Labeobarbus Aeneus Research Articles

Gyrodactylus sprostonae Ling, 1962 infects an indigenous cyprinid in southern Africa: An expanded description

Gyrodactylus sprostonae Ling, 1962 is a highly invasive parasite reported across freshwater environments of the northern hemisphere. The taxon was originally described from Carassius auratus (Linnaeus, 1758) and Cyprinus carpio Linnaeus, 1758 in China. This parasite has never been reported in Africa or the southern hemisphere. Recently, this taxon was collected from an indigenous yellowfish, Labeobarbus aeneus (Burchell, 1822), in the Vaal River, South Africa. The present study includes the conclusive identification of the gyrodactylid parasites collected from L. aeneus, including additional taxonomic data, using microscopy and molecular techniques. Microscopy included light microscopy (LM) of whole worms and scanning electron microscopy (SEM) of isolated haptoral sclerites. Additionally, morphometric data were obtained from SEM and compared to that generated using LM. For molecular analysis, the internal transcribed spacer (ITS) region of rDNA was amplified and phylogenetic topologies constructed. The specimens were morphometrically and genetically highly similar to other data for G. sprostonae. Additional point-to-point measurements and ITS rDNA sequences were generated for the taxon, contributing to the morphometric and molecular data for G. sprostonae. The study also includes the first study of the isolated haptoral sclerites of the taxon using SEM, with similar morphometric results to LM. This is the first record of G. sprostonae in the southern hemisphere and from a new, indigenous African host, L. aeneus, indicating host switching to smallmouth yellowfish. Furthermore, these results expand on the knowledge of the distribution of invasive parasites in South Africa, as well as Gyrodactylus species diversity in Africa.

Morphological description and molecular characterisation of Dactylogyrus matlopong sp. n. (Monogenea: Dactylogyridae) from the South African endemic Labeobarbus aeneus (Cyprinidae: Torinae).

Dactylogyrus Diesing, 1850 is the most species-rich genus in Platyhelminthes, with over 900 documented species, that are mostly strictly specific to freshwater cyprinoids. The morphological Dactylogyrus groups afrobarbae-type, carpathicus-type, pseudoanchoratus-type, and varicorhini-type are known to occur in Africa. This study describes a new species of Dactylogyrus of the varicorhini-type from the gills of the endemic smallmouth yellowfish Labeobarbus aeneus (Burchell) from the Vaal River, Free State Province, South Africa. Dactylogyrus matlopong sp. n. is unique among its varicorhini-type congeners mainly by the accessory piece of the male copulatory complex that presents a hook-shaped subunit with defined round base not reaching the male copulatory organ, combined with the presence of a conspicuous medial projection on the anterior margin of the ventral bar. Sequences of the partial 28S and 18S rRNA genes, together with entire ITS1 region, were generated for the first time for a species of Dactylogyrus from South Africa. Concatenated phylogenetic analyses of selected Dactylogyrus spp. showed that these parasites group according to their morphological types.

First record of trace element accumulation in a freshwater ectoparasite, Paradiplozoon ichthyoxanthon (Monogenea; Diplozoidae), infecting the gills of two yellowfish species, Labeobarbus aeneus and Labeobarbus kimberleyensis

