Are We Misinterpreting Seed Predation in Palms?

The inadvertent inclusion of weevil-infested seeds when evaluating seed predation by vertebrates, and particularly rodents, may lead to an overestimation of predation rates, thereby confusing the roles of rodents and invertebrates as ecological filters. A study of weevils, rodents and Syagrus romanzoffiana palm seeds indicates the usefulness of X-rays to improve evaluation of invertebrate seed predation.

Assessment of Ametryn Contamination in River Water, River Sediment, and Mollusk Bivalves in Sao Paulo State, Brazil

Sao Paulo state, Brazil, is one of the main areas of sugar cane agriculture in the world. Herbicides, in particular, ametryn, are extensively used in this extensive area, which implies that this herbicide is present in the environment and can contaminate the surface water by running off. Thereby, residues of ametryn were analyzed in samples of river water an river sediment and in freshwater bivalves obtained from the rivers Sapucai, Pardo and Mogi-Guacu in Sao Paulo State, Brazil. Samples were taken in the winter of 2003 and 2004 in two locations in each river. The specimens of freshwater bivalves collected and analyzed were Corbicula fluminea, an exotic species, and Diplodon fontaineanus, a native species. Additionally, the evaluation of the ability of bioconcentration and depuration of ametryn by the freshwater bivalve Corbicula fluminea was also performed. Ametryn concentrations in the samples were measured by liquid chromatography coupled to mass spectrometry. Residues of ametryn in water (50 ng/L) and in freshwater bivalves (2-7 ng/g) were found in the Mogi-Guacu River in 2004, and residues in river sediments were found in all rivers in 2003 and 2004 (0.5-2 ng/g). The observation of the aquatic environment through the analysis of these matrixes, water, sediment, and bivalves, revealed the importance of the river sediment in the accumulation of the herbicide ametryn, which can contaminate the biota.

From Midden to Sieve: The Impact of Differential Recovery and Quantification Techniques on Interpretations of Shellfish Remains in Australian Coastal Archaeology

Experimental mechanical sieving methods are applied to samples of shellfish remains from three sites in southeast Queensland, Seven Mile Creek Mound, Sandstone Point and One-Tree, to test the efficacy of various recovery and quantification procedures commonly applied to shellfish assemblages in Australia. There has been considerable debate regarding the most appropriate sieve sizes and quantification methods that should be applied in the recovery of vertebrate faunal remains. Few studies, however, have addressed the impact of recovery and quantification methods on the interpretation of invertebrates, specifically shellfish remains. In this study, five shellfish taxa representing four bivalves (Anadara trapezia, Trichomya hirsutus, Saccostrea glomerata, Donax deltoides) and one gastropod (Pyrazus ebeninus) common in eastern Australian midden assemblages are sieved through 10mm, 6.3mm and 3.15mm mesh. Results are quantified using MNI, NISP and weight. Analyses indicate that different structural properties and pre- and postdepositional factors affect recovery rates. Fragile taxa (T. hirsutus) or those with foliated structure (S. glomerata) tend to be overrepresented by NISP measures in smaller sieve fractions, while more robust taxa (A. trapezia and P. ebeninus) tend to be overrepresented by weight measures. Results demonstrate that for all quantification methods tested a 3mm sieve should be used on all sites to allow for regional comparability and to effectively collect all available information about the shellfish remains.

Respiratory and cardiovascular responses to hypoxia in the Australian lungfish

Simultaneous measurements of pulmonary blood flow (qPA), coeliacomesenteric blood flow (qCoA), dorsal aortic blood pressure (PDA), heart rate (fH) and branchial ventilation frequency (fv) were made in the Australian lungfish, /Neoceratodus forsteri, /during air breathing and aquatic hypoxia. The cho­linergic and adrenergic influences on the cardiovascular system were investigated during normoxia using pharmacological agents, and the presence of catecholamines and serotonin in different tissues was investi­gated using histochemistry. Air breathing rarely occurred during normoxia but when it did, it was always associated with increased pulmonary blood flow. The pulmonary vasculature is influenced by both a cho­linergic and adrenergic tonus whereas the coeliacomesenteric vasculature is influenced by a β-adrenergic vasodilator mechanism. No adrenergic nerve fibers could be demonstrated in /Neoceratodus /but catecholamine-containing endothelial cells were found in the atrium of the heart. In addition, serotonin-­immunoreactive cells were demonstrated in the pulmonary epithelium. The most prominent response to aquatic hypoxia was an increase in gill breathing frequency followed by an increased number of air breaths together with increased pulmonary blood flow. It is clear from the present investigation that /Neoceratodus /is able to match cardiovascular performance to meet the changes in respiration during hypoxia.

