Metavargula hex Kornicker 1989

Metavargula hex

Metavargula species A.—Komicker 1985:410–412 [part, including only specimens from samples DS-48 and DS-77].

ETYMOLOGY.—From the Greek hex (six).

HOLOTYPE.—Adult female on slide and in alcohol, MNHN Os 267, Muséum National d'Histoire Naturelle, Paris, France.

TYPE LOCALITY.—BIOGAS VI, R.V. Jean Charcot, west of Bay of Biscay, 47°31′48″N, 9°34′36″W, 4240 m, sta 3, sample DS-77, 24 Oct 1974.

PARATYPES.—BIOGAS III, R.V. Jean Charcot, sta 1: sample DS-48, 1 adult male (MNHN Os 268). BIOGAS VI, R.V. Jean Charcot, sta 3: sample DS-77, 2 juveniles (USNM 193345).

DISTRIBUTION.—In and west of Bay of Biscay, 4203–4240 m.

DESCRIPTION OF ADULT FEMALE (Figures 19, 20).—Carapace elongate with projecting caudal process below midheight (Figure 19a).

Infold (Figure 19b,c): Rostral infold with 2 bristles (1 long, 1 short) at inner end of incisur; and about 17 bristles (mostly forming row paralleling outer edge of rostrum) and 4 pores possibly representing bristle sockets; 1 small bristle near the 2 bristles at inner end of incisur. Anteroventral and ventral infold with 1 small bristle near inner end of incisur, followed by space and then about 60 short bristles along narrow list; list extending from below incisur to caudal process; list broad anterior to caudal process, with about 17–20 minute processes (with pore at tip) along posterior edge, 3 or 4 minute bristles just anterior to processes, about 11 bristles near anterior edge of list, and about 6 minute bristles near posterior edge of list dorsal to the processes; caudal process posterior to list with numerous minute pores (not shown on illustrated valve).

Selvage: Lamellar prolongation of selvage broad and indistinctly striate along lower margin of incisur (Figure 19b), narrow along anteroventral and ventral margin of valves and dorsal to caudal process; selvage absent at posterior end of caudal process and along upper edge of incisur; prolongation divided at innermost end of incisur; minute length of prolongation at inner end of incisur with ventral end at pair of bristles at inner end of incisur (Figure 19b).

Size: Length 4.02 mm, height 2.29 mm.

First Antenna (Figure 19d): 1st joint bare. 2nd joint with hairs on medial surface and ventral margin. 3rd joint with medial hairs and 2 spinous bristles (1 ventral, 1 dorsal). 4th joint with 2 spinous bristles (1 ventral, 1 dorsal). Sensory bristle of 5th joint with 8 long proximal filaments (filaments with short narrow proximal part; distal part about 1 width of proximal part) followed by 2 slender filaments (with spine at tip) and bifurcate tip. Medial bristle of 6th joint about same length as joint (tip of bristle broken on illustrated limb). 7th joint: a-bristle about same length but slightly broader than bristle of 6th joint; b-bristle about twice length of a-bristle, with 4 marginal filaments, some filaments with marginal spines; c-bristle longer than sensory bristle of 5th joint, with 8 marginal filaments and bifurcate tip (tip of bristle broken on illustrated limb, and not all filaments shown; some filaments with marginal spines). 8th joint: d- and e-bristles about longer than b-bristle, bare with blunt tips (d- and e-bristles not shown on illustrated limb); f-bristle about same length as sensory bristle of 5th joint, with 7 marginal filaments and bifurcate tip (tip of bristle broken on illustrated limb), some filaments with marginal spines; g-bristle about same length as c-bristle, with about 8 marginal filaments and bifurcate tip (tip broken on illustrated limb), some filaments with marginal spines.

Second Antenna (Figure 20a): Protopodite with short medial bristle (absent on left limb of illustrated specimen). Endopodite 2-jointed: 1st joint with 4 bristles (2 short, 1 medium, 1 long), longest with marginal spines; 2nd joint short, with long terminal bristle. Exopodite: 1st joint with few small spines along dorsal concave margin; joints 3–8 with basal spines increasing in length distally; basal spine of 8th joint almost same length as 9th joint; 9th joint with lateral spine about same length as joint; bristle of 2nd joint reaching past 9th joint, with about 24 ventral spines, no hairs, ultimate spine longer and stouter than others; bristles of joints 3–8 with natatory hairs, no spines; 9th joint with 4 bristles (3 long, 1 short), all with natatory hairs, no spines.

