A. Avenant-Oldewage

First maxillae suction discs in Branchiura (Crustacea): development and evolution in light of the first molecular phylogeny of Branchiura, Pentastomida, and other "Maxillopoda".

The fish ectoparasites Branchiura (Crustacea) display two different ways of attachment to the fish surface as adults: the first maxillae are either hooks (Dolops) or suction discs (Argulus, Chonopeltis, and Dipteropeltis). In larval Argulus foliaceus the first maxillae are hooks. With the first molecular phylogeny of the Branchiura as a background, the present paper discusses the evolutionary scenarios leading to hooks versus suction discs. Specific homologies exist between larval Argulus foliaceus hooks and adult Dolops ranarum hooks. These include the presence of a comparable number of segments/portions and a distal segment terminating in a double structure: a distal two-part hook (in Argulus) or one hook and an associate spine-like structure (in Dolops). In the phylogenetic reconstruction based on three molecular markers (mitochondrial 16S rRNA, nuclear 18S and 28S rRNA), Dolops ranarum is found to be in a sister group position to all other Branchiura, which in this analysis include six Argulus and one Chonopeltis sequences. Based on the molecular phylogeny a likely evolutionary scenario is that the ancestral branchiuran used hooks (on the first maxilla) for attachment, as seen in Dolops, of which the proximal part was subsequently modified into suction discs in Argulus and Chonopeltis (and Dipteropeltis). The sister group relationship of the Branchiura and Pentastomida is confirmed based on the most comprehensive taxon sampling until now. No evidence was found for a branchiuran in-group position of the Pentastomida.

ASPECTS OF THE MORPHOLOGY OF THE PARASITIC COPEPOD LERNAEA CYPRINACEA LINNAEUS, 1758 AND NOTES ON ITS DISTRIBUTION IN AFRICA

A morphological study on the ectoparasite Lernaea cyprinacea, found on Labeo rosae and Oreochromis mossambicus in the Olifants River in the Kruger National Park, South Africa, was done with the use of Scanning Electron Microscopy. Detailed descriptions are given of the appendages and their associated ornamentation. Significant morphological findings include the exact structure of the mandibles and the ornamentation on first pair of maxillae. Statistical analysis of the morphometrical data as well as the geographical distribution in Africa are shown.

Application of a fish health assessment index and associated parasite index to Clarias gariepinus (Teleostei: Clariidae) in the Vaal River system, South Africa

The aim of this study was to determine if the fish health assessment index (HAI) developed in the USA and associated parasite index (PI), when applied to Clarias gariepinus at two localities in the upper and middle Vaal River system, could distinguish between localities on the grounds of water quality. Elevated HAI values, correlating with poorer chemical and physical water quality, were recorded from the Vaal River Barrage site. Parasite data were congruent with the main PI premise that prevalence and intensity of endoparasite infection would be higher at the more polluted locality, with the converse being recorded for ectoparasites. It was therefore possible to distinguish between localities with different water quality, based on parasites present on the hosts.

Trace elements in sediments, blue spotted tilapia Oreochromis leucostictus (Trewavas, 1933) and its parasite Contracaecum multipapillatum from Lake Naivasha, Kenya, including a comprehensive health risk analysis.

This study presents the distribution of 15 major and trace elements in sediments and fish and their pericardial parasites from Lake Naivasha, Kenya. The lake is one of the few freshwater lakes in the Great Rift Valley and is under strong anthropogenic pressure mainly due to agricultural activities. Its fish provide a valuable protein source for approximately 100,000 people in the area. Fish and their parasites have been acknowledged as indicators of environmental quality due to their accumulation potential for both essential and nonessential trace elements. A total of 34 specimens of the blue spotted tilapia Oreochromis leucostictus and pooled samples of their pericardial parasite, the anisakid nematode Contracaecum multipapillatum (larvae 3), were examined. Element concentrations were determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and graphite furnace atomic absorption spectrometry (GF-AAS). The concentrations of elements in the sediments reflected the geology of the area and did not point to pollution: none of the investigated trace elements, including Pb, Cd, Cu, and Zn, showed elevated values. In contrast, concentrations in the fish muscle were elevated for Li, Sr, Cd, and Zn, with high target hazard quotients (THQ > 0.1) indicating a potential health risk to the consumers of this fish. Fish liver showed significantly higher concentrations of the trace elements Fe, Mn, Cd, and Cu compared to the muscle and C. multipapillatum. In the parasite, Zn had the highest concentration, but the worms only minimally accumulated trace elements in relation to their fish host.

