30 



R. BOTTGER-SCHNACK 



Oncaea praeclara Humes is regarded as a synonym of O. vemista, 

 on grounds that will be discussed below under O. venusta, Remarks. 



DESCRIPTION OF SPECIES 



Oncaea venusta Philippi, 1843 



Oncaea venusta Philippi (1843): 62-63, Tafel III, Fig. 2a-d. 



Oncaa venusta Giesbrecht, 1892 

 Oncaa venusta Farran, 1929 

 Oncaea praeclara Humes, 1988 



Reliable descriptions. Giesbrecht (1892): 590-604, 755, 756, 

 774, 789, Plate 2, Fig. 5, Plate 3, Fig. 7, Plate 47, Fig. 

 2,5,13,19,39,44,48,50,54,58 [as Oncaa venusta]; Farran (1929): 

 284-285, Fig. 33 [as Onccea venusta]; Wilson (1932): 353-354, Fig. 

 213a-d; Mori (1937, reprinted 1964): 119-120, Plate 66 Figs. 1-9; 

 Dakin & Colefax (1940): 116, Fig. 205A a-f; Sewell (1947): 263- 

 264; Olson [MS] (1949): 101-104, Plate XXIV Figs. 1-8 ( 9), Plate 

 XXV Figs. 11-13 (3);Tanaka(1960): 71-72; Corral Estrada (1970): 

 216-217; Chen et al. (1974): 40-41, Plate 6 Figs. 1-5; Ferrari 

 (1975): 225-228, Figs. 5I-K, 6A-D; Boxshall (1977b): 124-128 

 Figs. lla-k(9), 12a-d (6); Ho (1984): 41^44, Figs. 12-14; Humes 

 (1988): 475-485, Figs. la,b,d [not Fig. lc, e], 2a-i, 3a-g ( 9), 4a-g 

 (6) [as Oncaea praeclara]; Huys & Boxshall (1991): 286.289,445 

 Figs. 2.10.8.B, 2.10.10.A, 2.10.21.B, 2.10.21.D, 2.10.24.A; Heron 

 & Bradford-Grieve (1995): 33,36, Figs. 14e-l, 15a-j, 27b, 28; Itoh 

 [in: Chihara& Murano 1997]: 981-982, Plate 223 Figs. 371 (left) a- 

 b (f. venella), 371 (right) a-e (f. typica). 



DOUBTFUL DESCRIPTIONS. Razouls (1974): 236-237, Figs. 1 A-H 

 ( 9), 2A-C (<?); Humes (1988): only Fig. lc, e (as Oncaea praeclara). 



TYPE LOCALITY. Western Mediterranean Sea, near Palermo. 



Material examined. 



Red Sea: see below under O. venusta f. typica and f. venella 



Other areas: 



(1) Gulf of Naples, Italy; collected 1 February 1967; depth 0-100 

 m; leg. B. Scotto di Carlo; identified by G.A. Heron: 19, 1 6 in 

 alcohol (RBS). 



(2) Pacific Ocean, off Tanega Islands; R/V Toyoshio-maru; col- 

 lected 5 November 1994 with ORI-plankton net, mesh size 0.33 

 mm; oblique haul, depth 1600 m; leg. S. Ohtsuka: several 99 

 and <Jc?(RBS). 



(3) Sea of Japan, Tassha Bay, Sado Island; collected 1978 from 

 colonies of Solandria secunda (Inaba), a hydroid; depth 10m; 

 leg. and identified by J.-s. Ho; 4 99 in alcohol (RBS). 



(4) (a) North Pacific Ocean, Galapagos Rift, 00° 48.0'N, 086° 



13.0'W; collected 7 December 1979; DSRV Alvin dive no. 

 990; depth 245 1 m; 1 specimen in alcohol, labelled Oncaea 

 praeclara, Humes, 1988, holotype 9 (National Museum of 

 Natural History, Smithsonian Institution, Washington, DC, 

 reg. no. USNM 234 109): this vial contains Oncaea venusta 

 ( 1 9); parts of the specimen broke off during re-examination 

 and are mounted on slides in lactophenol [right antennule 

 (segment 4-6), left antenna (endopod segments 1 and 2), 

 right maxilliped (claw)]. 



(b) North Pacific Ocean, Galapagos Rift; further sampling data 

 not specified; 1 specimen in alcohol labelled: Acc.no. 37 66 

 47; O. praeclara, 13 August 1987 (USNM 234 111): this 

 vial contains Oncaea venusta ( 1 9). 