Mandible (Figure 19e,f): Coxale endite spinous, with 2 stout spinous processes and medial peg at tip, and small bristle near base. Basale: ventral margin with 2 small a-bristles, one small b-bristle, 2 c-bristles (1 long with wreaths of long hairs, 1 short, bare just proximal to long bristle), and 2 d-bristles (short slender bristle followed by long spinous bristle); dorsal margin with 3 bristles (1 distal to midlength, 2 terminal). Exopodite reaching just past distal end of 1st endopodial joint, hirsute distally, with 2 bristles on inner margin (distal bristle reaching just past midlength of proximal bristle). 1st endopodial joint with 4 ventral bristles (2 long, 1 short, 1 minute). 2nd endopodial joint: dorsal margin with about 20 bristles (5 of these much longer than others); ventral margin with bristles forming 3 distal groups of 1, 1, and 2 (medial of distal pair stouter than others and with spines on dorsal margin). End joint with 4 claws (lateral dorsal claw shorter than others) and 3 ringed bristles (lateral bristle about same length as longer claws and broader in proximal spines present along ventral margin of broad proximal part).

Maxilla (Figure 20b): Protopodite with plumose dorsal bristle. Endite I with 11 spinous bristles; endite II with 5 spinous bristles; endite III with 8 spinous bristles and 1 small proximal bare bristle. Basale with 2 bare bristles (1 long, 1 short and distal to other) at inner distal edge. Exopodite with 1 hirsute proximal bristle just distal to midlength (not shown on illustrated limb) and 2 terminal bristles of subequal length (about same length as proximal bristle; bristle closest to proximal bristle hirsute, other bare). 1st endopodial joint with 2 alpha-bristles (outer long, hirsute, inner shorter, bare), and 3 beta-bristles (outer and middle bristles pectinate, inner small bristle bare); cutting blade comprising 4 or 5 pointed teeth. End joint with 4 a-bristles, 3 b-bristles, 3 c-bristles, and 3 d-bristles.

Fifth Limb (Figure 20c–f): Protopodite with short, undulate, anterior, tooth-like process. Endites I-III obscure on specimen studied. Exopodite: anterior side of 1st joint with 2 spinous bristles near tooth of protopodite and 3 spinous bristles forming row closer to main tooth (Figure 20d); main tooth comprising smooth triangular tooth followed by 5 pectinate teeth (Figure 20e); 1 spinous bristle proximal to triangular tooth. 2nd exopodial joint with 5 a-bristles, about 6 b-bristles, 1 c-bristle and 1 d-bristle. 3rd joint with 3 bristles on inner lobe and 3 on hirsute outer lobe. 4th joint separated from 5th by suture, with hairs near margin and 5 bristles. 5th joint hirsute, with 2 bristles, and small spinous process on distal margin near boundary separating 4th and 5th joints. (The presence of 3 bristles rather than the 2 usually found on the outer lobe of the 3rd exopodial joint of both limbs of the specimen may be an aberration; only 2 were present on the male described herein.)

Sixth Limb (Figure 20g): 3 short bare bristles and 1 longer plumose bristle in place of epipodial appendage. Endite I with 3 small, hirsute, medial bristles and 1 long, spinous, terminal bristle; endite II with 4 small, hirsute, medial bristles and 2 long, stout, terminal bristles; endite III with 2 medium and 2 long, spinous, terminal bristles; endite IV with 1 or 2 medium and 2 long, spinous, terminal bristles. End joint with 18 bristles (last 3 hirsute to tip, others with long proximal marginal spines and short distal spines near tip).

Seventh Limb (Figure 20h): Illustrated limb with 11 proximal filaments with 2–5 bells and 11 terminal bristles with 2–5 bells; comb with 5 finger-like teeth (all with thin marginal hairs) opposite finger-like process with pointed tip and few faint marginal hairs. Opposite limb with 6 proximal bristles on peg side and only 1 (aberrant?) on comb side, and with 12 terminal bristles, 6 on each side; bristles with 2–5 bells; comb with 4 teeth (similar to those of illustrated limb) opposite finger-like process with rounded tip.

Furca: Each lamella with 8 claws decreasing in size proximally along lamella; right lamella slightly anterior to left; claws with teeth along posterior margin and short hairs along anterior margin; claws 1–5 curved, claws 6–8 linear; teeth forming medial row on claw 1 about same size, or only slightly larger, than teeth forming lateral row; spines on lamellae following claws.

Bellonci Organ (Figure 19g): Short, cylindrical, with small knob at tip.

Eyes: Lateral eyes absent. Medial eye small with brown pigment (Figure 19h)

Upper Lip (Figure 19h): Anterior part with numerous small glandular openings; paired part consisting only of stout tusks divided into proximal part with backward oriented process and long distal part with lateral and terminal glandular openings; proximal and distal parts separated by suture.

Genitalia: Oval ring on each side of body.

Posterior of Body: Without process.

Y-Sclerite: Typical for subfamily.

DESCRIPTION OF ADULT MALE (Figure 21).—Carapace similar in shape to that of female but smaller (Figure 21a).

Size: Length 2.98 mm, height 1.79 mm.

