SEVEN SPECIES OF RED SEA ONCAEA 



77 



P6 (Fig. 27E) represented by posterolateral flap closing off 

 genital aperture on either side; covered by pattern of denticles and 

 area of minute pits as in Fig. 27E; posterolateral corners rounded, 

 generally with bifid tips, as in Fig. 27F (aberrant stunted corner on 

 right side arrowed in Fig. 27E). 



Spermatophore oval (Fig. 27E, F), of variable size according to 

 state of maturity; swelling of spermatophore during development 

 not affecting shape and relative size of genital somite. 



Female copepodid stage v (Fig. 28). 



Body length: 640 um [Traditional method; 550 um]. 



Prosome 2.4 times length of urosome, excluding caudal rami, 

 about 2. 1 times urosome length including caudal rami. Integumental 

 pores on prosome as in Fig. 28 A, B. 



Urosome 5-segmented; proportional lengths (%) of urosomites 

 11.7:51.7: 11.5:8.9: 16.2. Proportional lengths (%) of urosomites 

 and caudal rami 10.0 : 44.0 : 9.8 : 7.6 : 13.8 : 14.8. 



Second urosomite 1.8 times as long as maximum width (meas- 

 ured in dorsal aspect) and 1.4 times as long as postgenital somites 

 combined (Fig. 28C). Paired slit-like structure located close to 

 dorso-lateral margin at about midlength along second urosomite 

 (Fig. 28C), representing precursors of adult genital apertures (Fig. 

 28E). Pore pattern on dorsal surface similar to adult female; entire 

 surface covered with numerous small pits. 



Anal somite shorter than caudal rami. 



Caudal ramus with length to width ratio 2.0 : 1 . Caudal setae with 

 proportional lengths as in adult female. 



P5 (Fig. 28F) similar to adult female. 



Antennule, antenna, mouthparts and swimming legs not examined. 



Taxonomy 



Oncaea waldemari has been referred to as Oncaea sp. AD (Bottger- 

 Schnack, 1994, 1995) or Oncaea sp. B (Bottger-Schnack. 1996) in 

 previous ecological studies. The original description of O. waldemari 

 by Bersano & Boxshall ( 1 994) shows an inconsistency between text 

 and figures with regard to the exopod segment of female P5, which 

 is described as being fused to the somite (p. 35), but is figured as 

 being delimited (their Fig. IB). Re-examination of the holotype and 

 female paratypes of the species during the present study gave clear 

 evidence, that the exopod of female P5 is free (as in Fig. 24G), and 

 that specimens from the Red Sea are conspecific. Slight differences 

 in body dimensions between the two descriptions are mainly brought 

 about by the different methods used throughout this study (telescop- 

 ing of somites) or appear to be variable between specimens (e.g. 

 length to width ratio of caudal ramus as discussed below). 



Based on the erroneous assumption of a fused P5 exopod in the 

 female, Bersano & Boxshall (1994) placed O. waldemari in a small 

 group of oncaeids together with O. petila, O. oralis, O. brocha and 

 O. compacta. The present redescription undoubtedly shows that the 

 species belongs to Oncaea s.str. and within this genus is most closely 

 related to O. curta, O. scottodicarloi and O. media. Major distinc- 

 tions between the three species are summarized in Table 5. Further 

 differences between O. waldemari and O. scottodicarloi include the 

 relative lengths of endopodal spines on P4, which are shorter in O. 

 waldemari. Males of O. waldemari can be separated from those of 

 O. media by the sexually dimorphic coxobasal seta of the antenna 

 (Table 5). Males of O. scottodicarloi lack this character; they can be 

 distinguished from O. waldemari by slight differences in element IV 

 on the antenna, the length of seta VII on the caudal ramus and the 

 ornamentation of the P6. 



Size variation 



The body length of O. waldemari varies considerably in different 



geographic regions (Table 7). Lengths of specimens from the Red 



Table 7 Body length (mm) and length to width ratio of female caudal 

 ramus (CR) of O. waldemari from various locations. 



Region 



9 



6 



CR 



South Atlantic, 



0.49-0.58 



0.36-0.41 



2.4-2.8 : 1 



Brazilian waters* 









Mediterranean 









(a) Adriatic Sea 



0.51-0.60 



0.40-0.46 



2.4: 1 



(b) Eastern Medit. 



0.50 







Plymouth Sound 



0.62-0.69 



0.50-0.52 



2.5: 1 



Red Sea 



0.42-0.50 



0.34-0.36 



2.3 : 1 



Arabian Sea 



0.47-0.52 



0.34:0.38 



no data 



Eastern Indian Ocean, 



0.48-0.54 



- 



2.2-2.4 : 1 



NW Cape Australia 









Western Subtropical Pacific, 



0.49-0.62 



- 



no data 



off Sagami Bay (Japan) 









*after Bersano & Boxshall (1994) 



Sea were in the lower end of the size range observed for other 

 regions or were smaller. 



Beside the difference in size, the length to width ratio of caudal 

 ramus (Table 7) and the form of the genital double-somite seemed to 

 be variable within an area as well as outside. Female paratypes of O. 

 waldemari from Brazilian waters exhibited a variable length to 

 width ratio of caudal ramus, which was not noticed the Red Sea 

 material. Specimens from Plymouth (see below) had a somewhat 

 shorter genital double-somite than the type collection, and within 

 the populations from the Adriatic and from Australian waters, 

 differences in length to width ratio of the genital double-somite, as 

 well as of the caudal ramus, were noted. This indicates considerable 

 intraspecific variation (morphs) in O. waldemari, which makes it 

 difficult to identify the species. More detailed taxonomic studies on 

 this small and widespread species, including alternative methods 

 such as molecular analyses, are necessary to ascertain the taxonomic 

 status of these morphs. 



The form of the bifid corners of genital lappets on male P6 was 

 slightly variable in Red Sea specimens. A corresponding variation in 

 male morphology was observed in O. media (cf. Fig. 16C) and had 

 previously been observed for another oncaeid, Triconia hawii 

 ( Bottger-Schnack, 1 999). It may be more widespread among oncaeids 

 than previously known. 



Other records of o. waldemari 



Malt ( 1982b) described the developmental stages of O. media from 

 Plymouth Sound and assigned the species to f. minor on the basis of 

 size. Re-examination of adult specimens from her collection indi- 

 cated that they are conspecific with O. waldemari, based on the 

 following characters (cf. Table 5): ( 1 ) ratio of genital double-somite 

 to rest of urosomites (2.0 : 1), (2) position of genital apertures (1/4 

 the distance from lateral margin), (3) length ratio of seta VI on CR 

 (3/4 length of seta IV), and (4) length to width ratio of P5 exopod 

 (1.3 : l).The length to width ratio of genital double-somite of Malt's 

 specimens was somewhat smaller (1.5 : 1) than in typical O. 

 waldemari and its form was not as elongate as in specimens from the 

 Red Sea, but resembled more that of O. scottodicarloi. However, 

 such variation was also observed in specimens from the Adriatic 

 during various seasons, and thus may indicate some intraspecific 

 variation. Males of O. media sensu Malt were assigned to O. 

 waldemari on the basis of antennary seta IV, which was slightly 

 curved and setiform (cf. Fig. 27H), rather than being spiniform as in 

 O. scottodicarloi. 



The records of O. waldemari from very distant localities in 

 tropical and temperate regions of the three great oceans indicate a 

 world-wide distribution of the species. However, some morphological 



