Order TETRAPHYLLIDEA van Beneden, 1850

Acanthobothrium thomasae [from Campbell & Beveridge 2002]

© Copyright Ian Beveridge. Melbourne University.

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Introduction

Tetraphyllidean cestodes are generally characterised by the presence of a scolex with four bothridia, segments with vitelline follicles arranged in two lateral bands, a lateral genital pore with the vagina entering the genital atrium anterior to the cirrus sac, and a medial tubular uterus. However, considerable variation occurs on this basic plan. The scolex may lack bothridia and possess instead four sessile glandular disks, may be cushion-like with a velum or consist of a single apical sucker and the vitelline follicles may be scattered. All members of the order are parasitic in the spiral valves of elasmobranchs or holocephalans (Euzet 1994). Cladistic studies of the Tetraphyllidea (Caira et al. 1999, 2001) have provided evidence to suggest that the Tetraphyllidea is not a monophyletic assemblage. Despite erection of the orders Rhinebothriidea by Healy et al. (2009), and Onchoproteocephalidea and Phyllobothriidea by Caira et al. (2014) to accommodate genera traditionally considered Tetraphyllideans, the family remains polyphyletic. The most recent phylogenetic analysis by Caira & Jensen (2017) has led to the recognition of six families, and four clades that remain unnamed and are referred to in the publication, and subsequent publications as Clades 1 through 4.

Euzet (1994) recognised eight families within the order, Cathetocephalidae Dailey & Overstreet, 1973; Chimaerocestidae Williams & Bray, 1984; Dioecotaeniidae Schmidt, 1969; Disculicepitidae Joyeux & Baer, 1936; Litobothriidae Dailey, 1969; Onchobothriidae Braun, 1900; Phyllobothriidae Braun, 1900; and Prosobothriidae Baer & Euzet, 1955. Of these eight families, only the Dioecotaeniidae remains a member of the Tetraphyllidea. The Cathetocephalidae was subsequently recognised as a separate order, the Cathetocephalidea, which also contains the Disculicepitidae. The Phyllobothriidea is currently also recognised as a separate order, the Phyllobothriidea, which also contains the Chimaerocestidae. Similarly, Lithobothriideae is now recognised as a separate order, the Lithobothriidea, and both Onchobothriidae and Prosobothriidae are now recognised as part of the Onchoproteocepahlidea.

At present, following Caira & Jensen (2017), the six families that are considered valid in the Tetraphyllidea are the Balanobothriidae, the Calliobothriidae, Dioecotaeniidae, Gastolecithiidae, Rhoptrobothriidae, and Serendipidae.

General References

Caira, J.N., Jensen, K., Waeschenbach, A., Olson, P.D. & Littlewood, D.T.J. 2014. Orders out of chaos — molecular phylogenetics reveals the complexity of shark and stingray tapeworm relationships. International Journal for Parasitology 44: 55-73

Caira, J.N., Jensen, K. & Healy, C.J. 1999. On the phylogenetic relationships among tetraphyllidean, lecanicephalidean and diphyllidean tapeworm genera. Systematic Parasitology 42: 77-151

Caira, J.N., Jensen, K. & Healy, C.J. 2001. Interrelationships among tetraphyllidean and lecanicephalidean cestodes. pp. 135-138 in Littlewood, D.J.T. & Bray, R.A. (eds). Interrelationships of the Platyhelminthes. London, UK : The Systematics Association, Taylor & Francis 356 pp.

Caira, J.N., Jensen, K. & Ruhnke, T.R. 2017. “Tetraphyllidea” van Beneden, 1849 relics. pp. 371–400 in Caira, J.N. & Jensen, K. (eds.). Planetary Biodiversity Inventory (2008–2017): Tapeworms from Vertebrate Bowels of the Earth. Lawrence, KS, USA : University of Kansas, Natural History Museum Vol. Special Publication No. 25.

Euzet, L. 1994. Order Lecanicephalidea Wardle & McLeod, 1952. pp. 195-204 in Khalil, L.F., Jones, A. & Bray, R.A. (eds). Keys to the Cestode Parasites of Vertebrates. Wallingford, UK : Commonwealth Agriculture Bureaux International 751 pp.

History of changes