Aimorn C. Stewart

The nematode fauna of a temperate Australian mangrove mudflat; its population density, diversity and distribution

The nematode fauna of an estuarine mangrove Avicennia marina mudflat in Southeastern Australia has been intensively studied. About 85% of the nematodes occur in the top cm of soft mud, but 5–7 species inhabit the deeper anoxic mud down to 10 cm, both at low and high tide. One square metre was intensively sampled from four zones with different nematode faunas. At the low tide zone 58% of the nematodes were epistrate feeders, including many diatom-feeders, but in the mangrove zone selective microbial feeders made up over 60% of the population, while between high water neap and high water spring, above the mangrove zone, omnivore/predators and plant root feeding nematodes increased in relative importance. Random replicate cores reliably sampled species occurrence, but gave a high variance in density estimates. Replicate aliquots from homogenised mud gave lower density variance. Nematode densities (maximum 5 × 106 m-2) were not as high as have been reported from non-mangrove estuaries in other countries, but were within the range found in mangroves elsewhere in Australia. Margalef Species Richness values ranged from 1.7 to 3.89, which is similar to values found in other mangroves mudflats in Australia. Nematode biomass ranged from 888 mg dry weight m2 (383 mg C m-2) at the low tide zone to 19 mg dry weight m-2 (8 mg C m-2) at the upper tide level.

The Mineral Composition of Intracellular Inclusions in Nematodes From Thiobiotic Mangrove Mud-Flats

Some marine nematodes from anoxic mangrove mud-flats contain densely packed intracellular inclusions within their tissues which are visible by light microscopy. Transmission electron microscopy of sections of Sabatieria wieseri, Terschellingia longicaudata and Sphaerolaimus papillatus shows these inclusions within the intestinal and other cells. Energy dispersive analysis of secondary X-rays by scanning electron microscopy of thick epoxy sections shows concentrations of Si, P, S, K, Ca and Fe in their tissues. EDS of secondary X-ray emissions from thin epoxy unstained sections by transmission electron microscopy shows these elements together with Na, Zn and Al concentrated in the intracellular inclusions. The physiological implications of these observations are discussed.

The nematode fauna of the Murray River estuary, South Australia; the effects of the barrages across its mouth

The littoral nematode fauna of the Murray River, South Australia, above and below the barrages that control the outflow of the river into the Southern Ocean has been investigated by taking cores of the sediment at monthly intervals for one year. Samples of river water were taken at the same time for chemical analysis and sediment particle size has also been investigated.At two sites below the barrages the salinity varied depending on the volume of water discharged through the barrages. It rose almost to that of sea water while they remained closed, but fell to that of the river water when they were all open and discharging large volumes of river water. The nematode population fluctuated from about 12 200 to 180 000 m-2 for nine months, but the numbers of live nematodes fell sharply in July through to September, accompanied by heavy nematode mortality, reaching 100% at one site in August. We attribute the mortality to a prolonged discharge of river water. More than 40 genera have been identified, most with cosmopolitan distributions.Above the barrages, at Mundoo and on Lake Alexandrina the water is fresh river water. The fauna was less dense than that below the barrages; with a maximum of 10000 m-2. It comprised genera typical of freshwaters overseas (no comparable studies of Australian freshwater nematodes have been reported), such as Eutobrilus, Tripyla and Ironus, together with two species from typical marine genera, i.e. Mesacanthion and Enoploides. The latter species is very similar to E. fuviatilis from the Volga river.It is suggested that low population density below the barrages, when compared with other estuaries, reflects periodic mortality in estuarine nematodes when salinity falls drastically, whilst above the barrages there is a mixture of tolerant estuarine and typical freshwater nematodes.

The Calorific Value of Caenorhabditis Elegans (Rhabditidae)

The calorific value of populations of Caenorhabditis elegans was measured by bomb-calorimetry. A value of 27.59 kj per g ash-free dry weight was obtained (= 6,316 calories per g). This value is high, but agrees well with calculations based on previously published analyses of lipid and glycogen reserves in Caenorhabditis sp. It is suggested that when harvested from a rich culture of bacteria Caenorhabditis has substantial lipid reserves accounting for its high calorific value.

Field and Laboratory Studies of Desmodora Cazca Gerlach, 1956 (Desmodoridae: Nematoda) From Mangrove Mud-Flats

Desrnodora cazca is widely distributed in Australia in mangrove mud-flats. Observations are made on its morphology by light and scanning electron microscopy. Its population density and distribution have been studied in a localised area on the Clyde River estuary in S.E. New South Wales, Australia. Quite large fluctuations were observed over the course of several years but at any one time its distribution within the mangroves was fairly uniform. It reproduces throughout the year. Estimates are given of its biomass, carbon and nitrogen content and oxygen consumption per m 2 . In laboratory culture it requires particles less than 200 μm and reproduces when fed with the diatom Cylindrotheca sp. Supplying this diatom labelled with [ 14 C]methylglucosc shows that these diatoms are food for D. cazca.

Criconemella a Vicenniae N. Sp. (Nematoda: Criconematidae) and Enchodel Us Coomansi N. Sp. (Nematoda: Nordiidae) Associated With the Roots of the Mangrove Avicennia Marina (Forsk.) Vierh

Two new species of nematode associated with the roots of mangroves, Avicennia marina are described, namely Criconemella avicenniae sp. nov. (Tylenchida, Criconematidae) and Enchodelus coomansi sp. nov. (Dorylaimida, Nordiidae). Both new species were found in the Hunter River estuary in south-eastern Australia where they occur in intertidal mud-flats. Criconemella avicenniae is close to C. goodeyi and C. paragoodeyi, but has more annules than both and different body proportions. Enchodelus coomansi differs from other species in possessing a tail spike in both sexes and in the more numerous medioventral supplements in the male.

Mesocestoides corti in the rat: Comparisons of Mesocestoides corti infections in rats and mice

Abstract Infections of M. corti in rats were compared with those in mice. The recoveries of parasites and their distribution were examined for 60 days after infection. During this period continuous and extensive multiplication occurred in mice. In rats there was an initial multiplication of tetrathyridia in the first 10 days followed by a decline in numbers. The relative distribution of tetrathyridia between the peritoneal cavity and liver was similar in both hosts.