chapter 3 - RiuNet

GENERAL INTRODUCTION
1. Reproductive biology of goal species
A wide diversity of reproductive strategies and fertilization modes can be
found in marine fish (Serrao and Havenhand, 2009). Most of them share a
common fertilization strategy, broadcast spawning, in which gametes both
from males and females are released into the seawater. However, despite
this common reproductive link, fish species have evolved in response to
several sets of selective pressures, so they often differ in terms of their key
reproductive traits. In this respect, having in-depth knowledge of each lifehistory
seems to be essential in order to understand the sperm biology of
each species.
The conservation status of the goal species of this thesis is currently frail.
The European eel (Anguilla anguilla) is classified as a Critically Endangered
Species according to the International Union for Conservation of Nature
(IUCN) Red List while, in the case of the pufferfish (Takifugu niphobles), the
current data about its population are deficient and several factors such as
habitat destruction or climatic change could contribute to making it
anendangered species. Therefore, the chapters in this thesis have a
common link: the development and improvement of different techniques
and protocols with the aim of increasing the knowledge about the sperm
biology of both species, thereby improving the reproductive performance
and even helping future breeding in captivity.
1.1 European eel
The European eel (Anguilla anguilla) is a marine fish belonging to a
primitive group called elopomorpha which appeared in the early evolution
of teleosts. Nowadays, the genus Anguilla is composed of 15 species
(Watanabe, 2003), which are widely distributed around the world
inhabiting tropical, subtropical and temperate areas.
The European eel species displays an interesting catadromous life history
strategy, and the mystery has been always linked to its biological cycle. In
this respect, the first surmise was reported by Aristotles around 350 BC,
9