BackgroundElevated levels of trace elements in the aquatic environment poses risks to the health of biota and humans. Parasites are important components in ecosystems; responding to changes in the health of aquatic ecosystems and can accumulate trace elements in their tissues to higher levels than their hosts. Monogeneans are an important group of fish ectoparasites being directly exposed to the aquatic environment. MethodsIn this study concentrations of Ti, Fe, Cu, Zn, Rb, Sr and Ag were analysed in the monogenean parasite, Paradiplozoon ichthyoxanthon (by total reflection x-ray fluorescence spectrometry and graphite furnace atomic absorption spectrometry), and the muscle, liver and gills of two host fish species, Labeobarbus aeneus and Labeobarbus kimberleyensis (by inductively coupled plasma -– mass spectrometry). ResultsMost striking was the accumulation pattern for Zn in parasites; mean levels of Zn were as high as 1448 and 1652 mg kg−1 dw, respectively, with no significant difference between the two host-parasite groups, leading to bioconcentration factors of approximately 93 (parasite/fish muscle) and 15 (parasite/fish liver). In addition, Fe was accumulated in the parasite to a higher degree compared to the fish hosts’ tissues. Cu levels were higher in P. ichthyoxanthon than in the muscle tissue of both host fishes, but lower than liver tissue. ConclusionThese findings demonstrate the usefulness of this parasite species as a sentinel organism in aquatic ecosystems it inhabits for Fe and Zn. Other trace elements under investigation were not accumulated higher in the parasite compared to its fish host. Lower Rb levels in the parasite compared to its hosts indicate no biomagnification of this metal. Further investigations are required to determine if similar trends in trace element accumulation occur in other monogeneans. Data availabilityAll data generated in the analysis of host and parasite tissues are presented in the manuscript.

Morphological and molecular description of Allocreadium apokryfi sp. n. (Digenea: Allocreadiidae) from native Labeobarbus aeneus (Cyprinidae) in South Africa, including notes on its biology, evolutionary history and an updated key of African Allocreadium.

Adult trematodes of Allocreadium Looss, 1900 (Digenea) infect the intestine of mostly freshwater fishes in Asia, Europe, Africa and the Americas. During routine parasitological surveys in the Vaal River system, adult trematodes were collected from the intestine of smallmouth yellowfish, Labeobarbus aeneus (Burchell). The trematodes were confirmed to represent a member of Allocreadium and did not match any existing taxon. Therefore, they are described as a new species, Allocreadium apokryfi sp. n. The morphology of the new species most closely resembles that of Allocreadium aswanense El-Naffar, Saoud et Hassan, 1984, but it differs from it by having a bipartite internal seminal vesicle, wider eggs, a shorter intertesticular distance, an intestinal bifurcation at the ventral sucker level, a ventral sucker that is larger than the oral sucker, and a genital pore near the intestinal bifurcation or the ventral sucker. The surface topology of the new species is notably different from that of other allocreadiids. Papillae were observed in the ventral sucker and surrounding both ventral and oral suckers, but the number and arrangement of the latter were not consistent among specimens. The protruding cirrus of A. apokryfi sp. n. was described using SEM and is the first such observation for the genus. Genetic characterisation showed that the new species was clearly distinct from other Allocreadium spp. using both 18S (nucleotide difference 1.3-9.1%) and 28S (4.7-6.5%) rDNA, forming a well-supported clade in Allocreadium. The presence of A. apokryfi sp. n. in a well-studied river is unexpected, and considering the diet of its host and the scarcity of Allocreadium in Africa, the possible biology of this species is discussed herein.

Abundance and Diversity of Fish Assemblages Along the River-Estuary Continuum in a Fluvially Dominated Southern African Coastal System

Estuaries are amongst the most productive ecosystems worldwide and provide nursery habitat for fish species of marine and freshwater origin; however, the distribution and community structure of fishes within freshwater-dominated coastal system is limited. This study presents an overview of the temporal and spatial patterns in the abundance, diversity and distribution of fishes along a river-estuarine continuum and compared them to other southern African estuaries. A total of 30 species belonging to 16 families were recorded in the Orange River Estuary (ORE) comprised mostly of freshwater (47%), marine (33%) and estuarine fishes (20%). Chelon richardsonii (marine estuarine-opportunist) and Gilchristella aestuaria (solely estuarine) were the numerically dominant species in the estuary with 63% and 20% of catches, respectively. The two species utilise a broad salinity range (0.l–34.9 PSU). Also, C. richardsonii dominated catches in the river section with 52% followed by Labeobarbus aeneus (freshwater straggler) and Pseudocrenilabrus philander (freshwater estuarine-opportunist) with 15% and 9%, respectively. Species diversity and catch-per-unit-effort (CPUE) revealed seasonal variation in fish assemblages during the high-flow and low-flow season but not inter-annually. This highlights the continuity in fish assemblages utilising the ORE. High catches (dominated by C. richardsonii) but low species diversity observed close to the mouth of the estuary agree with the biogeographical trend of decreasing species richness from east to west on the South African coast. In comparison with other estuaries, the ORE is freshwater dominated, whilst the Berg and Olifants estuaries are dominated by marine taxa but with similar richness values.

