66 



R. BOTTGER-SCHNACK 



1 0-20^1-0 m; total water depth 100 m: 1 9 dissected on 1 slide in 

 polyvinyl-lactophenol (RBS). 

 (6) Eastern Indian Ocean, NW Cape Australia, 21° 49.86'S, 114° 

 30.3, E: Stn. B; NWC 005/2; RV 'Lady Basten' leg 1630; 

 collected 26 October 1997 with 0.5 m WP-2 net with 0.073 mm 

 mesh, vertical haul; depth 0-20 m (leg. D. McKinnon): 4 9? 

 (RBS). 



Description. Note illustrations are based on 1(c). 



Adult female (Figs. 22, 23A-E). 



Body length (measured in lateral aspect; from anterior margin of 

 rostral area to posterior margin of caudal rami, calculated as sum of 

 individual somites): 803 urn [traditional method: (a) 600 urn, range: 

 540-610 urn, based on numerous specimens from southern Red Sea 

 and Gulf of Aden; (b) 510 um, range: 480-520 urn, based on 12 

 specimens from central Red Sea (Bottger-Schnack et al. (1989)]. 



Exoskeleton moderately chitinized. Prosome 2.8 times length of 

 urosome, excluding caudal rami, 2.4 times urosome length includ- 

 ing caudal rami. Integumental pores on prosome as indicated in Fig. 

 22A, B. 



Proportional lengths (%) of urosomites 10.6 : 63.8 : 7.7 : 7.2 : 

 10.6. Proportional lengths (%) of urosomites and caudal rami 9.2 : 

 55.3 : 6.7 : 6.3 : 9.2 : 13.4. 



Genital double-somite 1.5 times as long as maximum width 

 (measured in dorsal aspect) and 2.5 times as long as postgenital 

 somites combined (Fig. 22C); straight sclerotization between geni- 

 tal apertures, pore pattern on dorsal surface as indicated in Fig. 22C. 

 Armature of genital apertures represented by 1 spine and 2 minute 

 spinous processes (Fig. 22G). 



Anal somite 1.8 times wider than long; about 3/4 length of caudal 

 rami (Fig. 22C). Ornamentation as for O. venusta. 



Caudal ramus (Fig. 22F) about 2.3 times as long as wide, shorter 

 than reported by Heron & Bradford-Grieve. Dorsal seta (VII) half the 

 length of terminal accessory seta (VI), not 2/3 the length as reported 

 by Heron & Bradford-Grieve, plumose and bi-articulate at base. 



Antennule with minute element on 6th segment (arrowed in Fig. 

 22E), which was not mentioned in the original account. 



Antenna as figured by Heron & Bradford-Grieve (their Fig. 17m). 

 except for additional surface ornamentation on coxobasis similar to 

 O. waldemari (cf. Fig. 25 A) and 2 patches of spinules (not only l)on 

 anterior surface of distal endopod segment. 



Labrum (Fig. 23A, B) similar to O. waldemari, but fewer denti- 

 form processes medially on each lobe and free margin of integumental 

 pockets distinctly serrate (Fig. 23A). 



Mandible generally as figured by Heron & Bradford-Grieve, 

 dorsal blade ornamented with 1 additional minute dentiform process 

 at dorsal margin (Fig. 22H). Maxillule, maxilla and maxilliped 

 similar to O. waldemari, some ornamentation elements on syncoxa 

 of maxilla and on basis of maxilliped missing in the account of 

 Heron & Bradford-Grieve. 



Swimming legs 1^1 with armature as for genus and surface 

 ornamentation similar to O. waldemari (Fig. 26A-D), except for 

 anterior face of PI enp-1 and -2 with stronger spinules on distal 

 margin (Fig. 23C). PI exp-3 with outer distal spine slightly longer 

 than figured by Heron & Bradford-Grieve. P4 exp-3 and enp-3 (Fig. 

 23E) with outer distal spines somewhat longer than in original 

 account, outer endopodal spine reaching almost 1/2 length of distal 

 spine. 



P5 (Fig. 22F) with exopodal segment longer than figured by 

 Heron & Bradford-Grieve, ornamented with 3 spinules ventrally; 

 inner one of exopodal setae stouter and slightly shorter than outer 

 one. 