First Antenna (Figure 21b): Joints 1–6 similar to those of female except proximal part of stem of sensory bristle of 5th joint much stouter (width almost half that of distal margin of 5th joint) and long proximal filaments (8) broad paddle-like. 7th joint: a-bristle about longer than medial bristle of 6th joint; b-bristle about 3 times length of a-bristle, with stout proximal filament (with large marginal sucker and small protuberance near pointed tip), followed by 2 slender filaments (with 2 or 3 small suckers forming row) and 1 filament without suckers; c-bristle about twice length of sensory bristle of 5th joint, with stout proximal filament (with large marginal sucker), followed by 2 slender filaments (each with 2 or 3 small marginal suckers), 5 slender filaments (some with marginal spines), and bifurcate tip. 8th joint d- and e-bristles longer than b-bristle, bare with blunt tips; f-bristle about same size or slightly smaller than c-bristle, with 8 marginal filaments with marginal spines; g-bristle as long as c-bristle, with 9 marginal filaments with marginal spines.

Second Antenna (Figure 21c): Similar to that of female.

Mandible: Dorsal margin of 2nd endopodial joint with about 16 bristles; limb otherwise similar to that of female.

Maxilla (Figure 2d): Similar to that of adult female, except cusps of cutting tooth of 1st endopodial joint rounded. All bristles not shown on illustrated limb.

Fifth Limb (Figure 21e): Outer lobe of 3rd exopodial joint with only 2 bristles; limb otherwise similar to that of female.

Sixth Limb (Figure 21g): 1 spinous bristle and no or 1 short bristle in place of epipodial appendage. Endite I with 2 medial bristles and 1 terminal bristle; endite II with 3 medial and 2 terminal bristles; endite III with 3 terminal bristles; endite IV with 2 or 3 terminal bristles. End joint margin with 8 or 9 spinous bristles followed by short space and then 1 spinous and 2 hirsute bristles.

Seventh Limb (Figure 21h): Each limb with 3 or 4 proximal bristles (1 or 2 on each side), each with 3–5 bells, and 13 or 14 terminal bristles (6–8 on each side), each with 2–4 bells; terminus with 5 linear teeth with digitate tips opposite single similar tooth.

Furca, Bellonci Organ, Eyes, Upper Lip, Posterior of Body: Similar to those of adult female.

Genitalia (Figure 21i): Well developed, each limb with several lobes bearing small bristles; distal end broadly rounded.

COMPARISONS.—The new species M. hex differs from M. bilix in not having lateral eyes, in having 8 instead of 9 claws on each lamella of the furca, and in having only 4 instead of 5 bristles on the 1st joint of the endopodite of the 2nd antenna. The carapace of M. hex is longer than that of M. quintuplex (female 4.02 mm compared to 2.74–3.22 mm; male 2.98 mm compared to 2.38–2.67 mm); also, the longest epipodial bristle on the 6th limb of M. hex is spinous, whereas, the bristle is bare on M. quintuplex.

Metavargula species indeterminate

MATERIAL.—BIOGAS I, R.V. La Perle, sta Hors-Zone: sample DS-14, 2 juveniles (USNM 193346). BIOGAS V, R.V. Cryos, sta 2, sample DS-66, 3 juveniles (USNM 193262). BIOGAS VI, R.V. Jean Charcot, sta 3: sample DS-76, 1 instar III (USNM 193263).

DISTRIBUTION.—Known only from in and west of the Bay of Biscay at abyssal depths.

COMPOSITION.—The genus is proposed for a new species described herein, Rheina prex.

DIAGNOSIS (based only on type species).—Carapace elongate having caudal process curving upward and with truncate tip; type species large: length of female 3.72 mm, male 3.29 mm.

First Antenna: Sensory bristle of 5th joint with long slender proximal and short slender distal filaments; filaments of male sensory bristle not broad.

Second Antenna: Endopodite of male and female similar, 3 jointed: 1st joint with 5 bristles; 2nd joint elongate, bare; 3rd joint short with long terminal bristle. Bristle of 2nd exopodial joint with numerous ventral spines.

Furca: Type species with 9 claws on female and 7 on male; claw 2 fused to lamella.

Bellonci Organ: Short, cylindrical, with rounded tip.

Eyes: Medial eye small, unpigmented. Lateral eyes absent.

Upper Lip: With unpaired anterior part and paired well-developed posterior tusks extending past ventral edge of anterior part

COMPARISONS.—The new genus is defined mainly by having a 2nd antenna with a well-developed 3-jointed endopodite with an elongate bare 2nd joint; an upper lip with 2 long paired posterior tusks; and a sensory bristle of the 5th exopodial joint of the male 1st antenna with slender proximal filaments. Rheina differs from species of Vargula Skogsberg, 1920, and Sheina Harding, 1966, in not having a small bristle on the 2nd joint of the endopodite of the 2nd antenna. In Kornicker, 1983:19, “Key to genera of the Cypridina Group and Group?” R. prex runs down to Sheina because of the absence of a bristle on the 2nd endopodial joint of the 2nd antenna; however, in a restudy of the type species of Sheina by Kornicker (1986) it was shown that Sheina does have a bristle on the 2nd joint. Rheina differs from species of Bathyvargula and Metavargula in having an elongate 2nd joint on the endopodite of the 2nd antenna; also, known males of species Bathyvargula and Metavargula have very broad proximal filaments on the sensory bristle of the 1st antenna.