Stable isotopes reveal trophic linkages among fish species utilizing the Orange River Estuary Continuum

The Orange River is one of the longest rivers in southern Africa and one of the most regulated rivers in the world. Its estuary supports diverse marine and freshwater life, yet, ecosystem structure and functioning within the estuary are poorly understood. This study investigated trophic linkages and interactions among dominant fishes through carbon (δ13C) and nitrogen (δ15N) stable isotope (SI) ratios along a salinity gradient. The five dominant species utilizing the Orange River Estuary Continuum (OREC) included marine Chelon richardsonii, estuarine Gilchristella aestuaria, and freshwater species Labeobarbus aeneus, Pseudocrenilabrus philander and Mesobola brevianalis. Variations in SI ratios were associated with changes in body size, seasonality and salinity. Variability in seasons and the salinity continuum influenced SI ratios. Chelon richardsonii, P. philander and L. aeneus occupied the widest isotopic niche in the lower OREC, an indication of generalist feeding behaviour in these species. Mesobola brevianalis had the narrowest isotopic niche, perhaps suggesting more specialized feeding on zooplankton. Isotopic similarity was observed among the five co-occurring species, suggesting trophic overlap, particularly during the high-flow season when environmental variables, productivity and food availability are predominantly freshwater driven and uniform throughout the river estuary continuum. This study is the first to utilize δ13C and δ15N analyses to assess trophic dynamics of dominant species co-occurring in the estuary and estuarine-freshwater ecotone of the lower OREC.

Evaluating the suitability of fyke nets for small-scale fisheries in the Free State Province of South Africa

South Africa is under increasing pressure to develop small-scale fisheries in inland waters. To inform appropriate development of this sector in the Free State Province, the catch rate of double-ended fyke nets was evaluated using survey data from 20 impoundments sampled during the 2013/2014 summer season. Fyke nets were set over night and the total sample effort was 114 fyke net nights. Overall catch per unit effort (CPUE) was 16.8 ± 28.3 kg·net-1·night-1 and catch composition was dependent on impoundment, but generally comprised of a mixture of common carp Cyprinus carpio, African sharptooth catfish Clarias gariepinus, smallmouth yellowfish Labeobarbus aeneus, Orange River mudfish Labeo capensis and moggel Labeo umbratus. The influence of temperature and the potential benefits of baiting the nets were subsequently evaluated through monthly sampling in the hyper-eutrophic Krugersdrift Dam and at the oligotrophic Gariep Dam. Baiting did not significantly influence CPUE, which was significantly higher at Krugersdrift Dam (19.97 ± 23.22 kg·net-1·night-1) than at Gariep Dam (5.02 ± 6.05 kg·net-1·night-1). Increasing temperature had a positive effect on CPUE at Krugersdrift Dam but not at Gariep Dam. Species composition also differed between impoundments and, as a result, we conclude that seasonal catch rates and species compositions will need to be evaluated prior to implementation of fyke net fisheries in specific localities.

Lower vertebrates of Sehlabathebe National Park, Lesotho

Five snake, four lizard, nine amphibian (all anurans) and three fish species were recorded in the Apline grasslands of the Sehlabathebe National Park, South-Eastern Lesotho, Southern Africa. They include rare, threatened and endemic species, some of which are restricted to the Drakensberg / Maloti region. The following species were recorded: snakes Lamprophis aurora, L. fuscus, Hemachatus haemachatus, Bitis arietans, B. atropos; lizards Trachylepsis punctatissima, Tropidosaura montana, Pseudocordylus melanotus, Afroedura nivaria; amphibians (anurans) Xenopus laevis laevis, Bufo gariepensis nubicolus, Cacosternum striatum, Amietia dracomontana, A. angloensis, A. fuscigula, A. umbraculata, Strongylopus fasciatus, Semnodactylus wealii; fishes Labeobarbus aeneus, Pseudobarbus quathlambae and Oncorhynchus mykiss. Species with high conservation priorities include: Lamprophis fuscus, Tropidosaura cottrelli, Pseudocordylus spinosus, Amietia umbraculata, A. drakomontana, Strongylopus fasciatus and Pseudobarbus quathlambae.

