Early development and larval behaviour of a minnow,Barbus anoplus (Pisces: Cyprinidae)

The chubbyhead barb, Barbus anoplus, underwent a population explosion in the early phases of filling of Lake be Roux on the Orange River. This successful colonization was possibly related to the survival strategy of the young stages of this minnow. It is suggested that some of the development traits of B. anoplus enabled it to become the most widespread freshwater fish species south of the Limpopo River. The development and behaviour of embryos and larvae of B. anoplus are described and discussed with reference to their survival strategy and potential colonizing ability. Some of the protolarvae were pelagic and the relevance of this behaviour is noted.     

A new Barbus minnow (Pisces,Cyprinidae) from the eastern Cape Province,South Africa

A new cyprinid minnow taken from a tributary of the Kei River system, eastern Cape Province, Barbus amatolicus sp. nov., is described. The Amatola barb is most similar to the widespread and sympatric chubbyhead barb (Barbus anoplus) and the redtail barb (Barbus gumeyl) but differs most clearly in male secondary sexual characteristics (breeding colours and nuptial tubercles).     

The application of hCG, CPH and Ovopel in successful artificial reproduction of goldfish (Carassius auratus auratus) under controlled conditions

Artificial reproduction of fish is one of the main goals of aquaculture production. The aim of this study is to optimize the method of goldfish reproduction under controlled conditions by comparing the effectiveness of carp pituitary homogenate (CPH), Ovopel and human chorionic gonadotropin (hCG), administered as a one-off dose and inducing two spawns in the same fish within a short time period. Goldfish spawners were stimulated with hCG, CPH and Ovopel, and the results were compared to the fish from the control group, comprised of unstimulated fish. In another experiment, spawn were induced twice within an interval of 21 days with the same group of fish. The best results in the first experiment in terms of the percentage of ovulating females and survival to the eyed-egg stage were achieved after administering hCG (100% and 88.7%, respectively). However, the highest fecundity was observed in fish stimulated with Ovopel (89,960 eggs/kg). It was shown in the second experiment that female goldfish produce higher weight of eggs during the first spawning, but the number of eggs/BW ratio was higher during the next reproduction process. Survival, both that of embryos to the eyed-egg stage and that of spawners, is higher during the first reproduction act.     

Preliminary Observations on the Relationships of Barbus Species From Cape Coastal Rivers,South Africa (Cypriniformes: Cyprinidae)

Observations on the phylogenetic relationships of Barbus species from the southern Cape Province are made in the light of new data on the post-cranial axial skeleton and other osteological and anatomical features. Particular attention is paid to the relationships of the ‘red fin’ Barbus species, and new evidence on the problematical relationships of the rare African cyprinid species Oreodaimon quathlambae, is presented.     

The effect of temperature on the rate of passage of food in the smallmouth yellowfish,Barbus aeneus Burchell (Teleostei,Cyprinidae)

The effect of temperature on the rate of gut evacuation in Barbus aeneus was investigated in two ways. In the first, juvenile fish, kept under conditions of constant temperature, were fed marked food items and the time elapsing until these appeared in the faeces was noted. In the second, fish of a range of sizes were caught in the P.K. le Roux dam and immediately placed in cages in the dam to prevent their access to food. Groups of fish were sacrificed at intervals and the contents of standardized gut sections weighed. The field experiment was carried out in summer and in winter. The laboratory experiment yielded the relationship: P = 6270 × t^-2,11 where P is the passage time in hours and T is the temperature in °C. This gives passage times of the order of 8 h at 25°C and 39 h at 11,5°C. The field experiment indicated that there was an exponential relationship between degree of fullness and rate of evacuation, and that complete evacuation required about 24 h in summer, but more than 5 days in winter.     

Aspects of the biology of a rare redfin minnow,Barbus burchelli (Pisces,Cyprinidae), from South Africa

Burchell's redfin, Barbus burchelli is endemic to the Breede River and adjacent smaller river systems in the Cape Province. Negative human influences have led to a drastic decline in numbers of this medium-sized minnow, especially agricultural demand on the water resource and the introduction of exotic predatory fish. The breeding season is extended, from September to February, with a peak in December. The absolute fecundity of a 123 mm FL specimen was 10 678, which includes both mature and recruitment ova. Females grow larger (123 mm FL), and live longer (6 +years), than males (113 mm FL and 4 + years). 8. burchelli grow rapidly in their first year attaining a length of between 40 and 50 mm FL. Pronounced conical tubercles of sexually mature males erupt in spring, begin to show signs of wear in November and by March are worn or sloughed off. The survival of this species is dependent upon proper management of the Breede River system.     

