Isolation and characterization of 15 polymorphic microsatellite DNA loci from Argyrosomus japonicus (mulloway), a new aquaculture species in Australia

Fifteen microsatellite loci were isolated for population genetic studies of mulloway (Argyrosomus japonicus), a commercial/recreational fish species in Southern Australia. A genomic library was screened randomly for di- tri- and tetranucleotide repeats. Fifteen microsatellite marker loci were developed that were highly polymorphic (allele number ranged from four to 18). Observed and expected heterozygosities ranged from 0.17 to 1 and from 0.27 to 0.91, respectively. These markers have proven useful for estimating genetic variation and for evaluating population structure across the species' natural distribution. They also provide powerful tools for optimizing hatchery practices to conserve genetic diversity.     

A new species of Argyrosomus (Pisces, Sciaenidae) from Natal, South Africa

Argyrosomus thorpei sp. n. is described from 11 specimens and compared with its closest relatives A. hololepidotus and A. amoyensis.     

New pathological condition in cultured mulloway Argyrosomus japonicus: histopathological, ultrastructural and molecular studies

Mulloway Argyrosomus japonicus is a native fish species in Western Australia, for which aquaculture production has recently been developed. A single cohort was stocked in a cage offshore at Geraldton, Western Australia, at a water depth of 6 m. Fish appeared healthy before stocking. Routine histological analysis was carried out from 10 mo post stocking and until completion of harvest (about 2.5 yr post stocking). No gross pathology was evident. Microscopically, however, granulomatous lesions were present in the kidneys of almost 100% of the fish examined. Enclosed in the granuloma was an aggregate of organisms, 4.2 to 5.4 μm in diameter. Kidney granulomas appeared as multi-focal aggregates. Granulomas at different stages of formation and finally fibrosing granulomas were observed. Granulomas also appeared infrequently in other organs: a few granulomas were found in the liver and spleen and a single granuloma in the heart of one fish. Transmission electron microscopy (TEM) revealed that the organism was composed of 2 cells, an outer cell enclosing an inner cell. The inner cell was surrounded by a double membrane and the outer cell by a single membrane. Cellular material, presumably of parasitic nature, surrounded the outer cell. The organism contained primitive mitochondria and abundant free ribosomes. Small subunit ribosomal DNA (SSU rDNA) sequence obtained by PCR revealed an 84% sequence identity with the myxosporean Latyspora scomberomori. Based on TEM and preliminary molecular results, we suggest that the organism is the extrasporogonic developmental stage of a myxozoan parasite, which failed to form spores in the mulloway host.     

Development and ossification of the feeding apparatus in the larvae of two co‐occurring species of kob (Sciaenidae), Argyrosomus japonicus and Argyrosomus inodorus,in South Africa

The teeth of the oral jaws of two sympatric species of Argyrosomus, Argyrosomus japonicus and Argyrosomus inodorus, found along the South African coast developed first on the premaxilla and then on the dentary of the lower jaw. Teeth were observed on the premaxilla of A. inodorus [head length (L_H) = 1·0 mm; notochord length (L_N) = 2·7 mm] at a smaller size than in A. japonicus (L_H = 1·2 mm; L_N = 4·7 mm). The ventral elements of the gill arches (hypo‐ and basibranchials) were not ossified by the end of preflexion. The fifth ceratobranchial began ossifying and possessed pharyngeal teeth by 1·2 mm L_H (L_N = 4·7 mm) in A. japonicus and 1·1 mm L_H (L_N = 3·2 mm) in A. inodorus. To complement the osteological data, stomach contents were also analysed as a proxy for feeding apparatus functionality. Prey were first present in the stomach of A. japonicus at 1·2 mm L_H (L_N = 4·7 mm) and only 22% of the stomachs contained no prey suggesting that A. japonicus is already actively foraging by preflexion. In comparison, 83% of the stomachs of A. inodorus contained no prey and a single prey item was present in the largest examined specimen (L_H = 1·6 mm; L_N = 5·4 mm). Elements of the feeding apparatus begin to ossify early during ontogeny. While the overall pattern of ossification is similar between the two species, A. japonicus may be able to begin feeding at smaller head lengths relative to A. inodorus in their nursery habitats.     

