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This chapter discusses the composition of seagrass communities. Seagrass communities comprise epiphytes and sessile epifauna growing on seagrass leaves and rhizomes, as well as more mobile animals, many of which move between seagrass and other habitats at different times or life-cycle stages. These include herbivores (ranging from tiny feeders on microscopic epiphytic algae to massive turtles and seacows), detritus feeders, and predators.

This chapter presents summaries of each taxonomic group inhabiting temporary waters, providing examples of habitat-specific requirements and adaptations throughout. Insects and crustaceans are the dominant community members and, consequently, the best studied groups. However, information is also provided on lesser known groups, such as the prokaryotes, fungi, nematodes, tardigrades, and rotifers. Higher plants, fishes, amphibians, reptiles, birds, and mammals are discussed. Detailed case histories are given of the biotas from common habitat types. Global and regional comparisons of temporary water communities are made and commonality is demonstrated.

This chapter begins with a brief discussion of the factors that make crustaceans an excellent model for the study of aggressive behavior. It then discusses the natural contexts of aggression, aggression in development, aggressive behavior, dominance hierarchy formation, hormonal control of aggressive behavior, and neural mechanisms of aggressive behavior.

Walking with legs is the main form of locomotion in most species of decapod Crustacea. This chapter focuses on the walking movements in molluscs such as crayfish and lobster. In addition, some species, such as crayfish and lobsters, can swim both forward with the swimmerets and backward with flips of the abdomen. Crustaceans have been extensively examined at the behavioural, network, and cellular levels, and the corresponding neuronal mechanisms have been understood to a considerable extent. The lobster exhibits a walking pattern characteristic of many decapods, and can walk in any direction, using all or only a subset of ten walking legs. The coordination of the numerous legs in the walking crayfish or lobster is achieved due to the interactions between their controllers. Mutual influences between the leg controllers were revealed in experiments where the movement of one leg was perturbed. The locomotor system can be activated by stimulation of command neurons in both crayfish and lobsters.

This chapter focuses on locomotion in stick insects and locusts. To walk with their six legs is the main form of land locomotion in most insects. Most of the information available on the nervous control of walking in insects has been obtained from three animal models: the stick insect, the locust, and the cockroach. The goal of the chapter is not to present a detailed review of the field but rather to highlight how the studies of walking in two animal models have increased our understanding of basic principles of locomotor control. The insect leg consists of five segments: the coxa, the trochanter, the femor, the tibia, and the tarsus. Femor and trochanter are sometimes fused into one segment. Insects can walk both forward and backward. The main design of the walking control system in insects is similar to that in Crustacea. Each of the six legs is controlled by the leg controller.

This chapter focuses on the idea that during locomotion, each of the four limbs is driven by its individual control mechanism, which is relatively independent of the controllers for the other limbs. This idea emerged from the observation that, under certain conditions, the rhythms of stepping in different limbs may differ from each other. Divergence of rhythms of individual limbs was later observed by other investigators when the animal walked on a treadmill with split belts. Thus, the basic principle of the control of locomotion in walking animals, that is a considerable autonomy of the individual limb controllers, is common for different species – from crustaceans and insects to mammals. A detailed analysis of the motor pattern of the hind limb of the cat was carried out by a number of investigators. The step cycle in the cat consists of two principal parts, the stance (or support) phase and the swing (or transfer) phase. The three main joints (hip, knee, and ankle) of the hind limb perform considerable flexion–extension movements during the step cycle. To increase the speed of locomotion, there are two principal ways: to increase the frequency of stepping and to increase the amplitude of the stepping movements.

This chapter summarizes global patterns and mechanisms of both ecological and historical crustacean biogeography resulting in the contemporary species distributions described over the past decades. In the pelagic realm, hydrographic features such as ocean currents, physical depth profiles, and latitudinal temperature gradients are major structuring elements, as well as selection pressure exerted by the environment and species interactions, which have resulted in speciation over evolutionary time. Benthic crustacean distributions are additionally constrained longitudinally by continental barriers and submarine features such as ridges and seamounts. The main biogeographic patterns of both benthic and pelagic crustaceans are described for all ocean basins and the polar regions, of which the Indian Ocean is the least well studied. The Copepoda and Decapoda are generally represented with the highest number of described species, followed by Amphipoda and Isopoda. Life cycles with pelagic larvae (e.g., decapods and stomatopods) increase dispersal and enable wide distributions, while a lack of dispersive larvae promotes endemism in benthic forms (e.g., amphipods). Restricted regions with high species richness and endemism, such as the “coral triangle” (the Indo-Australian Archipelago), the Red Sea, and the Mediterranean, represent important biodiversity hotspots. Endemics are also suitable markers for past earth history events. Only a few studies cover the biogeography of crustacean taxa in all of the world’s oceans, but a few exceptions exist for decapods, amphipods, and isopods. Although the world’s oceans have been reasonably well studied for crustacean distribution and diversity, species complexes and cryptic species lacking morphological diagnostic features leave us with a large number of unconsolidated taxa. Emerging molecular tools may be able to assist with refinement of nomenclature and hence increase the resolution of crustacean biogeography in the future.

