Jo G. Van As

Gyrodactylus thlapi n. sp. (Monogenea) from Pseudocrenilabrus philander philander (Weber) (Cichlidae) in the Okavango Delta, Botswana

A new species of Gyrodactylus von Nordmann, 1832 and the first monogenean reported from Botswana is described from the cichlid Pseudocrenilabrus philander philander,bringing the number of gyrodactylids described from the African Continent to 18. Gyrodactylusthlapi n. sp. can be readily discriminated from the other described species almost exclusively by the shape of its hamuli, which have short roots and large, elongate ventral bar attachment points with the dorsal bar attachment point, demarcating the junction between the hamulus shaft and the root, positioned at the anterior terminus of the attachment plane. The marginal hooks of G. thlapi n. sp., which most closely resemble those of G. groschafti Ergens, 1973, are compared and discussed.

TAXONOMIC RE-EVALUATION OF THE SOUTH AFRICAN FISH HAEMOGREGARINE, DESSERIA FRAGILIS

Development stages of a haemogregarine were found in Giemsa-stained heart blood smears of 3 of the 4 horned blennies (Parablennius cornutus) captured at De Hoop Nature Reserve, South Africa. Gamonts of this haemogregarine conformed to an existing description of Desseria (Haemogregarina) fragilis from P. cornutus, but intraerythrocytic trophozoites, as well as meronts undergoing division, were reported for the first time for this species. A detailed redescription of D. fragilis allowed its taxonomic re-evaluation. Intraerythrocytic division excluded D. fragilis from Desseria, whereas morphometric similarities and identical patterns of development lead to the conclusion that D. fragilis is the cosmopolitan haemogregarine, Haemogregarina bigemina. Nomenclatural correction synonymizing the 2 species is recommended.

Unionicola (Iridinicola) botswaniana n. subgen., n. sp. (Acari: Unionicolidae) from freshwater mussels in Botswana

Abstract Unionicola (Iridinicola) botswaniana n. subgen., n. sp. (Hydrachnida: Unionicolidae) is described from freshwater mussels, Mutela zambesiensis and Aspatharia pfeifferiana, from Okavango River, Botswana, Africa. The new species is a unique mite with distinctive female genital field anatomy and leg chaetotaxy. This new mite extends our understanding of the morphology and biogeography of the genus in Africa. It further extends our knowledge of host selection and host-specificity among African Unionicola.

New records of digenean parasites of Clarias gariepinus (Pisces: Clariidae) from the Okavango Delta, Botswana, with description of Thaparotrema botswanensis sp. n. (Plathelminthes: Trematoda)

ABSTRACT Forty-two specimens of African sharptooth catfish Clarias gariepinus (Clariidae) were collected from a number of localities in the Okavango Delta in Botswana and examined for digenean parasites. The morphology of these parasites was studied using light and scanning electron microscopy. Six digenean species, four represented by adults and two by metacercariae, belonging to five different genera were collected from various organs within the fish. Clinostomoides brieni is described from the branchial chamber; a Neodiplostomum type metacercariae from the musculature; Phyllodistomimi bavuri and Phyllodistomum vanderwaali from the urinary bladder; Glossidium pedatum from the intestine and one new species, Thaparotrema botswanensis sp. n. from the gall bladder. These are all new geographical records for southern Africa.

Unionicola (Coelaturicola) gledhilli n. subgen., n. sp. (Acari: Unionicolidae) from freshwater mussels in Botswana and East Africa

Abstract Unionicola (Coelaturicola) gledhilli n. subgen., n. sp. (Hydrachnida: Unionicolidae) is described from freshwater mussels, Coelatura kunenensis Mousson, 1887 (Unionoida: Unionidae) from the Okavango River, Botswana, and Chambardia nyassaensis (Lea, 1864) (Unionoida: Iridinidae) from Lake Malawi, Malawi, East Africa. The new species has distinctive coxal plate and genital field morphologies. This new mite extends our understanding of the morphology and biogeography of the genus in Africa and the Southern Hemisphere. It further extends our knowledge of host selection and host-specificity among the Unionicola.

Redescription of Argulus multipocula Barnard, 1955 (Crustacea: Branchiura) collected on the west coast of SouthAfrica

Argulus multipocula Barnard, 1955 was originally described from a single female found in a littoral sample from the east coast of South Africa. We present a redescription of this species based on light and scanning electron microscope studies of 25 females collected from the southern mullet Liza richardsonii (Smith) on the west coast of South Africa.

A Brief History of Freshwater Fish Parasitology in Southern Africa

The paper presents an overview of the history of aquatic parasitology of freshwater fish in southern Africa. Aquatic parasitology has become a very popular field of specialisation in South Africa and is currently practised by a number of individual research groups at different universities. So far most research deals with parasites of wild fish rather than pathogens of aquaculture. It is written as a narrative and summarises the aquatic parasitology research mostly on fish parasites carried out at the universities of Cape Town, Free State, Johannesburg, Limpopo, Pretoria, North West and Sefako Makgatho Health Sciences. It is not intended to be a review in the classical way because it deals with parasites ranging from Protozoa to Arthropoda.

Pathology of eyes and brain of fish infected with diplostomids, southern Africa

Only a few reports exist on diplostomid metacercariae found in southern African fish and even less information is available on the pathology associated with these infections. During surveys conducted in December 2008 and August 2010, different fish species were collected from the Okavango (Botswana) and Orange—Vaal (South Africa) River Systems. Histological sections were done from intact Tilapia sparrmanii A. Smith, 1840 and Coptodon rendalli (Boulenger, 1896) eyes and the brains of infected Brycinus lateralis (Boulenger, 1900) in order to determine the precise site of infection and the possible pathological effects. It was found that the encapsulated diplostomids from the eyes of the infected haplotilapiine species from the Okavango System caused localised retinal and/or choroid detachments. No pathological effects were observed in the histological sections of the brains of B. lateralis that were infected with diplostomids, except for the presence of red blood or rodlet cells. Tilapia sparrmanii collected from the Orange River were not infected with diplostomids.

Ecology of Diplostomid (Trematoda: Digenea) Infection in Freshwater Fish in Southern Africa

The complex life cycles of most trematode parasites include three hosts. The first intermediate host is a snail, the second is normally a teleost fish and a piscivorous bird serves as the definitive host. Lymnaeid snails are most likely to be responsible for cercarial shedding, which infect exposed fish and in turn are eaten by piscivorous birds. From 2008 to 2010 fish in the Okavango and Orange-Vaal River Systems were collected and dissected in order to determine the prevalence and intensity of larval trematode infections in the eyes and brains. This paper discusses the possible ecological factors which can influence the probability of certain fish species becoming infected with diplostomid cercariae and hence metacercariae. The feeding strategies and sizes of piscivorous birds, which could act as definitive hosts for the adult worms, are summarized and discussed. Information on the snail species responsible for furcocercous cercarial shedding in the two study sites is also included.

Trichodina diaptomi (Ciliophora: Peritrichia) from Two Calanoid Copepods from Botswana and South Africa, with Notes on its Life History

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 Sramek-Husek, 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.