Vargula hex Kornicker 1994

Vargula hex

ETYMOLOGY.—From the Greek hex (six).

HOLOTYPE.—Partly dissected ovigerous female in alcohol in collection of the Museum of Victoria.

TYPE LOCALITY.—Slope 32, 38°21.90′S, 149°20.00′E, Victoria, S of Point Hicks; depth 1000 m.

PARATYPES.—Slope 32: USNM 193835, ovigerous female on slide and in alcohol; 4 ovigerous females in alcohol; adult female with choniostomatid copepod in marsupium, in alcohol; adult nonovigerous female in alcohol; USNM 193850, adult male on slide and in alcohol. Slope 33, partly dissected ovigerous female in alcohol. Slope 47: ovigerous female on slide and in alcohol; USNM 194026, adult male on slide and in alcohol.

DISTRIBUTION.—Slope 32, 1000 m. Slope 33, 930 m. Slope 47, 500 m.

DESCRIPTION OF ADULT FEMALE (Figures 6, 7, 110k,l).—Caudal process projecting posteriorly either forming shallow concavity where joining posterior margin of valve just dorsal to process (Figure 6i), or evenly rounded (Figure 6a), both types may be present on opposing valves of same specimen (Figure 6l,n).

Infold: Rostral infold with 20 divided bristles (Figure 6j); 1 pair of unequal bristles near inner end of incisur; 3 or 4 minute bristles near lower edge of inner end of incisur. Infold extending from incisur to midlength of ventral margin with 45 to 50 double bristles; infold from midlength of ventral margin to anterior end of caudal process with 4 double bristles. List anterior to caudal process broad, with many pore canals along posterior edge of ventral , about 25 of these projecting past posterior edge as minute processes, but edge appearing smooth at magnification of ×150 (×10 objective, ×15 ocular; Figure 6l–n,k), and 16–23 minute bristles (not all shown in Figure 6k) on medial surface near posterior edge.

Selvage: Outer margin of broad lamellar prolongation along ventral edge of incisur with minute spines; narrow anteroventral prolongation with minute crenulations (appearing like spines not extending past outer edge of selvage) along outer margin.

Central Adductor Muscle Attachments (Figure 6b): With about 19 ovoid attachments.

Carapace Size (length, height in mm): Slope 32: holotype, 2.84, 1.79. USNM 193835, 2.67, 1.69. Sta 32: 2.69, 1.70; 2.85, 1.73; 2.83, 1.79; 2.76, 1.73 (with parasite in marsupium). Slope 33: 2.65, 1.67. Slope 47: 2.40, 1.38. Length range 2.40–2.85 mm. Height 58%–63% of length.

First Antenna: 1st joint bare. 2nd joint with spines along ventral and dorsal margins and on medial and lateral surfaces. 3rd joint with short medial spines in 2 rows and 2 spinous bristles (1 ventral, 1 dorsal) (Figure 6o). 4th joint with 2 spinous bristles (1 ventral, 1 dorsal). Sensory bristle of 5th joint with 12 marginal filaments (some with a few proximal minute spines) and bifurcate tip. Medial bristle of 6th joint spinous. 7th joint: a-bristle about longer than bristle of 6th joint, with short marginal spines; b-bristle about longer than a-bristle, with 4 or 5 short marginal filaments and few spines on stem following last filament and 2 minute terminal spines; c-bristle about 4 times length of a-bristle, with 9 or 10 marginal filaments (some with few teeth) and bifurcate tip. 8th joint: d-and e-bristles about twice length of b-bristle, shorter than c-bristle, bare with blunt tips; f-bristle shorter than c-bristle, with 9 marginal filaments (some with few minute spines) and bifurcate tip; g-bristle longer than f-bristle, about same length as c-bristle, with 10 or 11 marginal filaments (some with few minute spines) and with bifurcate tip.

Second Antenna: Protopodite with short medial bristle either bare or with short spines (Figure 110k,l). Endopodite 3-jointed (Figure 6p,q): 1st joint short with 4 bare proximal bristles (1 long, 3 short) and 1 long 1 spinous distal bristle; 2nd joint elongate with 1 bristle (with few indistinct short spines) reaching past distal end of 3rd joint; 3rd joint short with long terminal bristle. Exopodite: 1st joint with indistinct spines along dorsal edge; bristle of 2nd exopodial joint reaching distal end of 8th joint, with 7–9 ventral spines and slender dorsal spine at base of slender ringed terminal part; bristles of joints 3–8 long with natatory hairs, no spines; 9th joint with 3 long bristles with natatory hairs and 1 short dorsal bristle with few short spines; joints 3–8 with basal spines increasing in length on distal joints; basal spine of 8th joint reaching past distal end of 9th joint; lateral spine of 9th joint about 1 times length of 9th joint; joints 2–8 with short spines in row along distal edge; 2nd joint also with numerous minute indistinct ventral spines near midlength.

