52 



R. BOTTGER-SCHNACK 



on the molecular genetics of O. venusta size variants from the 

 Atlantic is in progress and future morphological studies in other 

 areas are recommended. 



Other records of o. venusta 



O. venusta is widely distributed at mid- and low latitudes, between 

 approximately 50°S and 65°N (Malt, 1983a, b). Due to its relatively 

 large size and the characteristic habitus of the female, it is one of the 

 best documented oncaeid species in the world. 



Halim (1969) listed O. venusta as one of the 'perennial-indig- 

 enous' species of the Red Sea, being distributed throughout the main 

 basin and the Gulf of Suez all year round. His compilation of earlier 

 records did not differentiate between the two forms of the species, 

 which were found to exhibit considerable differences in regional and 

 seasonal distribution in the Red Sea (see below under Ecological 

 notes). 



Wilson (1932) recorded O. venusta as the most abundant species 

 of the genus in the Woods Hole region. The length range of his 

 specimens (92 1.1-1.27 mm, 88: 0.8-0.95 mm) indicates that he 

 had collected the typical form, however, his illustration of dorsal 

 aspect of the female (Fig. 213A; from W.M. Wheeler) shows the 

 form of genital double-somite to be more similar to f. venella. 



In the Western Pacific area, Mori (1937, reprinted 1964) figured 

 O. venusta from Japanese waters and Dakin & Colefax (1940) 

 recorded it as the commonest species in the coastal waters of 

 Australia (New South Wales). Chen et al. (1974) described the 

 species from the Yellow Sea and the East China Sea. Their illustra- 

 tion of P4 endopod (Plate 6, Fig. 3) shows 2 inner setae on distal 

 segment which is not found in any species of Oncaea s. str. This 

 requires confirmation. The length range reported by Mori ( 92 1 .0- 

 1.28 mm, 88: 0.8-1.0 mm) was smaller than the sizes reported by 

 Chen et al. (92 1.2-1.35 mm, 88: 0.9-1.1 mm), but the dorsal 

 habitus of females illustrated by these authors indicate that both 

 were dealing with f. typica. 



Olson (1949) recorded O. venusta from the East Pacific, off 

 Oregon, which according to its size ( 92 1.25 mm, 88: 0.9 mm) and 

 female habitus might belong to the typical form. The author did not 

 note any sexual dimorphism on the antenna or on the swimming 

 legs. 



Razouls (1974) figured O. venusta from the region of Banyuls- 

 sur-mer (Golfe du Lion) and summarized previous records from the 

 Mediterranean Sea. His illustrations lack many details, such as the 

 genital apertures on the female genital double-somite, several ele- 

 ments on the antennule, antenna, P5 and the basal seta on P2-P4; 

 moreover, the distal endopod spines in P2-P4 of his specimens are 

 figured much longer than usually found in O. venusta (especially in 

 P4). Further differences between his specimens and typical characters 

 of O. venusta are found in the female caudal ramus, which is less 

 than 3 times longer than wide and the length of caudal seta VI, which 

 is unusually short in both sexes. The coxobasal seta on the male 

 antenna was figured as long and plumose by Razouls, which is not 

 the case in O. venusta. In summary, positive identification of his 

 specimens can only be given after re-examination of his material. 



Ho (1984) redescribed O. venusta based on several females 

 collected from colonies of Solandria secunda (Inaba), a hydroid 

 found at 10 m depth in Tassha Bay, Sado Island (Japan). His 

 description differs from the present account in the setal formula of 

 PI endopod (4 instead of 5 setae on distal segment), in the armature 

 of the antennule (some elements missing on segment 4 and 5), and in 

 the armature of P6 (2 minute spinous processes not mentioned). 

 Four females from his collection were kindly made available by J.- 

 s. Ho. Re-examination showed that all specimens from Sado Island 

 exhibit the typical setal formula on PI enp-3 (5 setae). The insertion 



of the distalmost seta is hidden beneath the long terminal process (cf. 

