Comprehensive Description

Read full entry


Xandarasterope trux Kornicker, new species


Figure 74-81



ETYMOLOGY.—From the Latin trux (fierce).



HOLOTYPE.—NMV J40030, partly dissected female in alcohol.



TYPE LOCALITY.—Slope 69, 38°29.33'S, 149°19.98'E, Victoria, 76 km S of Point Hicks; depth 1840 m.



PARATYPES.—Slope 27: USNM 193861, ovigerous female on slide and in alcohol; USNM 193862, A-l male with choniostomatid copepod in marsupium, on slide and in alcohol; NMV J40028, partly dissected A-l male in alcohol. Slope 55: NMV J40027, undissected adult female in alcohol. Slope 69: USNM 193959, ovigerous female on slide and in alcohol; USNM 193960, adult male with choniostomatid copepods in marsupium on slide and in alcohol; NMV J40031, 4 undissected specimens in alcohol (length 1.76 mm, height 1.36 mm, male; 1 ovigerous female, 2 juveniles).



NONTYPE.—Slope 67: USNM 194005, partly dissected adult male in alcohol; NMV J40029, 1 juvenile male in alcohol.



DISTRIBUTION.—Slope 27,1500 m. Slope 55,1545 m. Slope 67,1277 m. Slope 69, 1840 m.



DESCRIPTION OF ADULT FEMALE.— Carapace ovoid in lateral view; height greatest just posterior to midlength; small incisur at midheight; tip of rostrum pointed. Anteroventral part of each valve ventral to incisur with lateral process (process more strongly developed along its anterior edge).


Infold: Rostral infold with about 86 bristles (about 60 bristles dorsal to list (bristles extending to anterior juncture), and about 26 bristles along list and between list and incisur; some bristles with bifurcate tip. Anteroventral and ventral infolds with total of about 100 bristles. Narrow list with anterior end ventral to incisur continues along ventral valve margin then broadens along posteroventral corner of valve. Broad posteroventral list with 24-28 wide flat triangular diaphanous bristles (some less than half length of others); bases of diaphanous bristles with tubular pores (1 or 2 large and up to 9 small pores); row of about 26 bristles near posterior edge of broad list (1 or 2 bristles between each pair of diaphanous bristles). Posteroventral infold between list and valve edge with row of 6 or 7 small processes and 12-16 bristles (5 or 6 anterior bristles opposite ventral 7 diaphanous bristles of broad list and dorsalmost bristle opposite dorsal diaphanous bristle, others present between small processes (1 or 2 between each pair of processes)); each process with 2 parallel lines (lines not observed on all specimens) leading to valve edge. Edge of valve with small widely separated pores; only on left valve posterior part of ventral infold with minute crescent-like structures similar to those of left valve of X. storthynx.


Selvage: Wide lamellar prolongation with fringe of long hairs at inner end of ventral margin of incisur.


Vestment: Vestment in vicinity of anterior juncture proximal to infold with long hairs or spines; a few spines on posterodorsal vestment just dorsal to broad posterior list Vestment in vicinity of posteroventral corner of valve lobate with internal soft structures forming cells.


Central Adductor Muscle Attachments: With about 45 oval attachments just anteroventral to valve midpoint.


Carapace Size (length, height in mm): Slope 27: USNM 193861, 2.06, 1.62, height 79% of length. Slope 55: NMV J40027, 2.00, 1.56, height 79% of length. Slope 69: NMV J4O030 (holotype), 1.98, 1.55, height 78% of length; USNM 193959, 1.83, 1.41, height 77% of length. Length range 1.83-2.06, height range 1.41-1.62; range of height as percent of length 77-79.


First Antenna: 1st joint spinous; small sclerotized medial process at midheight of suture separating 1st and 2nd joints. 2nd joint spinous, with stout spinous dorsal bristle and bare lateral bristle. 3rd and 4th joints with fairly straight suture separating them; 3rd joint with row of distal spines on ventral margin extending onto lateral surface, 1 small bare bristle on short ventral margin and 6 spinous bristles (medial of terminal pair with short spines, others with long spines) on long dorsal margin. 4th joint with few distal ventral spines, 2 short bare ventral bristles, and long dorsal bristle with short spines. 5th joint with smooth dorsal margin; sensory bristle with short proximal filament and 6 long terminal filaments. Medial bristle of 6th joint long spinous. 7th joint: a-bristle claw-like, about same length as bristle of 6th joint, with proximal spines on dorsal edge; b-bristle stout, about 1/3 longer than a-bristle, with 4 long marginal filaments; c-bristle reaching past sensory bristle of 5th joint, about 1/4 longer than f-bristle, with 8 marginal filaments. 8th joint: d-and e-bristles (d-bristle slightly narrower) about same length as f-bristle, bare with blunt tips; f-bristle bent dorsally, almost twice length of a-bristle, with 5 marginal filaments; g-bristle same length as c -bristle, with 7 marginal filaments.


