Showing papers by "James Cook University published in 1993"

Utilisation of a tropical bay as a nursery area by sharks of the families Carcharhinidae and Sphyrnidae

Abstract: At least eight species of sharks of the families Carcharhinidae and Sphyrnidae use Cleveland Bay in northern Australia as a communal nursery area.Carcharhinus dussumieri, C. fitzroyensis, C. limbatus andC. tilstoni use the bay as a seasonal primary nursery, with juveniles occurring in it for only a few months each year immediately after birth. Alternatively,Carcharhinus sorrah, Rhizoprionodon acutus andR. taylori use the bay as a year-round primary and secondary nursery, with juveniles remaining in it up to the size at maturity. AdultR. taylori also persist in the bay, a behavioural pattern possibly explained by their small maximum size. While present immediately after birth the type of utilisation pattern displayed bySphyrna lewini could not be clarified in this study. Although diets of these species in the bay are similar, there is probably little direct competition for food due to the highly productive habitats in the bay supporting an abundance of food resources. The highest numbers of juveniles occur when prey species are the most abundant, and when temporal separation of some seasonally-occurring species of sharks in effect.

Sediment-rejection efficiency of 22 species of Australian scleractinian corals

Abstract: Sediment-rejection rates of 22 Australian midshelf coral species were studied in situ between March and July 1988 at Lizard Island, Great Barrier Reef. Rejection rates of non-branching species were positively correlated with calice size and were faster for fine (63 to 250 μm) than for coarse (500 to 1000 μm) sediment at influxes of 200 mg/cm2. Increasing water turbulence was a more important influence on rejection rates for some species than for others. Most replicates of most species cleared all sediment in 2 d. Of those that did not, some Favia stelligera and Leptoria phrygia showed partial tissue death within 48 h, and Gardineroseris planulata showed partial tissue death within 6 d. Montipora aequituberculata, Porites lobata and P. lutea tolerated sediment for at least 6 d, and exhibited extensive tissue bleaching, but these tissues recovered after sediment removal. Sediment-rejection efficiency and sediment tolerance are not directly related, and wide interspecific differences may occur in both. These findings are correlated with differences in sediment-rejection mechanisms and with ecological distributions on the reef.

Link between gold provinces

Abstract: Low-salinity, high-temperature (>200 degrees C), reducing fluids are poorly represented in ore-forming processes, yet appear to account for 90 percent of the primary gold mined to date. Such fluids have been implicated in the formation of many Archcan greenstone, Witwatersrand, slate belt, and epithermal gold deposits. These low-salinity auriferous fluids occur in variable time, space, lithological sequence, and tectonic settings and are most easily explained by metamorphic devolatilization of mafic and/or graywacke successions.Metamorphism of chlorite-calcite-albite-quartz assemblages (e.g., mafic or graywacke) at the greenschist-amphibolite facies boundary occurs around 480 degrees + or - 20 degrees C (for 3-5 kbars) and produces large volumes of low-salinity, H 2 O-CO 2 fluid similar in composition to those recorded in many gold deposits. Widespread pyrite in the above assemblage typically leads to elevated levels of dissolved sulfur. Such conditions are ideal for gold transport as a molecular Au-S complex and can lead to deposits rich in gold relative to silver and base metals.Deposition of gold occurs in the temperature range of 250 degrees to 400 degrees C and can be facilitated by lower temperature, lower sulfur activity, and changes in oxygen activity. Lower sulfur activity is most readily achieved by fluid interaction with Fe-rich host rocks with the formation of pyrite or pyrrhotite, whereas lower oxygen activity is readily achieved by interaction with carbonaceous metasediments.Low-salinity fluids produced by metamorphic devolatilization provide a common theme embracing the formation of many Archcan greenstone, slate belt, Witwatersrand, and potentially epithermal gold deposits. It involves the common features of high geothermal gradient, low-salinity fluid, high Au/Ag, high Au/base metals, and broad synchroneity with metamorphism. It also accounts for the considerable variability in hosting structures, detailed timing relations, host rocks, alteration assemblages, and geologic age of different deposits. Interestingly, the similarities are explained by deeper processes, the differences by processes at or near the depositional sites.