Mandible: Coxale endite spinous, with 2 stouter spines at tip; slender cylindrical process (about half length of stouter of 2 spines) with terminal nipple between terminal spines; minute bristle near base of endite. Basale: ventral margin with 2 a-bristles (longer bristle spinous), 1 short lateral b-bristle, 2 c-bristles (proximal small, distal long, both with indistinct short spines), and 2 d-bristles (proximal short with short spines, distal very long with long proximal and short distal spines); dorsal margin with 1 bristle distal to midlength and 2 terminal bristles with short spines; medial surface with numerous rows of spines. Exopodite hirsute, reaching just past distal end of dorsal margin of 1st endopodial joint, with 2 subterminal bristles (proximal bristle about twice length of distal bristle, both with short spines). 1st endopodial joint with few indistinct minute terminal spines on dorsal margin, and 4 ventral bristles (1 minute, 1 short, and 1 long, all with short spines, 1 long with long proximal and short distal spines). 2nd endopodial joint: ventral margin with spines and 4 distal bristles (2 single ringed then 2 subterminal paired (lateral ringed, medial unringed sclerotized, about twice width of lateral bristle but slightly shorter)) (Figure 6c,r); USNM 193835: dorsal margin with 11 to 14 short spinous cleaning bristles (1 with stout spines), 5 long spinous bristles (none reach 3rd joint), and 2 medium spinous bristles; 3rd endopodial joint with 3 short claws with proximal ventral teeth and 4 bristles (ventral bristle minute, remaining bristles about same length as claws (lateral bristle near ventral end of joint with basal part slightly broader than basal parts of other bristles; tip of dorsal bristle pointed)). Correction: lateral bristle of subterminal pair on ventral margin of 2nd endopodial joint also ringed on V. ascensus (bristle incorrectly called medial bristle in Kornicker (1979:18) but correct in his illustration (1979, fig. 6g)).

Maxilla: Dorsal margin of coxale with plumose dorsal bristle. Endite I broad with 10 or 11 spinous bristles; endite II narrow with 5 spinous bristles (Figure 7a); endite III narrow with 5 terminal bristles (4 with long spines) and 1 short proximal bare bristle (this bristle could be on basale) (Figure 7a). Basale with 1 long and 1 short bristle on distal ventral corner. Exopodite hirsute, with 1 plumose proximal bristle and 2 terminal bristles (bristle closest to proximal bristle plumose, other with short spines) (Figure 7b). 1st endopodial joint spinous with 2 alpha- and 3 beta-bristles (outer with slender teeth, middle with short spines, inner bare) (Figure 7d) and large squarish cutting tooth (Figure 7c). 2nd endopodial joint with 4 a-bristles (anterior bare, next with few minute spines, next with stout anterior spines, posterior with small anterior spines) (Figure 7e), 3 pectinate b-bristles (Figure 7f), 3 c-bristles (Figure 7g), and 3 pectinate d-bristles (2 unringed, claw-like) (Figure 7h).

Fifth Limb: Endite I with 6 spinous bristles; endite II with 5 spinous bristles (endite II fragmented on USNM 193835); endite III with 7 spinous and pectinate bristles (Figure 7i). Protopodite with long slender tooth (Figure 7l). Main tooth with triangular tooth (with few minute spines (not shown)) and 6 pectinate teeth (Figure 7j); stout bristle with long proximal spines proximal to smooth tooth. Anterior side of 1st exopodial joint with 3 bristles in row and 1 bristle between them and tooth of protopodite (Figure 7l). 2nd exopodial joint with 4 unringed pectinate a-bristles, 4 ringed pectinate b′-bristles, and 4 ringed pectinate b″-bristles, posterior c-bristle and anterior d-bristle (Figure 7k,l). Inner lobe of 3rd exopodial joint with 1 proximal bristle (with long proximal and short distal spines) and 2 longer terminal bristles with small spines (Figure 7k); outer lobe of 3rd joint with 2 bristles (inner bristle with only short spines (holotype) or long proximal and short distal spines (USNM 193835), outer bristle with long proximal and short distal spines (Figure 7k,m). 4th exopodial joint separated from 5th exopodial by suture better defined on anterior side than on posterior side, with 3 or 4 bristles with short spines (Figure 7k,m). 5th exopodial joint with 2 terminal bristles with short spines, and either with cluster of spines or a small process with spines on inner edge. 4th and 5th exopodial joints and outer lobe of 3rd exopodial joint hirsute.

