Food and feeding habits of Oreochromis mossambicus (Peters) in hypertrophic Hartbeespoort Dam,South Africa

The diet of 745 Oreochromis mossambicus (Peters) of less than 0,5 up to 2000 g wet mass, in Hartbeespoort Dam, was determined from stomach content analysis. Samples of fish were selected to cover a whole annual cycle. Small fish fed initially on zoobenthos and zooplankton, but fish with a mass of over 4 g fed increasingly on Microcystis aeruginosa Kutzing and detritus until these food items formed the dominant food source in O. mossambicus over 8 g. Some cannibalism was encountered in fish up to 64 g in the summer months. The ratio of intestinal length to total length of fish ranged from 0,58 in the smaller fish to 11,02 in larger fish and this indicated that there was an ontogenetic adaptation from a carnivorous to a phytoplanktivorous/detritivorous diet. Feeding in juvenile fish studied over 24 h was found to be most intense in the early morning and late afternoon but remained high throughout daylight hours decreasing considerably at night. The daily ingestion rate of food in O. mossambicus in Hartbeespoort Dam was estimated at 453 mg/g of fish. This comprised 45% M. aeruginosa and 55% detritus. It was apparent that of this matter ingested only a small percentage would be assimilated. Oreochromis mossambicus shows feeding and breeding preadaptations which enable it to successfully exploit a lacustrine environment. These adaptations enable it to maintain a large population in Hartbeespoort Dam despite frequent winter mortalities caused by water temperatures below their tolerance limits.     

Movements of deep-sea red crab (Geryon maritae) off South West Africa/Namibia

Of 10 246 red crabs tagged between 1979 and 1984 on the continental slope of Namibia, a total of 1 604 were recaptured by commercial fishermen. Three tagging methods were tested. The most effective method was by inserting the tag through the epimeral suture. Though tagged crabs were released over a range of depths (from 400 to 900 m), the distances that they covered while at large were found to be unrelated to the depth at which they were released. No significant differences were found for distances moved by males compared to immature females, but differences (P< 0,01) did indicate that large males (≥105 mm carapace width (CW)) move farther than small males. Mature females moved significantly farther (P< 0,001) than the other crabs and over 32% moved > 100 km. The farthest distance covered by a single crab was 380 km. No seasonal trends regarding distances or direction moved were noted for either sex or size groupings examined. Mature females did show a tendency, although unrelated to season, to move northwards. Movements of crabs by depth suggested that, although crabs of all sizes and sexes move freely between depths, small males (< 100 mm CW) do tend to favour deeper water than larger males and vice versa. Female crabs tend to favour shallow depths and, of those tagged at 800 and 900 m, over 60% were recaptured shallower than 700 m. Based on the results of this study, it is considered that the movement patterns of G. maritae could best be described as nomadic. A possible reason for the fact that mature females display different movement patterns compared to other crabs in the population is discussed, as are possible implications to the fishery of crab movements between Namibia and Angola     

West Nile virus infection of Thoroughbred horses in South Africa (2000-2001)

REASONS FOR PERFORMING STUDY: West Nile virus (WNV) infection is endemic in southern Africa. With the recent emergence of WNV infection of horses in Europe and the USA the present study was performed to estimate the risk of seroconversion to WNV in a cohort of 488 young Thoroughbred (TB) horses. OBJECTIVES: To estimate the risk of seroconversion to WNV among a cohort of South African TB yearlings sold at the 2001 National Yearling Sales (NYS) and to determine whether the risk varied geographically. Two horses were also infected with a recent South African isolate of WNV to evaluate its virulence in horses. METHODS: Serum samples were collected from the cohort of 488 TB yearlings at the 2001 NYS. Serum samples that were collected from the same horses at the time that they were identified were sourced from our serum bank. Sera from 243 of the dams that were collected at the time that the foals were identified were also sourced from our serum bank. These sera were subjected to serum neutralisation (SN) tests for antibody to WNV. RESULTS: Approximately 11% of yearlings seroconverted to WNV on paired serum samples collected from each animal approximately 12 months apart. Studfarms with WNV-seropositive yearlings were widely distributed throughout South Africa and SN tests on sera from their dams indicated that exposure to WNV was even more prevalent (75%) in this population. Neurological disease was not described in any of the horses included in this study and 2 horses inoculated with a recent lineage 2 South African isolate of WNV showed no clinical signs of disease after infection and virus was not detected in their blood. CONCLUSIONS: Infection of horses with WNV is common in South Africa, but infection is not associated with neurological disease. POTENTIAL RELEVANCE: In contrast to recent reports from Europe, North Africa, Asia and North America, the results of our field and experimental studies indicated that exposure of horses to the endemic southern African strains of WNV was not associated with neurological disease.     

