Reproductive Biology of Crustaceans

Case Studies of Decapod Crustaceans

Elena Mente

• Publisher: CRC Press
• Year: 2008
• ISBN:
  9781000738049
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Marine Biology
• Index: Biological Sciences

Crustaceans adapt to a wide variety of habitats and ways of life. They have a complex physiological structure particularly with regard to the processes of growth (molting), metabolic regulation, and reproduction. Crustaceans are ideal as model organisms for the study of endocrine disruption and stress physiology in aquatic invertebrates. This book

1

An Overview

E. Mente¹ and C. Neofitou²

¹Assistant Professor, School of Agricultural Sciences, Department of Ichthyology and Aquatic Environment, University of Thessaly, GR- 38446 Volos, Greece. and Honorary Research Fellow, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, AB24 3TZ Aberdeen, UK. E-mails: [email protected]; [email protected]

²Professor, School of Agricultural Sciences, Department of Ichthyology and Aquatic Environment, University of Thessaly, GR- 38446 Volos, Greece. E-mail: [email protected]

Interest in the theoretical and the applied biology of crustaceans has been growing steadily over a long time, not only because of the commercial importance of the species but also because they are an excellent study species for physiological, biochemical and neurobiological research. This book is intended to provide a synthesis of the diverse of research that has been carried out on the reproductive biology of crustaceans and to emphasise as case studies current active research on lobsters and shrimps. In recent years the need to understand and control reproductive processes and mechanisms in crustaceans has been stimulated by increasing interest in the culture of shrimps, lobsters and crabs.

In the subphylum Crustacean there are 6 classes and the Malacostraca contain some 70% of all species (Chapter 2). However, within Malacostrace most of the species are contained within the three orders Decapoda, Amphipoda and Isopoda (Chapter 2). It seems that Crustacea have a multiplicity of groups but most of the species are concentrated in a few of these groups and the groups which are relatively poor in species are often important in terms of individuals (Warner, 1977). The decapod is the group that contains the most familiar crustaceans as, lobsters, shrimps and crabs. Convenient size, easy availability, important commercial fisheries species, complexity and diversity make the decapod model crustaceans to study.

The application of biotechnology to crustacean aquaculture is of an increasing in importance (Chapter 3). Early doubts that such approaches were not fruitful in view of the crude state of development of the aquaculture industry are replaced by the recognition that sophisticated molecular approaches are required to tackle key problems of disease recognition and control, and to achieve higher production through the development of domesticated strains. Progress in penaeid genetic and biotechnological research has been slow because of a lack of knowledge on fundamental aspects of their biology. However, data is beginning to emerge from research projects during the last decade, and this is likely to increase rapidly in the future. Highly variable markers are developed that allow the genetic variation in crustacean stocks to be assessed, even in highly inbred cultured lines. Greater attention is devoted to developing cell lines for crustaceans, and to the development of molecular probes for the identification of pathogens. Chapter 3 concludes that these newly emerged molecular techniques are transforming the research and practice of animal agriculture, and are instrumental in developing profitable, environmentally friendly agriculture and in meeting the demand of market worldwide. The complete genomic sequences and DNA microarrays featuring the whole genome of major farm animal species are expected to be available in the near future. Novel approaches to enhancing animal productivity and health are expected to be developed, and new biotherapeutics and new animal breeds with desired characteristics to be produced. In addition, transgenic farm animals appear to be a progressing avenue to much needed pharmaceuticals and immunologically suitable organs for transplantation.

The large variety of reproduction patterns in crustacean is a result of adaptive processes determined by evolutionary pressures to improve survival of the offspring (Hartnol and Gould, 1988). Knowledge of the reproductive biology of the species in relation to their growth patterns is important for sustainable future stocks assessments. Size at sexual maturity and fecundity are of great importance for understanding population dynamics and reproductive strategies (Kennelly and Watkins, 1994). Chapter 4 of this book explores some of the most important aspects of crustacean reproduction in relation to their exploitation by fisheries. It reviews relationships between size classes and fecundity, egg development and their spatial variability, catch-effort restrictions, minimum legal landing size, a ban on landings of berried females, closed seasons and protected areas. It discusses stock assessment methods and migration patterns. Environmental factors affect crustacean reproduction through modifications of size at maturity, delay in time of moulting and spawning and hatching periods. Temperature is an important factor affecting catch rates in the short term and this must be considered when using catch per unit effort as an abundance index. The presence of external and internal maturity indicators is more evident in females than in males and female maturity is more relevant for stock assessment. Therefore analysis of maturity in females is a more common practice in crustacean maturity studies. Chapter 4 presents a list of maturity indicators and their respective relationships to body size and maturity for different species of crustaceans around the world for both males and females. Knowledge on maturity and reproductive biology in relation to fishery practices is essential to achieve the sustainable management of the species. Future studies should focus on sustainable management in fishing resources in the ecosystem and trophic level context.

