Insights about Diversity of Tetrabothriidae (Eucestoda) among Holarctic Alcidae (Charadriiformes): What Is Tetrabothrius jagerskioeldi jagerskioeldi? ?

Abstract

Tetrabothriid cestodes are characteristic helminths that infect species of seabirds globally. We begin with the exploration of the diversity of tapeworms of the genus Tetrabothrius Rudolphi, 1819 (Eucestoda: Tetrabothriidae), some of which are distributed among seabirds of the family Alcidae (Charadriiformes) at boreal to higher latitudes of Holarctic seas. During the course of 2 decades of field inventory from 1975 through the early 1990s (in addition to earlier collections assembled by Robert L. Rausch and colleagues in Alaska initiated in the late 1940s), an extensive series of tapeworm specimens attributable to species of Tetrabothrius was recovered from seabirds across the North Pacific Basin. It was assumed based on published records of species richness in this fauna that a single species, Tetrabothrius jagerskioeldi Nybelin, 1916, would predominate among alcid hosts. In contrast, detailed study revealed considerable morphological complexity that could not be accommodated within a single species. Further, it was apparent that the limits for the primary morphological attributes of T. jagerskioeldi were not clearly defined. We redescribe T. jagerskioeldi based on direct examination of the type series of specimens from Sweden and an assemblage of specimens largely from alcid hosts from the North Pacific basin. Specimens of T. jagerskioeldi are diagnosed by a characteristic configuration of the genital atrium, position of the male and female genital canals, structure of the male and female organ systems, and numbers of testes. Based on the spectrum of characters we explored, it was apparent that numerous specimens of Tetrabothrius among genera and species of Alcidae from the North Pacific inventory could not be accommodated in T. jagerskioeldi and provisionally are referred to Tetrabothrius undescribed n. sp. pending ongoing evaluations. Superficially, these are all large and robust tapeworms referable to Tetrabothrius, potentially contributing to misidentifications and misattribution that have occurred both in the literature and in the few archived specimens in museums. We summarize the results of extensive inventory collections since 1950, establishing a distributional baseline for species of Tetrabothrius from a wide range of geographic localities and an assemblage of host species among the Alcidae and some species of Laridae, Stercorariidae, and Phalacrocoracidae. We further MANTER: Journal of Parasite Biodiversity Supplementary data tables follow the references. MANTER: Journal of Parasite Biodiversity 2