Trace element and metal sequestration in vitellaria and sclerites, and reactive oxygen intermediates in a freshwater monogenean, Paradiplozoon ichthyoxanthon.

Exposure to metals and other trace elements negatively affects infection dynamics of monogeneans, including diplozoids, but, physiological mechanisms linked to exposure have yet to be documented. In this study sequestration of trace elements and reactive oxygen intermediate production in the monogenean, Paradiplozoon ichthyoxanthon, was demonstrated. During dissection of host fish, Labeobarbus aeneus, the gills were excised and assessed for P. ichthyoxanthon, which were removed and frozen for fluorescence microscopy or fixed for transmission electron microscopy. Trace elements were sequestered in the vitellaria and sclerites in P. ichthyoxanthon, and the presence of reactive oxygen intermediates was observed predominantly in the tegument of the parasite. Trace elements and metals identified and ranked according to weight percentages (wt%) in the vitellaria were Cu > C > Au > O > Cr > Fe > Si while for the sclerites C > Cu > O > Au > Fe > Cr > Si were identified. For most element detected, readings were higher in the vitellaria than the sclerites, except for C and O which were higher in sclerites. Specifically for metals, all levels detected in the vitellaria were greater than in sclerites. Based on the proportion of trace elements present in the vitellaria and sclerites it appears that most trace elements including metals were sequestered in the vitellaria. The results of reactive oxygen intermediate production in the tegument of the parasite suggests either trace element accumulation takes place across the tegument or results from the action of the host’s immune response on the parasite. The results serve as the first demonstration of trace element sequestration and reactive oxygen intermediates in a freshwater monogenean parasite.

Hatchability and survival of oncomiracidia of Paradiplozoon ichthyoxanthon (Monogenea: Diplozoidae) exposed to aqueous aluminium.

BackgroundMonogenea is a diverse group of ectoparasites showing great potential as sentinel organisms for monitoring environmental health. Exposure to metals negatively affects infrapopulations of monogeneans and exposure to aluminium has been found to negatively impact the survival of gyrodactylids.MethodsSamples of infected host fish, the smallmouth yellowfish Labeobarbus aeneus (Cyprinidae), were collected from the Vaal Dam, South Africa and transported back to the laboratory in dark 160 l containers. Eggs of the monogenean Paradiplozoon ichthyoxanthon infecting L. aeneus were collected and exposed to varying concentrations of aluminium along with a control group in static tanks. The eggs were checked every 24 h and hatching commenced 13–14 days after exposure. Water samples were taken from exposure tanks and acidified for analysis of Al levels with inductively-coupled plasma mass spectrometry.ResultsHatching of eggs was variable between exposures, and in 30 μg Al/l and 60 μg Al/l was found to occur before eggs in control beakers, whereas, exposure to 120 μg Al/l delayed hatching and reduced hatchability. Survival of hatched oncomiracidia was concentration dependent and negatively correlated with aluminium concentrations. Lowest survival was recorded for 60 μg Al/l and 120 μg Al/l where all larvae died shortly after or during hatching. Normal development of embryos of P. ichthyoxanthon within eggs exposed to all doses of aluminium indicates that the egg shell is moderately impermeable to metals and inhibits movement of aluminium across the shell and interacting with developing embryos.ConclusionsHigher larval mortality rate in 120 μg/l exposure can be related to aluminium crossing the egg shell in the late stages and causing death of unhatched yet fully developed embryos, possibly due to changes in the permeability of the egg shell as embryos neared developmental completion. Accelerated death of oncomiracidia after hatching indicates sensitivity toward high concentrations of aluminium.

