Isolation and molecular identification of planctomycete bacteria from postlarvae of the giant tiger prawn, Penaeus monodon

Bacteria phenotypically resembling members of the phylogenetically distinct planctomycete group of the domain Bacteria were isolated from postlarvae of the giant tiger prawn, Penaeus monodon. A selective medium designed in the light of planctomycete antibiotic resistance characteristics was used for this isolation. Planctomycetes were isolated from both healthy and monodon baculovirus-infected prawn postlarvae, The predominant colony type recovered from postlarvae regardless of viral infection status was nonpigmented. Other, less commonly observed types were pink or orange pigmented, A planctomycete-specific 16S rRNA-directed probe was designed and used to screen the isolates for their identity as planctomycetes prior to molecular phylogenetic characterization. 16S rRNA genes from nine prawn isolates together with two planctomycete reference strains (Planctomyces brasiliensis and Gemmata obscuriglobus) were sequenced and compared with reference sequences from the planctomycetes and other members of the domain Bacteria, Phylogenetic analyses and sequence signatures of the 16S rRNA genes demonstrated that the prawn isolates were members of the planctomycete group, Five representatives of the predominant nonpigmented colony type were members of the Pirellula group within the planctomycetes, as were three pink-pigmented colony type representatives. Homology values and tree topology indicated that representatives of the nonpigmented and pink-pigmented colony types formed two discrete clusters within the Pirellula group, not identical to any known Pirellula species, A sole representative of the orange colony type was a member of the Planctomyces group, virtually identical in 16S rDNA sequence to P. brasiliensis, and exhibited distinctive morphology.

Net uptake of dissolved free amino acids by the giant clam, Tridacna maxima: alternative sources of energy and nitrogen?

The role of dissolved free amino acids (DFAA) in nitrogen and energy budgets was investigated for the giant clam, Tridacna maxima, growing under field conditions at One Tree Island, at the southern end of the Great Barrier Reef, Australia. Giant clams (121.5-143.7 mm in shell length) took up neutral, acidic and basic amino acids. The rates of net uptake of DFAA did not differ between light and dark, nor for clams growing under normal or slightly enriched ammonium concentrations. Calculations based on the net uptake concentrations typical of the maximum concentrations of DFAA found in coral reef waters (similar to 0.1 mu M)revealed that DFAA could only contribute 0.1% and 1% of the energy and nitrogen demands of giant clams, respectively. These results suggest that DFAA does not supply significant amounts of energy or nitrogen for giant clams or their symbionts.

Influence of field-based nutrient enrichment on the photobiology of the giant clam Tridacna maxima

Nutrients were added to 12 microatolls in One Tree Island lagoon every low tide for 13 mo to an initial concentration of 10 mu M (ammonium, N) and 2 mu M (phosphate, P). These concentrations remained above background for 2 to 3 h after addition. The addition of ammonium (N and NI-P but not P alone) significantly increased P, (gross photosynthesis) P,, (net photosynthesis) and R (respiration) per unit wet-tissue weight and cc (photosynthetic efficiency) in Tridacna maxima after 3 mo nutrient enrichment. These responses to small and transient changes in ammonium concentrations suggest that symbiotic clams are not nutrient-replete, and that even subtle changes in nutrients can have a measurable effect on photosynthesis. The same clams did not show significant differences in photosynthetic parameters 6 mo after the beginning of nutrient enrichment, suggesting that their previous responses had either been seasonal or that symbiotic clams such as T. maxima are able to adjust their photophysiology following external changes in nutrient concentrations.

Osmoregulation of the Australian freshwater crocodile, Crocodylus johnstoni, in fresh and saline waters

An unusual saltwater population of the "freshwater" crocodilian, Crocodylus johnstoni, was studied in the estuary of the Limmen Bight River in Australia's Northern Territory and compared with populations in permanently freshwater habitats. Crocodiles in the river were found across a large salinity gradient, from fresh water to a salinity of 24 mg.ml-1, more than twice the body fluid concentration. Plasma osmolarity, concentrations of plasma Na+, Cl-, and K+, and exchangeable Na+ pools were all remarkably constant across the salinity spectrum and were not substantially higher or more variable than those in crocodiles from permanently freshwater habitats. Body fluid volumes did not vary; condition factor and hydration status of crocodiles were not correlated with salinity and were not different from those of crocodiles from permanently fresh water. C. johnstoni clearly has considerable powers of osmoregulation in waters of low to medium salinity. Whether this osmoregulatory competence, extends to continuously hyperosmotic environments is not known, but distributional data suggest that C. johnstoni in hyperosmotic conditions may require periodic access to hypoosmotic water. The study demonstrates a physiological capacity for colonisation of at least some estuarine waters by this normally stenohaline freshwater crocodilian.