Paradiplozoon ichthyoxanthon n. sp. (Monogenea: Diplozoidae) from Labeobarbus aeneus (Cyprinidae) in the Vaal River, South Africa

A new species, Paradiplozoon ichthyoxanthon (Monogenea: Diplozoidae) is described from the gills of Labeobarbus aeneus (Cyprinidae) in the Vaal Dam and Vaal River Barrage in the Vaal River, South Africa. This species is the first in this genus from southern Africa; Paradiplozoon aegtyptense and Paradiplozoon ghanense have been described from northern Africa. The new species differs from all other Paradiplozoon species on the basis of the combination of morphological characteristics, namely disk-like haptor, eggs without filaments, clamp and central hook morphology and size of specimens. The species description is accompanied by a description of the reproductive organs. The internal transcribed spacer of the ribosomal gene (ITS2) was studied and the South African individuals formed a distinct clade, supporting the establishment of a new species.

The digestive system of the fish ectoparasite Dolops ranarum (Crustacea: Branchiura)

Reconstructions from serial sections reveal that the digestive system consists of a pharynx esophagus, crop, midgut, and rectum. Two main stems from the branched enteral diverticula are connected to the lateral regions of the crop by right rind left arms. Glandular tissue surrounds the enteral diverticula proximally. A strong sphincter separates the crop and midgut, whereas the midgut and rectum are separated by a weak sphincter. Cuboidal epithelium lines the pharynx, esophagus, crop, and rectum, whereas cuboidal and club‐shaped epithelia line the midgut. The cuboidal cells possess elongated nuclei and numerous vacuoles, suggesting that absorption takes place in the midgut.

Checklist of the fish parasitic genus Cichlidogyrus (Monogenea), including its cosmopolitan distribution and host species.

Current knowledge of the 85 species in the genus Cichlidogyrus, collected worldwide, including their hosts, localities and authors, is summarised in a table. Although these parasites occur mainly in Africa, representatives have been recorded on cichlids in Mexico. Their distribution and host specificity are commented on.

Comments on the morphology of the pre-oral spine in Argulus (Crustacea: Branchiura)

A histological study of the pre‐oral spine and associated structures in Argulus japonicus reveals that two exceptionally long and slender muscles casuse retraction of the spine into the spinal sheath. Originating from the body wall mid‐dorsally the two muscles proceed through the nerve ring and the blood‐filled lumen of the spinal sheath before being inserted on a bolster of tissue constituting the base of the spine. Movement of the spinal sheath is affected by two muscles originating from a common apodeme in the dorsal body wall, just posterior to the nauplius eye, and inserted on the lateral walls of the base of the spinal sheath.

Paradiplozoon vaalense n. sp. (Monogenea: Diplozoidae) from the gills of moggel, Labeo umbratus (Smith, 1841), in the Vaal River System, South Africa.

An unidentified monogenean diplozoid species was collected from the gills of moggel in the Vaal River and Vaal Dam, South Africa. Specimens were removed from gills of the hosts and observed using light and electron microscopy to compare these diplozoids with known species. The second internal transcribed spacer (ITS2) of the ribosomal gene was amplified, sequenced and compared to that of other diplozoid taxa. Morphological species delimitation was used to determine the identity of these diplozoids, but they did not match the description of any diplozoid taxa. This species is recognized by the specific size of the hooks, number of plicae in posterior and trapezoid anterior projection of the median sclerite connecting to the clamp jaws via a single sclerite, occasionally with two small additional sclerites. Genetic characteristics based on sequence data from the ITS2 region also distinguish this taxon from all other diplozoid taxa. This South African diplozoid grouped in the same clade as Paradiplozoon ichthyoxanthon Avenant-Oldewage, 2013. Data clearly indicate that diplozoids collected from moggel represent a new, distinct taxon of Paradiplozoon Akhmerov, 1974 and are described here as Paradiplozoon vaalense n. sp.

Argulus japonicus: sperm transfer by means of a spermatophore on Carassius auratus (L).

The process of sperm transfer is somewhat enigmatic in Argulus, even though copulation has been witnessed. A breeding colony of Argulus japonicus was kept under laboratory conditions in order to study reproduction in the species. Pairs in copula were removed and studied with histology and scanning electron microscopy to describe the mechanism of sperm transfer. Sections of copulating pairs revealed sperm on the accessory copulatory structures of the males swimming legs; and scanning electron microscopy showed that sperm transfer occurs in three phases which can be differentiated to 10 different stages. Sperm transfer occurs via a spermatophore which is extruded from the genital aperture of the male and is then transferred to the socket on the third pair of legs of the male, before being transferred into the spermathecae of the female via the spermathecal spines. This is the first observation of a spermatophore in Argulus.