Sixth Limb: With 4–6 epipodial bristles. Endite I with 3 spinous bristles (2 short medial, 1 long terminal); endite II with 5 spinous bristles (3 short medial, 2 long terminal; endite III with 4 bristles (1 medial, 3 terminal (shortest in middle)); endite IV with 3 or 4 bristles (1 medial, 2 or 3 terminal). End joint with 11–13 bristles (8–10 bristles with long proximal and short distal spines followed by space then stout bristle with long proximal and short distal spines and 2 stout plumose bristles). Medial surfaces of endites III and IV and end joint hirsute; lateral surface of end joint with stiff spines along ventral margin except near bases of 2 plumose bristles.

Seventh Limb: USNM 193835: limb with 26 bristles: distal group with 7 bristles on comb side and 6 on peg side. Proximal group with 6 bristles on comb side and 7 on peg side. Bristles with up to 5 bells. Comb with 15 teeth (7 long recurved alate midteeth, and 8 short truncate lateral teeth, 4 on each side) (not all teeth shown in Figure 7n). Single peg opposite comb. Nontype: each limb with 19–21 bristles: distal group with 4 to 6 bristles on comb side and 5 on peg side; proximal group with 4 or 5 bristles on comb side and 5 or 6 on peg side; bristles with 1–5 bells. Comb with 14 teeth (6 long recurved alate teeth and 8 short truncate teeth, 4 on each side). Single peg with minute terminal spines opposite comb. Limb not distally expanded.

Furca (Figure 7o): Each lamella with 9 claws; claws 2 and 4 nonarticulated; claw 3 slightly narrower than claw 4 at base; all claws with teeth along posterior edge (not shown); claw 1 also with row of medial teeth; right lamella anterior to left by width of base of claw 1.

Bellonci Organ (Figures 6e, 7p): Elongate (width 43%–52% of length) with small process at tip. Nontype: width about 59% of length.

Eyes: Medial eye with reddish brown pigment (Figures 6e, 7p). Lateral eye small, with reddish brown pigment around periphery, with 3 or 4 distinct amber-colored cells (Figure 7p,q) and also several unpigmented larger indistinct spheres (6e,f); eye visible through shell (Figure 6a,i).

Upper Lip (Figures 6g, 7r): Anterior unpaired part with fairly large glandular processes along distal margin. Each tusk with 4 step-like glandular processes along posterior edge, 3 medial processes near dorsal edge (Figure 7r), and 2 terminal; anterior edge of tusks with few long distal hairs (Figure 7r). Rounded lobe posterior to tusks hirsute.

Genitalia (Figure 6h): Small oval with attached spermatophore on each side of body anterior to furca.

Anterior of Body (Figure 7s): With rounded anterior process between medial eye and upper lip.

Posterior of Body: Evenly rounded, bare.

Y-Sclerite: With ventral branch typical for genus.

Number of Eggs: Slope 32: USNM 193835 with 15 eggs in marsupium; length of typical egg 0.54 mm. Holotype with 15 eggs in marsupium. Unnumbered specimen with about 19 eggs (counted through shell); length of 1 egg 0.40 mm. Slope 33: unnumbered specimen with 10 eggs in marsupium; length of typical egg 0.52 mm. Nontype, Slope 47: unnumbered specimen with 13 eggs in marsupium; length of 2 well-developed eggs, 0.46 mm, 0.48 mm.

Parasites: 1 adult nonovigerous female (length 2.76 mm, height 1.73 mm) from Slope 32 with female choniostomatid copepod in marsupium.

DESCRIPTION OF ADULT MALE (Figures 8–10, 110m).—Carapace similar to that of adult female but smaller (Figures 8a, 10a).