Damage, recovery and survival of 0-group mulloway, Argyrosomus japonicus, after simulated escape through square mesh

A laboratory experiment was carried out to quantify and compare the physical damage (measured as scale loss), recovery and survival of two size categories [small: 48–85 mm total length (TL); large: 78–148 mm TL] of 0‐group mulloway, Argyrosomus japonicus, after simulated escape through square‐shaped mesh (bar length of 21.5 mm). Regardless of their size, fish that were fatigued to exhaustion and forced through square meshes sustained significantly more (i.e. >1.8 times) scale loss than did control fish that were only fatigued. However, the total scale loss incurred was <5% and significantly improved 7 days after treatment. Survival rates over a 2‐week observation period were 100 and >97% for treatment and control fish, respectively. The results support the utility of square mesh for reducing the prawn‐trawl fishing mortality of unwanted bycatch.     

Derivation and dispersal of Acacia (Leguminosae), with particular reference to Australia, and the recognition of Senegalia and Racosperma

The morphology of seedlings, leaves, flowers and inflorescences, anatomy of the pod, the occurrence of extra-floral nectaries, free amino acids of the seeds, flavonoid compounds in heartwoods, cyanogenic compounds and porate, colporate and extraporate pollen, and susceptibility to rusts, all indicate that three genera, Acacia Miller, Senegalia Raf. and Racosperma Martius, should be recognized. These correspond to currently accepted subgenera of Acacia. The size of these more narrowly circumscribed genera is in keeping with the size of genera of other tribes of low diversity in Leguminosae. Acacia and Senegalia arose independently from the Ingeae, with Racosperma being derived from Senegalia. Section Filicinae is more advanced than section Senegalia of Senegalia , and sections Racosperma and Pukhella , both with at least some species with bipinnate foliage, are the most advanced of Racosperma , while the other sections Pleurinervia and Lycopodiifolia have only phyllodinous species. Long-range dispersal of Racosperma from the Australian region has occurred, but the broad pattern of distribution is interpreted in terms of plate tectonics. Racosperma was present in Australia in the late Cretaceous but did not become widespread until the general drying of the continent in the Miocene. The flora of SW Australia has been isolated from the rest of the continent by climatic barriers since the late Tertiary and has a high proportion of endemic species. Barriers to plant migration in the east have operated only intermittently and there is no area comparable in endemism to the southwest.     

Effect of short term exposure to the anaesthetic 2-phenoxyethanol on plasma osmolality of juvenile dusky kob, Argyrosomus japonicus (Sciaenidae)

The plasma osmolality of early juvenile dusky kob, Argyrosomus japonicus , exposed to 2-phenoxyethanol and control fish that were pithed prior to sampling, was investigated. Exposure to 2-phenoxyethanol, after 2, 4, 6, 8 and 10 min, did not alter plasma osmolality (Friedman test; P = 0.976). There was no significant relationship between the size of fish within the range 133–170 mm SL (40–85 g) and plasma osmolality. Finally, there was no significant difference in plasma osmolality between anaesthetized fish and the control group that were pithed directly after removal from the tanks. Anaesthetizing juvenile dusky kob with 2-phenoxyethanol prior to blood sampling did not affect plasma osmolality.     

Responses of ants to disturbance in Australia,with particular reference to functional groups

Abstract Ants are widely used as bioindicators in environmental assessment in Australia, partly because the responses of ant communities to disturbance are relatively well understood. In particular, the use of functional groups has provided a predictive framework for analysing ant community responses to disturbance in the absence of reliable information on the responses of individual species. Here we review 45 studies of the responses of Australian ant communities to disturbance, in order to: (i) identify individual species or species‐groups that respond consistently to disturbance; and (ii) examine the usefulness of the functional group scheme as a framework for predicting ant community responses under different disturbance regimes in different biogeographical regions. The most common forms of disturbance in our studies were fire (17 studies), mining (12; mostly studies of minesite restoration) and grazing (7), with other disturbances including clearing, logging, flooding, recreation, urbanization and farming. Responses of individual species were inevitably variable because of differences in vegetation type, severity of disturbance and time since disturbance. However, we identified a range of widespread species that showed predictable responses, including species of the metallica group of Rhytidoponera in temperate Australia (‘increasers’ in relation to disturbance), species of the terebrans and denticulatus groups of Camponotus (increasers), the aeneovirens group of Melophorus (increasers) from the arid zone, and Iridomyrmex pallidus (increaser) from the monsoonal region. The functional group scheme assessed here was not designed specifically in the context of disturbance, but nevertheless in some situations provides a useful framework for analysing ant community responses. Three distinct syndromes of functional group responses can be recognized. First, Dominant Dolichoderinae and Hot Climate Specialists are groups that prefer open environments, and tend to be favoured by low levels of disturbance in well‐forested habitats. Second, Opportunists and often also Generalized Myrmicinae are broadly adapted taxa with wide habitat tolerances, but are particularly sensitive to competitive interactions such that their responses oppose those of Dominant Dolichoderinae. Finally, Cryptic Species and Specialist Predators have highly specialized requirements that make them especially sensitive to disturbance. Functional groups are of most use in situations where disturbance causes substantial change in habitat structure, particularly in the ground‐layer. Functional groups are of least use in very open habitats, where disturbance merely increases what is already extensive bare ground, and has relatively little impact on microclimate. The ant functional group scheme can play an important role in assessing disturbance in mesic Australia, but may be of more limited use for this in the arid zone.     

