138 



R. BOTTGER-SCHNACK AND R. HUYS 



of individual somites measured in lateral view. In the case of 

 telescoping somites these lengths are measured from the anterior to 

 the posterior margin. This approach differs from that traditionally 

 used in oncaeid taxonomy, where the telescoping of somites is not 

 considered in length measurements. Thus, sizes of the species in this 

 paper are not directly comparable to those of previous descriptions 

 (e.g. Heron, 1977; Heron and Bradford-Grieve, 1995) or earlier 

 studies in the Red Sea (Bottger-Schnack et ai, 1989). Length data 

 given by the latter authors are only about 70% of the length pre- 

 sented in this paper, due to the excessive telescoping of somites in 

 the sorting medium. 



Descriptive terminology for body and appendages follows that of 

 Huys and Boxshall (1991). Abbreviations used in the text are: ae = 

 aesthetasc; CR = caudal rami. 



SYSTEMATICS 



Order POECILOSTOMATOIDA Thorell, 1859 

 Family ONCAEIDAE Giesbrecht, 1892 

 Genus ONCAEA Philippi, 1843 



Oncaea mediterranea (Claus, 1863) 



(Figs 1-5) 



SYNONYMS. Antaria mediterranea Claus, 1863; Oncata medi- 

 terranea (Claus, 1863); Oncda mediterranea (Claus, 1863). 



Original description. Claus (1863): 159-160, Tafel XXX, Fig. 



1-6 (9), 7(0"). 



Other DESCRIPTIONS. Giesbrecht (1892) [as Oncda mediterr- 

 anea]; Heron (1977) and Heron & Bradford-Grieve (1995) [as 

 Oncaea mediterranea]. 



Type locality. Tyrrhenian Sea; Messina. 



Material examined, (see Table I for locality data) 



(1) The Natural History Museum, London: Southern Red Sea: Stn 

 703; R/V Meteor leg 5/5; collected with MSN 0.05 mm net 

 (Haul 39/4); depth 50-100 m: 10 9 9 and lOcfcfin alcohol 

 (reg. nos 1996.1095-1114); leg. R. Bottger-Schnack; 



(2) Dr Bottger-Schnack (personal collection): 



(a) Southern Red Sea: Stn 703; R/V Meteor leg 5/5; collected 

 with MSN 0.05 mm net (Haul 39/4); depth 50-100 m; leg. 

 R. Bottger-Schnack: several 9 9 and cTcTin alcohol; 



(b) Central-Northern Red Sea: Stn 663; R/V Meteor leg 5/5; 

 collected with MSN 0.05 mm net (Haul 17/4); depth 50- 

 100 m; leg. R. Bottger-Schnack: several 9 9 and cTcTin 

 alcohol; 



(c) Eastern Mediterranean: Stn 44; R/V Meteor leg 5/1; col- 

 lected with MSN 0.05 mm net (Haul 31/5); depth 50-100 

 m; leg R. Bottger-Schnack: (i) small form: 1 9 and 1 

 cf dissected on slides, 1 9 in alcohol; (ii) broad form: 2 

 9 9 dissected on slides, 1 cf in alcohol. 



Adult female 



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

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

 individual somites): 1400 urn 



Exoskeleton well chitinized. Prosome 2.2 times length of urosome, 

 excluding caudal rami, 1.9 times urosome length including caudal 



rami. Leg 2-bearing somite without conspicuous dorso-posterior 

 projection (Fig. IB). Leg 3-bearing somite with conspicuous raised 

 pore protruding laterally (Fig. la). Other integumental pores on 

 prosome as indicated in Fig. 1A-B. Pleural areas of leg 4-bearing 

 somite with constricted posterolateral corners. 



Proportional lengths (%) of urosomites are 9.7 : 60.7 : 8.2 : 8.8 : 

 1 2.6. Proportional lengths (%) of urosomites and caudal rami are 8. 1 

 : 50.7 : 6.8 : 7.3 : 10.5 : 16.5. 



Genital double-somite nearly twice as long as maximum width 

 (measured in dorsal aspect) and twice as long as postgenital somites 

 combined; largest width measured at anterior third, posterior part 

 tapering gradually. Paired genital apertures located at about halfway 

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

 ture represented by 1 spine and 1 diminutive spinule (Fig. 1H). Pore 

 pattern on dorsal surface as indicated in Fig. 1C. 



Anal somite 1.3 times wider than long; about 2/3 the length of 

 caudal rami (Fig. 1C). Secretory pore discernible on either side of 

 anal opening. Anterior margin of anal opening (vestigial anal oper- 

 culum) with transverse row of minute denticles. Posterior margin of 

 somite finely serrate ventrally and laterally (Fig. ID). 



Caudal ramus (Fig. IF) about 3.0 times as long as wide. Armature 

 consisting of 6 elements: antero- and posterolateral setae long, 

 spiniform and unipinnate along medial margin; outer terminal seta 

 long and plumose; inner terminal seta longest and plumose; terminal 

 accessory seta more than 2/3 the length of outer terminal seta and 

 more than twice the length of caudal ramus; dorsal seta about 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. IF) with secretory pore near insertion of seta 

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



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

 ments measured along posterior non-setiferous margin 6.2 : 20.6 : 

 46.4 : 10.3 : 6.2 : 10.3. Armature formula: l-[3], 2-[8], 3-[5], 4- 

 [3+ae], 5-[2+ae], 6-[6+(l+ae)]. 



Antenna 3-segmented, distinctly reflexed (Fig. 2A). Coxobasis 

 with row of long, fine spinules or setules along outer and inner 

 margins and with few additional spinules on proximal and distal part 

 of outer (exopodal) margin; with bipinnate seta at inner distal corner. 

 Endopod segments unequal in length; proximal endopod segment 

 subtriangular forming outer lobate outgrowth bearing spinular patch, 

 with row of denticles along posterior inner margin. Distal endopod 

 segment slightly shorter than proximal exopod segment, with nar- 

 row cylindrical base articulating; with two patches of short spinules 

 along outer margin; lateral armature consisting of 1 unipinnate 

 spiniform seta and 3 curved setae, one of them sparsely pinnate, all 

 armature elements similar in length; distal armature consisting of 5 

 long unipinnate setae and 2 short naked setae; none of armature 

 elements spiniform or geniculate. 



Labrum (Fig. 2B-C) distinctly bilobed. Distal margin of each 

 lobe with 4 strong dentiform processes medially, short row of long 

 fine setules latero-distally and row of minute spinules laterally. 

 Lobes separated by semicircular vertex covered anteriorly by over- 

 lapping rows of hyaline petaloid flaps. Posterior part of medial 

 incision with four rounded integumental thickenings. Anterior sur- 

 face (Fig. 2B) with short row of spinules either side of median 

 swelling, raised row of small strong denticles latero-posteriorly; 

 median swelling with large secretory pore posteriorly. Posterior 

 surface (Fig. 2C) with group of 3 secretory pores located on proxi- 

 mal part of each lobe and an additional one basally. 



Mandible (Fig. 2D) with minute spinules on surface of coxa; 

 gnathobase with 5 elements: 1 at subdistal ventral corner, 2 along 

 distal margin and 2 along subdistal dorsal margin; ventral element 

 shorter than ventral blade, with long, fine setules along dorsal 



