B. Jamieson – Reproductive Biology and Phylogeny of Gymnophiona

Описание

Even today, several animal groups are little known – or even unknown – but
need to be deeply studied, especially as they may disappear. Among these little
known animals are the gymophionan amphibians, also called caecilians or
Apoda. The Gymnophiona is the third amphibian order, Anura and Urodela
being the two others. The Gymnophiona contained 170 species according to
Taylor (1968), but in their most recent works, Mark Wilkinson and Ronald
Nussbaum list 154 species belonging to 34 genera and 6 families (see chapter 2
of this volume).
For many years, studies on the Gymnophiona were disparate and still only
a few species have been deeply studied. The result is a fragmented knowledge
of these animals. Fortunately, in recent years, some new works have been published
on their systematics, using both the classical methods as well as immunology
and molecular biology. New data have also been obtained on the biology,
life history, reproductive biology, endocrinology and embryonic development
of several species. These fascinating aspects of the history of gymnophionan
studies are ably reviewed in the first chapter of this volume by Marvalee Wake.
Examining the publications on Caecilians, it appears evident that these
publications are very different one from another. Some of works and especially
the studies of the 19th century were very exhaustive, concerning a single species
deeply studied (i.e. Ichthyophis glutinosus, Sarasin and Sarasin 1887-1890),
more recently, other works have been devoted to the comparative study of one or
several organs in a large number of species (i.e. the papers of M.H. Wake on
urogenital organs). In contrast, other publications are short, concerning a special
point of anatomy or biology of a single species. Sometimes only a single rare
individual has been the subject of a study. Some species, such as Ichthyophis
glutinosus, Hypogeophis rostratus, Dermophis mexicanus, Gymnopis multiplicata
and Typhlonectes compressicauda have been deeply studied by several authors. In
contrast, other species, such as Microcaecilia unicolor or Grandisonia diminutiva
have been the subject of only a few works.
The topics covered in the various works are also disparate. Phylogenetic
systematics has been well studied, with several propositions for classification.
Some organs and functions, such as reproductive tracts and breeding, have
been the subject of several papers, concerning one or several species with comparative
aspects. In contrast, other organs and functions, such as circulatory or respiratory system, have not been exhaustively studied. Some aspects of developmental
biology were well studied in 19th century works and, over the last 15
years, these aspects have been the subject of renewed interest. This large disparity
in studies is certainly linked to the fact that Gymnophiona are burrowing
animals difficult to catch and living in tropical forests so that access of them is
often difficult and expensive. These animals are also difficult to breed in aquaria
or terraria because the natural conditions to which they are adapted are poorly
known, and reproduction is rarely obtained.
This book devoted to reproductive biology and phylogeny of Gymnophiona
begins with a chapter on the history of research on this group (M. H. Wake). In
the second chapter concerning the phylogeny of Gymnophiona with systematics,
M. Wilkinson and R. Nussbaum give the most recent classification of these
species with a useful diagnosis. Considering that caecilians belong to a very
little known order, even to scientists, chapter 3 contains general observations
on anatomy, physiology, with special references to male and female urogenital
systems. Because of inevitable delays from the beginning of the preparation to
editing of chapters, several new observations and results were published after
the general chapters had been written. Therefore chapter 4, devoted to the Mullerian
gland in Uraeotyphlus narayani or chapter 6 on spermatogenesis, give the
most recent results and augment chapter 3 in which more general and classical
data about male genital system are given.
In chapter 5, the endocrinology of reproduction in both males and females
is covered. Chapter 7 describes the structure of spermatozoa in several species
and draws some phylogenetic conclusions. Chapter 8 is devoted to oogenesis
and folliculogenesis. Chapter 9 concerns the embryonic development of genital
glands, a neglected aspect of caecilian anatomy. Chapter 10 is about parity;
chapter 11 investigates the peculiar case of viviparity in Typhlonectes
compressicauda, a unique feature (to present knowledge) in Gymnophiona. In
Chapter 11 concerning fertilization and embryonic development data include
normal tables for Ichthyophis glutinosus, I. kohtaoensis, and Typhlonectes
compressicauda with some observations on other species.
I thank Barrie Jamieson who invited me to become volume editor of this
work in the series “Reproductive Biology and Phylogeny” of which he is the
series editor and I am grateful to him for his advice and practical help throughout
all stages of preparation of this volume. I thank also the authors who accepted
to contribute to the volume. I thank particularly Marvalee H. Wake whose
work constituted one of the main bases for my own studies, and whom I have
met several times at congresses. I thank Mark Wilkinson whom I have known
for several years and who has spent a time in my own laboratory, Ronald
Nussbaum whose works are at the summit of systematics in Gymnophiona. I
also thank our Indian colleagues who have made fascinating recent major
contributions to the knowledge of these animals. I wish also to thank my colleagues
and fellows who contributed to the knowledge of these animals. I cannot
forget Jean Lescure (CNRS and Muséum National d’Histoire Naturelle,
Paris) with whom I visited French Guyana and collected animals. Lastly, I wish
also to particularly thank Michel Delsol, Honorary Professor at the Catholic University of Lyon and E.P.H.E., who welcomed me into his laboratory, more
than 25 years ago, and who initiated my work on Gymnophiona; I dedicate this
book to him in recognition of his support and our faithful friendship throughout
these long years of common work.