Wolbachia: why these bacteria are important to genome research

Intracellular bacteria of the genus Wolbachia were first discovered in mosquitoes in the 1920s. Their superficial similarity to pathogenic rickettsia initially raised interest in them as potential human pathogens. However, injection experiments with mice showed that they were non-pathogenic, and they were subsequently classified as symbionts of insects. Until the 1970s, Wolbachia was considered to infect a limited number of species of mosquitoes. It is now clear that Wolbachia is an extremely common intracellular agent of invertebrates, infecting nearly all the major groups of arthropods and other terrestrial invertebrates. Its wide host range and abundance can be attributed partly to the unusual phenotypes it exerts on the host it infects. These include the induction of parthenogenesis (the production of female offspring from unmated mothers) in certain insects, the feminization of genetic male crustaceans to functional phenotypic females, and the failure of fertilization in hosts when males and females have a different infection status (cytoplasmic incompatibility). All of these phenotypes favor maternal transmission of the intracellular Wolbachia. In the last year, Wolbachia has also been shown to be a widespread symbiont of filarial nematodes. It appears that Wolbachia is needed by the adult worm for normal fertility, indicating that Wolbachia is behaving like a classic mutualist in this case. This discovery exemplifies that the extent of the host range of Wolbachia and its associated phenotypes is still far from fully understood.

The diversity of the Digenea of Australian animals

The Digenea is one of five major helminth assemblages represented in Australian animals. History of the study of digeneans in Australia is reviewed briefly to show that it has never been subjected to the kind of sustained study needed to reach an understanding of it. The Australian vertebrate fauna comprises over 5500 species. These have so far been shown to harbour just over 70 families, about 306 genera and 566 species of digeneans. Digeneans occur in all classes of vertebrates in Australia but are distributed very unevenly; aquatic hosts are generally most heavily infected, but many terrestrial species are also infected. Particular weaknesses in knowledge of the fauna concern the bats, cetaceans and teleosts. Another weakness is in knowledge of life-cycles; representative life-cycles are known for only about 20 of the 70 families known in Australia. Estimates of the overall size of the fauna are dependent on an understanding of sampling strategies, the heterogeneity of distribution of the fauna, and the nature of host-specificity. These subjects are reviewed briefly and an estimate of the total fauna is made. There may be as many as 6000 species of digeneans in Australia. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd.

Rapid isolation of high-quality RNA from symbiotic dinoflagellates

This report details a reliable and efficient RNA extraction protocol for the symbiotic dinoflagellate Symbiodinium microadriaticum Freudenthal (Gymnodiniales, Dinophyceae). The method typically gives yields of 500 mu g total RNA from 0.4 g wet weight of algae, and, in comparison to current protocols, it is technically simple and less time consuming. This method isolates high-quality, intact RNA from in vine cultured as well as host-isolated cells, as demonstrated by spectrophotometry, gel electrophoresis, and northern analysis. The total RNA obtained was suitable for reverse transcription and PCR amplification of Symbiodinium cDNAs. We have successfully applied our method to isolate total RNA from a different dinoflagellate, Amphidinium carterae Hulburt (Gymnodiniales, Dinophyceae), found in symbiotic association with marine invertebrates.

Isolation of a cDNA for an octopamine-like, G-protein coupled receptor from the cattle tick, Boophilus microplus

Octopamine is a biogenic amine neurotransmitter of invertebrates that binds to a G-protein coupled receptor that has seven transmembrane domains. Formamidine pesticides like amitraz are highly specific agonists of the octopamine receptor. Amitraz is used extensively to control the cattle tick, Boophilus microplus, and many other ticks but now there are strains of ticks that are resistant to amitraz. We have isolated a cDNA from the cattle tick, B. miciroplus, that belongs to the biogenic amine family of receptors. The predicted amino acid sequence from this cDNA is most similar to octopamine receptors from insects. The nucleotide sequence of this gene from amitraz-resistant and amitraz-susceptible cattle ticks was identical. Thus, a point mutation/s did not confer resistance to amitraz in the strains we studied. Alternative explanations for resistance to amitraz in B. microplus are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.