Retroviruses of wild and cultured fish

Retroviruses comprise a large group of enveloped RNA viruses which have been found in a wide range of vertebrate species including fish. To date a number of fish retrovirus genomes have been partially or completely sequenced. Phylogenetic analysis and genome organization indicate a high diversity of fish retroviruses as well as some unique structural features that have not been found in any other retroviruses. Piscine retroviruses comprise both exogenous and endogenous viruses; most of them are associated with proliferative diseases. Because several of these proliferative diseases have a seasonal trend, they provide an excellent model for studying tumor development and regression. The aim of this work was to review the best-described fish retroviruses.     

Survival of Isospora suis oocysts under controlled environmental conditions

Isospora suis is a coccidian parasite infecting piglets soon after birth. While the gross epidemiology of I. suis is well known, little knowledge exists on the ecology of the oocysts. To study the development and survival of oocysts of I. suis under controlled laboratory conditions, known numbers of oocysts ( approximately 200 in each of 4 replicates) were exposed to all combinations of 4 relative humidities (53-100% RH) and 3 temperatures (20 degrees , 25 degrees , 30 degrees C). Determination of viability was based on morphological and fluorescent properties of the oocyst as well as on the permeability of the oocyst wall characterized by inclusion/exclusion of the fluorescent dye propidium iodide. The viability of the oocysts was studied over time by fluorescence and light microscopy until <5% of the oocysts were considered to be viable. The sporulation rate increased with temperature, however, the infective sporocyst stage was reached within 24h at all temperatures, while RH did not seem to affect sporulation. Results show a rapid reduction in viable oocysts exposed to high temperatures (25 degrees C and 30 degrees C) in combination with low relative humidities (53% RH and 62% RH), at which conditions oocysts died within 24h. Viability was higher when oocysts were exposed to higher relative humidities (75% RH and 100% RH) as well as a lower temperature (20 degrees C). However, even at 75% RH the oocysts died within 24-60 h at 30 degrees C to 20 degrees C, respectively, while the most favourable condition appeared to be 100% RH and 25 degrees C at which condition the percentage of viable oocysts decreased from 100% to 17% in 96 h. The results indicate that it may be possible to reduce the infection pressure of I. suis in modern sow herds by changing the environmental conditions and/or the management within the farrowing pens, and thereby increase animal welfare without relying on the use of routine medication.     

Some Blood Parameters of the Yellowfish (Barbus Holubi) and the Barbel (Clarias Gariepinus)

Haemoglobin concentrations, haematocrit values, red blood cell counts, red blood cell diameter, white blood cell counts and plasma haemoglobin concentrations were performed on the yellowfish (Barbus holubi) and the barbel (Clarias gariepinus). Wide variations were observed in haematocrit values and haemoglobin concentrations and statistically significant correlations existed between mean corpuscular volume and average corpuscular haemoglobin and between the red blood cell count and mean corpuscular volume in the case of the yellowfish and between the red blood cell count and haemoglobin concentration in the case of the barbel. It was found that the determination of one variable is not sufficient for the routine assessment of other haematological parameters in these fish due to poor correlations observed. This can only be done in the case of the variables mentioned.     

Evaluation of an atrophic rhinitis vaccine under controlled conditions.

A vaccine containing inactivated cultures of Bordetella bronchiseptica, toxigenic Pasteurella multocida type D and dermonecrotic P multocida type D toxoid in an oil-in-water adjuvant was given to seven sows, with seven others acting as controls. Half the piglets in each litter were exposed intranasally when four days old to B bronchiseptica and when eight days old to toxigenic P multocida type D. There was considerably less sneezing in the litters of the vaccinated sows and when the piglets were 10 weeks old, only 18 per cent had deformed snouts compared with 74 per cent in the litters of the control sows. The average liveweight gain of the piglets born to vaccinated sows was significantly better (P less than 0.05) between two and 10 weeks of age than that of the piglets born to unvaccinated sows, although there were no significant lower respiratory tract lesions in either group. The conchal atrophy scores were significantly lower (P less than 0.001) in the piglets from the vaccinated sows and were negatively correlated (r = -0.37) with increasing liveweight gain. In the liters of the vaccinated sows, P multocida was not isolated from the nasal passages of the in-contact piglets and from only 7 per cent of those deliberately exposed compared with 65 per cent and 79 per cent, respectively, in the litters of the control sows. P multocida was isolated post mortem from the tonsils of 23 per cent of the piglets of vaccinated sows and from 87 per cent of those from unvaccinated sows.     