Management of threatened insect species in Australia, with particular reference to butterflies

Abstract   Advances in determination of conservation status of insects through evaluation of threats (rather than simple 'rarity' alone) help to set priorities for allocation of conservation resources, and formulate effective legislative treatment and field management for the most needy species. Summaries of several recent conservation studies on butterflies exemplify the variety of practical needs, amongst which habitat protection and enhancement is paramount. However, the paucity of biological and distributional information on most Australian insects necessitates considerable flexibility in approach, so that perceptions of conservation need may be highly subjective. Listing species for protection and conservation priority must be viewed as a dynamic process, with opportunity for rapid action, either to list or de-list taxa as research and recovery actions lead to change in perceived or real status and conservation need.     

Saccadic head movements of the praying mantis, with particular reference to visual and proprioceptive information

ABSTRACT. Horizontal head movements of the praying mantis, Sphodromantis lineola Burm., were recorded continuously. They responded to the presence of a live blowfly prey in the antero-lateral visual field with a rapid saccadic head movement. The angular movement of a fixation saccade was correlated positively to the displacement of the prey from the prothoracic midline. Saccade magnitude and velocity are related. After the stimulus moved out of the visual field, the mantis made a second saccadic head movement, a return saccade towards the body midline. We observed return saccades in which the head overshot or undershot the body midline, as well as saccades which returned the head exactly to its initial position. In 92% of trials with intact mantids, the return movement succeeded eventually in rotating the head back to its initial position, whereas after removal of the neck hair plates this occurred in only 47% of trials. There is a consistent relation between saccade extent and velocity. Velocities of return saccades were slower than those of fixation saccades. It is suggested that sensory inputs from the neck hair plate proprioceptors modify both the magnitude and the angular velocity of fixation and return saccadic head movements.     

Neoechinorhynchus (Neoechinorhynchus) dorsovaginatus n. sp.(Acanthocephala: Neoechinorhynchidae) from the dusky kob Argyrosomus japonicus (Sciaenidae) on the southern coast of South Africa

Neoechinorhynchus (Neoechinorhynchus) dorsovaginatus n. sp. (Acanthocephala: Neoechinorhynchidae) is described from the dusky kob, Argyrosomus japonicus (Temminck & Schlegel) from the southern coast of South Africa in the Breede River Estuary. Like four other species of Neoechinorhynchus Stiles & Hassall, 1905, N. (N.) africanus Troncy, 1969, N. (N.) johnii Yamaguti, 1939, N. topseyi Podder, 1937 and N. (N.) tylosuri Yamaguti, 1939, the new species has a very long, slender body, cylindrical testes and cement-gland, anterior proboscis hooks much longer than the middle or posterior hooks, and a long neck. The new species is the only species of Neoechinorynchus having an antero-dorsal hump just posterior to the neck and a specialised vaginal sphincter and a gonopore on the dorsal side. It is closest to N. (N.) johnii, but is distinguished from it by: the size of the trunk, proboscis, anterior proboscis hooks, neck, and the posterior testis in relation to the cement-gland; the shape of cerebral ganglion and proboscis hook root; and the number of giant nuclei in the cement-gland.     