(c) North Pacific Ocean, Galapagos Rift, 00° 48.0'N, 086° 



13.0'W; collected 5 December 1979; DSRV Alvin dive no. 

 998; depth 2450 m; 1 specimen in alcohol labelled Oncaea 

 praeclara, Humes, 1988, 1 6 (USNM 234 112): this vial 

 contains Oncaea venusta (1 6, possibly f. typica). 



(d) North Pacific Ocean, Galapagos Rift, 00° 47'N, 086° 08'W; 

 collected 24 January 1979; DSRV Alvin dive no. 883; depth 

 2493 m; 4 specimens in alcohol labelled Oncaea praeclara, 

 3 66, 1 9 (USMN 2341 14): this vial contains a mixture of 

 O. venusta (1 ovigerous 9, 1 6), Oncaea sp. (1 6, possibly 

 venusta f. venella). Triconia sp. (1 6). 



(e) North Pacific Ocean, Galapagos Rift, 00° 48.25'N, 086° 

 13.48'W; collected 30 November 1979: DSRV Alvin dive 

 no. 983; (material donated to R. Bottger-Schnack by A. 

 Humes); 11 specimens in alcohol labelled Oncaea praeclara, 

 Humes 1988, 4 99, 166: this vial contains a mixture of O. 

 venusta (2 99, 3 66), O. media (2 99), O. clevei (1 6), 

 Oncaeidae indet. (2 66), Corycaeidae indet. (1 juvenile); 

 (RBS). 



(f) East Pacific Rise, 12° 48.52'N, 56°48'W; collected 22 

 November 1987, Hydronaut Cruise, Nautile dive 221; 

 depth 2630 m (material donated to R. Huys, NHM. by A. 

 Humes); 9 specimens in alcohol labelled O. praeclara, 

 Humes, 5 99, 5 66: this vial contains 5 99(1 9 ovigerous) 

 and 4 66 of O. venusta (all specimens empty exoskeletons 

 with no internal tissue). 



(5) Sargasso Sea, near Bermuda, 31° 37.94'N, 64° 09.45'W; col- 

 lected 9 July 1998 with 1 m net, mesh size 0.15 mm; depth 210 

 m; leg. D. Steinberg: several 99(ovigerous and non-ovigerous), 

 3 66 in alcohol, for molecular analysis (A. Bucklin, Durham, 

 New Hampshire); 2 99, 2 CV 99 in alcohol (RBS). 



Philippi 's (1843) description of O. venusta was the first account of 

 an oncaeid species. It was based on a single male specimen col- 

 lected in the western Mediterranean, near Palermo. Unfortunately, 

 the specimen was lost by accident before the author could com- 

 plete the description. Giesbrecht (1892) redescribed O. venusta in 

 more detail from the Gulf of Naples and recently. Heron & Brad- 

 ford-Grieve (1995) provided an excellent redescription of the 

 species based on material from the Gulf of Naples as well as from 

 other localities in the Atlantic and Pacific Ocean. Both authors do 

 not mention the existence of different size variants among O. 

 venusta, although the range of size variation was quite large in 

 Giesbrecht's specimens from the Pacific. In 1929, Farran 

 described two distinct size morphs of O. venusta, forma typica and 

 forma venella, from various Atlantic and Pacific locations, which 

 were separated mainly by their size and some minor morphologi- 

 cal characters. The two forms were distinguished in some of the 

 subsequent taxonomic descriptions (e.g. Tanaka, 1960; Ferrari, 

 1975; Boxshall, 1977b) and a third, 'robust' form was added by 

 Boxshall (1977b). In the Red Sea, both form variants of O. venusta 

 sensu Farran occur. They differ considerably in temporal and spa- 

 tial distribution (Bottger-Schnack, 1990b, 1995), thus indicating 

 the existence of reproductively isolated populations. A detailed 

 morphological examination of both size variants was undertaken 

 during the present study, including microstructures on the append- 

 ages and on the exoskeleton (pores, scales), partly by using SEM 

 analyses. The results pointed out several morphological diffe- 

 rences between the two forms not noted in the literature before, 

 but these were not regarded as sufficient to warrant recognition of 

 the two forms as separate species. In order to provide the 

 morphological basis required for future taxonomic analyses on O. 

 venusta, both forms are redescribed. A further approach to 

 differentiate the two forms using alternative methods, e.g. mole- 

 cular analysis, is currently in progress. 



