Bull. nat. Hist. Mus. bond. (Zool.) 67( I ):25-84 



yvf 3^'H 



Issued 28 June 2001 



Taxonomy of Oncaeidae (Copepoda, 

 Poecilostomatoida) from the Red Sea. 

 II. Seven species of Oncaea s.str. 



RUTH BOTTGER-SCHNACK 



Institut fiir Meereskitnde an der Universitat Kiel, Ditsternbrooker Weg 20, D-24105 Kiel, Germany. E-mail 

 address: dschnack@ifm.uni-kiel.de 



SYNOPSIS. Seven species of Oncaeidae (one of which is new to science) are described from the Red Sea. including a description 

 of the hitherto unknown male oi Oncaea clevei Friichtl. They all belong to Oncaea sensu stricto as defined in a phy logenetic study 

 of oncaeid species by Bottger-Schnack and Huys in 1998. The genus is defined by a combination of characters including the 

 absence of a conical process on the distal margin of the endopod of swimming leg 4. ornamentation of the labrum and mandibular 

 blade and sexual dimorphism in antennary setae and in endopods of swimming legs. Oncaea s. str. includes two subgroups, the 

 wm/jta-subgroup and the c/evei-subgroup, females of which can be separated by the absence or presence of a dorso-posterior 

 projection on the P2-bearing somite. Species of the venustasubgroup in the Red Sea include O. venusta Philippi. O. mediterranea 

 (Claus). O. media Giesbrecht. O. scottodicarloi Heron & Bradford-Grieve and O. waldemari Bersano & Boxshall; the clevei- 

 subgroup consists of O. clevei Friichtl and O. paraclevei sp. nov. Oncaea praeclara Humes is a junior subjective synonym of O. 

 venusta. O. philippinensis (Kazatchenko & Avdeev) as well as Oncaea sp. 1 and sp. 2 sensu Ferrari are regarded as species 

 inquirendae in Oncaea s.str. The type species of the genus. O. venusta. has two form variants, forma typica and forma venella 

 Farran. which can be distinguished by differences in size and in a few minor morphological characters. Their spatio-temporal 

 distribution differs considerably in the Red Sea. which may indicate reproductive isolation. The world-wide records of O. venusta 

 forms are reviewed and discussed. 



CONTENTS 



Introduction 25 



Material and Methods 27 



Generic diagnosis 28 



Description of species 30 



Oncaea venusta Philippi forma typica Farran 31 



O. venusta Philippi forma venella Farran 37 



O. mediterranea (Claus) 53 



O. media Giesbrecht 54 



O. clevei Friichtl 58 



O. scottodicarloi Heron & Bradford-Grieve 65 



O. waldemari Bersano & Boxshall 70 



O. paraclevei sp. nov 78 



Acknowledgements 82 



References 82 



INTRODUCTION 



Small copepod species of the family Oncaeidae are widely distrib- 

 uted in marine pelagic areas, extending from the epipelagic zone 

 (e.g. Boxshall, 1977a; Dessier & Donguy, 1985; Cowles et al., 

 1987) to the deep-sea (Wishner, 1979; Humes, 1988) and from 

 tropical (Tsalkina, 1970; Deevey & Brooks, 1977) to polar regions 

 (Hopkins, 1985; Richter, 1994; Metz, 1995). Due to their small size, 

 oncaeid copepods are often neglected or under represented in marine 

 plankton investigations, which are usually conducted with conven- 

 tional nets of 0.3 or 0.5 mm mesh sizes. In recent years, increasing 

 attention has been paid to the study of smaller mesozooplankton 

 organisms sampled with fine mesh nets of 0. 1 mm mesh size or less. 

 In particular, small oncaeid copepods were sampled in high abun- 

 dance by these nets (e.g. Bottger, 1982; Paffenhofer, 1983; Schnack 



et al.. 1985; Cowles et al, 1987; Bottger-Schnack, 1987) and 

 subsequent research topics have focussed on their community struc- 

 ture and biology [see Bottger-Schnack (1999) for a review of the 

 literature], thereby providing new insights into the largely unknown 

 ecological importance of this copepod group. 



Apart from ecological issues, the taxonomy of oncaeid species 

 has been the subject of increasingly detailed studies over the past 

 two decades (e.g. Boxshall, 1977b; Heron, 1977; Malt, 1982a, b, 

 1 983a, b, c, d; Heron et al. , 1 984; Krsinic & Malt, 1 985 ; Boxshall & 

 Bottger, 1987; Krsinic, 1988; Bottger-Schnack & Boxshall, 1990; 

 Heron & Bradford-Grieve, 1995; Bottger-Schnack & Huys, 1997a, 

 b, in press; Itoh [in: Chihara & Murano (1997)]). Despite these 

 efforts, however, the taxonomy of many oncaeid species is still 

 inadequate and particularly those species that are smaller than 0.5 

 mm have not been described in sufficient detail. Moreover, many 

 oncaeid species are morphologically very similar, and thus can be 



© The Natural History Museum. 2001 



