SEVEN SPECIES OF RED SEA ONCAEA 



31 



Oncaea venusta Philippi, 1843 forma typica Farran, 1929 



Oncaea venusta Farran ( 1 929): 284 [as Onccea venusta forma typica] 



Onc&a venusta forma typica Farran, 1 929 



TYPE LOCALITY. Not specified, various locations in the temperate 

 and tropical Atlantic, as well as south of New Zealand. 



Material examined. 



Central Red Sea, 21° 22.09'N, 38° 05.09'E: Stn. 664; R/V Valdivia 

 leg 29: collected 21 February 1981 with MSN 0.1 mm net (Haul 21 8/ 

 5); depth 0-50 m; total water depth ca 2000 m. 



(a) 5 99, 5 66 in alcohol (BMNH 1998.2777-2786). 



(b) 5 99, 5 66 in alcohol (ZMH K-39586). 



(c) 2 99dissected on slides, 1 9in alcohol; 3 66 dissected on slides, 

 1 6 in alcohol; 1 9, 1 6 in mating position in alcohol (RBS). 



Description. Note illustrations are based on (c). 



Adult female (Figs. 2-5, 8A-E, 9A-F). 



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



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



individual somites): 1615 um [traditional method 1 130 urn, range: 



1000-1230 um, based on 14 specimens (Bottger-Schnack et ai. 



1989)]. 



Exoskeleton heavily chitinized, covered with numerous granules, 

 forming long raised structures (lines), especially along lateral part of 

 cephalic shield (Fig. 8A). Prosome 2.1 times length of urosome, 

 excluding caudal rami, 1.7 times urosome length including caudal 

 rami. P2-bearing somite without dorso-posterior projection in lat- 

 eral aspect (Fig. 2B). P3-bearing somite with conspicuous raised 

 pore protruding laterally (Fig. 2A). Other integumental pores on 

 prosome as indicated in Fig. 2A, B. Pleural areas of P4-bearing 

 somite with rounded posterolateral corners. 



Proportional lengths (%) of urosomites 12.2 : 57.7 : 8.5 : 9.1 : 

 12.5. Proportional lengths (%) of urosomites and caudal rami 10.0 : 

 47.0:6.9:7.3 : 10.2: 18.6. 



Genital double-somite 1.5 times as long as maximum width 

 (measured in dorsal aspect) and 1.9 times as long as postgenital 

 somites combined (Fig. 2C); largest width measured at anterior two- 

 thirds, lateral margins of genital double-somite rounded, posterior 

 part tapering gradually. Paired genital apertures located at about 2/5 

 the distance from anterior margin of genital double-somite; arma- 

 ture represented by 1 spine and 2 minute spinous processes (Fig. 

 8B), only 1 of which discernible under light microscope (Fig. 2G). 

 Double-curved sclerotization between, but slightly anterior to, geni- 

 tal apertures, pore pattern on dorsal surface as indicated in Fig. 2C. 



Anal somite 1.6 times wider than long; about half the length of 

 caudal rami (Fig. 2C). Secretory pore discernible on either side of 

 anal opening and additional one near posterior margin. Anterior 

 margin of anal opening (vestigial anal opening) with transverse row 

 of minute denticles. Posterior margin of somite finely serrate ven- 

 trally and laterally (Fig. 2D). Ventral face with paired secretory pore 

 near posterior margin (Fig. 2C, cf. also Fig. 6E). 



Caudal ramus (Fig. 2F) about 3.5 times as long as wide. Armature 

 consisting of 6 elements: antero- and posterolateral setae (II+III) 

 long, spiniform and unipinnate along medial margin; outer terminal 

 seta (IV) long and plumose; inner terminal seta (V) longest and 

 plumose; terminal accessory seta (VI) more than 2/3 the length of 

 outer terminal seta and 1.4 times longer than caudal ramus; dorsal 

 seta (VII) about same length as posterolateral seta (III) and less than 

 half the length of terminal accessory seta, plumose and bi-articulate 

 at base. Inner margin of somite with fringe of long setules. Dorsal 

 anterior surface (Fig. 2F) with secretory pore near insertion of seta 

 II. Dorsal surface covered with numerous small scales (Fig. 2F). 



Antennule 6-segmented (Fig. 2E), relative lengths (%) of seg- 

 ments measured along posterior non-setiferous margin 8.4 : 27.6 : 

 39.3 : 10.7 : 4.7 : 9.3. Armature formula: l-[3], 2-[8], 3-[5], 4- 

 [3+ae], 5-[2+ae], 6-[6+(l+ae)]. Small element on segment 4 

 ornamented with row of scales along entire length, tip with tubular 

 extension (SEM observation, not figured). Small element on seg- 

 ment 6 (arrowed in Fig. 2E) with tubular extensions (Fig. 8C), 

 indicating sensory function. 



