REVUE SUISSE DE ZOOLOGIE 

 Tome 78. fasc. 1. n : 4: 187-207 — Juin 1971 



187 



Histological studv of 

 greatly enlarged pericardial sac 

 in the embryo of the 

 viviparous teleost Lebistes reticulatus 



by 



Yvette W. KUNZ 



Department of Zoology. University Collège. Dublin (Ireland) 



With 8 figures 



1. INTRODUCTION 



The Cyprinodontes are characterized in the embryo by a greatly expanded 

 pericardial sac. In some species the enlargement can be such that the sac is 

 drawn over the anterior part of the embryo. a process which is likened to the 

 formation of the serosa and amnion in higher vertebrates (Fraser. 1940; 

 Tavolga. 1949). 



The cyprinodont Lebistes reticulatus. Peters. is one of the species to hâve its 

 whole head covered by the pericardial sac during certain embryonic stages 

 (Kunz, 1964). The purpose of this study is to investigate the histological nature 

 of the expanded pericardial sac. to follow its formation and régression and to 

 discuss its possible functions. 



2. MATE RI AL AND METHODS 



Lebistes reticulatus is a member of the Cyprinodontes. family Poeciliidae. Il 

 is a viviparous fish. Sperm is stored within ovarian pockets. Females. once 

 inseminated. can produce several broods. Fertilization and development take 

 place within the ovarian follicles. 