Life-history consequences of divergent selection on egg size in Drosophila melanogaster

Life histories are generally assumed to evolve via antagonistic pleiotropy (negative genetic correlations) among traits, and trade-offs between life-history traits are typically studied using either phenotypic manipulations or selection experiments. We investigated the trade-off between egg size and fecundity in Drosophila melanogaster by examining both the phenotypic and genetic relationships between these traits after artificial selection for large and small eggs, relative to female body size. Egg size responded strongly to selection in both directions, increasing in the large-egg selected lines and decreasing in the small-egg selected lines. Phenotypic correlations between egg size and fecundity in the large-egg selected lines were negative, but no relationship between these traits occurred in either the control or small-egg selected lines. There was no negative genetic correlation between egg size and fecundity. Total reproductive allocation decreased in the small-egg selected lines but did not increase in the large-egg lines. Our results have three implications. First, our selection procedure may have forced females selected for large eggs into a physiological trade-off not reflected in a negative genetic correlation between these traits. Second, the lack of a negative genetic correlation between egg size and number suggests that the phenotypic trade-off frequently observed between egg size and number in other organisms may not evolve over the short term via a direct genetic trade-off whereby increases in egg size are automatically accompanied by decreased fecundity. Finally, total reproductive allocation may not evolve independently of egg size as commonly assumed.

Effects of habitat modification in mangroves on the structure of mollusc and crab assemblages

The abundance and species richness of mollusc and crab assemblages were examined in a subtropical mangrove forest in Moreton Bay, Queensland, Australia, which has been disturbed and damaged by the construction of a wooden boardwalk and a path. Sections of the forest immediately adjacent to the boardwalk and path were compared with reference areas to determine whether changes to the small-scale structural complexity within the forest affected the benthic fauna. The disturbed area was characterised by having 65-80% fewer pneumatophores, significantly fewer species and individuals of molluscs, but significantly more species and individuals of crabs than the reference areas. The abundance of mangrove pneumatophores and the attached epiphytic algae were manipulated at two sites to determine whether observed differences in these features could account for the differences in the assemblage of molluscs in the disturbed area of the forest compared with reference areas. Five experimental treatments were used: undisturbed controls, pneumatophore removals (abundance reduced by ca. 65%), epiphytic algal removals (algae removed from ca. 65% of pneumatophores), pneumatophore disturbance controls and algal disturbance controls. The experimental reduction of the abundance of mangrove pneumatophores and the associated epiphytic algae led to significant declines (by as much as 83%) in the number of molluscs utilising the substratum in the modified plots. There was no significant difference in the abundance of molluscs in the pneumatophore and algal removal plots suggesting any effect was primarily related to removal of the epiphytic algae from the surface of the pneumatophores. The responses by the biota to the changes in the physical environment demonstrate that even relatively small-scale modifications to the physical structure of subtropical mangrove forests can lead to significant effects on the diversity and abundance of macrobenthic organisms in these habitats. Such modifications have the potential to cause cascading effects at higher trophic levels with a deterioration in the value of these habitats as nursery and feeding grounds. Future efforts at conservation of these estuarine environments must focus on the prevention or reduction of modifications to the physical structure and integrity of the system, rather than just on the prevention of loss of entire patches of habitat. (C) 2000 Elsevier Science B.V. All rights reserved.

Evolution of local recruitment and its consequences for marine populations

Advantages of dispersal on the scales that are possible in a long pelagic larval period are not apparent, even for benthic species. An alternative hypothesis is that wide dispersal may be an incidental byproduct of an ontogenetic migration from and then back to the parental habitat. Under this hypothesis, the water column is a better habitat than the bottom for early development. Because the parental area is often an especially favorable habitat for juveniles and adults, selection may even favor larval retention or larval return rather than dispersal. Where larval capabilities and currents permit, a high percentage of recruits may then be produced from local adults. Expected consequences of a high proportion of local recruitment are stronger links between stock and recruitment, greater vulnerability to recruitment overfishing and local modifications of habitat, greater local benefits from fishery reserves, and possibly more localized adaptation within populations. Export of some larvae is consistent with a high proportion of retained or returning larvae, could stabilize populations linked by larval exchange, and provide connectivity between marine reserves. Even a small amount of larval export could account for the greater gene flow, large ranges, and long evolutionary durations seen in species with long pelagic larval stages.

