization allowed to identify all the plerocercoids as Clistobothrium sp., a cestode of the Phyllobothriidae family with Lamnidae sharks as definitive hosts, and cephalopods as second intermediate hosts. These findings represent the first molecular record of Clistobothrium sp. in D. pealeii, thus contributing to elucidate its poorly known life cycle. Even if not affecting consumer’s health, these visible parasites may represent a reason for disgust for consumers. Therefore, the results suggest that Food Business Operators should also check for the presence of these visible parasites during inspection and underline the importance of a correct consumers’ education.

Subcutaneous merocercoids of Clistobothrium sp. in two Cape fur seals (Arctocephalus pusillus pusillus)

Fur seals represent intermediate hosts of the cestode Clistobothrium. Large sharks are definitive hosts for these parasites. Two female, 25– and 27-year-old fur seals, caught in the 1980s at the South African coast, were examined pathomorphologically. Both animals showed multifocal, up to 1 cm in diameter large cavities of the thoracic and abdominal subcutaneous adipose tissue containing intraluminal metacestodes of tapeworms, which were surrounded by a locally extensive, pyogranulomatous panniculitis. The metacestodes (merocercoids) of one fur seal were isolated from the subcutaneous adipose tissue and characterized morphologically and for the first time from this host by molecular techniques. The morphometric data corresponded with ‘delphini'-morphotype merocercoids, but the sequence of the partial 28S ribosomal RNA gene identified them as conspecific with merocercoids of the morphotype ‘grimaldii’. These merocercoid types are morphologically Type XV metacestodes of marine tapeworms and represent different species of Clistobothrium. Sequence data were generated for 18S, ITS1, 5.8S, ITS2, partial 28S ribosomal DNA and partial mitochondrial cox1 gene and phylogenetic analysis of 18S rRNA and partial 28S rRNA genes identified the fur seal merocercoids as Clistobothrium species. However, it cannot yet be assigned to species level because of limited molecular data from adult stages. Most likely, both fur seals were infected as juveniles in their original habitat, the coastal regions of South Africa. The metacestode infection is probably an incidental finding, however, there is a chronic inflammatory reaction next to the subcutaneous merocercoids. It is noteworthy, that the merocercoids remain in a potentially infective stage even after more than 20 years.

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Subcutaneous metacestodes in fur seals cause asymptomatic chronic panniculitis.

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Metacestodes remain potentially infectious for more than 20 years.

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First molecular characterization of merocercoids from seals.

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Merocercoids of marine tapeworm (metacestode Type XV): delphini-morphotype but grimaldii-genotype.

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18S and 28S phylogeny verified Clistobothrium sp. as adult tapeworm.

Endo- and ectoparasites of large whales (Cetartiodactyla: Balaenopteridae, Physeteridae): Overcoming difficulties in obtaining appropriate samples by non- and minimally-invasive methods

Baleen and sperm whales, belonging to the Order Cetartiodactyla, are the largest and heaviest existent mammals in the world, collectively known as large whales. Large whales have been subjected to a variety of conservation means, which could be better monitored and managed if physiological and pathophysiological information, such as pathogen infections, could already be gathered from free-swimming animals instead of carcasses. Parasitic diseases are increasingly recognized for their profound influences on individual, population, and even ecosystem health. Furthermore, a number of parasite species have gained importance as opportunistic neozoan infections in the marine environment. Nonetheless, traditional approaches to study parasitic diseases have been impractical for large whales, since there is no current routine method for the capture and handling of these large animals and there is presently no practical method to obtain blood samples remotely from free-ranging whales. Therefore, we here not only intend to review the endo- and ectoparasite fauna of large whales but also to provide new insights in current available methods for gathering parasitological data by using non- or minimally invasive sampling techniques. We focus on methods, which will allow detailed parasitological studies to gain a broader knowledge on parasitoses affecting wild, free-swimming large whale populations.