Infold: Rostral infold with about 20 bristles, mostly divided (Figure 8b); usual pair of unequal bristles present just dorsal to inner end of incisur; 3 minute bristles just posterior to inner end of incisur. Infold extending from incisur to midlength of ventral margin with about 48 divided bristles, mostly along narrow list; infold from midlength of ventral margin to anterior end of caudal process with 4 bristles, all except last along narrow list. Broad list anterior to caudal process of left valve with row of 14 minute bristles at midwidth, and about 80 minute pore canals near posterior edge of ventral , some project slightly past posterior edge on minute processes, but posterior edge of list generally smooth (dorsal part of list shown in Figure 8c). Broad list anterior to caudal process of right valve of USNM 194026 with about same number of bristles as left valve but very indistinct, and about 47 minute processes (each with pore) along posterior edge, many projecting slightly past edge creating less smooth margin than on left valve (possibly, visibility of unevenness affected by orientation of list) (only 25 pores and processes shown in Figure 8d). (Counts of bristles, pores and processes were made using a compound microscope (×15 ocular, ×40 objective) on separated valves in glycerine in a depression slide and under a cover slip.)

Selvage: Proximal ridge of selvage along ventral edge of incisur with beaded row (Figure 8b). Anterior and anteroventral edge of rostrum with narrow lamellar prolongation with smooth outer margin; prolongation absent along dorsal edge of incisur; prolongation along ventral edge of incisur broad, striated, with minute spines along outer margin; prolongation along anteroventral and anterior of ventral edge of valve narrow, with closely spaced striations, and with minute serrations along outer margin; prolongation broad along posterior of ventral edge of valve and with smooth outer margin; selvage absent along edge of caudal process and posterior edge of valve dorsal to caudal process; selvage of ventral edge of right valve set well back from valve edge at ventral end of caudal process (Figure 8d). (Lamellar prolongation not shown.)

Carapace Size (length, height in mm): Slope 32: USNM 193850, 2.34, 1.61, height 69% of length. Slope 47: USNM 194026, 2.17, 1.37, height 63% of length.

First Antenna (Figures 8e,f, 10b,c): Joints 1–4 and 6 similar to those of adult female (Figures 8e, 10b). Sensory bristle of 5th joint with 11 or 12 long filaments (some with spines) and bifurcate tip. 7th joint: a-bristle similar to that of adult female; b-bristle about 3 times length of a-bristle, with 3 filaments (short stout proximal filament with bulbous base, large sucker and small triangular process; then 1 slender filament with minute spine and 4 or 5 small suckers, followed by 1 slender distal filament with minute spine and 4 or 5 small suckers) (Figure 10c); c-bristle about twice length of b-bristle, with 9 filaments (stout proximal filament similar to proximal filament of b-bristle but with larger sucker with minutely serrate edge, then slender filament with spine and 4 small suckers, followed by slender filament (with spines) adjacent to longer slender filament with spine and 4 small suckers, followed by 5 slender filaments (some with spines)) and bifurcate tip. 8th joint: d- and e-bristles slightly shorter than b-bristle, bare with blunt tips (Figure 10c); f-bristle almost twice length of b-bristle, angled dorsally, with 8 short marginal filaments (some with spines) and bifurcate tip; g-bristle about longer than f-bristle, with 9 short marginal filaments (some with spines) and bifurcate tip.

Second Antenna (Figures 8g, 10d, 110m): Bristle of 2nd exopodial joint with 8–13 (8 on USNM 194026, 11–13 on USNM 193850) stout ventral spines and no dorsal spines. Limb otherwise similar to that of adult female.

Mandible (Figures 8h,i, 10e,f): Similar to that of adult female except in having stouter unringed sclerotized medial bristle in terminal pair on ventral margin of 2nd endopodial joint (Figures 8i, 10f).

Maxilla (Figure 9a–c): Endite I of specimen examined with 11 spinous bristles on 1 limb and 9 on other. Limb otherwise similar to that of adult female.

Fifth Limb (Figures 9d–f, 10g): Epipodite with 55 bristles. Endite I with 6 spinous bristles; endite II with 1 minute anterior bristle and 5 spinous terminal bristles; endite III with 7 spinous and pectinate bristles (Figure 9d). Limb otherwise similar to that of adult female.

Sixth Limb (Figure 9g): With 4 or 5 epipodial bristles, and 7–9 bristles in anterior group of end joint Limb otherwise similar to that of adult female.