Chapter 5 reviews the different aspects of sexual selection and demonstrates the diversity of mating behaviour and mating systems in Crustacea. Numerous studies have investigated various factors influencing the mating behaviour, strategies and systems in crustaceans. Christy (1987) discussed the adaptive value of different mating strategies in male crabs. Hartnoll (2000) analysed the adaptive value of the two sexes to different mating strategies, considering mating strategy as a process of co-evolution in both sexes. He concluded that changes in mating strategy in crabs retaining indeterminate growth have been harder to account for especially in those retaining an aquatic habit at the same time. Further research is needed to clarify this uncertainty. Further research is also necessary to investigate the interplay of multiple ecological, reproductive and life history factors underlying the observed diversity in mating behaviour and mating systems. Crustaceans offer an excellent model for investigating the complex network of relationships caused by the interplay of multiple factors, and for studying current issues related to sexual selection such as sexual conflict, mate choice, male sperm limitation and sperm allocation. In-depth knowledge of the mating behaviour and an understanding of the interplay of multiple factors affecting the reproductive behavioural ecology of crustaceans would contribute to the conservation of these important macro-invertebrates and of the freshwater and marine ecosystems inhabited. Thiel, (2000) reviews parental care behaviour from different crustacean taxa and environments but no general pattern has been recognized. The high diversity of crustaceans with extended parental care suggests that this reproductive behaviour has evolved independently in a variety of crustacean taxa under a variety of environmental conditions (Thiel, 2000). The review indicates that very little is known about the behaviour of crustacean parents, the resources they invest into individual offsprings, the benefits and costs of this reproductive behaviour and the evolution of social behaviour.

Knowledge of reproductive biology of females has come mainly from studies on sexual maturity by macroscopical investigations and by histological methods (Adiyodi and Subramonian, 1983). To date eyestalk ablation still represents the most commonly used manipulation to induce maturation and spawning in female crustaceans. This is an outcome of the success of this method in increasing reproductive output and spawning frequency and of its achievement in shortening the latency to first spawn (Racotta et al. 2003). Female maturity is more easily defined since attached eggs provide conclusive proof although there are other indicators such as relative abdomen width (in Homarus), ovigerous setae and cement gland development (Aiken and Waddy 1980). The oocytes and ovaries of Nephrops species develop from white through yellow and pale green to very dark green at maturity (Table 1). The investigation on oogenesis in many crustacean mature females allows the identification of growing stages and their comparison between species. The literature for many crustaceans distinguishes 4 to 5 growing stages (Adiyodi and Subramonian, 1983). However, more species-specific research using histological, histochemical and ultrastructural approaches is needed to investigate egg (oocyte) development and improve understanding of oogenesis and management of crustacean. Central to female reproduction is the process of vitelogenesis including the biosynthesis of yolk proteins and their transport and storage in the ovary for sustenance of the developing embryo. In many decapoda, there is evidence that yolk protein synthesis depends on extraoocytic sequestration of vitellogenin, and haemolymph protein fraction specific to vitellogenic females (Desantis et al. 2001). Chapter 6 of this book focuses mainly on research on the hormonal control of vitellogenesis and ovarian maturation. It illustrates recent advances in identifying the pathways of vitellogenin synthesis and describes its main regulators and advances in their isolation and mode of action. The research detailed in Chapter 6 has shown that the endocrine regulation of both reproduction and molting is controlled by a complex interaction of neuropeptides, juvenoids and steroids. Although studies have confirmed that female gonadal development could successfully be induced through injections or transplants of these hormones and endocrine glands, the effects are highly variable depending on factors such as species, developmental stage of the animal and concentrations of hormones and neurotransmitters given. For future applications of hormones in the manipulation of breeding stocks in captivity, it is first necessary to fully understand the interactions and functions of these endocrine systems. Only then can research be directed at finding a hormonal treatment that has clear advantages over eyestalk ablation and that is also effective in terms of reproductive output. In species where close links exist between environmental factors and reproduction, the interruption of established metabolic pathways may have detrimental effects on the survival of the population and possibly also on their consumers. The resolution of connecting pathways between environmental stimuli and their hormonal responses would therefore be also beneficial for the conservation of populations in the wild.