A functional analysis of food procurement in two surgeonfish species, Acanthurus nigrofuscus and Ctenochaetus striatus (Acanthuridae)

Abstract: The mechanisms of food procurement in the surgeonfishesCtenochaetus striatus andAcanthurus nigrofuscus from the Great Barrier Reef were determined by functional analyses of the jaws and associated structural elements (based on myological and osteological examinations and X-ray photographs) and by video analyses of actions of the mouth and body during feeding.Acanthurus nigrofuscus has relatively robust jaw bones. The movement of the elements during mouth opening is limited with a mean maximum gape angle of 112.8°. Each bite is relatively fast and is characterized by a quick nip at algal filaments, usually followed by a sidewads flick of the head. The jaws bear several broad multidenticulate teeth. It appears that these teeth engage turf algal strands which are either sheared during mouth closure or torn off as the head flicks sideways. InC. striatus, the jaw bones are considerably lighter than those ofA. nigrofuscus. There is much greater movement of the elements during mouth opening, resulting in a mean maximum gape angle of 177.6°. Each bite is slower than inA. nigrofuscus and is characterized by a wide gape as the mouth is applied to the substratum followed by a quick, upward flick of the lower jaw, with no sideways flick of the head. The jaws bear numerous elongate flexible teeth, with expanded incurved denticulate tips; those on the dentary often possessing a pointed blade-like process. It appears that these teeth brush particulate and epiphytic material from the surface of the turf algal strands and other substrata. These observations demonstrate howA. nigrofuscus andC. striatus are able to remove microalgae and detritus, respectively, from the same substratum. The results also demonstrate how relatively small differences in morphology can have a profound influence on the feeding abilities and trophic ecology of fishes.

Precorrection: An Instructional Approach for Managing Predictable Problem Behaviors

Abstract: Demonstrates how an instructional strategy, precorrection, can be applied to changing chronic behavior problems

A comparison of the Og4C3 antigen capture ELISA, the Knott test, an IgG4 assay and clinical signs, in the diagnosis of Bancroftian filariasis.

Abstract: To compare methods for diagnosing Bancroftian filariasis, six hundred and seventy four people from rural areas of Papua New Guinea were screened using microfilaraemia, the Og4C3 antigen capture ELISA, an ELISA to detect IgG4 specific antibodies and clinical examination. Both ELISA tests detected around twice the number of positive cases than those detected by the presence of microfilariae alone. No correlation was found with clinical signs and laboratory tests. This study raises concern over the underestimation of the prevalence of filariasis due to ineffective diagnostic criteria. The two ELISA tests should be of value in epidemiological surveys and for monitoring filariasis control programs.

Antitumor and Cytotoxic Compounds from Marine Organisms

Abstract: An earlier review of antitumor and cytotoxic compounds from marine organisms which covered the literature into early 1986 was published in 1987 by Munro et al (1987) The current review is intended to provide a comprehensive review of the field from the beginning of 1986 to early 1991 The primary aim was to include all the marine natural products reported to have any type of cytotoxic or antitumor activity In addition to compounds reported to be toxic to a variety of cultured cancer cell lines, we have included compounds that show activity in the brine shrimp assay or which inhibit development of fertilized sea urchin or starfish eggs, simple assays which correlate to some extent with cytotoxicity A considerable literature has developed regarding some of the most promising marine antitumor agents, such as didemnin B, the bryostatins, and the dolastatins Information on some of the pharmacologic and mechanistic studies of these compounds has been included The chapter is organized according to structural type, although in some cases a given compound could be assigned equally well to different categories

Influence of season, ontogeny and tide on the diet of the temperate marine herbivorous fish Odax pullus (Odacidae)

Abstract: The diet of the temperate marine herbivorous fish Odax pullus (Pisces: Odacidae) was examined using gut-content analysis followed by principal-component analysis and analysis of variance. Fish were collected near Leigh, on the northeast coast of New Zealand, from February 1983 to September 1984. The data were categorised by size of fish, season, and state of tide. A major ontogenetic shift in diet was observed. Juveniles fed on animal material (crustaceans and gastropods), epiphytic rhodophytes, and some phaeophyte material. Adults fed almost exclusively on two phaeophyte taxa, the laminarian Ecklonia radiata and the fucoid Carpophyllum spp. Dietary selection was evident at the level of particular plant components; the diet of larger fish in spring samples was dominated by fucoid reproductive receptacles. There was no direct evidence of a tidal influence on diet composition of O. pullus, although the relative proportions of E. radiata and Carpophyllum spp. ingested by adult fish appeared to vary with tidal state. The volume of gut contents varied seasonally for all size classes, although the timing of peak annual food intake varied among size classes. Tidal state did not influence the volume of the gut contents. The ontogenetic and seasonal trends evident in the diet of O. pullus appeared to be related to a number of factors including relative gut length, gonad development, ontogenetic changes in feeding anatomy and seasonal changes in algal composition.