P6 (Fig. 22G) represented by operculum closing off each genital 



aperture; armed with a spine and 2 small spinous processes. 



Egg-sacs paired, oblong-oval; each sac containing 6 eggs (diameter 

 40-45 urn) (Bottger-Schnack, 1989, as O. media f. minor). 



Adult male (Fig. 23F-M). 



Body length: 607 pm [(a) 440-480 um, based on several specimens 

 from southern Red Sea and Gulf of Aden; (b) 410 um, range: 410- 

 440 um, based on 7 specimens from central Red Sea (Bottger- 

 Schnack et al. (1989)]. Sexual dimorphism in antennule, antenna, 

 maxilliped, endopods of P2-P4, P5-P6, caudal ramus and in genital 

 segmentation. 



Prosome 2.5 times length of urosome, excluding caudal rami, 2.2 

 times urosome length, including caudal rami. 



Proportional lengths (%) of urosomites (excluding caudal rami) 

 11.2 : 69.2 : 3.8 : 3.8 : 3.8 : 8.3; proportional lengths (%) of 

 urosomites (caudal rami included) 10.0 : 61.1 : 3.3 : 3.3 : 3.3 : 7.3 : 

 11.6. Caudal rami about 1.6 times longer than wide, shorter than in 

 female. Caudal setae with proportional lengths as in female, except 

 for seta VI 2.6 times the length of caudal ramus, and dorsal seta VII 

 2/3 the length of seta VI. 



Antennule with armature as for genus. 



Antenna with seta on coxobasis long and plumose as in female; 

 lateral armature on distal endopod segment differing from female, 

 element III much stouter and element IV spiniform and curved, 

 ornamented with dentiform processes along distal margin (arrowed 

 in Fig. 23H); both elements shorter than in female. 



Maxilliped as figured by Heron & Bradford-Grieve, except for 

 endopodal segment (claw) with concave margin naked, not 

 ornamented with short spinules pinnate as figured in their Fig. 18j. 



Swimming legs 1-4 with armature and ornamentation as in 

 female; terminal conical projections on P2-P3 enp-3 as in female. 

 Sexual dimorphism expressed in reduced spine lengths on enp-3, 

 most obvious in P3 (Fig. 23D, J) and in outer subdistal spine of P4 

 (Fig. 23E, M). Spine lengths on P2 enp-3 less reduced. 



P5 (Fig. 23K) exopod not delimited from somite, shape and 

 armature as in female, except for exopodal setae more spiniform and 

 shorter than in female; small plumose seta arising from lateral 

 surface of somite shorter than in female. 



P6 represented by posterolateral flap closing off genital aperture 

 on either side; covered by pattern of denticles as shown in Fig. 23L. 



Spermatophore not observed. 



Taxonomy 



O. scottodicarloi is the species previously referred to as O. media f. 

 minor in the quantitative studies of Bottger-Schnack (1990a, b, 

 1994, 1995). Specimens from the Red Sea agreed in almost every 

 detail with the original account of Heron & Bradford-Grieve (1995) 

 from the Mediterranean, except for their smaller size, which is 

 discussed below under 'Size variation'. The only other remarkable 

 difference in female morphology between the two regions was the 

 length to width ratio of caudal ramus, which was smaller in Red Sea 

 specimens (2.3:1) than in the original account (about 3:1). [In the 

 closely related O. waldemari, the length to width ratio of the caudal 

 ramus turned out to be a variable character at closer examination 

 (see below), which might also apply to O. scottodicarloi]. Other 

 slight differences between the two descriptions, such as the surface 

 ornamentation on mouthparts and antenna, as well as the minute 

 element on 6th segment of antennule, which was not mentioned by 

 Heron & Bradford-Grieve, are not regarded as substantial and/or 

 might have been overlooked in the original account. 



Males of O. scottodicarloi from the Red Sea differed from the 

 original account in the ornamentation of maxillipedal claw, which 

 was naked, while it had been described as having short spinules 

 along the concave margin by Heron & Bradford-Grieve (1995, p. 40, 