Second Antenna: Protopodite with abundant medial spines and small distomedial bristle. Endopodite 3-jointed with long terminal filament almost twice length of stem. Exopodite: 1st joint with few distal spines on dorsal concave margin; bristle of 2nd joint reaching 9th joint, with abundant very slender closely spaced ventral spines; bristles of joints 3-8 long, with natatory hairs, no spines; 9th joint with 3 bristles (2 long with natatory hairs, 1 short (dorsal) with short spines); joints 2-8 with minute spines forming row along distal margins; 9th joint with 1 or more small lateral spines on distal edge; branch with neither terminal medial spine on 1st joint nor basal spines on joints 2-8.


Mandible: Coxale endite: Ventral branch with small medial bristle near base, 3 or 4 oblique rows of spines, and 3 small teeth at tip; dorsal branch: Ventral margin with 4 nodes; main spine with fairly long hairs along posterior edge; abundant long hairs on margin between main spine and tip of branch (tip obscured); long hirsute dorsal bristle set back from tip of branch; dorsal margin of branch serrate distally. Basale endite with 4 spinous end bristles, 3 triaenid bristles with about 15 pairs of marginal spines, 2 dwarf bristles, and small glandular peg. Basale: ventral margin with 1 triaenid bristle (with 6-8 pairs of marginal spines plus terminal pair) near base of endite and proximal to well-developed U-shaped boss; several stout spines on margin near U-shaped boss; dorsal margin spinous, with 2 long equilength spinous terminal bristles; medial surface with abundant spines in dorsal half. Exopodite about half length of dorsal margin of 1st endopodial joint, hirsute with 2 small bristles. 1st endopodial joint with 3 long ventral bristles (shortest with short spines, others with long spines). 2nd endopodial joint fairly short. Ventral margin with 3 long terminal bristles with short spines; dorsal margin with stout a-, b-, c-, and d-bristles, 3 slender bristles proximal to a-bristle (1 of these medial; medial side spinous, with 10-14 cleaning bristles, and 1 long g-bristle distal to base of d-bristle; lateral side with 1 long e-bristle between b- and c -bristles and 1 long f-bristle between c- and d-bristles. 3rd endopodial joint with stout dorsal claw with ventral spines, 4 stout spinous bristles, and 1 slender shorter spinous bristle.


Maxilla: Epipodite extremely hirsute, reaching to about midlength of dorsal margin of basale. Endite I with 4 bristles (1 short bare, others long spinous); endite II with 4 bristles (1 minute bare, others long spinous). Basale spinous: Ventral margin with row of 5 bare bristles near midlength, 1 small bare distal bristle, and 1 long spinous terminal bristle; medial surface near dorsal margin with 2 bare bristles (1 proximal, 1 distal); lateral surface with 1 proximal bristle near midheight. 1st endopodial joint spinous, with short bare alpha-bristle and long beta-bristle with indistinct spines. 2nd endopodial joint with terminal bristle (with indistinct spines) shorter than beta-bristle.


Fifth Limb: Comb tapering distally, with stout spinous exopodial bristle reaching past tip; 2 short slender bristles just ventral to base of exopodial bristle; 2 pairs of lateral bristles with bases set back from ventral margin at midlength of comb; 1 lateral bristle near proximal pair with base almost on ventral margin; 3 additional lateral bristles (1 proximal, 2 distal) with bases almost on ventral margin.


Sixth Limb: Small medial bristle in proximal anterior corner. Anterior margin with 2 fairly closely spaced endite bristles. Lateral flap of skirt with small hirsute bristle. Anterior end of skirt with 3 or 4 small bristles; ventral and posteroventral margins with total of 20 or 21 bristles (14 or 15 ventral with long proximal and short distal spines plus 6 plumose bristles on posteroventral corner). Limb hirsute.


Seventh Limb: Each limb with 12 bristles (4 on terminal segment (2 on each side), 2 on next segment (1 on each side), 6 on proximal segments (3 on each side)); each bristle with 2-4 bells and without spines. Combs forming obtuse angle; each comb with 12 or 13 spinous teeth; teeth towards each end of comb slightly shorter. Limb increasing in width distal to proximal bristles.


