Alan Lymbery

Parasites can influence host behavior, and conversely, host behavior can affect encounters with parasites. These long-standing interactions are now further complicated by species movement around the globe. The list of introduced species that have become invasive includes parasites that have adapted to new hosts in areas of introduction, as well as invasive hosts that alter the association between existing parasite–host assemblages. Researchers have documented differences in rates of parasitism and in the consequences of parasite infection between invasive and native hosts, and sometimes these differences are a result of behavioral differences, either pre-existing host behaviors or host behaviors that are altered as a consequence of infection. Parasites have been shown to mediate interactions between native and invasive hosts; occasionally, these parasites determine the outcome of invasions. The effects on native species can be severe, and to that end, conservation biology now takes into account the invasions, parasites, and behavior. The knowledge of the mechanisms driving invasions is incomplete, as is our understanding of parasitism and behavior. It follows that there are many questions remaining about how parasites and the behavior of their hosts influence population dynamics and community structure in the context of species invasions.

Anisakiasis is a disease caused by human infection with larval roundworms belonging to the family Anisakidae. The two species most often associated with anisakiasis are Anisakis simplex and Pseudoterranova decipiens. Humans are accidental hosts, who usually become infected by eating raw or undercooked fishes that contain larval worms. Worms may penetrate the gastric or intestinal mucosa, and may also produce a strong allergic response. Anisakiasis occurs throughout the world, with foci in North Asia and West Europe. Control measures focus on postharvest handling, storage, and cooking procedures for fish, although it is not clear if these measures are sufficient to prevent an allergic response.

In 2001 scientists from the New South Wales National Parks and Wildlife Service (now Department of Environment and Climate Change), La Trobe University and an environmental consulting firm investigated a mysterious death of grass outside a cave in Australia’s Snowy Mountains. Heavy rains had washed dead bogong moths (Agrotis infusa) from the cave and grass touched by this outwash died. Investigations revealed that arsenic concentrated in the dead bogong moths poisoned the grass. Worryingly, arsenic occurred in the bodies or the droppings of three mammal species eating bogong moths, so arsenic contamination was spreading in the food chain. The arsenic came from the plains of Queensland and western New South Wales, where bogong moths breed in autumn (Figure 27.1). The grubs, called cutworm caterpillars, eat grasses and crops before pupating in the soil to develop into winged adult moths. Arsenic-based insecticides were used intensively in the early 20th century and some are still available, so cutworm caterpillars probably absorb arsenic when eating crops. The adults migrate to the Snowy Mountains, aestivating during summer in caves until cooler weather when they return to the plains (Figure 27.2). The bogong migration is amazing and inspirational, part of the natural legacy bequeathed by the Australian environment to its human occupants. By contrast, the moths’ residual arsenic toxicity is disturbing, showing how human intervention may squander or spoil rich natural assets. You are now, though, in a position to understand and to solve such environmental problems and to reflect on what the environment and its conservation mean to you. Chapter aims: In this final chapter we revisit the three case studies introduced in Chapter 1: Leadbeater’s possum, the crown-of-thorns starfish and the Corrigin grevillea. We show how theories and techniques described in this book are applied to these cases. To suggest what a career in environmental biology entails, we conclude with views from two eminent Australian environmental biologists. They describe the challenges of their careers and the changes in technology and in society’s attitudes they have seen.

Land and Water Australia’s 2002 terrestrial biodiversity assessment painted a grim picture for Australia’s terrestrial fauna. It was estimated that 27 species of mammals, 27 species or subspecies of birds, one reptile species and four frog species have become extinct in Australia since European settlement, with a further 253 species or subspecies currently threatened with extinction. Yet these figures, sobering as they are, are a massive underestimate of the extinction crisis facing Australia’s wildlife. The terrestrial biodiversity assessment considered only vertebrates (animals with backbones). However, the 6000 described species of vertebrates make up only about 6% of described animal species in Australia compared to about 100 000 described species of invertebrates (and there are at least 200 000 invertebrates still to be described). The lack of attention paid to the conservation of invertebrates is not because they are not endangered. The problem is lack of knowledge. In a scientific sense, we have much to learn about the taxonomy, biology, ecology and conservation status of invertebrates. Invertebrates are very often ignored or actively discouraged by the general public. However, they are critical components of ecosystems, providing integral links in the food chain as well as essential ecosystem services such as plant pollination, soil aeration, organic decomposition and pest control. Chapter aims: In this chapter we introduce you to the main phyla of invertebrate animals. Each phylum has a common evolutionary history and common features that have evolved to cope with environmental challenges (Chapter 13). This is the body plan and our coverage 01 each phylum begins by describing it. Next, we describe the organs and organ systems responsible for movement (skeletal and muscular systems), feeding (digestive system), transporting food and oxygen internally (respiratory and circulatory systems), excreting waste products (excretory system), coordinating bodily activities (nervous and endocrine systems) and reproducing (reproductive system).

