CUMACEA OF THE BENGUELA CURRENT 



By N. S. Jones, Ph.D. 



Marine Biological Station, Port Erin 



(Text-figs. 1-7) 



INTRODUCTION 



THROUGH the kindness of Dr N. A. Mackintosh, Deputy Director of the National Institute of 

 Oceanography, the Cumacea obtained by R.R.S. 'William Scoresby ' during 1950 in the Benguela 

 Current off the south-west coast of Africa were sent to me for examination. The ship made two surveys 

 of the region in this year, in March and in September-October, and most of the material is from the 

 first survey. 



I am much indebted to Dr T. J. Hart of the National Institute of Oceanography for information 

 and for sorting the Cumacea from the rest of the plankton. 



The Cumacea described in this paper were obtained in the vertical plankton net hauls, but more 

 specimens may be available when the horizontal catches have been sorted. Very large numbers of 

 individuals — up to about 7700 — were caught in some of the hauls. Cumacea were taken on the 

 continental shelf at varying distances offshore, and in depths between 64 and 204 m. The rich hauls 

 were all from depths of less than 150 m. and at distances of less than 30 miles from the coast. Full 

 details are available in the Station List R.R.S. 'William Scoresby' (1950), 1953. Cumacea did not 

 occur in nets fished at greater depths off the shelf. At all stations where oxygen determinations were 

 made the 2 concentration at the bottom was low. 



The presence of Cumacea in large numbers in vertical nets was unexpected, and raises certain 

 problems since they are normally bottom-living forms. When Cumacea have been caught in tow-nets 

 at night, adult males have usually predominated, especially when attracted by artificial light, although 

 in some recent records newly moulted adult or ovigerous females have outnumbered the males 

 (Hale, 19536). The hauls containing the largest numbers of specimens described here were made 

 during the hours of darkness, but all stages and both sexes were present and there was not an unduly 

 large proportion of adult males. It is possible that the presence of the animals in the upper layers was 

 not due to normal vertical migration. Although the species present in these hauls may be able to live 

 normally in the plankton, they show no special adaptations to this mode of life and their nearest 

 relatives are coastal bottom-living forms and it may be that they have been forced up from the bottom 

 by the low 2 concentration, as Dr Hart has suggested to me. One would hardly expect them to 

 inhabit the azoic mud which covers so much of the sea-floor in this region, but if they do not do so the 

 alternative habitats are either the narrow bottom zone close inshore — which may be aerated by surf 

 action — or else isolated patches surrounded by the so-called 'azoic zone' (Marchand, 1928; Currie, 

 1953; Copenhagen, 1953). On the other hand, the exceptionally large March haul of about 7700 

 individuals, which contained ovigerous females and adult males, as well as many juveniles, may re- 

 present a nuptial swarm (Forsman, 1938). 



Five species were present, of which three are previously undescribed. They are Bodotria glabra 

 sp.n., Upselaspis gen.n. caparti (Fage), Iphinoe fagei sp.n., /. africana Zimmer, and Diastylis rufescens 

 sp.n. Of these, the two species of Iphinoe, particularly /. fagei, were much the most abundant and 

 widespread. 



