58 



R. BOTTGER-SCHNACK 



1/2 length of the segment. Confusingly, Sewell refers to his figures 

 of swimming legs, but these are not given in his account. A relatively 

 long distal spine on P4 enp-3 is found in O. scottodicarloi, and it 

 might be that Sewell had mixed up the characters of both species in 

 his report. Since all three species of the O. media-complex (O. 

 media. O. scottodicarloi and O. waldemari are found in the Arabian 

 Sea (Bottger-Schnack, 1996, as O. media f. major, O. media f. minor 

 and Oncaea sp. B, respectively), it is conceivable that he included 

 the latter species in the lower size range of females as well. 



Mori (1937, reprinted 1964) described the species from Japanese 

 waters and Chen et al. (1974) recorded two size groups of O. media 

 from the East China Sea and the Yellow Sea. In both accounts, the 

 female genital double-somite is much shorter than in O. media sensu 

 Heron & Bradford-Grieve and also seta VI on caudal ramus is too 

 short. The same argument applies for the record of Dakin & Colefax 

 (1940) from Australian waters. Although the illustration of the male 

 antenna by Mori (his Plate 66, Fig. 17) shows a naked coxobasal 

 seta, positive identification cannot be made without a closer exam- 

 ination of the specimens, especially in view of the extremely wide 

 size range that was recorded for females (0.5-0.92 mm) in his 

 account. However, the occurrence of O. media in the marine plank- 

 ton of Japan has been confirmed in a recent excellent account by Itoh 

 [in Chihara & Murano, 1997]. 



Tanaka ( 1 960) recorded O. media from various locations in the East 

 China Sea, Indian Ocean and south of Cape of Good Hope. He 

 mentions the occurrence of two size groups, f. major and f. minor, 

 which covered an overall size range of 0.55-0.79 mm. Sizes of the two 

 groups were not recorded separately. His Plate XXXI, Fig. 4 clearly 

 shows the dorsal view of female O. media sensu Heron & Bradford- 

 Grieve, although he identified them as f. 'minor' . The different length 

 ratio between subdistal and distal spines on P4 enp-3, which accord- 

 ing to Heron & Bradford-Grieve (1995) separate O. media from O. 

 scottodicarloi, is not apparent between Tanaka's f. major and. f. minor 

 (his Figs. 5 and 6). So it cannot be judged whether his small sized 

 specimens are identical to O. scottodicarloi or probably belong to 

 another closely related species, such as O. waldemari. 



O. media f. minor sensu Malt (1982b) was assigned to O. 

 waldemari during the present study and will be discussed below. In 

 the identification key of oncaeids (Malt, 1983b) the separation 

 between males of O. media and O. venusta needs to be revised, since 

 the sexual dimorphism on antenna is found in both species, not only 

 in O. venusta, as was erroneously stated by Malt. 



Geographical distribution 



Oncaea media had been reported as O. media f. major in the 

 previous quantitative accounts of Bottger-Schnack (1990b, 1994, 

 1995, 1996, 1997). The species is distributed throughout the Red 

 Sea, but exhibits very variable abundances both seasonally and 

 regionally. During summer, the species occurred in minimal num- 

 bers in the southern Red Sea, but exhibited higher values to the 

 north, in the central-northern Red Sea, as well as to the south, in the 

 Gulf of Aden and Bab al Mandab area (Bottger-Schnack, 1995). 



In the northern Arabian Sea, O. media was found in appreciable 

 numbers, with abundances being one to two orders of magnitude 

 higher than in the Gulf of Aden and/or in the central Red Sea 

 (Bottger-Schnack, 1996). The species also occurred in the Eastern 

 Mediterranean Sea (Bottger-Schnack, 1997) in comparably low 

 numbers. 