In situ measures of spawning synchrony and fertilization success in an intertidal, free-spawning invertebrate

The rocky intertidal zone has the potential to be one of the harshest environments for free-spawning organisms, but empirical data on fertilization success are scarce. Here, I report on an intertidal, solitary ascidian, Pyura stolonifera, which was observed to spawn at low tide. At a scale likely to be most important to gametes (metres, duration of tide), approximately 30% of individuals in the population were spawning synchronously. Spawned gametes remained in a viscous matrix and this appeared to minimise their dilution. Fertilization success varied greatly among individuals (0 to 92%) and was related to the distance to the nearest neighbouring spawner. Occasional wave wash facilitated the movement of sperm between spawners. Fertilization success in some individuals was limited by the scarcity of sperm whilst the experimental addition of sperm did not increase success in others.

Larval activity levels and delayed metamorphosis affect post-larval performance in the colonial, ascidian Diplosoma listerianum

It is becoming widely recognized that extending the larval period of marine invertebrates, especially of species with non-feeding larvae, can affect post-larval performance. As these carry-over effects are presumed to be caused by the depletion of larval energy reserves, we predicted that the level of larval activity would also affect post-larval performance. This prediction was tested with the cosmopolitan colonial ascidian Diplosoma listerianum in field experiments in southern Australia. Diplosoma larvae, brooded in the parent colony, are competent to settle immediately after spawning, and they remain competent to metamorphose for > 15 h. Some larvae were induced to metamorphose 0 to 6 h after release, whilst others were induced to swim actively by alternating light and dark periods for up to 3 h prior to metamorphosis. Juvenile colonies were then transplanted to a subtidal field site in Port Phillip Bay and left to grow for up to 3 wk. Extending the larval period and increasing the amount of swimming both produced carry-over effects on post-larval performance. Colonies survived at different rates among experiments, but larval experience did not affect survival rates. Delays in metamorphosis and increased swimming activity did, however, reduce colony growth rates dramatically, resulting in 50% fewer zooids per colony. Moreover, such colonies produced initial zooids with smaller feeding structures, with the width of branchial baskets reduced by 10 to 15%. These differences in branchial basket size persisted and were still apparent in newly budded zooids 3 wk after metamorphosis. Our results suggest that, for D. listerianum, larval maintenance, swimming, and metamorphosis all use energy from a common pool, and increases in the allocation to maintenance or swimming come at the expense of post-larval performance.

Variation in the dispersal potential of non-feeding invertebrate larvae: the desperate larva hypothesis and larval size

For many species of marine invertebrates, variability in larval settlement behaviour appears to be the rule rather than the exception. This variability has the potential to affect larval dispersal, because settlement behaviour will influence the length of time larvae are in the plankton. Despite the ubiquity and importance of this variability, relatively few sources of variation in larval settlement behaviour have been identified. One important factor that can affect larval settlement behaviour is the nutritional state of larvae. Non-feeding larvae often become less discriminating in their 'choice' of settlement substrate, i.e. more desperate to settle, when energetic reserves run low. We tested whether variation in larval size (and presumably in nutritional reserves) also affects the settlement behaviour of 3 species of colonial marine invertebrate larvae, the bryozoans Bugula neritina and Watersipora subtorquata and the ascidian Diplosoma listerianum. For all 3 species, larger larvae delayed settlement for longer in the absence of settlement cues, and settlement of Bugula neritina larvae was accelerated by the presence of settlement cues, independently of larval size. In the field, larger W subtorquata larvae also took longer to settle than smaller larvae and were more discriminating towards settlement surfaces. These differences in settlement time are likely to result in differences in the distance that larvae disperse in the field. We suggest that species that produce non-feeding larvae can affect the dispersal potential of their offspring by manipulating larval size and thus larval desperation.