Linda Basson

Mobiline taxonomic data is mostly inferred from populations collected in and on hosts associated with aquaculture. Even though these conditions may be conducive for studies relating to the hosts, accurate taxonomic inferences of the symbionts will be problematic. The site for the present study was the Okavango Panhandle region in Northern Botswana, an isolated, natural area with minimal anthropogenic influences. Morphometric and molecular evidence revealed that anuran tadpole trichodinids, up to now reported as Trichodina heterodentata Duncan 1977 and T. hypsilepis Wellborn 1967 from multiple host types, are in fact a new, more host specific species. This study includes comprehensive denticle descriptions of both the anuran hosted trichodinid and the morphologically similar T. hypsilepis restricted to teleost hosts (previously T. heterodentata).

Mantoscyphidians occur in high numbers on the gills of South African Haliotis and limpet species. This provided the ideal opportunity to study asexual and sexual reproduction, for the first time in different African Mantoscyphidia Jankowski, 1985 populations. Descriptions of the reproductive processes found in scyphidiid peritrichs were until now, mostly based on line drawings. Scanning electronand light microscopy contributed uniquely, in providing detail information regarding binary fission, telotroch formation and conjugation. Mantoscyphidia spadiceae Botes, Basson and Van As, 2001 shed the most light on binary fission. Micronuclear division occurred first with the plane of fission already evident and macronuclear cleavage ended just before final separation took place. Fission is not complete until a small string of pellicle that joins the daughter cells finally separates. Information on telotroch development was gathered from M. branchi Van As, Basson and Van As, 1998 and M. spadiceae populations. Telotrochs were between 36.7 and 38.6% shorter than live, extended mantoscyphidians and their swimming action resembled mobiline peritrichs. Mantoscyphidia branchi populations also proved to be most useful for conjugation studies. Conjugation included three progamic nuclear divisions and preceded synkaryon formation and two metagamic nuclear divisions. The process required 24 hours to be completed.

During parasitological surveys in Tasmania (Australia), four introduced fish species were investigated for the presence of trichodinid ectoparasites. Five trichodinid species were found on the skin, fins and gills of two of these fishes, i.e. the tench Tinca tinca Linnaeus, 1758 and the red fin perch Perca fluviatillis Linnaeus, 1758. Four trichodinids are known species for which comparative descriptions are provided, i.e. Trichodina acuta Lom, 1961, T. esocis Lom, 1961, T. lepsii Lom, 1962 and Trichodinella epizootica (Raabe 1950) Šrámek- Hušek, 1953. A fifth species, i.e. Trichodina tunnae sp. n. is described as a new species from the red fin perch. All species are described using silver impregnated and hematoxylin stained specimens.

Members of the Urceolariidae Dujardin, 1941 have been found associated with a wide variety of invertebrate hosts from freshwater and marine habitats. Five species have been described from molluscan hosts from Europe and America. This paper deals with an urceolariid (Leiotrocha Fabre-Domergue, 1888) collected from the gills of Cellana radiata capensis (Gmelin, 1791) and Scutellastra exusta (Reeve, 1854) from the east coast of South Africa, as well as Patella depressa Pennant, 1777 and Cymbula safiana (Lamarck, 1891) from the bulge (west coast) of Africa. A higher prevalence was found on C. radiata capensis (89%) and P. depressa (72%) compared to the other two hosts. The urceolariid collected from the African limpets was identified as L. patellae (Cuénot, 1891). This is the first record of an urceolariid from any African hosts, including representatives of the Mollusca. Five urceolariid species were identified and described from gastropods, i.e. L. patellae Cuénot, 1891,U. karyolobia Hirshfield, 1949, U. cellanae Suzuki, 1950, U. viridis Richards, 1971 and U. parakorschelti Irwin, Sabetrasekh and Lynn, 2017. Motivation is provided why U. cellanae and U. viridis should be reallocated to the genus Leiotrocha, and U. karyolobia not. The taxonomic validity of the recent description of U. parakorschelti from limpets is commented on.

Trichodina heterodentata was first described from fish breeding farms in the Philippines by Bryan Duncan in 1977 as ectoparasites of imported cichlids, more specifically the southern African Oreochromis mossambicus (Peters, 1852) from the Limpopo River System. This trichodinid has subsequently been described from almost every continent, bar North America. Being a cosmopolitan species, with a preference for cichlid hosts, it has unambiguous morphological features, but with distinct variances between and within populations. After reviewing previous descriptions of North American trichodinids, analysing the morphological data (both generally published information along with the original type material from the Smithsonian Museum, Washington, U.S.A.) and investigating the distribution patterns of the southern African introduced O. mossambicus throughout the North American water systems, three of the four studied trichodinids (T. hypsilepis Wellborn, 1967, T. salmincola Wellborn, 1967 and T. vallata Wellborn, 1967) are proposed to represent the same species as T. heterodentata. According to nomenclature rules T. hypsilepis henceforth represents the valid taxon (synonyms: T. salmincola, T. vallata and T. heterodentata). This not only questions the validity of several trichodinid species, but also indicates the probability of an African alien introduction into North America.

Members of the genus Trichodina are mostly found on fish, but have also been recorded from a variety of other aquatic organisms, including calanoid copepods. So far, it appears that all the trichodinid populations collected from calanoids in various parts of the world are the same species, i.e. Trichodina diaptomi Šrámek-Hušek, 1953. This paper reports on a new record of T. diaptomi from Metadiaptomus meridianus in a large reservoir in South Africa, as well as on a new host species, Metadiaptomus transvaalensis, and the first record of T. diaptomi from pools in an ephemeral river in northern Botswana, therefore adding a new country to the distribution of this species. We used the history of the discovery of T. diaptomi in different parts of the world and came to the conclusion that it is a cosmopolitan species, exclusively associated with copepods of the order Calanoida. Based on existing information, T. diaptomi does not appear to have a reservoir host. Against this background, we provide a discussion on the possibility that, although no dormant stage has been recorded for any trichodinid, it may be possible that T. diaptomi possesses some form of diapause and that this might be related to that of calanoid copepods.

During surveys of parasites of the pepper cory Corydoras paleatus Jenyns, 1842 and sided-livebearer Jenynsia multidentata Jenyns, 1842 from Samborombón River, Argentina, Trichodina corydori n. sp., Trichodina cribbi Dove and O’Donoghue, 2005 and T. jenynsii n. sp.were morphologically studied. Taxonomic and morphometric data for these trichodinids based on dry silver nitrate-impregnated specimens are presented. Trichodina corydori is characterized by a prominent blade apophysis, the section connecting the blade and central part is short, and the adoral ciliary spiral makes a turn of 370–380°. Trichodina jenynsii is characterized by curved blades and prominently-shaped denticle rays that are characteristically extremely long, tapering to thin sharp points in adult specimens. This study is the first formal report of these trichodinids from South America, and the description of two new species.