Age and growth of the Australian sharpnose shark, Rhizoprionodon taylori , from north Queensland, Australia

Abstract: Age and growth were studied inRhizoprionodon taylori using specimens caught in Cleveland Bay, North Queensland, Australia. Von Bertalanffy growth parameters were estimated using three different techniques: vertebral ageing, back calculation and length frequency. Vertebrae from 138 specimens were sectioned and narrow circuli counted to estimate age. Marginal increment analysis verified that circuli were produced annually in late summer, probably as a result of stress during the mating season. The oldest female was 7 and male 6 years old. Von Bertalanffy growth parameters estimated from vertebral ageing data for males were tO = 0.410 yr, K = 1.337, L∞ = 652.2 mm, and for females tO = 0.455 yr, K = 1.013 and L∞ = 732.5 mm. Growth parameters determined by length frequency and back calculation techniques concurred with those from vertebral ageing. Growth of the 0+ age class was very rapid, averaging 140% of the size at birth in the first year. Males and females matured after only one year, the lowest age at maturity reported in the family Carcharhinidae. Annual growth increments decreased rapidly after maturity, and little growth occurred after three years.

Ignorance and Science: Dilemmas, Perspectives, and Prospects

Abstract: Recent decades have seen a dramatic increase in creative work on scientifc ignorance and uncertainty, which can be traced in part to a realization that ignorance and uncertainty cannot always be re...

Spectrum of Extraintestinal Disease Due to Aeromonas Species in Tropical Queensland, Australia

Abstract: During a 12-month period, the clinical spectrum of extraintestinal disease due to Aeromonas species was determined for 56 patients in tropical Queensland (Australia). Forty-six patients acquired their infection in the community, six patients were infected in the hospital, and four patients were colonized. Demographic risk factors included male gender (67%) and Aboriginal ethnic background (35%). The disease ranged from deep-seated infection (four cases) to soft-tissue infection of varying intensity (48 cases). Among patients whose infections were community acquired, 22 required hospitalization and 27 suffered trauma-associated infection. Seventeen patients (63%) in the latter group had lacerations to the hands and feet that were contaminated with surface water or soil. The appearance of the wounds was not pathognomonic, and diagnosis was made by laboratory evaluation. Aeromonas was the sole pathogen in nine patients. Polymicrobial infections were due to Aeromonas and mainly Staphylococcus aureus and/or mixed enteric bacteria. Aeromonas hydrophila was the most common species isolated (71%), followed by Aeromonas sobria (25%). In nine cases, the empirical antibiotic regimen prescribed did not adequately cover infection due to Aeromonas. Infection was seen regularly throughout the year, but a cluster of cases also occurred during the tropical Australian wet season.

Nutrient limitation in the giant clam-zooxanthellae symbiosis: effects of nutrient supplements on growth of the symbiotic partners

Abstract: The effect of ammonium (5, 10 μM N) and phosphate (2, 5, 10 μM P) on the growth of the giant clam Tridacna gigas and its symbiotic dinoflagellate Symbiodinium sp. was examined. A 3 mo exposure to these nutritients significantly increased the N or P composition of the soft tissues, as reflected in a corresponding change in C:N:P ratio. Furthermore, exposure to N or N+P markedly increased the amount of soft tissue, but P alone did not, demonstrating that increased availability of inorganic nitrogen enhances tissue growth of the clam host. With addition of N, or N+P, there was a significant increase in the total number of zooxanthellae per clam, with a corresponding decrease in chlorophyll a (chl a) content per zooxanthella. However, only with N+P was there an increase in the zooxanthellae mitotic index. The inverse relationship between zooxanthellae number and chl a per zooxanthella is consistent with phytoplankton studies indicating conditions of nutrient-limitation. Furthermore, the unaffected C:N:P composition of the zooxanthellae and their relatively low specific-growth rates (4 to 10%) also suggest that they are nutrient-limited in vivo. In particular, their high mean C:N:P ratio of 303:52:1 indicates that, relative to C, they are much more depleted in P and less in N than are free-living phytoplankton. Furthermore, polyphosphates (phosphate reserves) were undetectable, and the activity levels of acid phosphatase in the zooxanthellae were relatively high and not influenced by the host's exposure to increased P concentrations in the sea water, implicating the clam host in active regulation of P availability to its symbiotic algae. This is strong evidence that N-limitation of clam zooxanthellae is a function of the availability of ammonium to the symbiosis while, irrespective of nutrient levels in sea water, clam zooxanthellae still show characteristics of P-limitation.