南非Borakalalo国家公园二斑沙鸡(Pterocles bicinctus)的迁移(英文)

本文旨在描述可能引起南非Borakalalo国家公园内二斑沙鸡(Pterocles bicinctus)迁移行为的内在(繁殖)及外在因素(降雨量及植被情况)。该公园位于西北省比勒陀利亚以北80km,Jericho以北30km处。2010年,采取乘车辆沿固定路线穿越该保护区的方式搜集数据。车速为每小时10km,固定路线长为32km,调查强度为每月2天。二斑沙鸡平均每群2.47个个体。种群内雄性与雌性的比例为1:0.87。该鸟常出现在路边、遭踩踏过的矮草丛中或经焚烧但长出新叶的金合欢丛中。二斑沙鸡在该保护区主要出现在两个相对干燥的季节,即2–3月及7–9月。早晨在该公园的腹地能更多地观察到该鸟,而下午晚些时候,在Klipvoor河坝的水体边则可多见该鸟。讨论了可能影响二斑沙鸡迁移的5个因素,包括年降雨量、雨季中短时雨量大小、2–4km的日间饮水飞行、繁殖及草原植被情况。     

A check-list of the nematode parasites of South African Serpentes (snakes) and Sauria (lizards)

Published records, in combination with own data have been brought together to provide data on parasite/host relationships of reptiles that occur in the Republic of South Africa. A total of 62 nematode species belonging to 23 genera and 11 families are recorded from 20 snake and 21 lizard species. The genera Kalicephalus, Spauligodon, Ophidascaris and Abbreviata are especially well represented with between five and eight species per genus. The most nematode species were recorded from the flap-neck chameleon, Chamaeleo dilepis (eight), the puff-adder, Bitis arietans (eight) and the water monitor, Varanus niloticus (seven). All synonyms of parasites and hosts are given.     

Observations on the Amphipod Parathemisto Gaudichaudi (Guer.) off the West Coast of South Africa

Four distinct types of call are produced by male Ptychadena taenioscelis Laurent in breeding aggregations. The most common of these is the mating call. A male/male interaction or ‘chorus call’ is also produced regularly and its production is dependent on the presence of two or more individuals. A call with a territorial function and the release calls uttered by amplectant males are also described. The responses of calling males to the arrival of females and further males are discussed. Mention is made of the ovipositional behaviour of this species.     

Habitat preferences of three sympatric lacertid lizards in the arid Tankwa Karoo Basin of South Africa

Four lacertid lizards, Pedioplanis laticeps, P. lineo-ocellata, Meroles knoxii and Nucras tessellata, occur sympatrically on the arid plains of the Tankwa Karoo Basin in South Africa. The aim of this study was to determine whether the four species are spatially separated in terms of the microhabitat each species occupies, allowing them to occur in sympatry in this structurally simple system with a limited number of potential niches. The habitat preferences of the four species were investigated on the farm Gansfontein in the southwestern parts of the Tankwa Karoo Basin. The area was surveyed by walking transects through different habitat types and recording all active lizards. For each lizard observed, the species was identified and a photograph was taken of its microhabitat. At the end of the sampling period the microhabitats in which lizards were found were sorted into distinct types on the basis of substrate composition. During the survey, only one individual of N. tessellata was recorded, but sample sizes for the other three species were sufficiently large to provide a clear perspective of habitat segregation among the three species. The results showed that the three species are spatially separated at the study site, with P. lineo-ocellata being restricted to rocky areas, P. laticeps preferring gravel substrates and M. knoxii frequenting sandy areas. Although only anecdotal information is available, all indications are that the observed spatial separation of the three species is mainly the result of historical adaptation to the different substrate types.     