 Fig. 4A) and thus can easily be overlooked. Also, the armature of the 

 antennule and on P6 is the same as described here. Due to their large 

 size, Ho ascribed his specimens to f. typica and his opinion is 

 followed here, although some characters, such as proportional spine 

 lengths on P4 enp-3 were inconclusive in the two smaller specimens 

 (0.92-0.96 mm) examined. 



Humes (1988) described both sexes of a new species of Oncaea 

 s.str., O. praecalara, collected with slurp guns or box corers during 

 deep dives by manned deep-sea submersibles from the vicinity of 

 deep-sea hydrothermal vents in the eastern Pacific. The main 

 characters for the new species as summarized by Humes are: (1) its 

 relatively large size [ 1 .01-1 .3 mm in the female], (2) extremely long 

 caudal rami, about twice longer than anal somite and exhibiting a 

 length to width ratio between 4.96-6.7 : 1 (measured halfway down 

 the CR length), (3) sexual dimorphism on third segment of male 

 antenna (not on fourth segment, as erroneously stated in his ab- 

 stract), (4) labrum with nearly straight posteroventral margins. The 

 female holotype as well as female and male paratypes of O. praeclara 

 from the collection of the National Museum of Natural History, 

 Smithsonian Institution, were re-examined, in addition to several 

 samples of the species kindly made available by A.G. Humes. The 

 following measurements taken of the female holotype gave strong 

 evidence that O. praeclara is conspecific with Oncaea venusta: (1) 

 length to width ratio of CR 4.2 : 1 (measured halfway down the CR 

 length), 3.5 : 1 (measured proximally) [as reported in the present 

 account], (2) maxillipedal basis with spinular row along palmar 

 margin (not smooth as described by Humes, his Fig. 2h), (3) labrum 

 bilobate [ornamentation on lobes not discernible without dissection 

 of specimen], integumental pockets and slit-like pores on anterior 

 face present. The male paratype of O. praeclara can be assigned to 

 O. venusta on the basis of (1) the sexual dimorphism of antenna, 

 with coxobasal seta short and naked (not noted by Humes), seta I on 

 second endopod segment curved, and (2) the pore pattern on dorsal 

 surface of genital segment ( 1 1 pores). 



Humes' account of O. praeclara may have been based on two 

 different species: the form of the genital double-somite and the 

 position of the genital apertures differ considerably between his Fig. 

 la (habitus, dorsal) and Fig. lc (urosome, dorsal). The extremely 

 elongate CR noted by Humes (his Fig. lc, e) was found neither in the 

 female holotype nor in any of the specimens re-examined, but may 

 have been present in other specimens. Fig. lc and le (caudal ramus) 

 as well as Fig. 2h (maxilliped) of Humes ( 1988) are regarded here as 

 belonging to a different species, which, however, could not be traced 

 in his material, although some of the samples contained a mixture of 

 oncaeid species (see 'Material examined' above). The remaining 

 figures of Humes seem to be identical with O. venusta. Like Ho 

 (1984), Humes erroneously figured the distal endopod segment of 

 PI with 4 outer setae, instead of 5. He also missed one seta on the 

 distal armature in the male antenna. 



Huys & Boxshall (1991) illustrated several appendages and a 

 dorsal view of the female urosome of O. venusta, based on speci- 

 mens from the North Atlantic. Their Fig. 2.10. lO.Aof the mandible 

 shows 4 dentiform processes along the distal margin, whereas only 

 3 processes are found in specimens from the Red Sea (Fig. 3D, 7D) 

 and in those from the Gulf of Naples (Heron & Bradford-Grieve 

 1995, their Fig. 14J). The authors erroneously figured the female P5 

 with 1 exopodal seta only (their Fig. 2. 1 0.2 1 .B ), not with 2 setae as 

 usually found in O. venusta. 



Many more records of O. venusta from different localities of the 

 world ocean are known [see Malt (1983a) for a review], but are not 

 considered here, because they did not include figures or a descrip- 

 tion that positively identified the species. 