Glossocercus chelodinae (MacCallum, 1921) n. comb. (Cestoda : Dilepididae) from freshwater turtles in Australia and a redefinition of the genus Bancroftiella Johnston, 1911

Glossocercus chelodinae (MacCallum, 1921) n. comb. is redescribed from fresh material recovered from the intestine of an Australian freshwater turtle, Chelodina expansa. G. chelodinae can be distinguished from all other species of the genus by the shape of its rostellar hooks. it is suggested that this species has colonised fish-eating turtles from fish-eating birds. The morphological relationships among Parvitaenia, Bancroftiella and Glossocercus are discussed. The diagnosis of Bancroftiella is amended and marsupials are eliminated as hosts. Bancroftiella sudarikovi Spasskii & Yurpalova, 1970 becomes a synonym of Glossocercus glandularis (Fuhrmann, 1905); only B. tennis Johnston, 1911, the type-species, and B. ardeae Johnston, 1911 remain in the genus.

Giant protein kinases: Domain interactions and structural basis of autoregulation

The myosin-associated giant protein kinases twitchin and titin are composed predominantly of fibronectin- and immunoglobulin-like modules, We report the crystal structures of two autoinhibited twitchin kinase fragments, one from Aplysia and a larger fragment from Caenorhabditis elegans containing an additional C-terminal immunoglobulin-like domain, The structure of the longer fragment shoes that the immunoglobulin domain contacts the protein kinase domain on the opposite side from the catalytic cleft, laterally exposing potential myosin binding residues, Together, the structures reveal the cooperative interactions between the autoregulatory region and the residues from the catalytic domain involved in protein substrate binding, ATP binding, catalysis and the activation loop, and explain the differences between the observed autoinhibitory mechanism and the one found in the structure of calmodulin-dependent kinase I.

The Asian fish tapeworm, Bothriocephalus acheilognathi, in Australian freshwater fishes

Bothriocephalus acheilognathi was collected from 13 of 38 carp (Cyprinus carpio), 2 of 4 mosquito fish (Gambusia holbrooki), and 2 of 12 western carp gudgeon (Hypseleotris klunzingeri) in waterways of the Australian Capital Territory and New South Wales. This is the first record of this parasite in Australia, and its presence in H. klunzingeri is a new host record. B. acheilognathi presumably arrived in Australia with its introduced fish hosts and has since crossed into native fishes, This cestode may infect other native fish species, a potential that is significant given the high pathogenicity associated with infection in other known hosts.

A systemic parvo-like virus in the freshwater crayfish Cherax destructor

Systemic Cowdry Type A inclusions (CAs) were observed in a moribund Cherax destructor collected at an aquaculture farm in South Australia. Inclusions were most common in the gills and were associated with multifocal necrosis of the main gill axis and lamellae. The hepatopancreas was necrotic; however, only one CA was observed in the interstitial tissues. CAs were associated with necrosis in the abdominal and gut musculature. CAs were also observed in the spongy connective tissues and the epicardium. Empty capsids (17.5 +/- 0.5 nm) and microfilaments were most commonly observed within these inclusions by transmission electron microscopy. Complete icosahedral viral particles (20.8 +/- 1.2 nm) were difficult to distinguish within the viroplasm, but were visualised better in aggregates between the viroplasm and the inner nuclear membrane. The nucleolus was closely associated with the developing viroplasm, and was hypertrophied and segregated into its fibrillar and granular components. The virus was named Cherax destructor systemic parvo-like virus (CdSPV) on the basis of its histopathology, cytopathology and morphology. CdSPV is the first systemic virus described in a freshwater crayfish.

Notopronocephalus peekayi gen. et sp. n. (Digenea: Pronocephalidae) from Australian freshwater turtles

Notopronocephalus peekayi gen, et sp, n. is described from the intestine of Elseya latisternum Gray, 1867, E. dentata (Gray, 1863) and Emydura signata Ahl, 1932 from rivers in Queensland. The new genus is distinguished by the absence of ventral glands, simple (neither diverticulate nor sinuous) caeca terminating at the anterior margin of the testes, excretory arms not uniting in forebody, single ovary, two opposite testes close to the posterior end of the body, intracaecal genital pore, vitelline follicles anterior to the testes, cirrus-sac orientated obliquely and not divided into two portions, and the uterus intracaecal. This is the first pronocephalid to be described from an Australian freshwater turtle and the first from the family Chelidae.

Development of a genetic method to estimate effective spawner numbers in the NPF and Queensland tiger prawn fisheries

OBJECTIVES: 1. To critically evaluate a variety of mathematical methods of calculating effective population size (Ne) by conducting comprehensive computer simulations and by analysis of empirical data collected from the Moreton Bay population of tiger prawns. 2. To lay the groundwork for the application of the technology in the NPF. 3. To produce software for the calculation of Ne, and to make it widely available.