Bull. nut. Hist. Mus. Lond. (Zool.) 62(1): 41-70 



Issued 27 June 1996 



The life cycle of Paracyclops fimbriatus (Fischer, 

 1853) (Copepoda, Cyclopoida) 



S. KARAYTUG 



Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5 BD, UK, and School 

 of Biological Sciences, Queen Mary and Westfield College, Mile End Road, London El 4NS, UK 



G. A. BOXSHALL 



Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5 BD, UK 



CONTENTS 



Introduction 41 



Methods 41 



Description of Naupliar Stages 42 



Description of Copepodid Stages 48 



Discussion 67 



Acknowledgements 69 



References 70 



Synopsis. The complete life cycle of Paracyclops fimbriatus (Fischer, 1853) (Copepoda, Cyclopoida) is redescribed based 

 on cultured material. All 6 nauplius and 5 copepodid stages plus the adults are described in detail. Scanning electron 

 microscopy is used to elucidate the fine structure of some appendages, especially the male antennule, and to study body 

 ornamentation patterns. Sexual dimorphism is first apparent at the copepodid IV stage which has a more robust antennule 

 in the male than in the female. 



INTRODUCTION 



Paracyclops fimbriatus has been reported from a wide range of 

 freshwater habitats and the geographical records summarised by 

 Dussart & Defaye (1985) indicate a cosmopolitan distribution. 

 It has also been regularly recorded from subterranean waters 

 (Ito, 1954; Pesce & Galassi, 1987) and from waters with a salinity 

 of 31%"(L6ffler, 1961). Early reports of this species at great 

 depths in Lake Baikal (Mazepova, 1962) refer to the newly 

 recognized P. baikalensis Mazepova, 1978 (Mazepova, 1978). 



The genus Paracyclops comprises 24 species and subspecies 

 (Dussart & Defaye, 1985; Reid, 1987a, 1987b; Strayer, 1988). 

 The type species, P. fimbriatus, was originally described by 

 Fischer (1853), using material from St-Petersburg in Russia. 

 This taxon has been partially redescribed on numerous 

 occasions (for example Kiefer, 1929; Gurney, 1933; Lindberg, 

 1941; Dussart, 1969; Einsle, 1971). Some descriptions of 

 developmental stages have also been published; one of the most 

 accurate being that of Gurney (1933) but even that gives 

 insufficient data to characterise the copepodid stages. Other 

 descriptions have concentrated primarily on the naupliar instars 

 (Gurney, 1933; Dukina, 1956; Ewers, 1930), but these all lack 

 detail by modern standards. Although the general morphology 

 of cyclopoid naupliar stages has been known for a long time it is 

 only recently that detailed naupliar descriptions of freshwater 

 cyclopoid copepods have been published (Dahms & Fernando 

 1992, 1993, 1994). Systematic studies on naupliar stages can 



provide important information on the phylogenetic 

 relationships among copepods (Dahms, 1991a,b). 



In the present paper P. fimbriatus has been redescribed in 

 detail, including all its developmental stages, in order to provide 

 a base for comparison with other Paracyclops species. 



METHODS 



Adult females of P. fimbriatus were collected by plankton net 

 from Regent's Park pond (London) on 29.5.1994. Ovigerous 

 females were kept in plastic dishes filled with fresh water filtered 

 through a 35 um-mesh net. Water was changed at 2 day intervals 

 until the eggs hatched and the nauplius phase was completed. 

 The adult females were removed after hatching of their egg sacs. 

 Copepodid stages were placed in an aquarium tank in a constant 

 temperature room. 



The nauplii were examined as whole mounts. Broken 

 glass-fibres were used to prevent the nauplii from being 

 compressed by the coverslip and to facilitate rotation which 

 allowed viewing from all sides. 



Copepodids were dissected in lactophenol. All drawings were 

 made with the aid of a camera lucida using Nomarski 

 differential interference contrast. All measurements were made 

 with an ocular micrometer. Body lengths were measured from 

 the anterior to the posterior end of the body in nauplii, and from 

 the base of the rostrum to the posterior edge of the caudal rami 



©The Natural History Museum, 1996 