Antenna 3-segmented, distinctly reflexed (Fig. 3A). Coxobasis 

 with row of long, fine spinules or setules near outer margin and with 

 few additional denticles on proximal and distal part of outer 

 (exopodal) margin, curved row of denticles on posterior face; with 

 bipinnate seta at inner distal corner. Endopod segments unequal in 

 length; proximal endopod segment subtriangular forming outer 

 lobate outgrowth bearing patch of branched tubular extensions (Fig. 

 8D, E). with row of denticles along posterior inner margin. Distal 

 endopod segment distinctly shorter than proximal endopod seg- 

 ment, with narrow cylindrical base articulating; with two patches of 

 branched tubular extensions along outer margin (Fig. 8D); lateral 

 armature with 4 elements, numbered using Roman numerals in Fig. 

 3A: 1 unipinnate spiniform seta (III) and 3 curved setae (I, II, IV), 

 setae I and II sparsely pinnate, seta I shortest: distal armature 

 consisting of 7 elements: 1 long curved unipinnate seta (E), 4 

 slightly curved unipinnate setae of graduated length (A-D), seta D 

 being shortest, and 2 slender naked setae (F and G), similar in length 

 and shorter than seta D; none of armature elements spiniform or 

 geniculate. 



Labrum (Fig. 3B,C) distinctly bilobed. Each lobe with row of 

 minute denticles around outer ventral margin, row of long fine 

 setules latero-distally and dentiform processes converging and de- 

 creasing in size medially. Lobes separated by median concavity 

 covered anteriorly by overlapping rows of broad hyaline petaloid 

 flaps, flanked by paired slit-like pores on proximal part of each lobe 

 (Fig. 9A, B; position of pore arrowed in Fig. 3B). Anterior surface 

 with well developed integumental pockets (Fig. 9C) either side of 

 median swelling, free margin of pockets serrate (Fig. 9D); median 

 swelling with large secretory pore posteriorly. Posterior part of 

 medial incision ornamented with four rounded integumental 

 thickenings (Fig. 3C). Posterior surface with paired patch of very 

 long fine setules and 2 large secretory pores located on proximal part 

 of each lobe. 



Paragnaths (Fig. 5, 9C) with small lateral extensions, anterior 

 margin densely covered with several rows of long setules, median 

 bulge unornamented. 



Mandible (Fig. 3D) with few minute setules on surface of coxa; 

 gnathobase with 5 elements, indicated by capital letters in Fig. 3D: 

 1 at subdistal ventral -corner, 2 along distal margin and 2 along 

 subdistal dorsal margin; ventral element (A) shorter than ventral 

 blade, with long, fine setules along dorsal side; ventral blade (B) 

 strong and spiniform, with row of setules on posterior side; dorsal 

 blade (C) strong and broad, with 3 dentiform processes along distal 

 margin; dorsal elements setiform, the shorter (D) hyaline, flat and 

 densely setose, the longer (E) multipinnate. 



Maxillule (Fig. 3E) indistinctly bilobed, with numerous spinules 

 on anterior and posterior surfaces. Inner lobe subcylindrical, with 3 

 elements: outermost one spiniform, swollen at base, fringed with 

 coarse spinules, others setiform and bipinnate; innermost one located 

 along concave inner margin at some distance from other elements. 

 Outer lobe with 4 elements; outermost element spiniform, curved 

 and bipinnate along inner proximal margin, unipinnate along distal 

 margin, longer than the following; other elements bipinnate or 

 naked, element next to the innermost shortest. 



Maxilla (Fig. 3F) 2-segmented, comprising syncoxa and allobasis. 