The Relationships of the Avifauna of the South West Arid Area of Africa

Many white-faced whistling ducks (Dendrocygna viduata) have responded to European colonization by overwintering on irrigation and stock-watering ponds in the semi-arid interior of South Africa. I studied the body condition, diet, behaviour and moult intensity of whitefaced whistling ducks prior to departure for breeding areas during spring 1995. Other than higher protein levels in immature males than immature females, there were no sexual differences in body mass or levels of lipid, protein, or ash in adults or immatures. Adults were heavier than immatures and had higher levels of ash. There were no sex- or age-related differences in the proportion of individual food items consumed, 96.6% of which was maize. By foraging on neighbouring agricultural fields, birds were able to spend large portions (80%) of the day/night in comfort-related activities (preen, loaf, sleep) and little time foraging (8.8%) while on ponds. There were no sex- or age-related differences in overall moult intensity score or intensity of moult in 20 feather areas. With exception of primaries and secondaries, birds were moulting moderately to heavily in all feather regions. Agricultural ponds permit whitefaced whistling ducks to overwinter close to breeding areas, while the high availability and energy content of maize enables them to attain higher spring fat levels than birds that overwinter on traditional sites closer to the coast. Intensive agriculture has probably contributed to the population increase and range expansion of white-faced whistling ducks in South Africa.     

First report of Fascioloides magna (Bassi, 1875) in South Africa

Fascioloides magna from a Brahman heifer recently imported from the USA is recorded for the first time in South Africa. The pathological findings are briefly described. The possibility of this parasite becoming established in this country is also discussed.     

A New Species of Parategastes (Copepoda,Harpacticoida) from South Africa

A new species of the genus Parategastes Sars, 1904 (Copepoda, Harpacticoida) was found during an ecological study of zooplankton in Langvlei, one of the Wilderness Lakes near George on the southern Cape coast. The species, Parategastes coetzeel, is described and a key is given for the identification of the various species of Parategastes.     

Nematode parasites of Clarias gariepinus (Burchell, 1822) from the Rietvlei Dam, South Africa

Catfish, Clarias gariepinus, from the Rietvlei Dam near Pretoria, South Africa were examined for nematode parasites. Two species, Procamallanus laeviconchus in the stomach and Contracaecum spp. larvae in the abdominal cavity, were found. The morphology of these species, based on light and scanning electron microscopy, and how they compare with previously described specimens are discussed. Infection rates were mild compared to previous surveys although Contracaecum spp. had a high prevalence of 86%.     

Parasites of South African wildlife. II. Helminths of kudu, tragelaphus strepsiceros, from South West Africa/Namibia

A total of 23 kudu, Tragelaphus strepsiceros, were shot at 2-month intervals from June 1983 to April 1984 in the Etosha Game Reserve in the north of South West Africa/Namibia. The parasite survey conducted on these animals yielded 2 cestode and 12 nematode species. Haemonchus vegliai and Cooperia neitzi were the most prevalent nematodes and occurred in 13 animals each, followed by Cooperia acutispiculum and an Onchocerca sp. (9 animals each). The remaining nematodes were present in 4 (17%) or fewer of the antelope. C. neitzi was the most numerous nematode, a total of 3,564 being recovered from all the antelope, followed by C. acutispiculum (2,552) and H. vegliai (1,050). Individual total worm burdens varied from 4-1,326 with 2 kudu harbouring no worms. The mean burden of 399 worms was considered negligible. A single kudu was shot in the Namib-Naukluft Park in the south of the country. This animal harboured no parasites.     

Status and past and present distribution of elephants in the Kaokoveld,South West Africa/Namibia

The status and the past and present distribution of elephants (Loxodonta africana) in the Kaokoveld are examined. The elephants of the Kaokoveld are divided into a western and eastern ‘resident’ population with a transitional population in between. In 1983, 357 individual elephants were identified with 70 in the western desert-dwelling population, 207 in the eastern population and 80 in the transitional population. A distinction is made between permanent distribution and occasional wanderings. The available records indicate that elephants were present in the northern Namib Desert long before the advent of western man. From the present data it is also clear that man had little or no influence on the occupation of the western areas by elephants, but since 1880 man has caused a decline in elephant distribution and numbers. Currently the elephant’s status there seems relatively stable following intensified law enforcement. However, with the small population sizes, the situation remains vulnerable.     

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).     