Furca: Each lamella with 9 claws; proximal 2 claws bristle-like, indistinctly ringed; claws 1-7 with small teeth along posterior edge; claws 8 and 9 with small indistinct spines; claw 1 with few teeth very slightly longer than others (not with some very long teeth as in many other species of the subfamily); claws 1-5 with distal hairs along anterior edge. Each lamella with 2 indistinctly ringed spinous bristles on lateral edge (1 between claws 2 and 3, other between claws 3 and 4); anterior edge of each lamella with few small spines; claw 1 of right lamella anterior to claw 1 of left lamella by width of claw base. (Not all teeth on claws and not all spines or hairs shown.)


Bellonci Organ: Elongate with rounded tip.


Eyes: Lateral eyes absent Medial eye hirsute, unpigmented.


Lips: Upper lip a hirsute lobe on each side of depressed saddle; stout bifurcate spine on inner side of each lobe (spines visible in anterior view of USNM 193861 but not observed in lateral view). Saddle with several small anterior spines. Lower lip a hirsute lateral flap on each side of mouth.


Genitalia: Oval ring on each side of body anterior to furca.


Anterior of Body: Hirsute, without anterior process.


Posterior of Body: With thumb-like spinous posterodorsal process.


Y-Sclerite: Typical for subfamily.


Gills: 1 well-developed gills on each side.


Eggs: Slope 27: USNM 193861 with 10 eggs in marsupium (length of typical egg 0.42 mm; location of 3 eggs shown in Figure 15h [in cited text]). Slope 69: USNM 193959 with 6 eggs in marsupium (length of 3 eggs (mm): 0.50,0.50,0.56; location of 2 eggs shown in Figure 74a [in cited text]).



DESCRIPTION OF ADULT MALE.— Carapace differs from that of female in being smaller. Vertical row of hairs near posterior end usually present on male Cylindroleberidinae absent


Infold and Selvage: Not examined.


Central Adductor Muscle Attachments: About 42 ovoid attachments.


Carapace Size (length, height in mm): Slope 67: USNM 194005, 1.77, 1.29, height 77% of length. Slope 69: USNM 193960, 1.66, 1.21, height 73% of length. Length range 1.66-1.77, height range 1.21-1.29; range of height as percent of length 73-77.


First Antenna: 1st joint bare. 2nd joint spinous with long spinous dorsal bristle and short lateral bristle. 3rd joint with distinct suture separating it from 4th joint, with 1 small bare ventral bristle and 6 dorsal bristles (4 proximal single with long spines; next 2 paired (lateral with few short spines, medial longer and with many short spines)). 4th joint separated from 5th by oblique suture parallel to suture between 3rd and 4th joints, with 2 slender bare terminal ventral bristles and 1 long bare terminal dorsal bristle. 5th joint fused to 6th except for short medial suture at ventral margin (a small step in ventral margin where a muscle is attached may indicate location of division between 5th and 6th joints); sensory bristle with abundant thin filaments (not all shown). 6th joint with terminal medial bristle reaching past tip of a-bristle of 7th joint 7th joint: a-bristle claw-like with few indistinct distal spines; b-bristle about 1/3 longer than a-bristie, with 4 marginal filaments; c -bristle about 4 times longer than a-bristle, with 10 marginal filaments. 8th joint: d- and e-bristles filament-like, about twice length of a-bristle, bare with blunt tips; e-bristle stouter than d-bristle; f-bristle about twice length of a-bristle, with 6 marginal filaments; g-bristle about 2/3 length of c-bristle, with 8 marginal filaments.


Second Antenna: Protopodite with few distal dorsal spines and small bare distomedial bristle. Endopodite 3-jointed: 1st joint elongate bare; 2nd joint elongate with 3 distal bristles; 3rd joint elongate, narrow, reflexed on 2nd joint, with long proximal filament and about 6 minute terminal ridges. Exopodite: 1st joint with few distal spines on dorsal concave surface; bristle of 2nd joint reaches well past 9th joint, with long natatory hairs; bristles of joints 3-8 and 2 long bristles of 9th joint with natatory hairs, no spines; short dorsal bristle of 9th joint with few short spines or hairs; joints 2-8 each with long hairs on distal dorsal corner and row of minute spines along distal edge; 9th joint with row of minute lateral spines at distal 2/3 and with 3 minute lateral terminal spines similar to those along distal edges of joints 2-8.


Mandible: Coxale endite of USNM 193960 broken off. Basale endite with glandular peg, 2 dwarf bristles, 3 triaenid bristles with 8-13 pairs of weakly developed spines excluding terminal pair, and 4 spinous end bristles. Basale: Ventral margin with 1 small triaenid bristle (with 5 or 6 pairs of spines excluding terminal pair) close to base of endite and proximal to U-shaped boss, and several weak spines distal to U-shaped boss; dorsal margin with spines and 2 long stout terminal bristles with short marginal spines; medial surface with rows of spines. Exopodite hirsute, about xh length of dorsal margin of 1st endopodial joint, with 2 short bristles reaching midlength of 1st endopodial joint. 1st endopodial joint with 3 long ventral bristles (2 with long spines on proximal 2/3, 1 (shortest) with long spines on proximal 73 and short spines distally). 2nd endopodial joint with 16 cleaning bristles, otherwise similar to that of adult female. 3rd endopodial joint similar to that of adult female.