The animal kingdom includes many large and beautiful creatures. It is easy to engage the public’s sympathy for the plight of endangered animals such as tigers and pandas, or, closer to home, Tasmanian devils and numbats, and these animals are often the focus of intense conservation efforts. Parasites, on the other hand, live in or on other organisms. They are typically small, hard to see and often harm their hosts, so they are usually either ignored or regarded as a nuisance in practical conservation programs. This is a simplistic view. Parasites have vital roles to play in the functioning of natural ecosystems. In recent years it has been realised that many parasites are valuable indicator species, and their disappearance from an ecosystem is often a symptom of a deeper, underlying problem resulting from pollutants or other human impacts. Particularly important as indicators of environmental quality are parasites with complex life cycles, that travel through a range of different host species on their way from egg to adult. Figure 13.1, for example, shows the life cycle of a species of flatworm that lives in freshwater ecosystems in Australia. A parasite such as this may be a very sensitive indicator of environmental quality. The parasite and its various hosts are bound in a complex web of feeding interactions. They all have very different body structures and very different lifestyles and the environment in which they live must support all of these. If changes to the environment adversely affect any of its hosts, the parasite will be unable to complete its life cycle and will disappear. Despite their wide range of body structures and lifestyles, all the organisms in this complex web are animals. Unlike plants, most animals are motile and feed in many different ways and as a consequence have a much greater diversity of structure and function than do plants. Chapter aims: This chapter explains what all animals have in common, describes the influence of environment, lifestyle and size on how different animals solve the problems of life, and outlines how the main types of body plan found in the animal kingdom can be used to group and classify animals.

About 40 years ago, the first comprehensive biology textbook written specifically for Australian students opened with the photograph in Figure 1.1, showing a flock of sheep in a paddock. The scene was typical of many agricultural areas in Australia then, and remains so today. The authors commented on the questions a biologist might ask when viewing the picture: why do the sheep prefer to stand in the shade? Why are there no sheep under the far tree? Why are there no young trees in the paddock? Today, these questions seem less relevant. A contemporary biologist might ask: what was the landscape like before the establishment of European agriculture? Are there signs of land degradation and, if so, how could they be reversed? Is the agricultural production sustainable? If not, what are the implications for local human communities? These questions reveal a growing concern about the impacts of expanding human populations and the application of new technologies on the natural environment. Chapter aims: This chapter describes how the stress of the world’s dominant animal species, humans, has severely altered biodiversity and natural ecosystems. Three in-depth examples of environmental problems are introduced, together with an explanation of the knowledge and skills biologists need to reverse or mitigate such problems.

Using data from 57 sites across suburban Perth we tested the influence of Cat Density on species richness and community composition of passerine birds as well as the presence/absence of 15 common passerine species. Cat Density is not a significant predictor of any of the dependent variables. Instead passerine species richness declined with increasing Distance to Bushland and with increasing Housing Density, but increases proportionately with the Size of, Nearest Bushland > 5ha. Together, these predictors explained approximately half the variability in bird species richness (adjusted R2 for the complete data set = 0.414). Passerine community composition was significantly affected by Housing Density, Distance to, and Size of, Nearest Bushland > 5ha. These environmental variables, especially Housing Density, appeared to act principally by their effect on the number of small and medium sized insectivores. Attempts to predict the presence/absence of 15 common passerines did not yield clear results, although Housing Density appeared the most likely predictor. While cat predation might be significant adjacent to remnant bushland or other areas of conservation significance, blaming cats for bird conservation issues in long-established suburbs may be a scapegoat fro high residential densities, inappropriate landscaping at a range of scales or poor conservation of remnant bushland.