Comparative floral anatomy of Strobilanthinae (Acanthaceae), with particular reference to internal partitioning of the flower

This paper provides the first comparative survey of structural variation in inflorescence architecture and flower structure of Hemigraphis and other members of the subtribe Strobilanthinae (Acanthaceae). Several discrete structural characters are identified which may provide support for phylogenetic relationships within the group. These include (1) the presence or absence of an accessory bud, (2) the presence or absence of a hollow style, (3) the presence or absence of an abscission layer, (4) the number of stamens comprising the androecium, and (5) the pattern of filament detachment. The structure of the filament curtain, a complex structure that partitions the flower, is also investigated. A more precise term for this structure stapetal curtain is suggested since it is a result of close synorganisation between the filaments and corolla tube. This structure appears to have a wide distribution throughout Acanthaceae and is not confined to Ruellieae s.l., as previously described. The earlier characterisation of four discrete types of filament curtain is unsatisfactory, since many of the features used to distinguish them are continuous and not unique features of particular species.We acknowledge Richard Bateman, Mark Carine, Peter Endress, Colin Hughes, Toby Pennington and an anonymous reviewer for comments on this paper. ECM gratefully acknowledges Chrissie Prychid, Peter Gasson, and the late Tim Lawrence of the Micromorphology section, Royal Botanic Gardens, Kew for their assistance and encouragement and Jesus Cordero-Salvado for help with the figures. This work was supported by the Druce Fund from the University of Oxford.     

Movement in a large predatory fish: coral trout, Plectropomus leopardus (Pisces: Serranidae), on Heron Reef, Australia

 Movement by the larger more mobile species of coral reef fish plays a significant role in determining patterns in abundance and population structure. Fish movement is also relevant to the use and effectiveness of marine reserves in managing fish populations. Coral trout are large piscivorous serranids supporting major fisheries on the Great Barrier Reef (GBR). This study reports on the within-reef movement of the common coral trout, Plectropomus leopardus, at Heron Reef, southern GBR, over a twelve month period, investigated by tagging and underwater tracking. Tracking of coral trout revealed no apparent relationship between the area moved and stage of tide or time of day. However, movement areas were affected by the size of fish: in spring a linear relationship between fish size and area of movement was measured, but in summer the largest (male) fish moved over significantly smaller areas than medium-sized fish. Movement of males may be related to cleaning behaviour and spawning. Fifty nine percent (n=101) of the tagged fish were resighted over periods of 4–5 months, in “home sites” measuring ∼2000 m². Coral trout were not restricted to home sites, but moved on average 2 km along the reef slope; maximum distances of 7–7.5 km were measured. Coral trout appear to range as mobile, opportunistic predators, but also maintain home sites for access to shelter and cleaning stations. Accepted: 1 August 1996     

Seed development in Ipomoea lacunosa (Convolvulaceae), with particular reference to anatomy of the water gap

BACKGROUND AND AIMS: Disruption of one or both of the bulges (water gap) in the seed coat adjacent to the micropyle is responsible for breaking physical dormancy (PY) in seeds of Ipomoea lacunosa and other taxa of Convolvulaceae. Hitherto, neither ontogeny of these bulges nor onset of PY together with anatomical development and maturation drying of the seed had been studied in this family. The aims of this study were to monitor physiological and anatomical changes that occur during seed development in I. lacunosa, with particular reference to ontogeny of the water gap. METHODS: Developmental anatomy (ontogeny) of seed coat and dry mass, length, moisture content, germinability and onset of seed coat impermeability to water were monitored from pollination to seed maturity. Blocking/drying and dye-tracking experiments were done to identify site of moisture loss during the final stages of seed drying. KEY RESULTS: Physiological maturity of seeds occurred 22 d after pollination (DAP), and 100 % of seeds germinated 24 DAP. Impermeability of the seed coat developed 27-30 DAP, when seed moisture content was 13 %. The hilar fissure was identified as the site of moisture loss during the final stages of seed drying. The entire seed coat developed from the two outermost layers of the integument. A transition zone, i.e. a weak margin where seed coat ruptures during dormancy break, formed between the bulge and hilar ring and seed coat away from the bulge. Sclereid cells in the transition zone were square, whereas they were elongated under the bulge. CONCLUSIONS: Although the bulge and other areas of the seed coat have the same origin, these two cell layers underwent a different series of periclinal and anticlinal divisions during bulge development (beginning a few hours after pollination) than they did during development of the seed coat away from the bulge. Further, the boundary between the square sclereids in the transition zone and the elongated ones of the bulge delineate the edge of the water gap.     