Development and changes at settlement in the barbel structure of the reef fish, Upeneus tragula (Mullidae)

Abstract: The development of the sensory barbels of the tropical goatfish, Upeneus tragula (Mullidae), was examined from their first appearance early in planktonic life through to the reef-associated juvenile period. The structure of the barbel was examined histologically and found to represent an outgrowth of the gustatory (taste) system, composed of at least 50% sensory tissue at settlement. Abrupt changes in morphology were found to be coincident with the 6–12 h settlement period: barbels rapidly moved forward along the hyoid arch to abut the dentary; the length of the barbels increased by up to 52%; the epidermal layer increased to comprise 75% of the cross-sectional area; and the mean size of the taste bud cells increased by up to 100%. A strong relationship was found between barbel length and mean taste-bud size. This relationship was used to predict the mean taste-bud sizes for 237 newly-settled fish, collected as 12 samples over two recruitment seasons. Mean taste-bud size varied significantly among samples. Experiments examined whether food availability or temperature of the water within the pelagic phase influenced the size of the barbels at settlement. Food availability influenced the relationship between barbel length and fish size. Slower growing fish had larger barbels relative to fish length than those that grew faster. Temperature did not influence the relationship between barbel length and fish size. Variability in sensory development at settlement, and the factors which influence it, may have important ramifications for the potential success of the fish once on the reef.

A high accuracy microwave ranging system for industrial applications

Abstract: A microwave ranging system that employs a composite frequency modulated continuous wave/continuous wave (FMCW/CW) measurement technique is described. Conventional FMCW radar techniques are employed to find the approximate range of the target. An ambiguous but very accurate set of range solutions is also determined through a CW measurement. The correct, precision CW distance measurement is resolved on the basis of the approximate FMCW solution. An adaptive, spatial digital filtering routine applied to the FMCW radar measurements reduces the influence of clutter, ensuring reliable operation. An X-band prototype system that achieves submillimeter accuracy is described. >

Changes in the spectral absorption of cone visual pigments during the settlement of the goatfish Upeneus tragula: the loss of red sensitivity as a benthic existence begins

Abstract: The goatfish Upeneus tragula undergoes an abrupt metamorphosis at settlement when the pelagic larvae begin a reef-associated benthic mode of life. A microspectrophotometric investigation of the retinal visual pigments was carried out on fish prior to, during, and following settlement. It was found that the visual pigment in the long wavelength-absorbing member of the double cones in the dorsal retina changed rapidly from a rhodopsin with a wavelength of maximum absorption (λmax) of 580 nm to that of 530 nm. The second member of the double cones always had a rhodopsin with the λmax absorbing at shorter wavelengths. Prior to settlement the average for this class of cones was 487 nm whereas during and immediately following the settlement period the λmax recorded from individual outer segments was found to vary between 480 nm and 520 nm, with two possible classes of cone absorbance emerging within this range. These two classes of absorbance had average λmax values of 487 and 515 nm. The average λmax of the paired cone classes in one larger wild-settled fish were found to be at 506 nm and 530 nm. No change was detected in the λmax of the single cones or the rods which were always found to have a λmax of about 400 nm and 498 nm respectively. The loss of the redabsorbing pigment occurred over the same time scale as the metamorphosis of morphological features associated with the settlement process. It is thought that the loss of this visual pigment is associated with the change in light environment of the fishes as they leave the surface waters to begin a benthic mode of life in deeper water.

Feed resource base for scavenging village chickens in Sri Lanka.

Abstract: The productivity of a population of scavenging village chickens in Sri Lanka has been assessed, and the scavenging feed resource base has been measured and analysed. The laying period lasted 34 +/- 13 days and the batch size was about 20 eggs. The households ate 71% of the egg production. The mean egg weight was 48 g and the mean size of a set of eggs was 9.4. The hatching percentage was 67 +/- 32 and the liveweight at 70 days averaged 313 g with a range of 142 to 492, by which time 65% of the chicks hatched had died. The age at first lay averaged 211 days when the pullets weighed 1,160 g. The broody period lasted from 3 weeks to 4 months depending on whether the hen hatched eggs, and for how long she tended the brood. The laying hens were actively scavenging for most of the daylight hours. The average amount of scavenged feed per household flock per day was 550 g dry weight with a proximate composition of 9.4% crude protein, 9.2% ether extract and 5.4% crude fibre. More than 70% of the feed intake was household refuse (27% cooked rice, 30% coconut residue, 8% broken rice and 36% other scraps). The remainder was from the environment (13% grass shoots, 8% small metazoans and 7% paddy rice). Proximate analyses of crop contents, household refuse and its major components were carried out. Dietary Ca and P levels were low in the village, as were plasma levels of these minerals. On a balanced commercial diet plasma Ca was still lower than that of hybrid commercial chickens. Suggestions are made for improving the productivity of the scavenging system with no requirement for inputs, and with inputs.

