Bull. nat. Hist. Mus. Lord. (Zool.) 63(2): 137-147 



Issued 28 November 1997 



Morphological observations on Oncaea 

 mediterranea (Claus, 1863) (Copepoda, 

 Poecilostomatoida) with a comparison of Red 

 Sea and eastern Mediterranean populations 



R. BOTTGER-SCHNACK, 



Institutfiir Meereskunde am der Universitdt Kiel, Diisternbrooker Weg 20, D-24105 Kiel, Germany 



R. HUYS 



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



SYNOPSIS. The taxonomic status of the allegedly cosmopolitan Oncaea mediterranea (Claus, 1 863) is reviewed. Comparison 

 of Claus' fragmentary original description and the subsequent redescription by Giesbrecht in 1892 revealed significant 

 differences which might lead to taxonomic confusion. Most authors have adopted Giesbrecht's identification, but it is clear that 

 several, as yet unnamed, species have been recorded in the literature under the wrong name O. mediterranea. The species is 

 redescribed in detail on the basis of material from the Red Sea and eastern Mediterranean. The occurrence of two size morphs in 

 the eastern Mediterranean populations is briefly discussed. O. mediterranea sensu Bourne (1889) is regarded as species 

 inquirenda in the genus. 



INTRODUCTION 



Oncaea mediterranea (Claus, 1863) is one of the most widely 

 distributed oncaeids (Copepoda: Poecilostomatoida) and according 

 to the literature assumes a cosmopolitan distribution. It has been 

 recorded in epi- and mesopelagic layers of all three main oceans 

 between approximately 60° N and 60° S (Malt, 1983a: Fig. 14; 

 Heron and Bradford-Grieve, 1995). In some areas such as the 

 offshore waters of the Lebanon (Malt et al., 1989) it represents the 

 most common oncaeid. 



O. mediterranea is a well studied species. The naupliar develop- 

 ment has been documented by Hanaoka (1952), and Malt (1983c) 

 discussed the polymorphism and pore signature pattern of the 

 species. Paffenhofer (1993) obtained quantitative information on 

 reproduction rates and longevity of adult females. It was found that 

 early copepodids of O. mediterranea ingested about 100% of their 

 body weight daily when feeding at relatively high food levels. 

 Average reproduction rates of field-collected females ranged from 

 5.3 to 13.3 nauplii day 1 . According to Paffenhofer (1993) neither 

 nauplii, nor copepodids or adults of O. mediterranea create a 

 feeding current, and because of their limited swimming perform- 

 ance the encounter with food has to be created either by motile food 

 particles or by the copepod jumping repeatedly to locate a food-rich 

 environment. O. mediterranea has been observed on discarded 

 appendicularian houses (e.g. Alldredge, 1972) which probably serve 

 as a major constituent of detritus and a food source for copepods in 

 the epi- and mesopelagic zones (Ohtsuka et al., 1996). 



Like in many other so-called cosmopolitan planktonic species the 

 taxonomy of O. mediterranea is potentially confusing. Most identi- 

 fications of this species are based on the redescription of Giesbrecht 

 (1892) from the Gulf of Naples, which was excellent by contempo- 

 rary standards, and do not consider the type description of Claus 

 (1863, as Antaria mediterranea) from Messina. Comparison of 

 Claus' and Giesbrecht's text and illustrations casts certain doubts, as 

 to whether both descriptions are based on the same species. As part 



of an ongoing study on Red Sea oncaeids the taxonomic history of O. 

 mediterranea is reviewed and the species is redescribed herein on 

 the basis of material from the eastern Mediterranean and various 

 regions in the Red Sea. 



METHODS 



Oncaeids were collected using a multiple opening-closing net with 

 a mesh size of 0.05 mm during cruise 5/5 of R/V Meteor in the 

 Southern and Central Red Sea and in the Eastern Mediterranean Sea. 

 A station list and sampling data are given in Table 1. The plankton 

 was initially fixed in 4% formaldehyde-seawater solution buffered 

 with hexamethylene tetramine and transferred after ca 2 years into a 

 preservation fluid of 5% propylene glycol, 0.5% propylene 

 phenoxetol, and 94.5% filtered seawater (Steedman, 1976). Speci- 

 mens were dissected in lactic acid, and mounted on slides in 

 lactophenol. All figures have been prepared using a camera lucida 

 on a Leitz Dialux differential interference contrast microscope. 



Total body length and the ratio of prosome to urosome (excluding 

 caudal rami) were calculated as the sum of the middorsal lengths 



Table 1 Station data of sampling with 0.05 mm mesh multiple opening 

 closing net during R/V Meteor Cruise 5. 



Stn. Haul 



Date 



Time 



Latitude 



Longitude 



Depth of 



Total 



No. No. 



(1987) 





(°N) 



(°E) 



Haul (m) 



water 

 depth (m) 



Red Sea 















663 17/4 



20.07 



Day 



22°58.4' 



37°19.4' 



50-100 



1200 



703 39/5 



03.08 



Day 



15°34.8' 



41°54.9' 



0-50 



970 



39/4 











50-100 





Eastern Mediterranean 











44 31/5 



24.01 



Day 



34°07.1' 



31°54.7' 



0-50 



2530 



© The Natural History Museum, 1997 