Crustacean reproductive traits are highly diverse, and this chapter illustrates some of the most extreme cases, placing them in the context of the more typical crustaceans. It highlights, for example, the male and female records of size and age, the “hottest” and “coolest” reproducers, the longest penises, the largest sperm and eggs, the smallest and largest brood sizes, the longest mate guarding, the most massive sexually selected weapons, the flashiest courtship, the most fathers per brood, the longest incubation of broods, the smallest and largest larvae, the longest larval duration, the longest dormancy of eggs, and the oldest fossil evidence of penis, sperm, brood care, and larvae. Using these illustrious case studies, this chapter briefly examines the adaptive advantages of these extremes and discusses why few species have evolved unusual reproductive traits. Crustaceans indeed appear to hold animal records with respect to relative penis length, aflagellate sperm length, dormant egg viability and fossil ages of penis, giant sperm, and brood care. These captivating examples may be of applied importance in terms of restoring human-altered ecosystems (resurrection ecology using egg banks) and in management strategies of important fisheries.

This introductory chapter looks into the physiology and diversity of crabs, including certain species which defy conventional definitions of what a crab is. It largely concerns itself with the question of what makes a crab recognizable as a crab, by delving into the world of crustaceans, arthropods, decapods, and so on, in order to differentiate crabs from other similar marine life—such as lobsters. The chapter then provides classifications on the major families of Brachyuran (true) crabs, which are the largest group of crabs, as well as those of the anomuran crabs. Finally, the chapter highlights some notable species of crabs, rounding out the discussion by providing information on the largest, smallest, and oddest crabs to date.

This chapter provides an introduction to the Crustacea, one of the most abundant and diverse components of the plankton. Within a single net-haul, the vast diversity within this group, coupled with the large number of species and the morphological similarity both between species and between developmental stages, can often pose a significant identification challenge even to experienced taxonomists. Although all Crustacea originally share a common body plan, their morphology can differ quite markedly due to different degrees of expression of body segmentation patterns and as a result of the loss or morphological modifications of paired appendages. There is also considerable variation between groups in the structure and function of the appendages on different body regions.

This chapter examines the relationship between the fish faunas of the Amazon and Orinoco river basins and the distributions of species across the Vaupes Arch region and the Casiquiare Canal. It analyzes the differences and similarities in the two faunas and the historical and contemporary geographic and environmental factors that influence fish distributions, speciation, and adaptation. It explains that the Amazon and Orinoco river basins contain extraordinarily diverse assemblages of fishes, crustaceans, and other aquatic organisms, and have long been considered separate biogeographic provinces.

The benthic environment refers to the region defined by the interface between a body of water and the bottom substrate, including the upper part of the sediments, regardless of the depth and geographical location. Hence, benthic environments, their organisms, and their ecosystems are highly variable as they encompass the full depth range of the oceans with associated changes in physical and chemical properties as well as differences linked to latitudinal and geographical variation. The effects of ocean acidification on the full range of different benthic organisms and ecosystems are poorly known and difficult to ascertain. Nevertheless, by integrating our current knowledge on the effects of ocean acidification on major benthic biogeochemical processes, individual benthic organisms, and observed characteristics of benthic environments as a function of seawater carbonate chemistry, it is possible to draw conclusions regarding the response of benthic organisms and ecosystems to a world of increasingly higher atmospheric CO2 levels. The fact that there are large-scale geographical and spatial differences in seawater carbonate system chemistry (see Chapter 3), owing to both natural and anthropogenic processes, provides a powerful means to evaluate the effect of ocean acidification on marine benthic systems. In addition, there are local and regional environments that experience high-CO2 and low-pH conditions owing to special circumstances such as, for example, volcanic vents (Hall- Spencer et al . 2008 ; Martin et al . 2008 ; Rodolfo-Metalpa et al . 2010), seasonal stratification (Andersson et al . 2007), and upwelling (Feely et al . 2008 ; Manzello et al . 2008 ) that may provide important clues to the impacts of ocean acidification on benthic processes, organisms, and ecosystems. The objective of this chapter is to provide an overview of the potential consequences of ocean acidification on marine benthic organisms, communities, and ecosystems, and the major biogeochemical processes governing the cycling of carbon in the marine benthic environment, including primary production, respiration, calcification, and CaCO3 dissolution. The depth of the euphotic zone, i.e. the depth of water exposed to sufficient sunlight to support photosynthesis, varies depending on a range of factors affecting the clarity of seawater, including river input and run-off to the coastal ocean, upwelling, mixing, and planktonic production.