The association between body strike and dermatophilosis of sheep under controlled conditions

The association of dermatophilosis with body strike of sheep caused by Lucilia cuprina was studied in a controlled environment. When sheep with areas of wet normal fleece and areas of wet fleece containing scabs induced by infection of the skin with Dermatophilus congolensis were exposed to gravid L. cuprina the files oviposited only on dermatophilosis-affected areas. In wet dermatophilosis-affected fleece, naturally oviposited L. Cuprina eggs hatched and the larvae developed to the second instar stage. Artificially implanted L cuprina eggs hatched in both wet dermatophilosis-affected fleece and wet normal fleece. In wet dermatophilosis-affected fleece the larvae from implanted eggs developed normally but in wet normal fleece they did not develop past the first instar stage. It was concluded that wet but otherwise uncomplicated dermatophilosis lesions are attractive to L. cuprina and provide sufficient protein to allow larval development to take place.     

Lamproglena hoi n.sp. (Copepoda: Lernaeidae) from two yellowfish hosts, Barbus marequensis and Barbus polylepis, caught in a river in Mpumalanga, South Africa.

Lamproglena hoi n.sp. species was collected from the gill filaments of largescale yellowfish, Barbus marequensis A. Smith, 1841 and smallscale yellowfish, Barbus polylepis Boulenger, 1907 from the Spekboom River, Mpumalanga, South Africa. The genus Lamproglena is characterized. Morphological features of L. hoi are described and illustrated by means of drawings and scanning electron micrographs. This species is also compared with congener species described from other Barbus spp.     

Basic reproduction number of African swine fever in wild boars (Sus scrofa) and its spatiotemporal heterogeneity in South Korea

BackgroundAfrican swine fever (ASF) is a hemorrhagic fever occurring in wild boars (Sus scrofa) and domestic pigs. The epidemic situation of ASF in South Korean wild boars has increased the risk of ASF in domestic pig farms. Although basic reproduction number (R₀) can be applied for control policies, it is challenging to estimate the R₀ for ASF in wild boars due to surveillance bias, lack of wild boar population data, and the effect of ASF-positive wild boar carcass on disease dynamics.ObjectivesThis study was undertaken to estimate the R₀ of ASF in wild boars in South Korea, and subsequently analyze the spatiotemporal heterogeneity.MethodsWe detected the local transmission clusters using the spatiotemporal clustering algorithm, which was modified to incorporate the effect of ASF-positive wild boar carcass. With the assumption of exponential growth, R₀ was estimated for each cluster. The temporal change of the estimates and its association with the habitat suitability of wild boar were analyzed.ResultsTotally, 22 local transmission clusters were detected, showing seasonal patterns occurring in winter and spring. Mean value of R₀ of each cluster was 1.54. The estimates showed a temporal increasing trend and positive association with habitat suitability of wild boar.ConclusionsThe disease dynamics among wild boars seems to have worsened over time. Thus, in areas with a high elevation and suitable for wild boars, practical methods need to be contrived to ratify the control policies for wild boars.     

Reproduction of Labeo umbratus (Pisces,Cyprinidae) in Wuras Dam,a shallow,turbid impoundments

Female Labeo umbratus reach sexual maturity at a larger size than males and dominate the population in fish over 450 mm in length. The gonads are large (up to 20% of total body mass) and they have a high fecundity which increases linearly with an increase in body mass. Successful spawning is dependent on suitable floods during the spawning season which extends from November to March or April. Spawning apparently occurred in the impoundment. All females did not spawn simultaneously and evidence suggests that individuals might spawn more than once during a particular season.     

Growth of Serpulina (Treponema) hyodysenteriae under iron-restricted conditions.

Reference strains of Serpulina hyodysenteriae expressed at least three iron-regulated proteins with apparent molecular masses of > 200, 134, and 109 kDa when grown under iron-restricted conditions. Cells of S. hyodysenteriae grown under these conditions also showed increased outer membrane bleb formation when examined by electron microscopy after negative staining. S. hyodysenteriae did not use the 2 most common types of siderophore, namely catechol and hydroxamate. Western blotting with serum from a pig experimentally infected with S. hyodysenteriae B204 indicated that the 109-kDa major iron-regulated protein was expressed in vivo and was conserved among all strains tested.