Seventh Limb: USNM 193850: 1 limb with 23 bristles (distal group with 6 bristles on comb side and 5 on peg side; proximal group with 6 bristles on comb side and 6 on peg side). Other limb with 21 bristles (distal group with 7 bristles on comb side and 5 on peg side; proximal group with 4 bristles on comb side and 5 on peg side). Bristles with 1–5 bells. Comb with 8 short truncate teeth, 4 on each side of about 6 long recurved alate teeth (with small triangular tooth between bases). Single peg opposite comb. USNM 194026 (Figure 9h): each limb with 19 or 20 bristles; distal group with 5 or 6 bristles on comb side and 5 on peg side; proximal group with 4 brisües on comb side and 5 on peg side. Bristles with 1–5 bells. Comb with 12 teeth (6 long recurved alate midteeth, and 6 short truncate lateral teeth, 3 on each side). Single peg with minute terminal spines opposite comb.

Furca (Figures 9i, 10h): 3rd claw about same width or very slightly narrower than claw 4. Furca otherwise similar to that of adult female.

Bellonci Organ: USNM 193850: width 43% of length (Figure 10i). USNM 194026: width about 75% of length (Figure 9j).

Eyes: Medial eye similar to that of adult female (Figures 9j, 10i), Lateral eye small, with reddish brown pigment, several small amber-colored cells, and about 4 indistinct unpigmented spheres (Figures 9j,k, 10i).

Upper Lip (Figures 9l, 10j) and Anterior of body (Figures 9l, 10m): Similar to those of adult female.

Genitalia (Figure 10k,l): Well-developed lobes on each side of body.

Posterior of Body: Posterodorsal margin slightly more undulate than that of adult female (Figures 9m, 10n). USNM 194026 with 5 weakly defined segments dorsal to girdle (Figure 9m).

VARIABILITY.—The male and female from Slope 47 are shorter and more elongate than those from Slopes 32 and 33. The posterior end of valves either has a caudal process with a slight concavity at its dorsal end, or is without a concavity. In some specimens a concavity is present on one valve but not on the other. The 3rd joint relative to the 2nd joint of the endopodite of the 2nd antenna is slightly longer on the specimens from Slope 47 than those from Slopes 32 and 33. The outer lobe of the 3rd exopodial joint of the 5th limb has an inner bristle with long proximal and short distal spines on USNM 193835, but has only short spines on other specimens examined (4 including holotype). The fused 4th and 5th exopodial joints of the 5th limb have a cluster of spines on the inner edge on USNM 193835, whereas the holotype has a cluster of spines on one limb and a small process bearing spines on the other, and the remaining specimens examined (3) have a spinous process on both limbs. The Bellonci organ in the adult male from Slope 47 is shorter than that of the female from that station as well as the females (3) and male from Slopes 32 and 33.

COMPARISONS.—Vargula hex is morphologically close to V. ascensus and V. antarctica. It differs from both species in having the bristle of the 2nd endopodial joint of the 2nd antenna longer than the 3rd joint; the bristle is shorter than the 3rd joint in V. ascensus and either shorter or the same length in V. antarctica. The carapace of V. hex (female length 2.40–2.85 mm) is much smaller than that of V. antarctica (female length 3.42–3.9 mm (excluding Poulsen's specimen from Australia discussed below)). Skogsberg (1920:268) reported that the main tooth of the 1st exopodial joint of the male 5th limb (1 limb examined) of V. antarctica bears 8 teeth. The main tooth of V. hex bears only 7 teeth, but I think it probable that most specimens of V. antarctica also have 7 teeth, which is the usual number possessed by members of the genus (Kornicker, 1991, table 2). The posterior edge of the upper lip of V. hex is more step-like than that of V. antarctica (Müller, 1908, pl. 4:13; Kornicker, 1979, fig. 8b,c).

Poulsen (1962:181) referred 2 specimens (1 adult female, 1 juvenile) collected at a depth of 70–100 m off the SE coast of Australia to V. antarctica, an identification that was questioned by Kornicker (1975:135). The adult female is only 3.0 mm long, smaller than specimens of V. antarctica from elsewhere (3.4–3.9 mm). Poulsen's female is slightly larger than females of V. hex reported here (length 2.40–2.85 mm). Because of the difference in length as well as the quite different depths at which they were collected I have not referred Poulsen's specimens to V. hex herein, but they could be conspecific.