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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 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.

This chapter reviews the current state of knowledge about the diversity in physiological responses (including energy metabolism, acid–base balance, and biomineralization) to ocean acidification (OA) in four major taxonomic groups of marine calcifiers—corals, molluscs, crustaceans, and echinoderms. The interactive effects between acidification and other commonly occurring environmental factors, such as temperature, salinity, hypoxia, and trace metals, on the physiology of these animal calcifiers is reviewed. Assessment of the inter-phylum and inter-species variability in response of OA (either alone or in combination with other stressors) is critical in identifying most vulnerable ecosystems as a focus for conservation efforts, reducing the impact of other stressors such as pollution, and aquaculture efforts to improve resilience of existing stocks of economically important marine organisms.

This chapter briefly describes the diversity in the functional morphology of the crustacean reproductive organs from both macroscopic and microscopic approaches. The genital ducts in both females and males show large morphological variability. This anatomical diversity is proposed to be partially driven by the environment since some similar morphofunctional patterns are found in similar habitats. Specially, different patterns of sperm storage are discussed within the framework of sperm competition. Reproductive morphology in hermaphroditic and intersex species is also included and compared, highlighting the significance of these reproductive models. Finally, morphological comparative studies are proposed to address questions related to the evolution of general and particular designs and primitive and advanced patterns, as well as the study of the embryological development of the reproductive system as a key to understand the differences between and within taxa and neurohormonal pathways of sexual differentiation and endocrine disruption.

The myriad behaviors characteristic of crustaceans reflect the diverse lifestyles (pelagic, benthic, terrestrial, parasitic, sessile) of this large taxon. These behaviors are controlled by nervous systems whose basic structure is conserved across the Crustacea. Crustacean nervous systems are also characterized by extensive taxon-specific adaptations, including marked reductions (e.g., sessile barnacles) and increases (e.g., territorial stomatopods) in complexity. This chapter outlines the organization of the sensory and central nervous systems of the principal crustacean taxa, highlighting both conserved and specialized features.

The science of natural history is built on twin pillars: cataloging the species found in nature, and reflecting on the variety and function of body plans into which these species fit. We often use two terms, diversity and disparity, in this connection, but these terms are frequently used interchangeably and thus repeatedly confused in contemporary discourse about issues of function and form. Nevertheless, diversity and disparity are distinct issues and must be treated as such; each influences our views of the evolution and morphology of crustaceans

The evolutionary history of the postantennular appendages of Crustacea is reviewed, including information on limb development early in the evolutionary lineage of this taxon. Further changes of the appendages and the effects on the feeding and locomotory system are followed along the evolutionary lineage of the crustaceans into the crown group, Eucrustacea. Acknowledging these changes is crucial to understand the high degree of variation of modern crustacean limb morphology and to overcome difficulties in recognizing their common features in terms of homology and relationships. Other strategies that evolved subsequently in eucrustacean ingroups include the arrangement of limbs into functional units and consequent changes in their morphologies, and the high modification of limbs for very specific purposes, for example, reproduction/copulation. Lastly, limbs are also lost repeatedly in various taxa. Reconstructing the evolutionary history of limbs along different crustacean lineages is still a major task for future research.

This chapter reviews the current knowledge on pheromones of aquatic animals. Pheromones are chemical signals used for communication within a species. It has been found that species from many different animal taxa use pheromones underwater. These include reptiles, amphibians, fish, crustaceans, molluscs, rotifers, and polychaetes. The chapter then summarizes the results from species of all the different taxa, focusing on some recurrent themes and mechanisms found across taxa in aquatic pheromone research. It also states that pheromones undergo the same evolutionary selection mechanisms as other communication signals, emphasizing that signalling is adaptive for the signaller, and responding to the signal is adaptive for the receiver.

Sea ice covers a significant area of the polar regions, particularly in winter. This chapter discusses the formation and nature of different types of sea ice. The biological makeup of sea ice communities, which includes a significant metazoan component, is complex. Sea ice photosynthetic communities are often dominated by highly abundant diatoms. Sea ice communities face the challenge of continuous freezing temperatures and considerable variations in salinity, as well as low levels of photosynthetically active radiation. Despite the challenging environment, biological activity in the sea ice can be high and this is illustrated by an exploration of photosynthesis and bacterial production rates. Bacteria and phototrophs are in turn exploited by a range of protozoan and metazoan grazers within the sea ice community. Viruses appear to be important in sea ice, as they are in glacial environments (cryoconite holes), and may play an important role in carbon cycling. By comparison, lake ice is poorly researched, but functional largely cyanobacterial communities have been described in the perennial ice covers of lakes in the McMurdo Dry Valleys of Antarctica. Annual ice covers on alpine lakes support microbial communities that include rotifers. The limited information on photosynthetic rates and rates of bacterial production in lake ice are outlined.

The Arthropoda is one of the largest phyla in the animal kingdom, with the insects alone purportedly consisting of several million living species. The other arthropods are estimated to be more than 100,000. The fossil record both of living and extinct groups dates back to the Early Cambrian and provides important insights about the evolution of the phylum. There are two or three subphyla comprised of a number of subgroups: Pycnogonida, Chelicerata (Xiphosura + Arachnida), and Mandibulata (Crustacea + Tracheata (= Hexapoda + Myriapoda)). However, more recent evidence from morphological and molecular studies point to Hexapoda as an ingroup of the Crustacea. The name Pancrustacea may be applied for the clade, while ‘crustaceans’ may be used for the non-hexapod groups. The Myriapoda appears to be the sister group of the Pancrustacea. The Pycnogonida has been interpreted as the sister group of the Euchelicerata (Xiphosura + Arachnida), while the Pentastomida has been placed within the Arthropoda as the sister group of the Branchiura.