Seasonal variation in abundance (central red sea) 

 O. media was recorded from the central-northern Red Sea during 

 winter (Bottger-Schnack, 1990b) and summer (Bottger-Schnack, 

 1995), but not during autumn, when it was completely absent or 

 occurred as solitary finds only (Bottger-Schnack, 1990a, b). Due to 



its seasonality, the species had previously been assumed to be of 

 southern origin (Bottger-Schnack, 1990b), but subsequent data from 

 the summer season did not point to a consistent seasonal variation in 

 the central Red Sea (Bottger-Schnack, 1995). 



Vertical distribution and vertical migration 

 O. media was generally confined to the epipelagic zone (0-150 m) 

 in the Red Sea, with few, isolated finds down to 900 m. The species 

 had a unimodal distribution pattern with maximum densities in the 

 upper epipelagic (0-50 m) and was classified as non-migratory 

 during winter in the central Red Sea (Bottger-Schnack, 1990b). In 

 the Gulf of Aden and Strait of Bab al Mandab, maximum densities 

 were found at a depth of 0-20 m and 0-60 m, respectively, during 

 summer (unpubl. data). By this, the species tended to be vertically 

 separated from the two related species, O. scottodicarloi and O. 

 waldemari, which generally occurred deeper and over a much wider 

 depth range in that area. 



Oncaea clevei Friichtl, 1923 



Oncea clevei Fruchtl(1923): 455, Tafel 26, Figs. 19-22 (9 only). 



Oncaea conifera Cleve, 1901 



Reliable descriptions. Friichtl (1924): 22-23, 89-91, Figs. 

 14.15, 60-70 (9 only); Itoh [in: Chihara & Murano (1997)]: 979, 

 Fig. 361a, d,f(9only). 



Doubtful descriptions. Sewell (1947): 258 [as Onccea clevei]; 

 Tanaka ( 1 960): 66, Plate XXVIII. Figs. 7-13; Chen et al. ( 1 974): 42, 

 Plate 7, Figs. 4-7. 



TYPE locality. Aru Archipelago, Indo-Pacific area. 



Preliminary note. The original description of Friichtl (1923, 

 1924) lacks many details, particularly in the mouthparts, of which 

 he described only the maxilliped. A detailed redescription of O. 

 clevei from the Red Sea is given below, including a description of 

 the hitherto unknown males. During the course of the study a 

 closely related species was found, which is described as a new 

 species, O. paraclevei sp. nov. A comparison of morphological 

 characters separating the two species is included under O. 

 paraclevei see Remarks. 



Material examined. 



(1) Central Red Sea, 21° 25.53'N, 38° 01.91'E: Stn. 130; JUV 

 Valdivia leg 29: collected 28 October 1980 with MSN 0.1 mm 

 net (Haul 117/5); depth 0-20 m; total water depth 1960 m. 



(a) 2 99 in alcohol (BMNH 1998.2803-2804). 



(b) 2 99 in alcohol (ZMH K-39574). 



(c) 1 9 partly dissected (maxilliped and maxilla on slides), 1 9 

 in alcohol (RBS). 



(2) Southern Red Sea, 15° 34.8'N, 41° 54.9E: Stn. 703; RW Meteor 

 leg 5/5: collected 03 August 1987 with MSN 0.05 mm net (Haul 

 39/5); depth 0-50 m; total water depth 970 m. 



(a) 1 8 partly dissected (urosome on slide), remaining speci- 

 men in alcohol (BMNH 1 998.2805), 3 86 in alcohol (BMNH 

 1998.2806-2808). 



(b) 1 8 dissected on 10 slides (ZMH K-39575a-i), 1 9,3 86 m 

 alcohol (ZMH K-39576). 



(c) 2 99. 3 86 in alcohol (RBS). 



(3) Gulf of Aden, 1 1° 55.5'N, 43° 37.9'E: Stn. 631a; R/V Meteor leg 

 5/5: collected 11 July 1987 with MSN 0.05 mm net (Haul 3/5); 

 depth 0-50m; total water depth 1400 m. 



(a) 1 9, 1 8 (mating position, 8 lacking urosome) in alcohol 

 (BMNH 1998.2809-2810). 



(b) 1 9, 1 8 (mating position) in alcohol (ZMH K-39577). 