In this chapter the primary emphasis is on spatial scales of disturbances, and we will follow on from our earlier discussions on the mechanisms of competition and predation and the controversy over their importance in controlling species richness. Huston (1994) realized that the effects of competition, predation, and general physical disturbance were similar in that individuals were removed from the assemblage. We now show that there is a need to link these aspects with the tolerances of individual species, for example to determine in which of these cases the organisms are absent because the conditions now fall outside the optimal tolerance ranges. Thus we discuss disturbance as a general phenomenon which includes the effects of any processes that lead to a reduction in numbers of individuals and/or biomass. Disturbance includes physical disturbance as well as biological processes such as the effects of competition and predation on assemblages. The spatial scales covered range from micrometres to many hundreds of kilometres for the effects of bottom trawling, which is now considered to be one of the most serious and damaging threats to sediment habitats and assemblages. Disturbance effects caused by trawling and by pollution are considered in the following chapters. First, it is necessary to consider scale since many new insights have developed in the past few years of research. In the past couple of decades a new branch of ecology, landscape ecology, has developed, devoted to considering patterns over large areas, and a terminology of spatial scales has been defined. Grain is the first level of spatial resolution; it relates to the individual data unit and can be described as fine-grained to coarse-grained. Extent refers to the overall size of the study area. A map of 100 km2 and one of 100 000 km2 differ in extent by a factor of 1000. Grain and extent are illustrated in Fig. 6.1. A third component is lag, which is the betweensample distance. Figure 6.2 summarizes temporal and spatial scales of disturbances (modified from Zajac et al. 1998). The figure shows the main types of disturbances affecting soft-sediment systems, and separates them into natural and anthropogenic effects (see also Chapter 11, which indicates some of the management responses to these effects).

Given the discussion above regarding natural changes in the marine benthos, we should now consider the human-mediated (anthropogenic) changes and the response of benthic systems to human impacts. From the 1960s to the 1980s the general opinion seemed to be that pollution (considered in the next chapter) was the most important marine problem, but we now realize that habitat change and habitat loss are of greater concern: see, for example, the Quality Status Report 2000 (OSPAR 2000). One of the greatest effects on the integrity of the seabed and hence its biota is now known to be caused by bed trawling. This has now generated an enormous literature, and the reader is directed to Daans and Eleftheriou (2000) and Hollingworth (2000) for more details. We can take this information and summarize the overall ecosystem effects of fisheries in detailed flow diagrams (referred to as ´horrendograms´!) to show the interlinked and complex nature of the impact—the effects trawling are included here, but see also those in McLusky and Elliott (2004) (e.g. Fig. 8.1). Historically, the effects of trawling on benthos caused concern as early as 1376 when a petition was made to the English parliament by fishermen concerned over the damage done to the seabed and fisheries by bottom trawling (De Groot 1984). This was despite the gear used by sailing vessels in those days being relatively light and towed at slow speeds and in shallow water only. When steam trawlers were developed in the early 1900s, everything changed. The weight and size of trawls increased and use of tickler chains (mounted on the bottom rope to disturb bottom-living fish upwards and into the trawl net) were of great concern, although studies done in the 1970s to allay the fears of fishermen did not find long-term effects on macrobenthos (Jones 1992). At the end of World War II the otter trawl was developed and its use became widespread. This and the beam trawl (see Fig. 8.4) were (and still are) the types of gear most widely used to fish the seabed.

A widely accepted definition of marine pollution is “the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities including fishing, impairment of the quality for use of seawater, and reduction of amenities”. (Wells et al. 2002). This differs from contamination since it results in biological damage, whether to the natural or human system, whereas contamination can be regarded merely as the introduction of substances by human activities (McLusky and Elliott 2004). Furthermore, pollution and pollutants can refer to biological and physical materials as well as chemicals (Gray 1992, Elliott 2003). In the case of the benthos, there is an extensive literature indicating that every type of pollutant has an effect on the benthos and so it is not surprising that the benthos is the mainstay of any monitoring and investigative programme. Pollution can affect organisms living in sediments by physical variables associated with the pollution source, such as increased sedimentation of particles, which leads to smothering of the fauna. In such cases the effect can in fact be regarded as a disturbing factor if the effects lead to mortality of individuals (Gray 1992). Alternatively, pollution can affect the fauna by toxicity where increased concentrations of contaminants lead to biochemical and physiological effects and ensuing mortality if certain thresholds for adaptation are exceeded. Here, however, we first treat the effects of the most widespread form of pollution affecting the marine environment— increased organic matter in sediments. Excess organic matter enters the marine environment principally as sewage, although it can also include waste from paper pulp mills or changed river run-off, for example. Excess organic matter causes physical effects such as smothering and also leads to reduced oxygen concentrations in the water column or pore-water in sediments. Sewage discharged into confined bodies of water frequently leads to the well-known symptoms termed eutrophication, resulting, in the most extreme cases, in a total lack of oxygen and the presence of hydrogen sulfide in the sediment, with a corresponding absence of fauna (e.g. de Jonge and Elliott 2001).