Palm, H.W. (1995). Untersuchungen zur Systematik von Rüsselbandwürmern (Cestoda: Trypanorhyncha) aus atlantischen Fischen. Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel. 275: 238 pp.

199235

Palm, H.W.

1995

275: 238 pp

Publication

Trypanorhynch cestodes are characterized by the possession of a scolex bearing 4 evertible hooked tentacles and 2 or 4 suckers, by which the cestodes move through and attach to the digestive tract of their elasmobranch final hosts. In their life cycles, these cestodes use invertebrates as first intermediate hosts, plus teleosts and some invertebrates as second and parafhenic hosts. The presence of the metacestode stage in the musculature of fishes can decrease the commercial value of affected stocks world wide. The purpose of the present study was to develop a new classification of trypanorhynch cestodes as a basis for a natural system. This was neccessary because of weaknesses in existing systems that cause identification of many of the approximately 200-250 valid species to be difficult. Currently, the armature of the tentacles in the metacestodes and adults is used as the major character in all the superfamiles: Homeacanthoidea, Heteracanthoidea, Otobothrioidea and Poecilacanthoidea. This system has grouped some families together that share similar tentacle arrangements but have few other morphological similarities in common. Light- and scanning electron microscopy were used to assess the morphology, the tentacles and the surface of the scolices of 29 trypanorhynchs from the Atlantic Ocean and 2 species from the Pacific Ocean from all four superfamilies. Fresh material was collected from teleosts and elasmobranchs along the coasts of Brazil, Nigeria and the southern Gulf of Mexico coast of the USA; preserved material was obtained from collections in Brazil, England Russia and USA. Species descriptions mostly followed existing standards; however, the orientation of tentacle surfaces and numbering of hooks were reinterpreted Arising from this was the development of a hook formula which summarizes the characteristic armature of a trypanorhynch species. The hook formula as well as the SEM micrographs were fundamental in the development of an identification key for the described Atlantic species. For 17 of these species the first SEM documentation is presented At present, this study is the most comprehensive compilation of trypanorhynch surface ultrastructure, and it has demonstrated again the potential of rnicrotriche morphology as a systematic character. The following features are reported for the first time: 1. absence of microtriches from Pterobothrium heteracanthum, 2. circular fields of microtriche-free surface on the apex of the scolex of Poecilancistrum caryophyllum, 3. regularly arranged clumps of cilia-like microtriches on the bothridia of Patellobothrium quinquecatenatum, and 4. surface hooks on the bothridia of Tentaculariidae. For the first time, the reduction of tentacular hooks was demonstrated. The two species Pterobothrium acanthotruncatum Escalante & Carvajal, 1984 and Ototobothrium crenacolle Linton. 1890 are proposed as junior subjective synonyms of P. heteracanthum Diesing. 1850 and O. cysticum Mayer. 1842. respectively. Four new species and two new genera are reported: Grillotia kovalevae sp. now distinguished by having 2 bothridia without ciliated pits and a metabasal armature with 7 calary and 2 intercalary hooks, and Pseudogrillotia zerbiae sp. nov., distinguished by the presence of 2 bothridia without ciliated pits and a metabasal armature with 7 calary hooks and a band of hooks on the external surface. The new genus Poeciloacanthum with the species Poeciloacanthum oweni gen. et sp. nov. is characterized by having ciliated pits on the borders of 2 bothridia and a single chainette on the external tentacle surface. The other new genus Pseudolacistorhynchus with the species Pseudolacistorhynchus noodti gen. et sp. nov. has 2 bothridia without ciliated pits and a single chainette on the external surface, completing the rows of 5 calary and 3 intercalary hooks.

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