Arthropod parasites of Hartmann's mountain zebra, Equus zebra hartmannae, in South West Africa/Namibia

Twelve Hartmann's mountain zebra, Equus zebra hartmannae, were shot for arthropod parasite recovery during the period June 1980-June 1981 on a farm in the Khomas Hochland region of South West Africa/Namibia. Four species of Gasterophilus larvae, 1 species of Rhinoestrus larvae and 3 ixodid tick species were recovered. The seasonal prevalence of the Gasterophilus species larvae and of Rhipicephalus evertsi mimeticus was determined. Three horses examined on the same farm were infested with larvae of 2 Gasterophilus species and with the same ixodid tick species as the zebras.     

Sessile peritrichs (Ciliophora: Peritricha) from freshwater fish in the Transvaal,South Africa

Sessile peritrichs (Ciliophora: Peritricha) were collected from freshwater fish in lakes, rivers, streams and fish-ponds in the Transvaal, South Africa Nine species of the genus Apiosoma Blanchard, 1885 are described, i.e. seven new species; A. caulata sp.n., A. curvinucleata sp.n, A. micralesti sp.n., A. mothlapitsis sp.n., A. obliqua sp.n., A. phiala sp.n. and A. viridis sp.n., and two known species; A. nasal is (Timofeev, 1962) and A. piscícola Blanchard, 1885. One new species of the genus Ambiphrya Baabe, 1952 is described, i.e. A. neobolae sp.n. A new sgenus, Scopulata gen.n. is proposed for species with a broad scopula and compact macronucleus. Two previously described Scyphidia species are incorporated in this genus, i.e. S. dermata (Viljoen & Van As, 1983) comb.n. and S. epibranchialis (Viljoen & Van As, 1983) comb.n., as well as a new species, S. constricta sp.n. Compendiums of all the known fish-associated species of these genera are provided.     

Ectoparasites of dogs belonging to people in resource-poor communities in North West Province, South Africa

A total of 344 dogs belonging to people in resource-poor communities in North West Province, South Africa, was examined for ectoparasites, and all visible arthropods were collected from the left side of each dog. By doubling these numbers it was estimated that the dogs harboured 14,724 ixodid ticks, belonging to 6 species, 1,028 fleas, belonging to 2 species, and 26 lice. Haemaphysalis leachi accounted for 420 and Rhipicephalus sanguineus for 14,226 of the ticks. Pure infestations of H. leachi were present on 14 dogs and of R. sanguineus on 172 dogs. Small numbers of Amblyomma hebraeum, R. appendiciulatus, R. evertsi evertsi and R. simus were also collected. The predominance of R. sanguitneus accounts for the high prevalence of canine ehrlichiosis (Ehrlichia canis) within the survey region, compared to canine babesiosis (Babesia canis), which is transmitted by H. leachi, and is a much rarer disease.     

Burrow architecture of the Damaraland mole-rat (Fukomys damarensis) from South Africa

The burrow architecture (length, internal dimensions, fractal dimension of tunnel systems, number of nesting chambers and surface mounds) was investigated in the Damaraland mole-rat (Fukomys damarensis). A total of 31 animals were caught from five different colonies and their burrow systems were excavated in their entirety. The mean and SD colony size was 6 ± 3.3, with a range of 2–10 mole-rats. The sex ratio tended to be male biased 1.21:1. Males had a body mass of 80.5 ± 33.8 g, but were not significantly different to those of females, which had a mean body mass of 83.4 ± 24.9 g. The burrow system of the Damaraland mole-rats follows the same general architectural plan as recorded for other species of mole-rat with either one or two more centrally based, deeper, more permanent burrows that often connect to a nest area, which is used for resting and rearing offspring. The burrow systems contained several more superficial secondary tunnels at a shallower depth. The secondary tunnels accounted for up to 80% of the total burrow system. The mean length of the burrow system was 130 m and covered an area of 1 403 m². The mean number of secondary branches in a burrow system was 10. The mean fractal dimension was 1.15, which implies the mole-rats do not explore their surrounding environment particularly efficiently when compared with that of other mole-rat species, but this may relate to the size of the main food resource, the Eland bean (Elephantorrhiza elephantina), which is randomly distributed and fed on in situ. Our study showed that colony size influences the size and complexity of the burrow system, with larger colonies having a longer burrow system covering a greater area with more secondary tunnels than that of smaller colonies.