Population crash in Lesotho's endemic Maloti minnow Pseudobarbus quathlambae following invasion by translocated smallmouth yellowfish Labeobarbus aeneus

Abstract A genetically distinct population of the Maloti minnow Pseudobarbus quathlambae (Lesotho's only endemic fish) is known only from the Mohale catchment, and was formerly abundant in the Senqunyane, Bokong and Jorodane rivers which flow into Mohale Reservoir. Situated ~4 km downstream of Mohale Reservoir, the Semongkoaneng waterfall has historically prevented larger fish species from moving upstream into areas inhabited by P. quathlambae. After the filling of the Mohale Reservoir in 2003, an inter‐basin transfer (IBT) linking it to Katse Reservoir was opened and in 2006 the smallmouth yellowfish Labeobarbus aeneus, a larger more aggressive species, was recorded in the reservoir, presumably introduced via the IBT. The objectives of the present study were to: (1) establish whether any additional non‐native fish species were present in the Mohale catchment; (2) ascertain whether L. aeneus has dispersed into the rivers flowing into Mohale Reservoir; and (3) gauge whether the Mohale population of P. quathlambae is in decline. Twenty‐eight sites situated on major rivers flowing into the reservoir, and four sites in the reservoir itself, were surveyed to evaluate changes in fish populations and habitat quality. Results indicate that P. quathlambae has all but disappeared from its natural range: only five individuals were recorded in the Jorodane and Bokong rivers, and none were recorded in the Senqunyane River – a former stronghold for the species. On the other hand, L. aeneus was recorded in all three rivers and is probably responsible for the decline of the P. quathlambae population, given that there does not appear to have been major deterioration in habitat conditions. Another non‐native fish, the Orange River mudfish Labeo capensis, was recorded in the Mohale catchment for the first time. Urgent conservation action is required to prevent the Mohale lineage of P. quathlambae from becoming extinct. Copyright © 2016 John Wiley & Sons, Ltd.

Diel movement of smallmouth yellowfish Labeobarbus aeneus in the Vaal River, South Africa

Diel movements of Orange–Vaal smallmouth yellowfish Labeobarbus aeneus (Burchell, 1822) in the Vaal River, South Africa, were determined by externally attaching radio transmitters to 11 adult fish and manually tracking them between March and May 2012. Twenty-four radio telemetry monitoring surveys produced 2 304 diel tracks. At night, yellowfish displayed a preference for slow shallow (<0.3 m s−1, <0.5 m) and fast shallow habitats (>0.3 m s−1, <0.3 m), whereas by day they avoided these habitats, preferring fast deep areas (>0.3 m s−1, >0.3 m). The average total distance of 272 m moved per 24-hour period was three times greater than the diel range, and the average maximum displacement per minute was significantly higher in daytime (4 m) than at night (1.5 m). These findings suggest that L. aeneus is active primarily during the day in fast-flowing, deeper waters, and relatively inactive at night, when it occupies shallower habitats. This behaviour should be further explored to identify causal mechanisms underlying the diel habitat shifts in this species such as water temperature, foraging tactics and/or predator avoidance.

Seasonal occurrence and microhabitat specificity of Paradiplozoon ichthyoxanthon Avenant-Oldewage in Avenant-Oldewage et al., 2014 (Monogenea: Diplozoidae) infecting Labeobarbus aeneus (Burchell) (Teleostei: Cyprinidae) from the Vaal Dam, South Africa: water quality and host size as determining factors?

