96 



D. JAUME AND G.A. BOXSHALL 



Maxillule with praecoxal arthrite (Fig. 9C) well developed, armed 

 distally with 4 stout, denticulate spines, plus 6 more proximal 

 elements, ranging from a tiny seta to a thick denticulate spine. Palp 

 (Fig. 9D) comprising coxobasis with medial gnathobase-like struc- 

 ture and minute endopodal segment bearing 2 setae; distal margin of 

 coxobasal gnathobase provided with 9 irregular blades; coxobasis 

 with 2 setae located subapically on dorsal margin and single seta, 

 representing exopod, located proximally on distal surface. 



Maxilla (Fig. 9E) well developed, 4-segmented. Praecoxa and 

 coxa incompletely separate. Praecoxa naked, lacking endites. Coxa 

 with proximal endite represented by single seta; distal endite power- 

 fully developed, bearing 2 stout, spinulate spines, proximal spine 

 bearing single, conspicuous strong spinule on outer margin and row 

 of thinner spinules on inner margin. Basis with endite bearing 3 

 unequal, claw-like setae. Endopod 1 -segmented, armed with total of 

 3 stout spine-like setae, 1 naked seta and 1 very reduced seta. 



Maxilliped (Fig. 9F) 5-segmented, prehensile. Syncoxa bearing 2 

 weakly developed endites provided with single seta each. Basis with 

 inner margin covered by patch of setules and single seta positioned 

 distally. Endopod 3-segmented, first segment short, unarmed; sec- 

 ond segment elongate, inner margin covered by patch of setules, 

 armed with 2 setae laterally; small distal segment with 2 stout, 

 curved claws plus 2 accessory setae. 



Swimming legs 1 to 4 (Fig. 1 0) biramous, both rami 3-segmented. 

 Legs subequal in size except first somewhat smaller. Intercoxal 

 sclerites lacking ornamentation and getting progressively narrower 

 from legs 1 to 4. All spines on segments flanged bilaterally with 

 serrate hyaline frill except distalmost spine on exopod of leg 1, 

 which is flanged with frill on outer side only, inner side adorned with 

 row of setules. Secondary ornamentation and pore pattern on seg- 

 ments as figured; pores on coxa and basis possibly overlooked. 

 Armature as follows: 



Coxa 



Basis Exopod 



Endopod 



Legl 



0-1 



1-1 



Leg 2 



0-1 



1-0 



Leg 3 



0-1 



1-0 



Leg 4 



0-1 



1-0 



I-1;I-1;III,I,4 0-l;0-2;I-II-III 



I-1;I-1;III,I,IV+1 0-1 ;0— 2;I-II-III 



I-1;I-1;III,I,V 0-l;0-2;I-II-III 



I-1;I-1;II,I,V 0-1;0-II;I-II-II 



Fifth legs (Fig. 8H) uniramous, 3-segmented, joined by smooth 

 intercoxal sclerite. Coxa and basis separate, former naked, latter 

 with single seta on outer margin. Distal segment (exopod) elongate, 

 about 2.5 times as long as wide; armature consisting of flanged spine 

 as long as segment located two-thirds of distance along outer 

 margin, plus 2 flanged spines and single seta on distal margin; distal 

 seta shorter than both spines and segment itself; distal spines located 

 either side of seta, flanged, both clearly longer than segment, inner 

 longer, about 1 .5 times as long as segment. Secondary ornamenta- 

 tion of spinules present on outer margin of exopod of some 

 individuals, similar to that figured on female leg 5 (Fig. 1 IE), not 

 present in figured specimen (Fig. 8H). 



Adult female. Body (Figs 1 1 A, B) up to 0.74 mm long, resem- 

 bling male. Urosome 5-segmented; genital and first abdominal 

 somites partially fused to form genital double-somite. Genital dou- 

 ble-somite (Fig. 11C) symmetrical, subdivided dorsally by partial 

 suture line; single copulatory pore opening mid-ventrally about 

 one-third of distance along somite, connected via copulatory duct 

 to fused seminal receptacles. Paired gonopores located laterally; 

 gonopores covered by opercula, each consisting of lobe projecting 

 dorsally bearing 2 setae and 1 tiny spine. Tapering soft lobe point- 

 ing posteriorly located at both sides of somite just behind 



operculum. Entire hyaline frill present along posterior margin of 

 somite. 