Table 1 Ovary staging based on ovary colour for Nephrops.

Knowledge of male reproductive biology and physiology is less developed. Hence, further research on the hormonal control of male reproduction and factors affecting their reproduction activities is necessary. Research on crustacean endocrinology is still needed. Chapter 7 gives a brief historical overview of hormonal regulation of reproduction in male crustaceans, including the androgenic gland hormone (AGH), and some details of recent work on its isolation, characterization, and mode of action. It also summarises evidence for the role of other chemical mediators in the regulation of male reproduction (ecdysteroids, vertebrate-like steroids, and methyl farnesoate). The isolation and characterization of crustacean pheromones is important for both basic research and for the development of novel methods of harvesting commercially important fisheries species and for the control of nuisance and alien crustaceans. Whether testosterone has a physiological role in male reproduction in crustaceans is an issue where further research is needed. However, reports suggest that ecdysteroids are involved in male reproduction. Except for the ecdysteroid receptor, research on crustacean hormone receptors is limited. The identification of the AGH in decapod crustaceans enables a better understanding of the regulation of sexual differentiation and masculine reproductive physiology. If the AG active factor is found to be a member of the insulin-like super family, this would support the view that insulin may have evolved in the context of regulating sexual differentiation. Chapter 7 concludes that there are indications of other chemical mediators involved in male reproduction. These factors include neurotransmitters and peptides such as gonad-inhibiting hormone (GIH, also known as vitellogenesis-inhibiting hormone, VIH). Most of the work on these factors is focused on females. More research needs to be conducted to determine if these factors have a role in male reproduction. Due to the biological importance of Crustacea, it is likely that much more research would be devoted to the determination of the effects of exogenous chemicals upon various physiological processes, including male reproduction. Crustaceans are likely to be useful indicator species for environmental contamination.

Many factors play an important role on growth and maturation processes such as the irregular and relatively asynchronous molting, the extended spawning season, the number of spawnings, the prolonged period of recruitment and the duration of larval stages (Sarda and Demestre, 1989; Demestre and Fortuño, 1992; Kapiris and Thessalou-Legaki, 2001). Hartnoll’s (1982) review on growth in crustaceans covers both absolute and relative growth. Hartnoll’s (2001) review identifies four aspects of crustacean growth: the hormonal control of moulting, the effects of external factors, the patterns of growth and the determination of age. He concludes that despite the development of modelling approaches and an increased body of data our understanding of the underlying principle of the diversity of crustacean growth patterns remains speculative. The adaptive value of the great diversity of growth patterns in crustaceans is not adequately explained and further research is needed beyond the descriptive phase. The interrelationships between reproductive and molt cycles during the reproductive season are discussed in Chapter 9. The results of the chapter stress the necessity for further molecular research on the patterns of expression of genes under the control of eyestalk neuropeptides in both the molt and reproductive cycles.

Chapter 11 reviews the reproductive biology of shrimps and reports biological differences between wild and captive shrimps. The most enigmatic phenomenon is the female’s “abstinence” from reproduction in captivity. Further research, inclu...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Preface
• Acknowledgements
• Table of Contents
• List of Contributors
• 1. An Overview
• 2. Phylogeny Biology and Ecology of Crustaceans (Phylum Arthropoda; Subphylum Crustacea)
• 3. Aspects on Population and Aquaculture Genetics of Crustaceans
• 4. Reproduction of Crustaceans in Relation to Fisheries
• 5. Mating Behaviour
• 6. Endocrine Control of Female Reproduction
• 7. Male Reproductive Hormones
• 8. Nutrition in Relation to Reproduction in Crustaceans
• 9. Coordination of Reproduction and Molt in Decapods
• 10. Reproductive Biology and Growth of Marine Lobsters
• 11. Male and Female Reproduction in Penaeid Shrimps
• 12. Reproduction and Growth of Decapod Crustaceans in Relation to Aquaculture
• 13. The Crustacean Nephrops norvegicus: Growth and Reproductive Behaviour
• 14. Implementation of Failure Mode and Effects Analysis (FMEA), Cause and Effect Diagram, HACCP and ISO 22000 to the Reproductive Cycle and Growth of Crustaceans in Cultured Conditions
• Index
• Color Plate Section