This is the first study detailing the microhabitat specificity of the monogenean parasite, Paradiplozoon ichthyoxanthon Avenant-Oldewage in Avenant-Oldewage et al., 2014. Samples of the monogenean were collected from the gills of the smallmouth yellowfish Labeobarbus aeneus (Burchell) from the Vaal Dam, South Africa, over four seasons with the use of gill nets. Host condition factor fluctuated between the different seasons, with the highest values recorded in summer. Adults and diporpas of P. ichthyoxanthon were found in all four seasons. Adult parasites predominantly infect the first gill arch, whereas diporpas were found on the second and fourth arches. In utero eggs were also found throughout the sampling seasons and their number negatively correlated with the condition factor of the host. The occurrence of adults and diporpas of P. ichthyoxanthon correlated with the size of the host but not the condition factor. Water quality of the study site also had little correlational relationship with the occurrence of the parasites and fluctuations were related to season. The main factor that may drive the microhabitat specificity of P. ichthyoxanthon is the flow of water over the surfaces of the gills and chances of the parasites becoming dislodged. Size of the attachment organs has also been shown to play a role in this specificity, because smaller attachment structures favour stronger holdfast to areas where flow might be stronger compared to larger attachment structures.

Success of a large riverine cyprinid smallmouth yellowfish Labeobarbus aeneus in a southern African impoundment

AbstractRheophilic cyprinids have been detrimentally affected by impoundments, which alter flow regimes, the physical environment and block migration routes. Initial evidence for a southern African cyprinid, smallmouth yellowfish Labeobarbus aeneus, suggested that dependence on riverine spawning areas limits their success within the turbid impoundments of the Orange River system. However, well‐established impoundment populations have since been documented. A comprehensive assessment of L. aeneus biology and population dynamics was undertaken to understand the drivers of successful colonisation in Lake Gariep, South Africa's largest impoundment. Labeobarbus aeneus exhibited slow growth, delayed maturity and longevity, most likely resulting in slow population growth rates. Highest adult and juvenile abundances were observed &gt;100 km from the inflowing Orange River during the peak and post‐spawning seasons, respectively, suggesting that the species displays high ecological plasticity and may not be dependent on inflowing rivers for spawning. Meta‐analyses of life history parameters indicated consistency among riverine and lacustrine populations. Although experiencing an initial lag phase, L. aeneus has successfully adapted to the lacustrine environment.

Physiological response of one of South Africa’s premier freshwater sport angling species, the Orange-Vaal smallmouth yellowfish Labeobarbus aeneus, to catch-and-release angling

The practice of catch-and-release fishing has been widely promoted by angling fraternities as a fisheries manage- ment tool. The aim of this investigation was to determine the physiological response of Orange-Vaal smallmouth yellowfish, Labeobarbus aeneus, to catch-and-release angling in the Vaal River, South Africa. Fish were collected using standard fly-fishing techniques, anaesthetised in clove oil and blood was drawn from the caudal vein; thereafter the fish were weighed, measured, revived and released. Blood plasma was analysed for concentra- tions of glucose, cortisol and lactate to determine the effects of angling duration, fish size and water tempera- ture. Larger fish were angled for a longer duration compared with smaller fish. Levels of glucose were affected by water temperature (influenced by time of year). Plasma glucose concentrations decreased with greater angling duration. Few individuals (n = 12) showed increased plasma cortisol concentrations. In extended-capture fish (angled for >1 min), lactate concentrations increased significantly above values for rapid-capture fish (angled for >30 s). These data suggest that catch-and-release causes physiological stress to fish, but nonetheless this practice can be a valuable fisheries management tool to ensure the sustainability of fish populations. Other factors beyond the ‘angling’ time are likely to contribute to physiological disruptions in homeostasis and therefore handling and air exposure of angled fish should be included in future catch-and–release angling studies. In addition, the longer-term impact of angling on fish health should also be determined.