Antennules (Fig. 1 ID) 21 -segmented, not extending beyond pos- 

 terior margin of cephalosome (Figs 1 1A,B), symmetrical. Segmental 

 fusion pattern and armature as follows: Segment 1 (corresponding to 

 fused ancestral segments I to V), 8 setae; segment 2 (fused ancestral 

 segments VI and VII), 4 setae; segments 3 to 9 (VIII to XIV), 2 setae 

 each; segments 10 to 13 (XV to XVIII), 1 seta each; segment 14 

 (XIX), naked; segment 15 (XX), 1 seta; segment 16 (XXI), 1 seta + 

 aesthetasc; segment 17 (XXII), naked; segment 18 (XXIII), 1 seta; 

 segment 19 (XXIV), 2 setae; segment 20 (XXV), 2 + aesthetasc; 

 segment 21 (fused XXVI to XXVIII), 7 + aesthetasc. 



Segmentation and setation of other cephalosomic appendages and 

 swimming legs 1 to 4 as in male. 



Fifth legs (Fig. 1 IE) resembling those of male, but with shorter 

 exopod, about twice as long as wide; inner distal spine almost twice 

 as long as segment; spine on outer margin clearly longer than 

 segment. Secondary ornamentation of spinules on outer margin of 

 exopod not discernible in some individuals. 



Remarks. The genus Euryte typically contains shallow water 

 hyperbenthic species, although Brady (1910) reported the genus 

 from depths of 320 m in the Antarctic and some species have been 

 found living in the interstices of coarse sand, or in association with 

 seaweed or corals. Ten species are currently recognized, distributed 

 worldwide (Gurney, 1927b; Sewell, 1949; Herbst, 1989; Humes, 

 1991; 1992), with the possible exception of the Pacific coast of 

 South America. Apart from the original contributions by Giesbrecht 

 (1900) and Sars (1913-1918), new species have been described 

 mainly on the basis of a biometric analysis of characters that have 

 otherwise proved to exhibit high intra-populational variability (such 

 as the relative legth of caudal rami), or that may vary significantly in 

 their measurements simply according to the precise angle of obser- 

 vation (such as the relative length of the armature elements on the 

 distal segment of the endopod of leg 4). Such characters are widely 

 used in the two identification keys available for the genus ( Vervoort, 

 1964; Herbst, 1989), and their use has resulted in the false impres- 

 sion of cosmopolitanism of some taxa (viz. E. longicauda and E. 

 robusta Giesbrecht, 1900; see Kiefer (1929) and Sewell (1949)). 



The type material for most species of Euryte is no longer extant. 

 This hampers the necessary revision of the genus, that could permit 

 the critical reevaluation of all those taxa established on the basis of 

 variable characters. 



Using material from the type locality of both species (the Gulf of 

 Naples), Giesbrecht (1900) differentiated E. longicauda Philippi. 

 1 843 from E. robusta Giesbrecht, 1 900 mainly by the proportions of 

 the caudal rami and by details of the armature of the male antennule. 

 The proportions of the caudal rami of the Mallorcan population 

 overlap the characteristic values for both species given by Giesbrecht 

 (1900). The armature of the male antennule, however, corresponds 

 to that of E. longicauda: the cup-shaped segment 1 carries 2 slender 

 setae, whereas in E. robusta it carries a characteristic robust, S- 

 shaped spine plus a seta. On this basis we have assigned the Euryte 

 from the Mallorcan caves to E. longicauda. 



The differential diagnosis separating E. longicauda from Mallorca 

 from E. robusta can be completed as follows (see the detailed 

 illustrations of the latter species in Huys & Boxshall, 1991): in E. 

 longicauda the proximal spine on the distal coxal endite of the 

 maxilla of both sexes is armed with a single, strong spinule on one 

 side and a row of thinner spinules on the other side; in E. robusta 

 both sides are armed with thin spinules. Additionally, in£. longicauda 

 there is a transverse dorsal suture midway along the female genital 

 double-somite that seems to be absent in E. robusta. 





