Last Updated: June 10, 2026
MORPHOLOGY: Segmentation complete. Scolex with four muscular bothridia (rectangular to round, flat or sucker-like – Priapocephalus). Rostellum absent. Reproductive organs single in segment; testes few to multiple; genital atrium unilateral, muscular; cirrus-sac oval or elongate; cirrus unarmed; ovary medullary, highly elongated; vitellarium compact, anteroventral to ovary; uterus a transverse tube dorsal to ovary, with single or multiple pores. Eggs with three membranes.
DIVERSITY: About 65 nominal species in 6 genera (genus Tetrabothrius containe 4 subgenera).
PHYLOGENETIC RELATIONSHIPS: Tetrabothriidea have been classified among Pseudophyllidea, Cyclophyllidea and Tetraphyllidea. Phylogenetic analyses currently supported monophyly for the Tetrabothriidea located between Mesocestoidea and Cyclophyllidea.
DEFINITIVE HOSTS: Marine homoeotherms – seabirds (74% of known species), cetaceans (22%) and pinnipeds (4%). Genus Tetrabothrius (42 species in seabirds, 8 in cetaceans), Chaetophallus (2 in seabirds), Strobilocephalus (1 in cetaceans), Priapocephalus (3 in cetaceans), Trigonocotyle (3 in cetaceans), and Anophryocephalus (3 in pinnipeds).
SITE IN DEFINITIVE HOST: Intestine.
GEOGRAPHIC DISTRIBUTION: Cosmopolitan, mostly in Polar Regions. Predominantly in pelagic ecosystem.
LIFE-CYCLES: Any life-cycle have yet to be elucidated, but are considered to involve crustaceans, cephalopods, and (or) teleosts as an intermediate hosts.
Selected References:
Temirova, S. I., and A. S. Skrjabin. 1978. Tetrabothriids and mesocestodes – cestodes of birds and mammals. Principles of cestodology. K. M. Ryzhikov (ed.). Volume IX. Nauka, Moscow, Russia, 198 p. [In Russian.] PDF
Hoberg, E. P. 1989. Phylogenetic relationships among genera of the Tetrabothriidae (Eucestoda). Journal of Parasitology 75: 617-626. PDF
Hoberg, E. P. 1994. Order Tetrabothriidea Baer, 1954. In Keys to the cestode parasites of vertebrates, L. F. Khalil, A. Jones, and R. A. Bray (eds.). CAB International, Wallingford, U.K., p. 295-304. PDF
Taxon Coordinator:
Eric P. Hoberg
US National Parasite Collection
USDA, Agricultural Research Service
Beltsville, Maryland, U.S.A.
