Order TRYPANORHYNCHA Diesing, 1863

<I>Hornelliella annandalei</I> [from Campbell & Beveridge]

Hornelliella annandalei [from Campbell & Beveridge]

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Order TRYPANORHYNCHA Diesing, 1863

Compiler and date details

February 2014 - ABRS, following instruction from Professor Ian Beveridge, University of Melbourne

26 January 2005

Introduction

The cestode order Trypanorhyncha is one of the more unusual orders of cestodes. It is characterised by the presence, at the apex of the scolex, of four eversible tentacles, which often bear a complex array of diverse hooks used for attachment to the mucosa of the gastrointestinal tracts of elasmobranch fishes, the only known hosts of adults of this cestode order. Larval stages, known either as plerocerci or post larvae, are found in the body cavities of teleost fishes, crustaceans or, rarely, reptiles (Dollfus 1942). Life cycles of few species are known, but the currently established pattern involves development of a procercoid in a crustacean intermediate host followed by the development of a plerocercus in a teleost (Ruskowski 1934; Sakanari & Moser 1989). Alternative life cycles involve the development of a plerocercus in the first, crustacean, intermediate host, followed by completion of the life cycle in an elasmobranch (Mattis 1986).

The systematics of the order are far from being resolved, with the taxonomy of several genera inquirenda and some hundreds of species inquirendae remaining to be resolved (Schmidt 1986). The most recent classifications are those of Campbell & Beveridge (1994), in which tentacular armature is considered the most important taxonomic feature, following Dollfus (1942), and that of Palm (1997) in which the armature is considered to be of secondary importance. A preliminary cladistic analysis of the order (Beveridge et al. 1999) provides some evidence in support of both classifications. A more recent comprehensive classification has been proposed by Palm (2004) incorporating some of the data derived from the cladistic analysis. More recent molecular studies by Palm et al. (2009) and Olson et al. (2010) suggest that further revision of the systematics of the order is warranted.As the classification of the order is unresolved, the most recent comprehensive, phenetic classification of Campbell & Beveridge (1994) is utilised here.

The Australian fauna is still poorly known but consists of a number of cosmopolitan species, as well as species restricted to the Indo-Pacific region. Current estimates suggest that 43% of the currently known fauna may be endemic (Beveridge & Jones 2002). The majority of the known trypanorhynch families have already been found in the Australian region. Those which have not been found thus far are members of the Rhinoptericolidae Carvajal & Campbell, 1975.

Dibothriorhynchus maccallumi MacCallum, 1921 was described from a shark, purportedly from Australia, which died in the New York Aquarium (MacCallum 1921). The host, Sphyrna tiburo (Linnaeus, 1758), is, however, an American species (Compagno 1984). As a consequence, this species is not included in the records provided below.