Echinoderms Through Time

Echinoderms are now considered as a biological and geological model that underlies researches of primary importance. The extent of the contributions made by the International Echinoderm Conferences to various fields of research is attested by the scope covered by presentation at the international conferences. These proceedings contain the complete papers or abstracts of all the presentations and posters presented at the eighth International Echinoderm Conference, held in Dijon, France in September, 1994. Coverage includes: general; extinct classes; crinoids; asteroids; ophiuroids; holothuroids; and echinoids.

Echinoderms, including feather stars, seastars, brittle stars, sea urchins and sea cucumbers, are some of the most beautiful and interesting animals in the sea. They play an important ecological role and several species of sea urchins and sea cucumbers form the basis of important fisheries. Over 1000 species live in Australian waters, from the shoreline to the depths of the abyssal plain and the tropics to Antarctic waters. Australian Echinoderms is an authoritative account of Australia’s 110 families of echinoderms. It brings together in a single volume comprehensive information on the identification, biology, evolution, ecology and management of these animals for the first time. Richly illustrated with beautiful photographs and written in an accessible style, Australian Echinoderms suits the needs of marine enthusiasts, academics and fisheries managers both in Australia and other geographical areas where echinoderms are studied.

Echinoderms are now considered as a biological and geological model that underlies researches of primary importance. The extent of the contributions made by the International Echinoderm Conferences to various fields of research is attested by the scope covered by presentation at the international conferences. These proceedings contain the complete papers or abstracts of all the presentations and posters presented at the eighth International Echinoderm Conference, held in Dijon, France in September, 1994. Coverage includes: general; extinct classes; crinoids; asteroids; ophiuroids; holothuroids; and echinoids.

The history of life on earth is largely reconstructed from time-averaged accumulations of fossils. A glimpse at ecologic-time attributes and processes is relatively rare. However, the time-sensitive and predictability of echinoderm disarticulation makes them model organisms to determine post-mortem transportation and allows recognition of ecological-time data within paleocommunity accumulations. Unlike many other fossil groups, this has allowed research on many aspects of echinoderms and their paleocommunities, such as the distribution of soft tissues, assessment of the amount of fossil transportation prior to burial, determination of intraspecific variation, paleocommunity composition, estimation of relative abundance of taxa in paleocommunities, determination of attributes of niche differentiation, etc. Crinoids and echinoids have received the most amount of taphonomic research, and the patterns present in these two groups can be used to develop a more thorough understanding of all echinoderm clades.

Echinoderms and prochordates occupy a key position in vertebrate evolution. The genomes of sea urchin share 70% homology with humans. Researches on cell cycle in sea urchin and phagocytosis in asteroids have fetched Nobel Prizes. In this context, this book assumes immense importance. Echinoderms are unique, as their symmetry is bilateral in larvae but pentamerous radial in adults. The latter has eliminated the development of an anterior head and bilateral appendages. Further, the obligate need to face the substratum for locomotion and acquisition of food has eliminated their planktonic and nektonic existence. Egg size, a decisive factor in recruitment, increases with decreasing depths up to 2,000-5,000 m in lecithotrophic asteroids and ophiuroids but remains constant in their planktotrophics. Smaller ( 110 mm) asteroids generate planktotrophic eggs only. Publications on sex ratio of echinoderms indicate the genetic determination of sex at fertilization but those on hybridization, karyotype and ploidy induction do not provide evidence for heterogametism. But the herbivorous echinoids and larvacea with their gonads harboring both germ cells and Nutritive Phagocytes (NPs) have economized the transportation and hormonal costs on gonadal function. Despite the amazing potential just 2 and 3% of echinoderms undergo clonal reproduction and regeneration, respectively. Fission is triggered, when adequate reserve nutrients are accumulated. It is the most prevalent mode of clonal reproduction in holothuroids, asteroids and ophiuroids. However, budding is a more prevalent mode of clonal reproduction in colonial hemichordates and urochordates. In echinoderms, fission and budding eliminate each other. Similarly, autoregulation of early development eliminates clonal reproduction in echinoids and solitary urochordates. In pterobranchs, thaliaceans and ascidians, the repeated and rapid budding leads to colonial formation. Coloniality imposes reductions in species number and body size, generation time and life span, gonad number and fecundity as well as switching from gonochorism to simultaneous hermaphorditism and oviparity to ovoviviparity/viviparity.

The quantification of morphology through time is a vital tool in elucidating macroevolutionary patterns. Studies of disparity require intense effort but can provide insights beyond those gained using other methodologies. Over the last several decades, studies of disparity have proliferated, often using echinoderms as a model organism. Echinoderms have been used to study the methodology of disparity analyses and potential biases as well as documenting the morphological patterns observed in clades through time. Combining morphological studies with phylogenetic analyses or other disparate data sets allows for the testing of detailed and far-reaching evolutionary hypotheses.

Echinoderms, including feather stars, seastars, brittle stars, sea urchins and sea cucumbers, are some of the most beautiful and interesting animals in the sea. They play an important ecological role and several species of sea urchins and sea cucumbers form the basis of important fisheries. Over 1000 species live in Australian waters, from the shoreline to the depths of the abyssal plain and the tropics to Antarctic waters. Australian Echinoderms is an authoritative account of Australia’s 110 families of echinoderms. It brings together in a single volume comprehensive information on the identification, biology, evolution, ecology and management of these animals for the first time. Richly illustrated with beautiful photographs and written in an accessible style, Australian Echinoderms suits the needs of marine enthusiasts, academics and fisheries managers both in Australia and other geographical areas where echinoderms are studied.

This book compiles for the first time the development of echinoderm research in Latin America. The book contains 17 chapters, one introductory, 15 country chapters, and a final biogeographic analysis. It compiles all the investigations published in international and local journals, reports, theses and other gray literature. Each chapter is composed of 7 sections: introduction describes the marine environments, and main oceanographic characteristics, followed by a history of research account divided by specific subjects. The next section addresses patterns of distribution and diversity. A specific section would explain fishery or aquaculture activities. The next sections deal with environmental and anthropogenic threats that are affecting echinoderm, and any conservation or management action. Finally, a section with conclusions, needs and new lines of research. The book will include two appendixes with species lists of all echinoderms with bathimetric data, habitat and distribution.