Factors affecting litter processing by Anisocentropus kirramus (Trichoptera: Calamoceratidae) from an Australian tropical rainforest stream

Abstract: SUMMARY 1 Larvae of the caddisfly Anisocentropus kirramus are common leaf shredders in rainforest streams in tropical Queensland. Laboratory experiments were undertaken to examine the effects of (a) differences in leaf species, age and degree of conditioning, (b) leaf preferences, (c) temperature and (d) larval stage on processing of leaf litter by A. kirramus. 2 Leaf species (five tested), age (fresh v senescent) and condition (conditioned in stream v unconditioned) each had a significant effect on the amount of leaf material that was processed. For most species, conditioned leaves were processed faster but for one species unconditioned leaves were processed faster. Senescent leaves were processed more rapidly than green leaves in three species but not in the other two. Given a choice of leaf types A. kirramus actively selected leaves that were processed faster; no preference was shown between two different ‘fast’ leaves. 3 Processing occurred at all temperatures tested (10, 18 and 25°C), with the processing rate increasing with temperature. Younger instar larvae processed leaves at a greater rate per unit body weight (up to 343% day−1) than older instars. Final instar (5) larvae were capable of processing some tough leaves that younger instars did not process. 4 In rainforest streams, processing of leaves by A. kirramus takes place throughout the year. Its ability to process green leaves is important because of the high input of fresh green leaves into tropical streams, and because of the severe depletion of the supply of conditioned leaves and fine detritus after floods.

Factors Affecting the Progression towards Burnout: A Comparison of Professional and Volunteer Counsellors:

Abstract: This study compared professional and volunteer counsellors on a number of key variables in the progression to burnout, namely, stressors, strain, defensive coping, social support, Type A personality, and breakdown. Job stressors unique to each group were identified but there was overwhelming evidence for professionals and volunteers belonging to a homogeneous counselling population as evidenced by similarity across major constructs. Path analysis supported theoretical formulations on burnout by Maslach and Cherniss, and gave support to Lin, Dean, and Ensel's argument that social support may act as a buffer to burnout.

Episodic post‐glacial sea‐level rise and the sedimentary evolution of a tropical continental embayment (Cleveland Bay, Great Barrier Reef shelf, Australia)

Abstract: Cleveland Bay is a 400 km2 landlocked tropical embayment located at 19° S and 146° 55´E The bay is protected from the dominant southeasterly tradewind by Cape Cleveland, but lies open to northerly and northeasterly weather and to the effects of occasional tropical cyclones. Water‐motion within the bay is dominated by the effects of refracted southeasterly‐generated waves (mostly 0.5–1.2 m high, 4–6 s period) and by semi‐diurnal tidal currents, which reach speeds of 15–30 cm/s during spring tides. Residual circulation within the bay is anticlockwise and results in preferential sediment accumulation on the eastern side. The bay contains three main Holocene stratigraphic units (A‐C) which rest on weathered Late Pleistocene clay. The Pleistocene land surface is planar, dips seawards at 0.8 m/km and is incised by a major complex of fluvial and tidal channels. Seismic unit C encompasses cross‐bedded or draped fill of the channel system. Seismic unit B, occurring laterally to C, comprises massive grey mud with m...

Granitoids of the Dry Valleys area, southern Victoria Land, Antarctica: Plutons, field relationships, and isotopic dating

Abstract: Detailed mapping throughout much of the Dry Valleys area indicates the region is underlain by 15 major granitoid plutons and numerous smaller plugs and dikes. Intrusive relationships of these plutons and dikes indicate repeated intrusion of superficially similar granitoids at different times. Sufficient internal lithologjc variation occurs within individual plutons, to allow correlation with several of the previously defined granitoid units based on lithologic character. Consequently, previous subdivision schemes based on lithology are no longer tenable and are here replaced with a subdivision scheme based on the identification of individual plutons. The elongate, concordant Bonney, Denton, Cavendish, and Wheeler Plutons, which range in composition between monzodiorite and granodiorite, are the oldest relatively undeformed plutons in the Dry Valleys area. Each pluton is characterised by flow alignment of K‐feldspar megacrysts, hornblende, biotite, and mafic enclaves. Field relationships and radio...