Mechanisms for enhancing nutrient uptake in plants,with particular reference to mediterranean South Africa and Western Australia

The major constraints to nutrient uptake by vascular plants in mediterranean South Africa and Western Australia are: very infertile soils, relatively low temperatures when water availability is high, and hot, dry summers. These constraints are partly overcome through increased efficiency of uptake, tapping novel sources of nutrients, and prolonging water uptake. Absorptive area per unit “cost” may be enlarged directly through increased fineness of the root system and proliferation of long root hairs. This reaches its greatest development in the root clusters of the Proteaceae (proteoid roots), Restionaceae (“capillaroid” roots) and Cyperaceae (dauciform roots). Absorptive area is increased indirectly through fungal hyphae which extend from hairless rootlets into the soil. Two major groups can be recognised: general (VA mycorrhizas) and host-specific (ericoid, orchid and sheathing mycorrhizas). Mycorrhizas are the most widespread specialised modes of nutrition and are probably universal in such major taxa here asPodocarpus, Acacia, Fabaceae, Poaceae, Asteraceae, Rutaceae, terrestrial orchids, Ericales and Myrtaceae. General mycorrhizas are the least drought-adapted of mechanisms for maximising absorptive area. All have been implicated in enhancing P uptake through increasing access to inorganic P, solubilisation and shortening the diffusion path. However, selective uptake of other nutrients, especially N, by host-specific mycorrhizas may be equally important. Included under novel sources of nutrients are free N₂ (utilised by N₂-fixing nodules), small-animal prey (carnivorous leaves) and persistent leaf bases (aerial roots ofKingia australis). Both legume and non-legume N₂-fixing species are well-represented in these two regions, with stands of individual species in southwestern Australia estimated to contribute 2–19 kg N/ha/yr to the ecosystem. Free nitrogen fixation requires additional nutrients, especially Mo and Co, but is enhanced following fires and by supplementary uptake mechanisms, especially VA mycorrhizas. Southwestern Australia is particularly rich in carnivorous species. Nitrogen, P, K and S are important nutrients absorbed, with digestion aided by enzymes provided by bacteria and the glands. Parasitic plants both tap novel sources of nutrients and capitalise on any efficient water and nutrient uptake mechanisms of the hosts. Root parasites are better represented than stem parasites in mediterranean South Africa and Western Australia. Phosphorus and K in particular are absorbed preferentially by the haustoria, but much remains to be known about their modes of operation. Maximum activity of all uptake mechanisms, except those attached to some deep-rooted plants, is restricted to winter-spring. Most new seasons’s rootlets and specialised roots are confined to the uppermost 15 cm of soil, especially in or near the decomposing litter zone. Nutrient uptake is further enhanced by the tendency for the rootlets to cluster, trapping water by capillary action and prolonging nutrient release. As an early product of decomposition, N tends to be available as NH₄ (rather than NO₃) and it is absorbed preferentially by almost all specialised modes of nutrition. Microorganisms are required in the formation and/or functioning of all these structures, except haustoria. Uptake mechanisms which are optional to the plant reach their peak contribution to the root system at soil nutrient levels well below those required for greatest plant growth, when they may be absent altogether. It is only over the narrow range of nutrient availability, where shoot content of a nutrient is greater in the presence of the mechanism than in its absence (other factors remaining constant), that specialised modes can be termed nutrient-uptake “strategies.” For all specialised modes of nutrition, the component genera are better represented in these two regions than in the surrounding more fertile, arid to subtropical regions of much greater area. Endemism of species with each mode exceeds that for the two floras overall (75%). This is taken as preliminary evidence that specialised modes of nutrition are best represented in nutrient-poor soils. While they serve to limit nutrient loss from the ecosystem, their proliferation is therefore not necessarily a response to increasing “leaks” in the system. A hierarchical scheme of the functional/structural relationships between the various mechanisms is presented, starting with the rootless, VA-mycorrhizal plant as the most primitive condition. Taxa with many of the specialised modes of nutrition at present in southwestern South Africa and Western Australia have been evident in the pollen record since the early Tertiary Period. The absence of ectomycorrhizal forests in mediterranean South Africa, in marked contrast to Western Australia, can be traced to differences in their paleohistory. In both regions, the combination of fluctuating, but essentially diminishing, nutrient and water availability that began with the first mediterranean climate < 5 million years ago resulted in decimation of the less-tolerant rainforest ancestors on the one hand, and remarkable rates of speciation of the pre-adapted sclerophyll nucleus on the other.