Aspects of the morphology of the juvenile life stages of Paradiplozoon ichthyoxanthon Avenant-Oldewage, 2013 (Monogenea: Diplozoidae)

There are eight life stages in the life-cycle of Diplozoon paradoxum and limited knowledge of the life-cycle for other diplozoid genera exists. The aim of this study was to record the number of life-stages of Paradiplozoon ichthyoxanthon obtained from, Labeobarbus aeneus and Labeobarbus kimberlyensis, in the Vaal Dam from 2005 to 2007. Six larval life stages and one adult stage of P. ichtyoxanthon were identified from specimens collected in vitro and in situ. In vitro, eggs hatched after 21 days at 18°C. Eggs collected during winter were significantly larger than those laid during spring or summer. Paradiplozoon ichthyoxanthon oncomiracidia have peripheral eyes with pink pigmentation, a tubular anterior bladder-like structure, bicuspid basal pharynx valve and a branched digestive caecum and residual shell material or vitellaria in the caecum. Immature reproductive tissue connected to the ventral sucker and dorsal papillae were noted for the first time in diporpa. Large nervous ganglia and innervation of muscle were observed around the ventral sucker.

Validation of the periodicity of growth increment deposition in otoliths from the larval and early juvenile stages of two cyprinids from the Orange–Vaal river system, South Africa

This study tested the hypothesis that growth increments in larval largemouth yellowfish Labeobarbus kimberleyensis and smallmouth yellowfish L. aeneus from the Orange–Vaal river system, South Africa, are deposited daily. The periodicity of increment formation was determined by regular sampling and counting of increments deposited in the otoliths collected from a total of 52 smallmouth and 41 largemouth laboratory-reared larvae. Increments were counted using a compound light microscope under transmitted light at 100–400 magnification. Linear regression models were fitted to the known age post-fertilisation and the age estimated using increment counts to test the correspondence between the two for each species. Regression models explained 89–99% of the variability in estimated age from increment counts, depending on the upper age cut-off applied to the data. The slopes of the regression models were significantly lower than 1.0, which indicated that increment counts were consistently lower than actual ages and this disparity increased for older individuals. It was, therefore, confirmed that larvae and juveniles of both largemouth and smallmouth yellowfish deposited increments on a near-daily basis, and that counts are a reliable estimate of age up to c. 100 d.

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.

Age, growth rate and size at sexual maturity of Labeobarbus aeneus (Teleostei: Cyprinidae) in the middle Vaal River, South Africa

Age structure, growth and size at sexual maturity of smallmouth yellowfish, Labeobarbus aeneus (Burchell), were assessed in 2008–2009. Despite its angling and food importance, little has been published on many aspects of its ecology and biology, specifically its age structure in the Vaal River system. Of 193 L. aeneus collected by gillnetting, 96 were assessed for sexual maturity, and ages were estimated using scales (n = 143) and whole otoliths (n = 167). Whole otoliths were found to be the most appropriate method for ageing. Both males and females were present in all age classes, which ranged from 2 to 19 years. Males may live longer (maximum 19 years) than females (maximum 16 years). Fish matured relatively late in life, the males at 3 years and females at 5 years, corresponding to lengths of 254 and 375 mm FL, respectively. Growth was shown to be fairly slow, as asymptotic growth was reached only at 8 years.

Seasonal growth of the attachment clamps of a Paradiplozoon sp. as depicted by statistical shape analysis

Geometric morphometric methods using computer software is a more statistically powerful method of assessing changes in the anatomy than are traditional measurements of lengths. The aim of the study was to investigate whether changes in the size and shape Paradiplozoon sp. permanent attachment clamps could be used to determine the duration of the organsism’s life-cycle in situ. A total of 149 adult Paradiplozoon sp. ectoparasites were recovered from Labeobarbus aeneus and Labeobarbus kimberlyensis in the Vaal Dam. The software tool tpsDIG v.2.1 was used on six digitised landmarks placed at the junctures between the sclerites of the attachment clamps from digital micrographs. The tpsSmall v. 2.0 and Morphologika 2 v. 2.5 software tools were used to perform principal component analysis (PCA) on this multivariate dataset. The PCA analysis indicated that the increase in size and linear change in shape of the selected landmarks, were significant predictors of the sampling season. This study suggests that it takes one year for the permanent attachment clamps of a Paradiplozoon sp. to grow to their maximum size in the Vaal Dam. Key words: Diplozoidae, Labeobarbus aeneus, Labeobarbus kimberlyensis , Vaal Dam, morphometrics.