Maxilla: Basale with 4 long ventral bristles at midlength (1 less than on female); limb otherwise similar to that of adult female.


Fifth Limb: Exopodial bristles similar to those of adult female.


Sixth Limb: Anteroventral corner with 3 spinous bristles; ventral and posteroventral margins with total of 14-16 bristles; limb otherwise similar to that of adult female.


Seventh Limb: USNM 193960: Terminus with opposing combs, each with 8-10 spinous teeth. Margin between combs of male limb more concave than on adult female; limb otherwise similar to that of adult female. USNM 194005 (1 limb examined) with 14 bristles (9 in proximal group, 5 in distal group).


Furca, Bellonci Organ, Eyes, Lips, Anterior and Posterior of Body, and Y-Sclerite: Similar


to those of adult female.


Genitalia: 1 or 2 lobes on each side of body anterior to furca.


Parasites: USNM 193960 with choniostomatid copepods (1 female, 1 copepodite) inside marsupium.



DESCRIPTION OF A-l MALE.—Carapace similar in shape to that of adult female.


Infold and Selvage: Not examined.


Central Adductor Muscle Attachments: Similar to those of adult female.


Carapace Size (length, height in mm): Slope 27: USNM 193862, 1.65, 1.42; NMV J40028,1.65,1.42.


First Antenna: Similar to that of adult female, including numbers of filaments on sensory bristle of 5th joint and bristles of joints 7 and 8.


Second Antenna: Protopodite and exopodite similar to those of adult female. Endopodite 3-jointed: 1st joint short bare; 2nd joint elongate with 2 short distal bristles; 3rd joint long, tapering distally, with minute nipple at tip, and long proximal filament almost twice length of joint.


Mandible: Bristles of dorsal margin of basale and exopodite similar to those of adult female. Remaining part of appendage not examined in detail.


Maxilla: 4 instead of 5 bare ventral bristles at midlength of basale; limb otherwise similar to that of adult female.


Fifth Limb: Comb similar to that of adult female.


Sixth Limb: Not examined.


Seventh Limb: Same number and distribution of bristles as on adult female; bristles cylindrical, similar to those of adult female (not strongly tapered as on juveniles of some other species of Cylindroleberidinae); bristles with 1-3 bells. Angle between combs obtuse but smaller than angle on adult female; each comb with 7 spinous teeth.


Furca: Similar to that of adult female except with only 8 claws (claw 8 ringed, bristle-like) and 1 lateral bristle (between claws 2 and 3). Teeth along posterior margins of claws 1-7 similar to those of adult female.


Bellonci Organ: Similar to that of adult female.


Eyes: Lateral eyes absent. Medial eye similar to that of adult female.


Gills: 7 well-developed gills on each side reaching just past posterior edge of body.


Parasites: USNM 193862 with female choniostomatid copepod in marsupium.



REMARKS.—The adult male USNM 194005 is designated a nontype because the anteroventral margin of the valve has a lateral process much smaller than on other specimens referred to the species. The lateral process is the main character separating X. trux and X. storthynx; USNM 194005 is referred to trux rather than storthynx because of its 7th limb having only 14 bristles, and the small size of the carapace.



SEXUAL DIMORPHISM.—Carapace of male smaller than that of the female. 1st antenna with usual dimorphism present in the Cylindroleberidinae, except male limb with fused 5th and 6th joints and f-bristle not long. Male 2nd antenna with fewer spines on protopodite, with endopodite formed as clasper, and with longer bristle on 2nd exopodial joint (bristle having natatory hairs, not short slender spines as on female). Exopodite of male mandible slightly shorter than that of female. Margin of 7th limb between opposing combs more concave on male than on female.



COMPARISONS.—The carapace of the female X. trux differs from that of the female X. storthynx in being smaller (length 1.83-2.06 mm compared to 2.22-2.39 mm), in having a well-developed lateral process on the anteroventral part of the valve, and in having fewer small bristles on the broad posteroventral list The appendages of females of the 2 species differ in X. trux in having fewer triaenid bristles on the basale of the mandible and in having 12 rather than 17-22 bristles on the 7th limb.”



(Kornicker & Poole, 1996, p.131-142)


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

Belongs to 0 communities

This taxon hasn't been featured in any communities yet.

Learn more about Communities


EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!