An updated concept and revised composition for Hamacreadium Linton, 1910 (Opecoelidae: Plagioporinae) clarifies a previously obscured pattern of host-specificity among species

The present concept of the trematode genus Hamacreadium Linton, 1910 encompasses considerable morphological variability and includes species reported from a broad range of fishes. These include herbivores and planktivores, despite the life-cycle of the type-species, Hamacreadium mutabile Linton, 1910, being known to use fishes as intermediate hosts. Reports of H. mutabile are numerous, spanning the west Atlantic, east Pacific and Indo-west Pacific, whereas other nominal species are infrequently reported and several inadequately described. Following a comprehensive review, a strict revised morphological definition is proposed for the genus. Several nominal species are excluded, but, conversely, finer distinctions are recognised among the species concluded to genuinely belong in the genus. Justified records for species retained in the genus are overwhelmingly from fishes of the families Lutjanidae Gill (snappers) and Lethrinidae Bonaparte (emperors), revealing a previously concealed pattern of host-specificity. For H. mutabile, it is argued that only records from western Atlantic lutjanid fishes should be considered genuine; those from plausible Indo-Pacific fishes most likely represent different species. In addition to H. mutabile, eight species are recognised: Hamacreadium cribbi Bray & Justine, 2016, Hamacreadium hainanense Shen, 1990, Hamacreadium interruptum Nagaty, 1941, Hamacreadium lethrini Yamaguti, 1934, Hamacreadium longivesiculum (Yamaguti, 1952) n. comb., Hamacreadium lutiani (Shen, 1990) n. comb., Hamacreadium morgani Baz,1946 and Hamacreadium phyllorchis (Bilqees, 1976) Cribb, 2005. A key to species of Hamacreadium and comprehensive lists of all host-locality records are included.

Nuclear rDNA ITS sequence variation in the trematode genus Echinostoma: an aid to establishing relationships within the 37-collar-spine group

SUMMARYThe taxonomic history of members of the 37-collar-spine group within the genus Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5·8S and ITS2 of 7 nominal species belonging to this group, Echinostoma trivolvis (Cort, 1914), E. revolution (Frölich, 1802), E. caproni Richard, 1964, E. liei Jeyarasasingam et al. 1972, E. paraensei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. hortense (Asada, 1926). Five of the eight species were clearly distinguishable using ITS data. Sequences from the remaining three taxa, E. caproni, E. sp.II and E. liei were identical to one another and the group containing these taxa was distant from other 37-collar-spine species on a phylogenetic tree. E. trivolvis and E. paraensei form a second, but less distinct group within the 37-collar-spine group. The resolution obtained using DNA sequencing will assist in the current reclassification of the group. It also provides a model for future work on sibling species.

Renicola glacialissp. nov., a New Trematode from the North Sea Fulmar,Fulmarus glacialis(L.), with Observations on its Pathology

A new species Renicola glacialis sp. nov., belonging to the trematode genusRenicola, is described.The species is distinguished from most other renicolids by its relatively large size. Two other species within this size range have been recorded; while it is easy to separateR. glacialisfrom one of these species (R. goliathWright, 1957) the poor description of the other (R. secundaSkrjabin, 1924) renders a detailed comparison meaningless. However, the differences in host and geographic location between this andR. glacialisare considered sufficiently great to justify the erection of a new species.The pathology ofR. glacialisis discussed; recently established worms elicit only a slight host tissue response, but older infections are invested by a thick connective tissue sheath. The latter shows maximum development around dead worms and is accompanied by pronounced eosinophilia.Attention has been drawn to the use of the excretory vesicle as a diagnostic character. Four distinctly different forms have been described, and it is suggested that this character, together with certain other morphological features, would provide a useful key for the identification of renicolids once such information is available.

Fascioliasis

Fascioliasis, a disease caused by flukes of the Trematode genus Fasciola, is responsible for economic losses in many countries. Sheep and cattle are commonly attacked but other domestic animals, game animals and other wild animals may also be infected. Control measures embrace dosing with drugs (of which there are many, of varying efficacy and safety), attacking the snail intermediate hosts with molluscicides, destroying the habitat of the snail through drainage or ensuring that sheep and cattle are isolated from infective areas.